WorldWideScience

Sample records for alkaline cementitious materials

  1. Chemical evolution of cementitious materials

    International Nuclear Information System (INIS)

    Lothenbach, Barbara; Wieland, Erich

    2012-01-01

    Barbara Lothenback of EMPA, Switzerland gave an overview of the status of thermodynamic modelling for cementitious systems. Thermodynamic modelling of cementitious systems has been greatly facilitated in recent years by the development of more sophisticated geochemical software, of solid solution models for various cement phases, and by the collection of thermodynamic data for minerals relevant to cementitious systems over a wide range of temperature (0 to 100 deg. C). Based on these developments, thermodynamic modelling, coupled with kinetic equations that describe the dissolution of clinker as a function of time, can be used to: - Quantify the liquid and solid phase compositions of ordinary Portland cement and blended cements during the hydration process. - Evaluate compositional changes that occur in cementitious materials due to the use of various aggregates and other mineral additives (e.g. silica fume and blast furnace slag). - Predict degradation of cement in contact with the repository environment. Discussion of the paper included: What is our understanding of where aluminium resides in low-pH cements and what is our ability to model the behaviour of aluminium in these systems? The location of aluminium in low-pH cements depends on the overall Ca/Si ratio of the system and on the pH, but some aluminium enters the CSH gel as a CASH gel phase. The Swiss disposal programme is currently conducting some experiments to investigate this topic

  2. Fracture propagation in cementitious materials

    DEFF Research Database (Denmark)

    Skocek, Jan

    , it is experimentally observed and numerically veried that the cracking plays an important role in mode-I as well as compressive experiments. The approximative particle model extended for materials with heterogeneous matrices predicts strengths matching favorably experimental records in a qualitative way.......Mechanical behavior of structures made from cementitious materials has been successfully modeled using non-linear fracture mechanics in recent decades. On the structural scale, an assumption of homogeneity of the material is valid and well established theories can be applied. However, if focus...... is put on phenomena of a similar scale as is the characteristic size of inhomogeneities of the material, a model which re ects the heterogeneous nature of the material needs to be applied. This is, indeed, the case for prediction of mechanical properties of a material based on the knowledge of properties...

  3. Engineered cementitious composites with low volume of cementitious materials

    NARCIS (Netherlands)

    Zhou, J.; Quian, S.; Van Breugel, K.

    2010-01-01

    Engineered cementitious composite (ECC) is an ultra ductile cement-based material reinforced with fibers. It is characterized by high tensile ductility and tight crack width control. Thanks to the excellent performance, ECC is emerging in broad applications to enhance the loading capacity and the

  4. Supplementary cementitious materials

    International Nuclear Information System (INIS)

    Lothenbach, Barbara; Scrivener, Karen; Hooton, R.D.

    2011-01-01

    The use of silica rich SCMs influences the amount and kind of hydrates formed and thus the volume, the porosity and finally the durability of these materials. At the levels of substitution normally used, major changes are the lower Ca/Si ratio in the C-S-H phase and consumption of portlandite. Alumina-rich SCMs increase the Al-uptake in C-S-H and the amounts of aluminate containing hydrates. In general the changes in phase assemblages are well captured by thermodynamic modelling, although better knowledge of the C-S-H is needed. At early ages, 'filler' effects lead to an increased reaction of the clinker phases. Reaction of SCMs starts later and is enhanced with pH and temperature. Composition, fineness and the amount of glassy phase play also an important role. Due to the diverse range of SCM used, generic relations between composition, particle size, exposure conditions as temperature or relative humidity become increasingly crucial.

  5. Time-dependent fracture of cementitious materials

    NARCIS (Netherlands)

    Van Zijl, G.P.A.G.; De Borst, R.; Rots, J.G.

    2000-01-01

    The response of cementitious materials is highly time dependent. On the one hand, it can lead to delayed collapse of structures fabricated of such materials. On the other hand, the time dependence is associated with the relaxation of peak stresses, which avoids, or postpones damage. A finite element

  6. Review on supplymentary cementitious materials used in inorganic polymer concrete

    Science.gov (United States)

    Srinivasreddy, K.; Srinivasan, K.

    2017-11-01

    This paper presents a review on various supplementary cementitious materials generated from industries are used in concrete, which one is considered a waste material. These materials are rich in aluminosilicates and are activated by sodium/potassium based alkaline solution to form geopolymer concrete. When these geopolymer concrete is used in civil engineering applications has showed better or similar mechanical properties and durability properties than ordinary Portland cement concrete. This paper also given the overview on sodium hydroxide (NaOH) & sodium silicate solution (Na2SiO3) ratios, curing adopted for different geopolymer concretes and the effect of adding fibres in geopolymer concretes.

  7. Chloride diffusion in partially saturated cementitious material

    DEFF Research Database (Denmark)

    Nielsen, Erik Pram; Geiker, Mette Rica

    2003-01-01

    The paper proposes a combined application of composite theory and Powers' model for microstructural development for the estimation of the diffusion coefficient as a function of the moisture content of a defect-free cementitious material. Measurements of chloride diffusion in mortar samples (440 kg...

  8. Cellulose nanomaterials as additives for cementitious materials

    Science.gov (United States)

    Tengfei Fu; Robert J. Moon; Pablo Zavatierri; Jeffrey Youngblood; William Jason Weiss

    2017-01-01

    Cementitious materials cover a very broad area of industries/products (buildings, streets and highways, water and waste management, and many others; see Fig. 20.1). Annual production of cements is on the order of 4 billion metric tons [2]. In general these industries want stronger, cheaper, more durable concrete, with faster setting times, faster rates of strength gain...

  9. Can superabsorbent polymers mitigate shrinkage in cementitious materials blended with supplementary cementitious materials?

    DEFF Research Database (Denmark)

    Snoeck, Didier; Jensen, Ole Mejlhede; De Belie, Nele

    2016-01-01

    shrinkage in materials blended with fly ash or blast-furnace slag remain scarce, especially after one week of age. This paper focuses on the autogenous shrinkage by performing manual and automated shrinkage measurements up to one month of age. Without superabsorbent polymers, autogenous shrinkage......A promising way to mitigate autogenous shrinkage in cementitious materials with a low water-to-binder ratio is internal curing by the use of superabsorbent polymers. Superabsorbent polymers are able to absorb multiple times their weight in water and can be applied as an internal water reservoir...... was reduced in cement pastes with the supplementary cementitious materials versus Portland cement pastes. At later ages, the rate of autogenous shrinkage is higher due to the pozzolanic activity of the supplementary cementitious materials. Internal curing by means of superabsorbent polymers is successful...

  10. Cementitious porous pavement in stormwater quality control: pH and alkalinity elevation.

    Science.gov (United States)

    Kuang, Xuheng; Sansalone, John

    2011-01-01

    A certain level of alkalinity acts as a buffer and maintains the pH value in a stable range in water bodies. With rapid urban development, more and more acidic pollutants flow to watersheds with runoff and drop alkalinity to a very low level and ultimately degrade the water environment. Cementitious porous pavement is an effective tool for stormwater acidic neutralization. When stormwater infiltrates cement porous pavement (CPP) materials, alkalinity and pH will be elevated due to the basic characteristics of cement concrete. The elevated alkalinity will neutralize acids in water bodies and maintain the pH in a stable level as a buffer. It is expected that CPP materials still have a certain capability of alkalinity elevation after years of service, which is important for CPP as an effective tool for stormwater management. However, few previous studies have reported on how CPP structures would elevate runoff alkalinity and pH after being exposed to rainfall-runoff for years. In this study, three groups of CPP specimens, all exposed to rainfall-runoff for 3 years, were used to test the pH and alkalinity elevation properties. It was found that runoff pH values were elevated from 7.4 to the range of 7.8-8.6 after infiltrating through the uncoated specimens, and from 7.4 to 8.5-10.7 after infiltrating through aluminum-coated specimens. Runoff alkalinity elevation efficiencies are 11.5-14.5% for uncoated specimens and 42.2% for coated specimens. The study shows that CPP is an effective passive unit operation for stormwater acid neutralization in our built environment.

  11. Self-degradable Cementitious Sealing Materials

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T.; Butcher, T., Lance Brothers, Bour, D.

    2010-10-01

    A self-degradable alkali-activated cementitious material consisting of a sodium silicate activator, slag, Class C fly ash, and sodium carboxymethyl cellulose (CMC) additive was formulated as one dry mix component, and we evaluated its potential in laboratory for use as a temporary sealing material for Enhanced Geothermal System (EGS) wells. The self-degradation of alkali-activated cementitious material (AACM) occurred, when AACM heated at temperatures of {ge}200 C came in contact with water. We interpreted the mechanism of this water-initiated self-degradation as resulting from the in-situ exothermic reactions between the reactants yielded from the dissolution of the non-reacted or partially reacted sodium silicate activator and the thermal degradation of the CMC. The magnitude of self-degradation depended on the CMC content; its effective content in promoting degradation was {ge}0.7%. In contrast, no self-degradation was observed from CMC-modified Class G well cement. For 200 C-autoclaved AACMs without CMC, followed by heating at temperatures up to 300 C, they had a compressive strength ranging from 5982 to 4945 psi, which is {approx}3.5-fold higher than that of the commercial Class G well cement; the initial- and final-setting times of this AACM slurry at 85 C were {approx}60 and {approx}90 min. Two well-formed crystalline hydration phases, 1.1 nm tobermorite and calcium silicate hydrate (I), were responsible for developing this excellent high compressive strength. Although CMC is an attractive, as a degradation-promoting additive, its addition to both the AACM and the Class G well cement altered some properties of original cementitious materials; among those were an extending their setting times, an increasing their porosity, and lowering their compressive strength. Nevertheless, a 0.7% CMC-modified AACM as self-degradable cementitious material displayed the following properties before its breakdown by water; {approx}120 min initial- and {approx}180 min final

  12. Development of ductile cementitious composites incorporating microencapsulated phase change materials

    NARCIS (Netherlands)

    Savija, B.; Lukovic, M.; Chaves Figueiredo, S.; de Mendoca Filho, Fernando Franca; Schlangen, H.E.J.G.

    2017-01-01

    Abstract In the past two decades, much research has been devoted to overcoming the inherent brittleness of cementitious materials. To that end, several solutions have been proposed, mainly utilizing fibres. One of the most promising classes of materials is strain hardening cementitious composite

  13. Corrosion aspects of steel radioactive waste containers in cementitious materials

    International Nuclear Information System (INIS)

    Smart, Nick

    2012-01-01

    Nick Smart from Serco, UK, gave an overview of the effects of cementitious materials on the corrosion of steel during storage and disposal of various low- and intermediate-level radioactive wastes. Steel containers are often used as an overpack for the containment of radioactive wastes and are routinely stored in an open atmosphere. Since this is an aerobic and typically humid environment, the steel containers can start to corrode whilst in storage. Steel containers often come into contact with cementitious materials (e.g. grout encapsulants, backfill). An extensive account of different steel container designs and of steel corrosion mechanisms was provided. Steel corrosion rates under conditions buffered by cementitious materials have been evaluated experimentally. The main conclusion was that the cementitious environment generally facilitates the passivation of steel materials. Several general and localised corrosion mechanisms need to be considered when evaluating the performance of steel containers in cementitious environments, and environmental thresholds can be defined and used with this aim. In addition, the consequences of the generation of gaseous hydrogen by the corrosion of carbon steel under anoxic conditions must be taken into account. Discussion of the paper included: Is crevice corrosion really significant in cementitious systems? Crevice corrosion is unlikely in the cementitious backfill considered because it will tend to neutralise any acidic conditions in the crevice. What is the role of microbially-induced corrosion (MIC) in cementitious systems? Microbes are likely to be present in a disposal facility but their effect on corrosion is uncertain

  14. Recent Advances in Intrinsic Self-Healing Cementitious Materials.

    Science.gov (United States)

    Li, Wenting; Dong, Biqin; Yang, Zhengxian; Xu, Jing; Chen, Qing; Li, Haoxin; Xing, Feng; Jiang, Zhengwu

    2018-03-25

    Self-healing is a natural phenomenon whereby living organisms respond to damage. Recently, considerable research efforts have been invested in self-healing cementitious materials that are capable of restoring structural integrity and mechanical properties after being damaged. Inspired by nature, a variety of creative approaches are explored here based on the intrinsic or extrinsic healing mechanism. Research on new intrinsic self-healing cementitious materials with biomimetic features is on the forefront of material science, which provides a promising way to construct resilient and sustainable concrete infrastructures. Here, the current advances in the development of the intrinsic healing cementitious materials are described, and a new definition of intrinsic self-healing discussed. The methods to assess the efficiency of different healing mechanisms are briefly summarized. The critical insights are emphasized to guide the future research on the development of new self-healing cementitious materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Entombment Using Cementitious Materials: Design Considerations and International Experience

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Roger Ray

    2002-08-01

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing an overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective.

  16. Entombment Using Cementitious Materials: Design Considerations and International Experience

    International Nuclear Information System (INIS)

    Seitz, R.R.

    2002-01-01

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing a n overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective

  17. Entombment Using Cementitious Materials: Design Considerations and International Experience

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, R.R.

    2002-05-15

    Cementitious materials have physical and chemical properties that are well suited for the requirements of radioactive waste management. Namely, the materials have low permeability and durability that is consistent with the time frame required for short-lived radionuclides to decay. Furthermore, cementitious materials can provide a long-term chemical environment that substantially reduces the mobility of some long-lived radionuclides of concern for decommissioning (e.g., C-14, Ni-63, Ni-59). Because of these properties, cementitious materials are common in low-level radioactive waste disposal facilities throughout the world and are an attractive option for entombment of nuclear facilities. This paper describes design considerations for cementitious barriers in the context of performance over time frames of a few hundreds of years (directed toward short-lived radionuclides) and time frames of thousands of years (directed towards longer-lived radionuclides). The emphasis is on providing a n overview of concepts for entombment that take advantage of the properties of cementitious materials and experience from the design of low-level radioactive waste disposal facilities. A few examples of the previous use of cementitious materials for entombment of decommissioned nuclear facilities and proposals for the use in future decommissioning of nuclear reactors in a few countries are also included to provide global perspective.

  18. A review: Self-healing in cementitious materials and engineered cementitious composite as a self-healing material

    DEFF Research Database (Denmark)

    Wu, Min; Johannesson, Björn; Geiker, Mette

    2012-01-01

    Cementitious materials are the most widely used building materials all over the word. However, deterioration is inevitable even since the very beginning of the service life, then maintenance and repair work, which are often labor- and capital-intensive, would be followed. Thus, self-healing of th......Cementitious materials are the most widely used building materials all over the word. However, deterioration is inevitable even since the very beginning of the service life, then maintenance and repair work, which are often labor- and capital-intensive, would be followed. Thus, self......-healing of the affected cementitious materials is of great importance. Self-healing phenomenon in cementitious materials has been noticed and been studying for a long time. The possible mechanisms for self-healing phenomenon in cementitious materials, which are summarized based on substantial experimental studies...... to its unique micro-crack behavior and tight crack-width control property combined with its relatively high percentage of cementitious components and low water–binder ratio....

  19. Micro- and macroscale coefficients of friction of cementitious materials

    International Nuclear Information System (INIS)

    Lomboy, Gilson; Sundararajan, Sriram; Wang, Kejin

    2013-01-01

    Millions of metric tons of cementitious materials are produced, transported and used in construction each year. The ease or difficulty of handling cementitious materials is greatly influenced by the material friction properties. In the present study, the coefficients of friction of cementitious materials were measured at the microscale and macroscale. The materials tested were commercially-available Portland cement, Class C fly ash, and ground granulated blast furnace slag. At the microscale, the coefficient of friction was determined from the interaction forces between cementitious particles using an Atomic Force Microscope. At the macroscale, the coefficient of friction was determined from stresses on bulk cementitious materials under direct shear. The study indicated that the microscale coefficient of friction ranged from 0.020 to 0.059, and the macroscale coefficient of friction ranged from 0.56 to 0.75. The fly ash studied had the highest microscale coefficient of friction and the lowest macroscale coefficient of friction. -- Highlights: •Microscale (interparticle) coefficient of friction (COF) was determined with AFM. •Macroscale (bulk) COF was measured under direct shear. •Fly ash had the highest microscale COF and the lowest macroscale COF. •Portland cement against GGBFS had the lowest microscale COF. •Portland cement against Portland cement had the highest macroscale COF

  20. Obtaining cementitious material from municipal solid waste

    Directory of Open Access Journals (Sweden)

    Macías, A.

    2007-06-01

    Full Text Available The primary purpose of the present study was to determine the viability of using incinerator ash and slag from municipal solid waste as a secondary source of cementitious materials. The combustion products used were taken from two types of Spanish MSW incinerators, one located at Valdemingómez, in Madrid, and the other in Melilla, with different incineration systems: one with fluidised bed combustion and other with mass burn waterwall. The effect of temperature (from 800 to 1,200 ºC on washed and unwashed incinerator residue was studied, in particular with regard to phase formation in washed products with a high NaCl and KCl content. The solid phases obtained were characterized by X-ray diffraction and BET-N2 specific surface procedures.El principal objetivo del trabajo ha sido determinar la viabilidad del uso de las cenizas y escorias procedentes de la incineración de residuos sólidos urbanos, como materia prima secundaria para la obtención de fases cementantes. Para ello se han empleado los residuos generados en dos tipos de incineradoras españolas de residuos sólidos urbanos: la incineradora de Valdemingómez y la incineradora de Melilla. Se ha estudiado la transformación de los residuos, sin tratamiento previo, en función de la temperatura de calentamiento (desde 800 ºC hasta 1.200 ºC, así como la influencia del lavado de los residuos con alto contenido en NaCl y KCl en la formación de fases obtenidas a las diferentes temperaturas de calcinación. Las fases obtenidas fueron caracterizadas por difracción de rayos X y área superficial por el método BET-N2.

  1. Compositions and use of cementitious materials: experience from Onkalo

    International Nuclear Information System (INIS)

    Hansen, Johanna

    2012-01-01

    Johanna Hansen of Posiva in Finland summarised experiences of working with cementitious materials in the Finnish disposal programme. Posiva is responsible for geological disposal of spent nuclear fuel from the Finnish nuclear power plants at Loviisa and Olkiluoto. Posiva plans to submit a construction license application in 2012 and, if approved, repository construction will begin in 2014-2015. The geologic disposal facility will be a KBS-3 type repository at a depth of 400 to 500 m in crystalline bedrock. Construction of the repository will require using a large quantity of cementitious materials. A 2007 estimate indicated that approximately 20 million kilograms of cementitious material will be introduced into the repository, although much of this material will be removed, with only approximately 6 million kilograms remaining in the repository after closure, mostly in the form of tunnel plugs. To minimise the potential negative effects of cementitious materials, low-pH cement and colloidal silica both were studied as alternative materials. Based on experience gained in constructing the ONKALO underground characterisation facility, Posiva decided that from the spring 2008 onwards, mainly low-pH cement will be used as grouting material because the grout cannot be removed for repository closure. The low-pH grout is composed of Portland cement, silica fume, and super-plasticizer. Various recipes were tested in the laboratory, and field mixing and grouting tests were conducted at ONKALO. The effects of organics on radionuclide retention and the leaching of organics from the cement also were evaluated. The studies indicated no impediments to the use of low-pH grout at ONKALO and showed that low-pH cementitious grout has better penetration ability and stiffness than regular grout. It was also concluded that the amount of cementitious materials in the repository can be reduced with careful design; for this, cooperation is needed between repository designers and long

  2. Reduction of minimum required weight of cementitious materials in WisDOT concrete mixes.

    Science.gov (United States)

    2011-12-01

    "This project was designed to explore the feasibility of lowering the cementitious materials content : (CMC) used in Wisconsin concrete pavement construction. The cementitious materials studied included : portland cement, fly ash, and ground granulat...

  3. Electro-decontamination of cementitious materials

    International Nuclear Information System (INIS)

    Ben-Hadj-Hassine, S.

    2012-01-01

    The end of operations in nuclear facilities is followed by various decontamination and decommissioning operations. Similar to other electrochemical techniques such as re-alkalinisation and chloride extraction, an electrokinetic remediation process is being developed as a specific method for deeply contaminated concrete structures. Two cements, an ordinary Portland and a 30% slag cement, have been chosen for the conducted work.Mortars and concretes are contaminated by adding non-radioactive cesium in the batch water, cesium being a representative specie of deep encountered contaminants. The conducted experimental and numerical work have focused on three main aspects: characterizing and understanding the cesium transport mechanisms, assessing the electro-remediation process at lab-scale and evaluating the real scale constraints. Using existing knowledge of chloride transport mechanisms, experiments have been conducted to characterize the cesium interactions with cementitious phase and ionic transport in saturated materials. A numerical model have then been developed to describe the cesium transport, taking into account the ionic activity coefficients and interactions with solid phases. Indeed, lab-scale experiments have demonstrated that electro-remediation reduced to 20-50% the initially contained cesium after a three weeks treatment. Treated samples analysis confirmed that deeply diffused cesium is migrating to the surface. Moreover, conducted experiments showed the consistency between the different materials properties, applied currents and decontamination efficiency. A comparative analysis of experiments carried on samples with different shapes, formulations and contamination modes helped assessing and optimizing the process efficiency for various continuous and variable applied currents. Finally, electro-remediation experiments have also been carried on 1m 2 concrete slabs. Liquid catholyte and anolyte solutions are replaced by alumina gels and cellulose pastes

  4. Preliminary evaluation of the reuse of cementitious materials

    CSIR Research Space (South Africa)

    Paige-Green, P

    2010-08-01

    Full Text Available and demolition waste are being generated on an ongoing basis. Many of these materials still contain significant proportions of cementitious components that can be used to improve the quality of the materials being recycled, but can also lead to problems with over...

  5. Thermal energy storage based on cementitious materials: A review

    Directory of Open Access Journals (Sweden)

    Khadim Ndiaye

    2018-01-01

    Full Text Available Renewable energy storage is now essential to enhance the energy performance of buildings and to reduce their environmental impact. Many heat storage materials can be used in the building sector in order to avoid the phase shift between solar radiation and thermal energy demand. However, the use of storage material in the building sector is hampered by problems of investment cost, space requirements, mechanical performance, material stability, and high storage temperature. Cementitious material is increasingly being used as a heat storage material thanks to its low price, mechanical performance and low storage temperature (generally lower than 100 °C. In addition, cementitious materials for heat storage have the prominent advantage of being easy to incorporate into the building landscape as self-supporting structures or even supporting structures (walls, floor, etc.. Concrete solutions for thermal energy storage are usually based on sensible heat transfer and thermal inertia. Phase Change Materials (PCM incorporated in concrete wall have been widely investigated in the aim of improving building energy performance. Cementitious material with high ettringite content stores heat by a combination of physical (adsorption and chemical (chemical reaction processes usable in both the short (daily, weekly and long (seasonal term. Ettringite materials have the advantage of high energy storage density at low temperature (around 60 °C. The encouraging experimental results in the literature on heat storage using cementitious materials suggest that they could be attractive in a number of applications. This paper summarizes the investigation and analysis of the available thermal energy storage systems using cementitious materials for use in various applications.

  6. Thermodynamics of Autogenous Self-healing in Cementitious Materials

    NARCIS (Netherlands)

    Huang, H.

    2014-01-01

    Concrete is a brittle composite cementitious material that easily fractures under tensile loading. Microcracks can appear throughout the concrete prior to application of any load because of temperature-induced strain and autogenous and drying shrinkage. There is no doubt that these cracks provide

  7. Electrochemical migration technique to accelerate ageing of cementitious materials

    Science.gov (United States)

    Babaahmadi, A.; Tang, L.; Abbas, Z.

    2013-07-01

    Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW) takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen's micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium.

  8. Electrochemical migration technique to accelerate ageing of cementitious materials

    Directory of Open Access Journals (Sweden)

    Abbas Z.

    2013-07-01

    Full Text Available Durability assessment of concrete structures for constructions in nuclear waste repositories requires long term service life predictions. As deposition of low and intermediate level radioactive waste (LILW takes up to 100 000 years, it is necessary to analyze the service life of cementitious materials in this time perspective. Using acceleration methods producing aged specimens would decrease the need of extrapolating short term data sets. Laboratory methods are therefore, needed for accelerating the ageing process without making any influencing distortion in the properties of the materials. This paper presents an electro-chemical migration method to increase the rate of calcium leaching from cementitious specimens. This method is developed based on the fact that major long term deterioration process of hardened cement paste in concrete structures for deposition of LILW is due to slow diffusion of calcium ions. In this method the cementitious specimen is placed in an electrochemical cell as a porous path way through which ions can migrate at a rate far higher than diffusion process. The electrical field is applied to the cell in a way to accelerate the ion migration without making destructions in the specimen’s micro and macroscopic properties. The anolyte and catholyte solutions are designed favoring dissolution of calcium hydroxide and compensating for the leached calcium ions with another ion like lithium.

  9. Rheology of Cementitious Materials: Alkali-Activated Materials or Geopolymers

    OpenAIRE

    Puertas F.; Alonso M.M:; Gismera S.; Lanzón M.; Blanco-Varela M.T.

    2018-01-01

    A clear alternative to reach the goal of sustainable development in the Construction Sector is the development of alternative building materials to Ordinary Portland Cement (OPC) in a more energetically as well as environmentally eco-efficient way. Alkaline cements (Alkali-Activated Materials, AAMs) and geopolymers meet these requirements; and they are based on the alkali activation of aluminosilicates (mainly waste and industrial by-products, such as blast furnace slag, fly ash and ceramic w...

  10. TECHNETIUM SORPTION BY CEMENTITIOUS MATERIALS UNDER REDUCING CONDITIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, D.; Estes, S.; Arai, Y.; Powell, B.

    2012-01-31

    The objective of this study was to measure Tc sorption to cementitious materials under reducing conditions to simulate Saltstone Disposal Facility conditions. Earlier studies were conducted and the experimental conditions were found not to simulate those of the facility. Through a five month subcontract with Clemson University, sorption of {sup 99}Tc to four cementitious materials was examined within an anaerobic glovebag targeting a 0.1% H2(g)/ 99.9% N{sub 2}(g) atmosphere. Early experiments based on Tc sorption and Eh indicated that 0.1% H{sub 2}(g) (a reductant) was necessary to preclude experimental impacts from O{sub 2}(g) diffusion into the glovebag. Preliminary data to date (up to 56 days) indicates that sorption of {sup 99}Tc to cementitious materials increased with increasing slag content for simulated saltstone samples. This is consistent with the conceptual model that redox active sulfide groups within the reducing slag facilitate reduction of Tc(VII) to Tc(IV). These experiments differ from previous experiments where a 2% H{sub 2}(g) atmosphere was maintained (Kaplan et al., 2011 (SRNL-STI-2010-00668)). The impact of the 2% H{sub 2}(g) reducing atmosphere on this data was examined and determined to cause the reduction of Tc in experimental samples without slag. In the present ongoing study, after 56 days, Tc sorption by the 50-year old cement samples (no slag) was undetectable, whereas Tc sorption in the cementitious materials containing slag continues to increase with contact time (measured after 1, 4, 8, 19 and 56 days). Sorption was not consistent with spike concentrations and steady state has not been demonstrated after 56 days. The average conditional K{sub d} value for the Vault 2 cementitious material was 6,362 mL/g (17% slag), for the TR547 Saltstone (45% slag) the conditional K{sub d} was 1258 mL/g, and for TR545 (90% slag) the conditional K{sub d} was 12,112 mL/g. It is anticipated that additional samples will be collected until steady state

  11. Impact of carbonation on water transport properties of cementitious materials

    International Nuclear Information System (INIS)

    Auroy, Martin

    2014-01-01

    Carbonation is a very well-known cementitious materials pathology. It is the major cause of reinforced concrete structures degradation. It leads to rebar corrosion and consequent concrete cover cracking. In the framework of radioactive waste management, cement-based materials used as building materials for structures or containers would be simultaneously submitted to drying and atmospheric carbonation. Although scientific literature regarding carbonating is vast, it is clearly lacking information about the influence of carbonation on water transport properties. This work then aimed at studying and understanding the change in water transport properties induced by carbonation. Simultaneously, the representativeness of accelerated carbonation (in the laboratory) was also studied. (author) [fr

  12. Corrosion of cementitious materials under geological disposal conditions with resulting effects on the geochemical stability of clay minerals

    Energy Technology Data Exchange (ETDEWEB)

    Herbert, H.J.; Meyer, Th. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koln (Germany)

    2001-07-01

    The long-term behaviour of cemented fly ashes and bentonite (MX80) has been investigated in high saline solutions by means of a cascade experiment, batch experiment and by the geochemical modelling of the observed reactions. In contact to IP21 the degradation of CSH phases in the cementitious material could be proposed indicated by the accumulation of Ca in solution. In contact to NaCl brine only a small amount of Ca in solution could be detected indicating a slight dissolution of CSH phases in the cementitious material. Considering the good agreement between the time accelerating laboratory scale cascade experiment and the modelled reaction path using the computer code EQ3/6 we conclude, that it is possible to predict the chemical behaviour of cementitious materials in salt solutions. The degradation experiments with MX80 and cementitious material in NaCl and IP21 solution showed an accumulation of Si and Al in solution and then a remove possibly indicating the formation of new phases. In contact to high saline solutions a reduction of swelling pressure of MX80 at various reduced initial dry densities could be observed in comparison to pure water. Moreover a reduced water-uptake of MX80 in contact to high saline and alkaline solution was obtained. (authors)

  13. Corrosion of cementitious materials under geological disposal conditions with resulting effects on the geochemical stability of clay minerals

    International Nuclear Information System (INIS)

    Herbert, H.J.; Meyer, Th.

    2001-01-01

    The long-term behaviour of cemented fly ashes and bentonite (MX80) has been investigated in high saline solutions by means of a cascade experiment, batch experiment and by the geochemical modelling of the observed reactions. In contact to IP21 the degradation of CSH phases in the cementitious material could be proposed indicated by the accumulation of Ca in solution. In contact to NaCl brine only a small amount of Ca in solution could be detected indicating a slight dissolution of CSH phases in the cementitious material. Considering the good agreement between the time accelerating laboratory scale cascade experiment and the modelled reaction path using the computer code EQ3/6 we conclude, that it is possible to predict the chemical behaviour of cementitious materials in salt solutions. The degradation experiments with MX80 and cementitious material in NaCl and IP21 solution showed an accumulation of Si and Al in solution and then a remove possibly indicating the formation of new phases. In contact to high saline solutions a reduction of swelling pressure of MX80 at various reduced initial dry densities could be observed in comparison to pure water. Moreover a reduced water-uptake of MX80 in contact to high saline and alkaline solution was obtained. (authors)

  14. Degradation of cellulosic materials under the alkaline conditions of a cementitious repository for low- and intermediate level radioactive waste. Pt. III. Effect of degradation products on the sorption of radionuclides on feldspar

    International Nuclear Information System (INIS)

    Loon, L.R. van; Glaus, M.A.; Laube, A.; Stallone, S.

    1999-01-01

    The effect of degradation products of different cellulosic materials on the sorption behaviour of Th(IV), Eu(III) and Ni(II) on feldspar at pH 13.3 was studied. For all three metals, a decrease in sorption could be observed with increasing concentration of organics in solution. For Th(IV), α-ISA is the effective ligand present in the solutions of degraded cellulose, independent on the type of cellulose studied. For Eu(III), α-ISA is the effective ligand in the case of pure cellulose degradation. In the case of other cellulosic materials, unknown ligands cause the sorption reduction. For Ni(II), also unknown ligands cause sorption reduction, independent on the type of cellulose studied. These unknown ligands are not formed during alkaline degradation of cellulose, but are present as impurities in certain cellulosic materials. (orig.)

  15. Analytical and numerical models of transport in porous cementitious materials

    International Nuclear Information System (INIS)

    Garboczi, E.J.; Bentz, D.P.

    1990-01-01

    Most chemical and physical processes that degrade cementitious materials are dependent on an external source of either water or ions or both. Understanding the rates of these processes at the microstructural level is necessary in order to develop a sound scientific basis for the prediction and control of the service life of cement-based materials, especially for radioactive-waste containment materials that are required to have service lives on the order of hundreds of years. An important step in developing this knowledge is to understand how transport coefficients, such as diffusivity and permeability, depend on the pore structure. Fluid flow under applied pressure gradients and ionic diffusion under applied concentration gradients are important transport mechanisms that take place in the pore space of cementitious materials. This paper describes: (1) a new analytical percolation-theory-based equation for calculating the permeability of porous materials, (2) new computational methods for computing effective diffusivities of microstructural models or digitized images of actual porous materials, and (3) a new digitized-image mercury intrusion simulation technique

  16. Transport properties of damaged materials. Cementitious barriers partnership

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-11-01

    The objective of the Cementitious Barriers Partnership (CBP) project is to develop tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in low-level waste storage applications. One key concern for the long-term durability of concrete is the degradation of the cementitious matrix, which occurs as a result of aggressive chemical species entering the material or leaching out in the environment, depending on the exposure conditions. The objective of the experimental study described in this report is to provide experimental data relating damage in cementitious materials to changes in transport properties, which can eventually be used to support predictive model development. In order to get results within a reasonable timeframe and to induce as much as possible uniform damage level in materials, concrete samples were exposed to freezing and thawing (F/T) cycles. The methodology consisted in exposing samples to F/T cycles and monitoring damage level with ultrasonic pulse velocity measurements. Upon reaching pre-selected damage levels, samples were tested to evaluate changes in transport properties. Material selection for the study was motivated by the need to get results rapidly, in order to assess the relevance of the methodology. Consequently, samples already available at SIMCO from past studies were used. They consisted in three different concrete mixtures cured for five years in wet conditions. The mixtures had water-to-cement ratios of 0.5, 0.65 and 0.75 and were prepared with ASTM Type I cement only. The results showed that porosity is not a good indicator for damage caused by the formation of microcracks. Some materials exhibited little variations in porosity even for high damage levels. On the other hand, significant variations in tortuosity were measured in all materials. This implies that damage caused by internal pressure does not necessarily create additional pore space in

  17. Transport properties of damaged materials. Cementitious barriers partnership

    International Nuclear Information System (INIS)

    Langton, C.

    2014-01-01

    The objective of the Cementitious Barriers Partnership (CBP) project is to develop tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in low-level waste storage applications. One key concern for the long-term durability of concrete is the degradation of the cementitious matrix, which occurs as a result of aggressive chemical species entering the material or leaching out in the environment, depending on the exposure conditions. The objective of the experimental study described in this report is to provide experimental data relating damage in cementitious materials to changes in transport properties, which can eventually be used to support predictive model development. In order to get results within a reasonable timeframe and to induce as much as possible uniform damage level in materials, concrete samples were exposed to freezing and thawing (F/T) cycles. The methodology consisted in exposing samples to F/T cycles and monitoring damage level with ultrasonic pulse velocity measurements. Upon reaching pre-selected damage levels, samples were tested to evaluate changes in transport properties. Material selection for the study was motivated by the need to get results rapidly, in order to assess the relevance of the methodology. Consequently, samples already available at SIMCO from past studies were used. They consisted in three different concrete mixtures cured for five years in wet conditions. The mixtures had water-to-cement ratios of 0.5, 0.65 and 0.75 and were prepared with ASTM Type I cement only. The results showed that porosity is not a good indicator for damage caused by the formation of microcracks. Some materials exhibited little variations in porosity even for high damage levels. On the other hand, significant variations in tortuosity were measured in all materials. This implies that damage caused by internal pressure does not necessarily create additional pore space in

  18. Degradation of cementitious materials associated with salstone disposal units

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, F. G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-09-01

    The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed “saltstone”. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of a saltstone disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions.

  19. Technetium Sorption by Cementitious Materials Under Reducing Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Daniel I. [Savannah River Site (SRS), Aiken, SC (United States); Estes, Shanna L. [Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC (United States); Powell, Brian A. [Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC (United States)

    2012-09-28

    The objective of this study was to measure technetium ({sup 99}Tc) sorption to cementitious materials under reducing conditions to simulate Saltstone Disposal Facility conditions. {sup 99}Tc(VII) batch sorption experiments were conducted for 319 days in an inert glovebag with a variety of cementitious materials (aged cement, Vault 2, TR545, and TR547) containing varying amounts of blast furnace slag. Between 154 and 319 days, the {sup 99}Tc aqueous concentrations tended to remain constant and samples amended with different initial {sup 99}Tc concentrations, tended to merge at about 10{sup -9} M for Vault 2 (17% slag) and TR545 (90% slag) and 10{sup -8} M for TR547 (45% slag). This data provided strong evidence that solubility, and not adsorption (K{sub d} values), was controlling aqueous {sup 99}Tc concentrations. Laboratory data superimposed over thermodynamic speciation diagrams further supported the conclusion that solubility, and not adsorption controlled {sup 99}Tc aqueous concentrations. The oxidation state of the aqueous {sup 99}Tc at the end of the sorption experiment was determined by solvent extraction to be almost entirely {sup 99}Tc(VII). The pH of the present system was ~11.8. Previously proposed solubility controlling phases including Tc-sulfides may be present, but do not appear to control solubility. After the 319 day sorption period, the suspensions were removed from the glovebag and a desorption step under oxic conditions was conducted for 20 days by adding oxic, pH-buffered solutions to the suspensions. {sup 99}Tc aqueous concentrations increased by more than an order of magnitude and Eh increased by several hundred millivolts within 24 hours after the introduction of the oxic solutions. These desorption results are consistent with re-oxidation and dissolution/desorption of {sup 99}Tc(IV) phases possibly present in the cementitious materials after the anoxic sorption step of the experiment. Aqueous {sup 99}Tc concentrations continued to increase

  20. Hybrid fiber reinforcement and crack formation in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Pereira, E.B.; Fischer, Gregor; Barros, J.A.O.

    2011-01-01

    reinforcement systems. The research described in this paper shows that the multi-scale conception of cracking and the use of hybrid fiber reinforcements do not necessarily result in an improved tensile behavior of the composite. Particular material design requirements may nevertheless justify the use of hybrid......- to the macroscale. In this study, the performance of different fiber reinforced cementitious composites is assessed in terms of their tensile stress-crack opening behavior. The results obtained from this investigation allow a direct quantitative comparison of the behavior obtained from the different fiber...

  1. Mortar incorporating supplementary cementitious materials: Strength ...

    African Journals Online (AJOL)

    This research studies the effect different SCMs (natural pozzolan (PN) / limestone fine (FC) at various replacement levels) on the physical and mechano-chemical resistance of blended mortar. The paper primarily deals with the characteristics of these materials, including heat of hydration, strength and effects of aggressive ...

  2. Engineering Properties and Correlation Analysis of Fiber Cementitious Materials.

    Science.gov (United States)

    Lin, Wei-Ting; Wu, Yuan-Chieh; Cheng, An; Chao, Sao-Jeng; Hsu, Hui-Mi

    2014-11-20

    This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%), water/cement ratio (0.35 and 0.55) and steel fiber dosage (0.5%, 1.0% and 2.0%). The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysis of variance to realize the relevancy and significance between material parameters and those mechanical properties. Test results illustrate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages, as well as the optimum mixture of the fiber cementitious materials is 5% replacement silica fume and 2% fiber dosage. In addition, the Pearson correlation coefficient was conducted to evaluate the influence of the material variables and corresponds to the experiment result.

  3. Engineering Properties and Correlation Analysis of Fiber Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Wei-Ting Lin

    2014-11-01

    Full Text Available This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%, water/cement ratio (0.35 and 0.55 and steel fiber dosage (0.5%, 1.0% and 2.0%. The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysis of variance to realize the relevancy and significance between material parameters and those mechanical properties. Test results illustrate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages, as well as the optimum mixture of the fiber cementitious materials is 5% replacement silica fume and 2% fiber dosage. In addition, the Pearson correlation coefficient was conducted to evaluate the influence of the material variables and corresponds to the experiment result.

  4. A mathematical model in charactering chloride diffusivity in unsaturated cementitious material

    NARCIS (Netherlands)

    Zhang, Y.; Ye, G.; Pecur, I.B.; Baricevic, A.; Stirmer, N; Bjegovic, D.

    2017-01-01

    In this paper, a new analytic model for predicting chloride diffusivity in unsaturated cementitious materials is developed based on conductivity theory and Nernst-Einstein equation. The model specifies that chloride diffusivity in unsaturated cementitious materials can be mathematically described as

  5. Rheological properties of cementitious materials containing mineral admixtures

    Energy Technology Data Exchange (ETDEWEB)

    C.K. Park; M.H. Noh; T.H. Park [Korea Institute of Industrial Technology, Cheonan (Republic of Korea)

    2005-05-01

    The rheological properties of cementitious materials containing fine particles, such as mineral admixtures (MA), were investigated using a Rotovisco RT 20 rheometer (Haake) with a cylindrical spindle. The mineral admixtures were finely ground blast furnace slag, fly ash and silica fume. The cementitious materials were designed as one, two and three components systems by replacement of ordinary Portland cement (OPC) with these mineral admixtures. The rheological properties of one-component system (OPC) were improved with increasing the dosage of PNS-based superplasticizer. For two-components systems, yield stress and plastic viscosity decreased with replacing OPC with blast furnace slag (BFS) and fly ash (FA). In the case of OPC-silica fume (SF) system, yield stress and plastic viscosity steeply increased with increasing SF. For three components systems, both OPC-BFS-SF and OPC-FA-SF systems, the rheological properties improved, compared with the sample with SF. In the two and three components systems, the rheological properties of samples containing BFS improved much more than with FA replacement alone.

  6. Variability Of KD Values In Cementitious Materials And Sediments

    International Nuclear Information System (INIS)

    Almond, P.; Kaplan, D.; Shine, E.

    2012-01-01

    Measured distribution coefficients (K d values) for environmental contaminants provide input data for performance assessments (PA) that evaluate physical and chemical phenomena for release of radionuclides from wasteforms, degradation of engineered components and subsequent transport of radionuclides through environmental media. Research efforts at SRNL to study the effects of formulation and curing variability on the physiochemical properties of the saltstone wasteform produced at the Saltstone Disposal Facility (SDF) are ongoing and provide information for the PA and Saltstone Operations. Furthermore, the range and distribution of plutonium K d values in soils is not known. Knowledge of these parameters is needed to provide guidance for stochastic modeling in the PA. Under the current SRS liquid waste processing system, supernate from F and H Tank Farm tanks is processed to remove actinides and fission products, resulting in a low-curie Decontaminated Salt Solution (DSS). At the Saltstone Production Facility (SPF), DSS is mixed with premix, comprised of blast furnace slag (BFS), Class F fly ash (FA), and portland cement (OPC) to form a grout mixture. The fresh grout is subsequently placed in SDF vaults where it cures through hydration reactions to produce saltstone, a hardened monolithic waste form. Variation in saltstone composition and cure conditions of grout can affect the saltstone's physiochemical properties. Variations in properties may originate from variables in DSS, premix, and water to premix ratio, grout mixing, placing, and curing conditions including time and temperature (Harbour et al. 2007; Harbour et al. 2009). There are no previous studies reported in the literature regarding the range and distribution of K d values in cementitious materials. Presently, the Savannah River Site (SRS) estimate ranges and distributions of K d values based on measurements of K d values made in sandy SRS sediments (Kaplan 2010). The actual cementitious material K d

  7. VARIABILITY OF KD VALUES IN CEMENTITIOUS MATERIALS AND SEDIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Almond, P.; Kaplan, D.; Shine, E.

    2012-02-02

    Measured distribution coefficients (K{sub d} values) for environmental contaminants provide input data for performance assessments (PA) that evaluate physical and chemical phenomena for release of radionuclides from wasteforms, degradation of engineered components and subsequent transport of radionuclides through environmental media. Research efforts at SRNL to study the effects of formulation and curing variability on the physiochemical properties of the saltstone wasteform produced at the Saltstone Disposal Facility (SDF) are ongoing and provide information for the PA and Saltstone Operations. Furthermore, the range and distribution of plutonium K{sub d} values in soils is not known. Knowledge of these parameters is needed to provide guidance for stochastic modeling in the PA. Under the current SRS liquid waste processing system, supernate from F & H Tank Farm tanks is processed to remove actinides and fission products, resulting in a low-curie Decontaminated Salt Solution (DSS). At the Saltstone Production Facility (SPF), DSS is mixed with premix, comprised of blast furnace slag (BFS), Class F fly ash (FA), and portland cement (OPC) to form a grout mixture. The fresh grout is subsequently placed in SDF vaults where it cures through hydration reactions to produce saltstone, a hardened monolithic waste form. Variation in saltstone composition and cure conditions of grout can affect the saltstone's physiochemical properties. Variations in properties may originate from variables in DSS, premix, and water to premix ratio, grout mixing, placing, and curing conditions including time and temperature (Harbour et al. 2007; Harbour et al. 2009). There are no previous studies reported in the literature regarding the range and distribution of K{sub d} values in cementitious materials. Presently, the Savannah River Site (SRS) estimate ranges and distributions of K{sub d} values based on measurements of K{sub d} values made in sandy SRS sediments (Kaplan 2010). The actual

  8. Technetium Sorption By Cementitious Materials Under Reducing Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Daniel I. [Savannah River National Lab., Aiken, SC (United States); Estes, Shanna L. [Clemson Univ., SC (United States). Environmental Engineering and Earth Sciences; Arai, Yuji [Clemson Univ., SC (United States). College of Agriculture, Forestry and Life Sciences; Powell, Brian A. [Clemson Univ., SC (United States). Environmental Engineering and Earth Sciences

    2013-07-18

    The objective of this study was to measure Tc sorption to cementitious materials under reducing conditions to simulate Saltstone Disposal Facility conditions. Earlier studies were conducted and the experimental conditions were found not to simulate those of the facility. Through a five month subcontract with Clemson University, sorption of {sup 99}Tc to four cementitious materials was examined within an anaerobic glovebag targeting a 0.1% H{sub 2}(g)/ 99.9% N{sub 2}(g) atmosphere. Early experiments based on Tc sorption and Eh indicated that 0.1% H{sub 2}(g) (a reductant) was necessary to preclude experimental impacts from O{sub 2}(g) diffusion into the glovebag. Preliminary data to date (up to 56 days) indicates that sorption of {sup 99}Tc to cementitious materials increased with increasing slag content for simulated saltstone samples. This is consistent with the conceptual model that redox active sulfide groups within the reducing slag facilitate reduction of Tc(VII) to Tc(IV). These experiments differ from previous experiments where a 2% H{sub 2}(g) atmosphere was maintained (Kaplan et al., 2011 (SRNL-STI-2010-00668)). The impact of the 2% H{sub 2}(g) reducing atmosphere on this data was examined and determined to cause the reduction of Tc in experimental samples without slag. In the present ongoing study, after 56 days, Tc sorption by the 50-year old cement samples (no slag) was undetectable, whereas Tc sorption in the cementitious materials containing slag continues to increase with contact time (measured after 1, 4, 8, 19 and 56 days). Sorption was not consistent with spike concentrations and steady state has not been demonstrated after 56 days. The average conditional K{sub d} value for the Vault 2 cementitious material was 873 mL/g (17% slag), for the TR547 Saltstone (45% slag) the conditional K{sub d} was 168 mL/g, and for TR545 (90% slag) the conditional K{sub d} was 1,619 mL/g. It is anticipated that additional samples will be collected until steady state

  9. Degradation Of Cementitious Materials Associated With Saltstone Disposal Units

    International Nuclear Information System (INIS)

    Flach, G. P; Smith, F. G. III

    2013-01-01

    The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed ''saltstone''. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of an SDF disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions. The nominal value (NV) is an intermediate result that is more probable than the conservative estimate

  10. Degradation Of Cementitious Materials Associated With Saltstone Disposal Units

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P; Smith, F. G. III

    2013-03-19

    The Saltstone facilities at the DOE Savannah River Site (SRS) stabilize and dispose of low-level radioactive salt solution originating from liquid waste storage tanks at the site. The Saltstone Production Facility (SPF) receives treated salt solution and mixes the aqueous waste with dry cement, blast furnace slag, and fly ash to form a grout slurry which is mechanically pumped into concrete disposal cells that compose the Saltstone Disposal Facility (SDF). The solidified grout is termed “saltstone”. Cementitious materials play a prominent role in the design and long-term performance of the SDF. The saltstone grout exhibits low permeability and diffusivity, and thus represents a physical barrier to waste release. The waste form is also reducing, which creates a chemical barrier to waste release for certain key radionuclides, notably Tc-99. Similarly, the concrete shell of an SDF disposal unit (SDU) represents an additional physical and chemical barrier to radionuclide release to the environment. Together the waste form and the SDU compose a robust containment structure at the time of facility closure. However, the physical and chemical state of cementitious materials will evolve over time through a variety of phenomena, leading to degraded barrier performance over Performance Assessment (PA) timescales of thousands to tens of thousands of years. Previous studies of cementitious material degradation in the context of low-level waste disposal have identified sulfate attack, carbonation influenced steel corrosion, and decalcification (primary constituent leaching) as the primary chemical degradation phenomena of most relevance to SRS exposure conditions. In this study, degradation time scales for each of these three degradation phenomena are estimated for saltstone and concrete associated with each SDU type under conservative, nominal, and best estimate assumptions. The nominal value (NV) is an intermediate result that is more probable than the conservative

  11. Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

    Science.gov (United States)

    Dey, Vikram

    The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

  12. Cementitious building material incorporating end-capped polyethylene glycol as a phase change material

    Science.gov (United States)

    Salyer, Ival O.; Griffen, Charles W.

    1986-01-01

    A cementitious composition comprising a cementitious material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the compositions are useful in making pre-formed building materials such as concrete blocks, brick, dry wall and the like or in making poured structures such as walls or floor pads; the glycols can be encapsulated to reduce their tendency to retard set.

  13. Structural and mechanical study of concrete made from cementitious materials of low environmental impact

    Science.gov (United States)

    González, A. K.; Montaño, A. M.; González, C. P.; Santos, A.

    2017-12-01

    This work shows the results obtained by replacing Type I Portland®, by cementitious geopolymers materials, derived from minerals, in concrete mixtures. Synthesis of both geopolymers through alkaline activation of two alluminosilicates: Bentonite and Pumice with sodium silicate (Na2SiO3). XRD, SEM and XRDE are used to structural study of new geopolymers. Concrete mixtures with replacement of Portland have 10% and 30% of geopolymer. Finally, concrete mortars formed were mechanically analysed according to ICONTEC 220 at 7, 14, 28, 41, 90 and 120 days of cure. Results shows that compressive strength of concrete from Bentonite and Pumice are almost the same for the standard concrete at 28 days of cure. At 90 days of cure, compression resistance of concrete from Pumice at 10% is even higher than those that standard concrete shows.

  14. 3D morphological and micromechanical modeling of cementitious materials

    International Nuclear Information System (INIS)

    Escoda, Julie

    2012-01-01

    The goal of this thesis is to develop morphological models of cementitious materials and use these models to study their local and effective response. To this aim, 3D images of cementitious materials (mortar and concrete), obtained by micro-tomography, are studied. First, the mortar image is segmented in order to obtain an image of a real microstructure, to be used for linear elasticity computations. The image of concrete is used, after being processed, to determine various morphological characteristics of the material. A random model of concrete is then developed and validated by means of morphological data. This model is made up of three phases, corresponding to the matrix, aggregates and voids. The aggregates phase is modelled by implantation of Poisson polyhedra without overlap. For this purpose, an algorithm suited to the vector generation of Poisson polyhedra is introduced and validated with morphological measurements. Finally, the effective linear elastic properties of the mortar and other simulated microstructures are estimated with the FFT (Fast-Fourier Transform) method, for various contrasts between the aggregates and matrix' Young moduli. To complete this work, focused on effective properties, an analysis of the local elastic response in the matrix phase is undertaken, in order to determine the spatial arrangement between stress concentration zones in the matrix and the phases of the microstructure (aggregates and voids). Moreover, a statistical fields characterization, in the matrix, is achieved, including the determination of the Representative Volume Element (RVE) size. Furthermore, a comparison between effective and local elastic properties obtained from microstructures containing polyhedra and spheres is carried out. (author)

  15. X-ray Computed Microtomography technique applied for cementitious materials: A review.

    Science.gov (United States)

    da Silva, Ítalo Batista

    2018-04-01

    The main objective of this article is to present a bibliographical review about the use of the X-ray microtomography method in 3D images processing of cementitious materials microstructure, analyzing the pores microstructure and connectivity network, enabling tthe possibility of building a relationship between permeability and porosity. The use of this technique enables the understanding of physical, chemical and mechanical properties of cementitious materials by publishing good results, considering that the quality and quantity of accessible information were significant and may contribute to the study of cementitious materials development. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Bioreceptivity evaluation of cementitious materials designed to stimulate biological growth.

    Science.gov (United States)

    Manso, Sandra; De Muynck, Willem; Segura, Ignacio; Aguado, Antonio; Steppe, Kathy; Boon, Nico; De Belie, Nele

    2014-05-15

    Ordinary Portland cement (OPC), the most used binder in construction, presents some disadvantages in terms of pollution (CO2 emissions) and visual impact. For this reason, green roofs and façades have gain considerable attention in the last decade as a way to integrate nature in cities. These systems, however, suffer from high initial and maintenance costs. An alternative strategy to obtain green facades is the direct natural colonisation of the cementitious construction materials constituting the wall, a phenomenon governed by the bioreceptivity of such material. This work aims at assessing the suitability of magnesium phosphate cement (MPC) materials to allow a rapid natural colonisation taking carbonated OPC samples as a reference material. For that, the aggregate size, the w/c ratio and the amount of cement paste of mortars made of both binders were modified. The assessment of the different bioreceptivities was conducted by means of an accelerated algal fouling test. MPC samples exhibited a faster fouling compared to OPC samples, which could be mainly attributed to the lower pH of the MPC binder. In addition to the binder, the fouling rate was governed by the roughness and the porosity of the material. MPC mortar with moderate porosity and roughness appears to be the most feasible material to be used for the development of green concrete walls. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Interaction of cementitious materials with high-level waste

    International Nuclear Information System (INIS)

    Lemmens, Karel; Cachoir, Christelle; Ferrand, Karine; Mennecart, Thierry; Gielen, Ben; Vercauter, Regina

    2012-01-01

    Document available in abstract form only: Since a few years, the Belgian agency for radioactive waste (ONDRAF/NIRAS) has selected the Supercontainer design with an Ordinary Portland Cement (OPC) buffer as the reference design for geological disposal of High-Level Waste (HLW) and Spent Fuel (SF) in the Boom Clay formation. The Boom Clay beneath the Mol-Dessel nuclear zone is a reference methodological site for supporting R and D. Compared to the previous bentonite based reference design, described in detail in the final SAFIR 2 report, the supercontainer will provide a highly alkaline chemical environment allowing the passivation of the surface of the overpack and the inhibition of its corrosion. The Supercontainer will contribute to the containment of radionuclides, but it will also have an effect on the retardation of radionuclide release from the waste and it will retard the migration of the released radionuclides. In the Supercontainer design, the canisters of HLW or SF will be enclosed by a 30 mm thick carbon steel overpack and a concrete buffer about 700 mm thick. The overpack will prevent contact with the (cementitious) pore water during the thermal phase. On the other hand, once the overpack will be locally perforated, the high pH of the incoming water may have an impact on the lifetime of the vitrified waste or spent fuel. The behaviour of these waste forms in disposal conditions has been studied for several decades, but the vast majority of published data is related to the interaction with backfill or host rock materials at near-neutral pH. Very few studies have been reported for alkaline media, at pH >11. Hence, a research programme including new experiments, was started at the Belgian Nuclear Research Centre (SCK.CEN) and at INE (FZK) to assess the rate at which the radionuclides are released by the vitrified waste and spent fuel in such an environment. The presence of concrete will have an impact on the behaviour of the vitrified HLW and spent fuel. For

  18. Implications of the use of low-pH cementitious materials in high activity radioactive waste repositories

    International Nuclear Information System (INIS)

    Garcia Calvo, J.L.; Alonso, M.C.; Fernandez Luco, L.; Hidalgo, A.; Sanchez, M.

    2008-01-01

    One of the most accepted engineering construction concepts for high radioactive nuclear waste of underground repositories considers the use of low pH cementitious materials, in order to avoid the formation of an alkaline plume fluid which perturbs one of the engineered barriers of the repository, the bentonite. The accepted solution to maintain the bentonite stability, which is function of the pH, is to develop cementitious materials that generate pore waters with pH ≤ 11, because the corrosion velocity of the clay is significantly reduced below this value. The IETcc-CSIC has focused the research activity on low-pH cementitious materials using two cements: Ordinary Portland Cements (OPC) and Calcium Aluminates Cements (CAC). In both cases, the achievement of a low-pH environment implies the use of high content of mineral admixtures to prepare the binder. Obviously, the inclusion of high contents of mineral admixtures in the cement formulation modifies most of the concrete 'standard' properties and the microstructure of the obtained cement products. When designing a concrete based on low-pH binders, not only the functional requirements have to be reached but also the modifications of the basic properties of the concrete must be taken into account. Besides, due to the location and the long service life of this type of products, their durability properties must be also guaranteed. This paper deals with the procedure followed in the design of a specific application of low pH cements; for instance, the shotcrete plug fabrication. The challenge of this type of use (shotcreting) is more complex taking into account that requires the employment of additives that must be compatible with the concrete mixture. Furthermore, their effectiveness must be assured without increase the pH above the admissible levels. Therefore, their compatibility with admixtures is tested in the present work. The compliance of the requirements for a shotcrete plug was evaluated at laboratory scale

  19. Applications of graphite-enabled phase change material composites to improve thermal performance of cementitious materials

    Science.gov (United States)

    Li, Mingli; Lin, Zhibin; Wu, Lili; Wang, Jinhui; Gong, Na

    2017-11-01

    Enhancing the thermal efficiency to decrease the energy consumption of structures has been the topic of much research. In this study, a graphite-enabled microencapsulated phase change material (GE-MEPCM) was used in the production of a novel thermal energy storage engineered cementitious composite feathering high heat storage capacity and enhanced thermal conductivity. The surface morphology and particle size of the microencapsulated phase change material (MEPCM) were investigated by scanning electron microscopy (SEM). Thermal properties of MEPCM was determined using differential scanning calorimetry (DSC). In addition, thermal and mechanical properties of the cementitious mortar with different admixtures were explored and compared with those of a cementitious composite. It was shown that the latent heat of MEPCM was 162 J/g, offering much better thermal energy storage capacity to the cementitious composite. However, MEPCM was found to decrease the thermal conductivity of the composite, which can be effectively solved by adding natural graphite (NG). Moreover, the incorporation of MEPCM has a certain decrease in the compressive strength, mainly due to the weak interfaces between MEPCM and cement matrix.

  20. Cracking Tendency Prediction of High-Performance Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Ke Chen

    2014-01-01

    Full Text Available The constraint ring test is widely used to assess the cracking potential for early-age cementitious materials. In this paper, the analytical expressions based on elastic mechanism are presented to estimate the residual stresses of the restrained mortar ring by considering the comprehensive effects of hydration heat, autogenous and drying shrinkage, creeping, and restraint. In the present analytical method, the stress field of the restrained ring is treated as the superposition of those caused by hydration heat, external restraint, autogenous and drying shrinkage, and creep. The factors including the properties of materials, environmental parameters such as relative humidity and temperature, the geometry effect of specimen, and the relative constraint effects of steel ring to mortar ring, are taken into account to predict the strain development with age of mortar. The temperature of the ring, the elastic modulus, the creep strain, and the split tensile strength are measured to validate the model. The age of cracking is predicted by comparing the estimated maximum tensile stress of the restrained mortar ring with the measured split tensile strength of specimen. The suitability of the present analytical method is assessed by comparing with the restraint ring test and a soundly good agreement is observed.

  1. Assessment of the Durability of Cementitious Materials in Repository Environment

    International Nuclear Information System (INIS)

    Vicente, R.; Marumo, J.T.; Miyamoto, H.; Isiki, V.L.K.; Ferreira, E.G.

    2013-01-01

    The Radioactive Waste Management Laboratory of the Energy and Nuclear Research Institute is developing the concept of a borehole repository for disused sealed radioactive sources drilled in a deep granite batholite. In this concept, the annular space between the well steel casing and the geological formation is backfilled with cement paste. The hardened cement paste functions as an additional barrier against the escape of radionuclides from the repository and their migration to the environment. It also functions as an obstacle to the flow of groundwater between different layers of the geological setting crossed by the borehole. The long term behavior of hydrated cement compounds is yet incompletely known and therefore more research is needed to increase the confidence on the performance of the material under the repository conditions as required. For the repository to achieve the required performance, the cement paste must be durable. However, in a deep repository, the cementitious materials is exposed to the deleterious action of high temperatures and pressures, the radiation field created by the radioactive sources and aggressive ion species that may be present in groundwater. Furthermore, it is necessary to consider that the cement paste is unstable in the long term because its microstructure and mineralogy change with time as the cement gel components recrystallize and react chemically with materials of the repository environment. In principle, the lifetime of this material could be determined based on the study of its long-term behavior, which, in turn, could be estimated from the extrapolation of short-term results, by accelerating, under controlled laboratory conditions, the composition changes and the loss of mechanical strength and cohesion induced by any detrimental component of the repository environment. Loss of mechanical strength, dimensional variations, changes in chemical-mineralogical composition, and leaching of hydrate compounds are all possible

  2. Development of Ecoefficient Engineered Cementitious Composites Using Supplementary Cementitious Materials as a Binder and Bottom Ash Aggregate as Fine Aggregate

    Directory of Open Access Journals (Sweden)

    Jin Wook Bang

    2015-01-01

    Full Text Available The purpose of this study is to develop ecoefficient engineered cementitious composites (ECC using supplementary cementitious materials (SCMs, including fly ash (FA and blast furnace slag (SL as a binder material. The cement content of the ECC mixtures was replaced by FA and SL with a replacement rate of 25%. In addition, the fine aggregate of the ECC was replaced by bottom ash aggregate (BA with a substitution rate of 10%, 20%, and 30%. The influences of ecofriendly aggregates on fresh concrete properties and on mechanical properties were experimentally investigated. The test results revealed that the substitution of SCMs has an advantageous effect on fresh concrete’s properties; however, the increased water absorption and the irregular shape of the BA can potentially affect the fresh concrete’s properties. The substitution of FA and SL in ECC led to an increase in frictional bond at the interface between PVA fibers and matrix, improved the fiber dispersion, and showed a tensile strain capacity ranging from 3.3% to 3.5%. It is suggested that the combination of SCMs (12.5% FA and 12.5% SL and the BA aggregate with the substitution rate of 10% can be effectively used in ECC preparation.

  3. Appraisal of a cementitious material for waste disposal: Neutron imaging studies of pore structure and sorptivity

    International Nuclear Information System (INIS)

    McGlinn, Peter J.; Beer, Frikkie C. de; Aldridge, Laurence P.; Radebe, Mabuti J.; Nshimirimana, Robert; Brew, Daniel R.M.; Payne, Timothy E.; Olufson, Kylie P.

    2010-01-01

    Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials.

  4. Timing of Getter Material Addition in Cementitious Wasteforms

    Science.gov (United States)

    Lawter, A.; Qafoku, N. P.; Asmussen, M.; Neeway, J.; Smith, G. L.

    2015-12-01

    A cementitious waste form, Cast Stone, is being evaluated as a possible supplemental immobilization technology for the Hanford sites's low activity waste (LAW), which contains radioactive 99Tc and 129I, as part of the tank waste cleanup mission. Cast Stone is made of a dry blend 47% blast furnace slag, 45% fly ash, and 8% ordinary Portland cement, mixed with a low-activity waste (LAW). To improve the retention of Tc and/or I in Cast Stone, materials with a high affinity for Tc and/or I, termed "getters," can be added to provide a stable domain for the radionuclides of concern. Previous testing conducted with a variety of getters has identified Tin(II)-Apatite and Silver Exchanged Zeolite as promising candidates for Tc and I, respectively. Investigation into the sequence in which getters are added to Cast Stone was performed following two methods: 1) adding getters to the Cast Stone dry blend, and then mixing with liquid waste, and 2) adding getters to the liquid waste first, followed by addition of the Cast Stone dry blend. Cast Stone monolith samples were prepared with each method and leach tests, following EPA method 1315, were conducted in either distilled water or simulated vadose zone porewater for a period of up to 63 days. The leachate was analyzed for Tc, I, Na, NO3-, NO2- and Cr with ICP-MS, ICP-OES and ion chromatography and the results indicated that the Cast Stone with getter addition in the dry blend mix (method 1) has lower rates of Tc and I leaching. The mechanisms of radionuclide release from the Cast Stone were also investigated with a variety of solid phase characterization techniques of the monoliths before and after leaching, such as XRD, SEM/EDS, TEM/SAED and other spectroscopic techniques.

  5. Development and Demonstration of Material Properties Database and Software for the Simulation of Flow Properties in Cementitious Materials

    Energy Technology Data Exchange (ETDEWEB)

    Smith, F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-03-30

    This report describes work performed by the Savannah River National Laboratory (SRNL) in fiscal year 2014 to develop a new Cementitious Barriers Project (CBP) software module designated as FLOExcel. FLOExcel incorporates a uniform database to capture material characterization data and a GoldSim model to define flow properties for both intact and fractured cementitious materials and estimate Darcy velocity based on specified hydraulic head gradient and matric tension. The software module includes hydraulic parameters for intact cementitious and granular materials in the database and a standalone GoldSim framework to manipulate the data. The database will be updated with new data as it comes available. The software module will later be integrated into the next release of the CBP Toolbox, Version 3.0. This report documents the development efforts for this software module. The FY14 activities described in this report focused on the following two items that form the FLOExcel package; 1) Development of a uniform database to capture CBP data for cementitious materials. In particular, the inclusion and use of hydraulic properties of the materials are emphasized; and 2) Development of algorithms and a GoldSim User Interface to calculate hydraulic flow properties of degraded and fractured cementitious materials. Hydraulic properties are required in a simulation of flow through cementitious materials such as Saltstone, waste tank fill grout, and concrete barriers. At SRNL these simulations have been performed using the PORFLOW code as part of Performance Assessments for salt waste disposal and waste tank closure.

  6. Ultrasonic assessment of early age property development in hydrating cementitious materials

    Science.gov (United States)

    Wang, Xiaojun

    The internal structure (microstructure) of cementitious materials, such as cement paste, mortar and concrete, evolves over time because of cement hydration. The microstructure of the cementitious phase plays a very important role in determining the strength, the mechanical properties and the long-term durability of cementitious materials. Therefore any understanding of the strength gain and the long-term durability of cementitious materials requires a proper assessment of the microstructure of its cementitious phase. Current methods for evaluating the microstructure of the cement are invasive and primarily laboratory-based. These methods are not conducive for studying the pore structure changes in the first few hours after casting since the changes in microstructure occur on a time scale that is an order of magnitude faster than the time required for sample preparation. The primary objective of the research presented in this thesis is to contribute towards advancing the current state-of-the-art in assessing the microstructure of cementitious systems. An ultrasonic wave reflection technique which allows for real-time assessment of the porosity and the elastic modulus of cementitious materials is developed. The test procedure for monitoring changes in the amplitude of horizontally polarized ultrasonic shear waves from the surface of hydrating cement paste is presented. A theoretical framework based on a poro-elastic idealization of the hydrating cementitious material is developed for interpreting the ultrasonic reflection data. The poro-elastic representation of hydrating cementitious material is shown to provide simultaneous, realistic estimates of porosity and shear modulus for hydrating cement paste and mortar through setting and early strength gain. The porosity predicted by the poro-elastic representation is identical to the capillary water content within the cement paste predicted by Powers' model. The shear modulus of the poro-elastic skeleton was compares

  7. Cementitious materials for radioactive waste management within IAEA coordinated research project - 59021

    International Nuclear Information System (INIS)

    Drace, Zoran; Ojovan, Michael I.

    2012-01-01

    The IAEA Coordinated Research Project (CRP) on cementitious materials for radioactive waste management was launched in 2007 [1, 2]. The objective of CRP was to investigate the behaviour and performance of cementitious materials used in radioactive waste management system with various purposes and included waste packages, waste-forms and backfills as well as investigation of interactions and interdependencies of these individual elements during long term storage and disposal. The specific research topics considered were: (i) cementitious materials for radioactive waste packaging: including radioactive waste immobilization into a solid waste form, (ii) waste backfilling and containers; (iii) emerging and alternative cementitious systems; (iv) physical-chemical processes occurring during the hydration and ageing of cement matrices and their influence on the cement matrix quality; (v) methods of production of cementitious materials for: immobilization into wasteform, backfills and containers; (vi) conditions envisaged in the disposal environment for packages (physical and chemical conditions, temperature variations, groundwater, radiation fields); (vii) testing and non-destructive monitoring techniques for quality assurance of cementitious materials; (viii) waste acceptance criteria for waste packages, waste forms and backfills; transport, long term storage and disposal requirements;and finally (ix) modelling or simulation of long term behaviours of cementations materials used for packaging, waste immobilization and backfilling, especially in the post-closure phase. The CRP has gathered overall 26 research organizations from 22 Member States aiming to share their research and practices on the use of cementitious materials [2]. The main research outcomes of the CRP were summarized in a summary report currently under preparation to be published by IAEA. The generic topical sections covered by report are: a) conventional cementitious systems; b) novel cementitious

  8. LONG-TERM TECHNETIUM INTERACTIONS WITH REDUCING CEMENTITIOUS MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, D.; Lilley, M.; Almond, P.; Powell, B.

    2011-03-15

    Technetium is among the key risk drivers at the Saltstone Facility. The way that it is immobilized in this cementitious waste form is by converting its highly mobile Tc(VII) form to a much less mobile Tc(IV) form through reduction by the cement's blast furnace slag. This report includes a review of published data and experimental results dealing with Tc leaching from Portland cement waste forms. The objectives for the literature study were to document previous reports of Tc interactions with slag-containing cementitious materials. The objectives for the laboratory study were to measure Tc-saltstone Kd values under reducing conditions. From the literature it was concluded: (1) Spectroscopic evidence showed that when Tc(IV) in a slag-cement was exposed to an oxidizing environment, it will convert to the more mobile Tc(VII) species within a short time frame, 2.5 years. (2) SRS saltstone will reduce Tc(VII) in the absence of NaS or sodium dithionite in a reducing atmosphere. (3) Only trace concentrations of atmospheric oxygen (30 to 60 ppm O{sub 2}; Eh 120 mV) at the high pH levels of cementitious systems is required to maintain Tc as Tc(VII). (4) Experimental conditions must be responsible for wide variability of measured K{sub d} values, such that they are either very low, {approx}1 mL/g, or they are very high {approx}1000 mL/g, suggesting that Tc(VII) or Tc(IV) dominate the systems. Much of this variability appears to be the result of experimental conditions, especially direct controls of oxygen contact with the sample. (5) A field study conducted at SRS in the 1980s indicated that a slag-saltstone immobilized Tc for 2.5 years. Below background concentrations of Tc leached out of the slag-containing saltstone, whereas Tc leached out of the slag-free saltstone at the rate of nitrate loss. One possible explanation for the immobilization of Tc in this study was that the slag-saltstone maintained reducing conditions within the core of the 55-gallon sample, whereas

  9. Rheology of Cementitious Materials: Alkali-Activated Materials or Geopolymers

    Directory of Open Access Journals (Sweden)

    Puertas F.

    2018-01-01

    Understanding and controlling the rheology of the AAMs systems will ultimately determine whether they can be implemented in the market, and will open up greater competitive possibilities in a crisis-affected sector. A systematic study of the factors that affect the rheological properties of AAMs (pastes, mortars and concretes is therefore necessary in order to ultimately develop more resistant and durable materials.

  10. Behaviour of cementitious materials: sulfates and temperature actions

    International Nuclear Information System (INIS)

    Barbarulo, Remi

    2002-09-01

    The research work presented in this Ph.D. thesis is related to the nuclear waste underground repository concept. Concrete could be used in such a repository, and would be subjected to variations of temperature in presence of sulfate, a situation that could induce expansion of concrete. The research was lead in three parts: an experimental study of the possibility of an internal sulfate attack on mortars; an experimental study and modeling of the chemical equilibriums of the CaO-SiO 2 -Al 2 O 3 -SO 3 -H 2 O system; and a modeling of the mechanisms of internal and external sulfate attacks, and the effect of temperature. The results show that mortars can develop expansions after a steam-cure during hydration, but also when a long steam-cure is applied to one-year-old mortars, which is a new point. Ettringite precipitation can be considered as responsible for these expansions. The experimental study of the CaO-SiO 2 -Al 2 O 3 -SO 3 -H 2 O system clarified the role of Calcium Silicate Hydrates (C-S-H) on chemical equilibriums of cementitious materials. Sulfate sorption on C-S-H has been studied in detail. The quantity of sulfate bound to the C-S-H mainly depends on the sulfate concentration in solution, on the Ca/Si ratio of the C-S-H and is not significantly influenced by temperature. Aluminium inclusion in the C-S-H seems to be a significant phenomenon. Temperature increases the calcium sulfo-aluminate solubilities and thus increases sulfates concentration in solution. A modeling of the chemical system is proposed. Simulations of external sulfate attack (15 mmol/L of Na 2 SO 4 ) predict ettringite precipitation at 20 and 85±C. Simulation of internal sulfate attack was performed at a local scale (a hydrated cement grain). An initial inhomogeneity can lead, after a thermal curing at 85±C, to ettringite precipitation in zones originally free from ettringite. This new-formed ettringite could be the origin of the expansions. (author) [fr

  11. Selection of Nutrient Used in Biogenic Healing Agent for Cementitious Materials

    NARCIS (Netherlands)

    Tziviloglou, E.; Wiktor, V.A.C.; Jonkers, H.M.; Schlangen, H.E.J.G.

    2017-01-01

    Biogenic self-healing cementitious materials target on the closure of micro-cracks with precipitated inorganic minerals originating from bacterial metabolic activity. Dormant bacterial spores and organic mineral compounds often constitute a biogenic healing agent. The current paper focuses on the

  12. Significance of Shrinkage Induced Clamping Pressure in Fiber-Matrix Bonding in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Stang, Henrik

    1996-01-01

    used in high performance cementitious composite materials.Assuming a Coulomb type of friction on the fiber/matrix interface andusing typical values for the frictional coefficient it is shownthat the shrinkage induced clamping pressure could be one of the mostimportant factors determining the frictional...

  13. Micromechanical properties of a new polymeric microcapsule for self-healing cementitious materials

    NARCIS (Netherlands)

    Lv, Leyang; Schlangen, H.E.J.G.; Yang, Z.; Xing, Feng

    2016-01-01

    Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol-formaldehyde) (PF) microcapsules that aim to provide a

  14. Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Na; Li, Hongxu [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, Yazhao [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Xiaoming, E-mail: liuxm@ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-04-05

    Highlights: • Cementitious material was designed according to [SiO{sub 4}] polymerization degree of raw materials. • The cementitious material composed of calcium silicate slag yields excellent physical and mechanical properties. • Amorphous C–A–S–H gel and rod-like ettringite are predominantly responsible for the strength development. • Leaching toxicity and radioactivity tests show the cementitious material is environmentally acceptable. - Abstract: Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al{sub 2}O{sub 3} from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C–A–S–H gel, rod-like ettringite and hexagonal-sheet Ca(OH){sub 2} with small amount of zeolite-like minerals such as CaAl{sub 2}Si{sub 2}O{sub 8}·4H{sub 2}O and Na{sub 2}Al{sub 2}Si{sub 2}O{sub 8}·H{sub 2}O. As the predominant hydration products, rod-like ettringite and amorphous C–A–S–H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities.

  15. Durability of low-pH cementitious materials based on OPC or CAC

    International Nuclear Information System (INIS)

    Garcia Calvo, J.L.; Sanchez, M.; Alonso, M.C.; Fernandez Luco, L.

    2015-01-01

    Low pH cementitious materials are considered to be used in underground repositories for high level waste but there are still some characteristics related to their long-term durability that must be analyzed in depth. In this sense, different shrinkage tests have been made using low-pH cement formulations based on Ordinary Portland Cement (OPC) or Calcium Aluminate Cement (CAC), on mortar and concrete specimens. The obtained results show that, regarding the autogenous shrinkage, low-pH cementitious materials show similar values than those observed in the reference samples. In fact, the main shrinkage problems in the low-pH materials are related with those based on OPC with high silica fume contents in drying conditions. Besides, as the use of reinforced concrete can be required in underground repositories, the susceptibility of reinforcements to corrosion when using low-pH cementitious materials based on OPC was analyzed, using two different reinforcements: carbon steel and galvanized steel. The lower pore solution pH of the low-pH OPC based materials generates the corrosion of the carbon steel reinforcement. However, when galvanized steels are used, any corrosion problem is detected regardless of the cement formulation. (authors)

  16. Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

    International Nuclear Information System (INIS)

    Naus, Dan J.; Mattus, Catherine H.; Dole, Leslie Robert

    2007-01-01

    The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a 'primer' on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a 'bench-scale' laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the 'primer,' a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures

  17. Final Report - Assessment of Potential Phosphate Ion-Cementitious Materials Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Naus, Dan J [ORNL; Mattus, Catherine H [ORNL; Dole, Leslie Robert [ORNL

    2007-06-01

    The objectives of this limited study were to: (1) review the potential for degradation of cementitious materials due to exposure to high concentrations of phosphate ions; (2) provide an improved understanding of any significant factors that may lead to a requirement to establish exposure limits for concrete structures exposed to soils or ground waters containing high levels of phosphate ions; (3) recommend, as appropriate, whether a limitation on phosphate ion concentration in soils or ground water is required to avoid degradation of concrete structures; and (4) provide a "primer" on factors that can affect the durability of concrete materials and structures in nuclear power plants. An assessment of the potential effects of phosphate ions on cementitious materials was made through a review of the literature, contacts with concrete research personnel, and conduct of a "bench-scale" laboratory investigation. Results of these activities indicate that: no harmful interactions occur between phosphates and cementitious materials unless phosphates are present in the form of phosphoric acid; phosphates have been incorporated into concrete as set retarders, and phosphate cements have been used for infrastructure repair; no standards or guidelines exist pertaining to applications of reinforced concrete structures in high-phosphate environments; interactions of phosphate ions and cementitious materials has not been a concern of the research community; and laboratory results indicate similar performance of specimens cured in phosphate solutions and those cured in a calcium hydroxide solution after exposure periods of up to eighteen months. Relative to the "primer," a separate NUREG report has been prepared that provides a review of pertinent factors that can affect the durability of nuclear power plant reinforced concrete structures.

  18. A new system for crack closure of cementitious materials using shrinkable polymers

    International Nuclear Information System (INIS)

    Jefferson, Anthony; Joseph, Christopher; Lark, Robert; Isaacs, Ben; Dunn, Simon; Weager, Brendon

    2010-01-01

    This paper presents details of an original crack-closure system for cementitious materials using shrinkable polymer tendons. The system involves the incorporation of unbonded pre-oriented polymer tendons in cementitious beams. Crack closure is achieved by thermally activating the shrinkage mechanism of the restrained polymer tendons after the cement-based material has undergone initial curing. The feasibility of the system is demonstrated in a series of small scale experiments on pre-cracked prismatic mortar specimens. The results from these tests show that, upon activation, the polymer tendon completely closes the preformed macro-cracks and imparts a significant stress across the crack faces. The potential of the system to enhance the natural autogenous crack healing process and generally improve the durability of concrete structures is addressed.

  19. A fully general and adaptive inverse analysis method for cementitious materials

    DEFF Research Database (Denmark)

    Jepsen, Michael S.; Damkilde, Lars; Lövgren, Ingemar

    2016-01-01

    are applied when modeling the fracture mechanisms in cementitious materials, but the vast development of pseudo-strain hardening, fiber reinforced cementitious materials require inverse methods, capable of treating multi-linear σ - w functions. The proposed method is fully general in the sense that it relies...... on least square fitting between test data obtained from various kinds of test setup, three-point bending or wedge splitting test, and simulated data obtained by either FEA or analytical models. In the current paper adaptive inverse analysis is conducted on test data obtained from three-point bending...... of notched specimens and simulated data from a nonlinear hinge model. The paper shows that the results obtained by means of the proposed method is independent on the initial shape of the σ - w function and the initial guess of the tensile strength. The method provides very accurate fits, and the increased...

  20. Effect of various supplementary cementitious materials on rheological properties of self-consolidating concrete

    OpenAIRE

    Saleh Ahari, Reza; Erdem, Tahir Kemal; Ramyar, Kambiz

    2015-01-01

    In design of self-consolidating concrete (SCC) for a given application, the mixture's rheological parameters should be adjusted to achieve a given profile of yield stress and plastic viscosity. Supplementary cementitious materials (SCM) can be useful for this adjustment in addition to their other advantages. In this study, the rheological properties of 57 SCC mixtures with various SCM were investigated for a constant slump flow value. For this aim, various amounts of silica fume (SF), metakao...

  1. Wet-Treated MSWI Fly Ash Used as Supplementary Cementitious Material

    OpenAIRE

    Keppert, Martin; Siddique, Jamal Akhter; Pavlík, Zbyšek; Černý, Robert

    2015-01-01

    Municipal solid waste incineration (MSWI) is a common technique in treatment of domestic waste. This technique annually produces approximately 25 Mt solid residues (i.e., bottom and fly ash) worldwide which is also a major issue in current research. In this research we are concerned with reusing the fly ash (FA) as supplementary cementitious material (SCM) in concrete. Such application solves the problem with heavy metal immobilization as well. To remove the high content of undesired soluble ...

  2. Long Term Behaviour of Cementitious Materials in the Korean Repository Environment

    International Nuclear Information System (INIS)

    Park, J.-W.; Kim, C.-L.

    2013-01-01

    The safe management of radioactive waste is a national task required for sustainable generation of nuclear power and for energy self-reliance in Korea. After the selection of the final candidate site for low- and intermediate-level waste (LILW) disposal in Korea, a construction and operation license was issued for the Wolsong LILW Disposal Center (WLDC) for the first stage of disposal. Underground silo type disposal has been determined for the initial phase. The engineered barrier system of the disposal silo consists of waste packages, disposal containers, backfills, and a concrete lining. Main objective of our study in this IAEA-CRP is to investigate closure concepts and cementitious backfill materials for the closure of silos. For this purpose, characterisation of cementitious materials, development of silo closure concept, and evaluation of long-term behaviour of cementitious materials, including concrete degradation in repository environment, have been carried out. The overall implementation plan for the CRP comprises performance testing for the physic-chemical properties of cementitious materials, degradation modelling of concrete structures, comparisons of performance for silo closure options, radionuclide transport modelling (considering concrete degradation in repository conditions), and the implementation of an input parameter database and quality assurance for safety/performance assessment. In particular, the concrete degradation modelling study has been focused on the corrosion of reinforcement steel induced by chloride attack, which was of primary concern in the safety assessment of the WLDC. A series of electrochemical experiments were conducted to investigate the effect of dissolved oxygen, pH, and Cl on the corrosion rate of reinforcing steel in a concrete structure saturated with groundwater. Laboratory-scale experiments and a thermodynamic modelling were performed to understand the porosity change of cement pastes, which were prepared using

  3. Micromechanical Properties of a New Polymeric Microcapsule for Self-Healing Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Leyang Lv

    2016-12-01

    Full Text Available Self-healing cementitious materials containing a microencapsulated healing agent are appealing due to their great application potential in improving the serviceability and durability of concrete structures. In this study, poly(phenol–formaldehyde (PF microcapsules that aim to provide a self-healing function for cementitious materials were prepared by an in situ polymerization reaction. Size gradation of the synthesized microcapsules was achieved through a series of sieving processes. The shell thickness and the diameter of single microcapsules was accurately measured under environmental scanning electron microscopy (ESEM. The relationship between the physical properties of the synthesized microcapsules and their micromechanical properties were investigated using nanoindentation. The results of the mechanical tests show that, with the increase of the mean size of microcapsules and the decrease of shell thickness, the mechanical force required to trigger the self-healing function of microcapsules increased correspondingly from 68.5 ± 41.6 mN to 198.5 ± 31.6 mN, featuring a multi-sensitive trigger function. Finally, the rupture behavior and crack surface of cement paste with embedded microcapsules were observed and analyzed using X-ray computed tomography (XCT. The synthesized PF microcapsules may find potential application in self-healing cementitious materials.

  4. The evaluation of solidifying performance of heavy metal waste using cementitious materials (2)

    International Nuclear Information System (INIS)

    Fujita, Hideki; Harasawa, Shuichi

    2005-02-01

    Some of radioactive waste generated from JNC's facilities contain the poisonous substances such as lead, cadmium and mercury. In order to establish an appropriate method of the treatment of these heavy metals, solidification performance was evaluated using cementitious materials. In this report, the solidification performance of lead and mercury, which accounts for relatively high ratio in total wastes, was evaluated. The results are summarized below: 1. The test of stabilization process of mercury. The conversion process from mercury to the powdery mercury sulfide (red) was examined on the beaker scale. As a result, it was confirmed that the conversion was possible using the liquid phase reaction at 80deg C by the addition of sulfur powder with the NaOH solution. After the process, the mercury concentration in the filtrate was relatively high (0.6 mass%), so it was judged that the reuse of the recovered mercury waste fluid was indispensable. 2. The fabrication and evaluation of solidified wastes. The solidified waste were fabricated with cementitious material, and were evaluated by the measurement of one-axis compressive strength, the elution ratio of lead, mercury and so on. Powdery lead sulfide and the mercury sulfide of reagent were used as model waste. (1) solidification test of the lead waste. It was confirmed one-axis compressive strength for all solidified waste to pass the technical standards 15 kg/cm 2 (1.5 Mpa) for homogeneously solidified waste as the Low-level Radioactive Waste Disposal Center in Aomori Prefecture, and as for the elution ratio of lead, it had obtained the better result (0.06 mg/L) at the case of solidification of sulfide lead 30 mass% packed in the total solidified waste by using Highly Fly-ash contained Silica fume Cement (HFSC) than standard value (0.3 mg/L) at Regulations of Waste Management and Public Cleansing Law. Additionally, it was confirmed the using admixture of the inorganic reducing agent such as the Iron (II) chloride

  5. Cost-Effective Cementitious Material Compatible with Yucca Mountain Repository Geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dole, LR

    2004-12-17

    The current plans for the Yucca Mountain (YM) repository project (YMP) use steel structures to stabilize the disposal drifts and connecting tunnels that are collectively over 100 kilometers in length. The potential exist to reduce the underground construction cost by 100s of millions of dollars and improve the repository's performance. These economic and engineering goals can be achieved by using the appropriate cementitious materials to build out these tunnels. This report describes the required properties of YM compatible cements and reviews the literature that proves the efficacy of this approach. This report also describes a comprehensive program to develop and test materials for a suite of underground construction technologies.

  6. Hydration mechanism and leaching behavior of bauxite-calcination-method red mud-coal gangue based cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Na; Li, Hongxu [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Xiaoming, E-mail: liuxm@ustb.edu.cn [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-08-15

    Highlights: • Nanocrystalline regions in size of ∼5 nm were found in the amorphous C-A-S-H gel. • A hydration model was proposed to clarify the hydration mechanism. • The developed cementitious materials are environmentally acceptable. - Abstract: A deep investigation on the hydration mechanism of bauxite-calcination-method red mud-coal gangue based cementitious materials was conducted from viewpoints of hydration products and hydration heat analysis. As a main hydration product, the microstructure of C-A-S-H gel was observed using high resolution transmission electron microscopy. It was found that the C-A-S-H gel is composed of amorphous regions and nanocrystalline regions. Most of regions in the C-A-S-H gel are amorphous with continuous distribution, and the nanocrystalline regions on scale of ∼5 nm are dispersed irregularly within the amorphous regions. The hydration heat of red mud-coal gangue based cementitious materials is much lower than that of the ordinary Portland cement. A hydration model was proposed for this kind of cementitious materials, and the hydration process mainly consists of four stages which are dissolution of materials, formation of C-A-S-H gels and ettringite, cementation of hydration products, and polycondensation of C-A-S-H gels. There are no strict boundaries among these four basic stages, and they proceed crossing each other. Moreover, the leaching toxicity tests were also performed to prove that the developed red mud-coal gangue based cementitious materials are environmentally acceptable.

  7. Early-age characteristics of red mud-coal gangue cementitious material.

    Science.gov (United States)

    Zhang, Na; Sun, Henghu; Liu, Xiaoming; Zhang, Jixiu

    2009-08-15

    This experimental research was to investigate the possibility of incorporating red mud and coal gangue as raw materials for the production of red mud-coal gangue cementitious material, abbreviated as RGC, including analyses of its chemical composition, physical properties, mechanical properties and hydration products. The red mud and coal gangue (at a ratio of 3:2) were mixed together and shaped in small spheres with a water to solid ratio of 0.30 and then calcined at 600 degrees C for 2h. Subsequently, the RGC was prepared by blending 50% the resultant red mud-coal gangue mixtures, 24% blast-furnace slag, 20% clinker and 6% gypsum. The hydration products of RGC were characterized by XRD, TG-DTA and SEM-EDS. The results showed that it is feasible to use red mud and coal gangue to replace up to 50% of the raw materials to produce cementitious material, which can be called as silica-alumina based cementitious material. The hydration products of RGC are mostly ettringite, calcium hydroxide and C-S-H gel. As the dominant products, C-S-H gel and ettringite are principally responsible for the strength development of RGC in early hydration process. The content of Ca(OH)(2) initially increased but later was depleted after reaching the peak value at 21 days. Moreover, it is found that the composition of the C-S-H gel shifted towards higher Si, Al and Na contents with the increase of hydration age, whereas that of Ca shifted towards lower content.

  8. Preparation of Cementitious Material Using Smelting Slag and Tailings and the Solidification and Leaching of Pb2+

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2015-01-01

    Full Text Available The composite cementitious materials were prepared with lead-zinc tailings, lead-zinc smelting slag, and cement clinker. The effect of material ratio on the mechanical properties, the phase analysis, and microstructures were investigated. The effect of the pH and stripping time on the leaching amount of lead ion was discussed. The results show that the additive amount of the tailings should be minimized for the cementitious materials meeting the strength requirements, controlled within 10%. The leaching amount of cementitious materials remains low in a larger range of pH, which can effectively reduce the leaching of heavy metal lead. The leaching kinetics of lead ions in the three kinds of samples could be better described by the pseudo-second-model.

  9. Studies of ancient concrete as analogs of cementitious sealing materials for a repository in tuff

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Langton, C.A.

    1989-03-01

    The durability of ancient cementitious materials has been investigated to provide data applicable to determining the resistance to weathering of concrete materials for sealing a repository for storage of high-level radioactive waste. Because tuff and volcanic ash are used in the concretes in the vicinity of Rome, the results are especially applicable to a waste repository in tuff. Ancient mortars, plasters, and concretes collected from Rome, Ostia, and Cosa dating to the third century BC show remarkable durability. The aggregates used in the mortars, plasters, and concretes included basic volcanic and pyroclastic rocks (including tuff), terra-cotta, carbonates, sands, and volcanic ash. The matrices of ancient cementitious materials have been characterized and classified into four categories: (1) hydraulic hydrated lime and hydrated lime cements, (2) hydraulic aluminous and ferruginous hydrated lime cements ({plus_minus} siliceous components), (3) pozzolana/hydrated lime cements, and (4) gypsum cements. Most of the materials investigated are in category (3). The materials were characterized to elucidate aspects of the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical, mineralogical, and microstructural factors. Their durability was found to be affected by the matrix mineralogy, particle size, and porosity; aggregate type, grading and proportioning; and the methodology of placement. 30 refs.

  10. Study on reinforcement of soil for suppressing fugitive dust by bio-cementitious material

    Science.gov (United States)

    Zhan, Qiwei; Qian, Chunxiang

    2017-06-01

    Microbial-induced reinforcement of soil, as a new green and environmental-friendly method, is being paid extensive attention to in that it has low cost, simple operation and rapid effects. In this research, reinforcement of soil for suppressing fugitive dust by bio-cementitious material was investigated. Soil cemented by bio-cementitious material had superior mechanical properties, such as hardness, compressive strength, microstructure, wind-erosion resistance, rainfall-erosion resistance and freeze-thaw resistance. The average hardness of sandy soil, floury soil and clay soil is 18.9 º, 25.2 º and 26.1 º, while average compressive strength of samples is 0.43 MPa, 0.54 MPa and 0.69 MPa, respectively; meanwhile, the average calcite content of samples is 6.85 %, 6.09 %, and 5.96 %, respectively. Compared with the original sandy soil, floury soil and clay soil, the porosity decreases by 38.5 %, 33.7 % and 29.2 %. When wind speed is 12 m/s, the mass loss of sandy soil, floury soil and clay soil cemented by bio-cementitious material are all less than 30 g/(m2·h). After three cycles of rainfall erosion of 2.5 mm/h, the mass loss are less than 25 g/(m2·h) and the compressive strength residual ratio are more than 98.0 %. Under 25 cycles of freeze-thaw, the mass loss ratio are less than 3.0 %.

  11. Impact of cementitious materials decalcification on transfer properties: application to radioactive waste deep repository

    International Nuclear Information System (INIS)

    Perlot, C.

    2005-09-01

    Cementitious materials have been selected to compose the engineering barrier system (EBS) of the French radioactive waste deep repository, because of concrete physico-chemical properties: the hydrates of the cementitious matrix and the pH of the pore solution contribute to radionuclides retention; furthermore the compactness of these materials limits elements transport. The confinement capacity of the system has to be assessed while a period at least equivalent to waste activity (up to 100.000 years). His durability was sustained by the evolution of transfer properties in accordance with cementitious materials decalcification, alteration that expresses structure long-term behavior. Then, two degradation modes were carried out, taking into account the different physical and chemical solicitations imposed by the host formation. The first mode, a static one, was an accelerated decalcification test using nitrate ammonium solution. It replicates the EBS alteration dues to underground water. Degradation kinetic was estimated by the amount of calcium leached and the measurement of the calcium hydroxide dissolution front. To evaluate the decalcification impact, samples were characterized before and after degradation in term of microstructure (porosity, pores size distribution) and of transfer properties (diffusivity, gas and water permeability). The influence of cement nature (ordinary Portland cement, blended cement) and aggregates type (lime or siliceous) was observed: experiments were repeated on different mortars mixes. On this occasion, an essential reflection on this test metrology was led. The second mode, a dynamical degradation, was performed with an environmental permeameter. It recreates the EBS solicitations ensured during the re-saturation period, distinguished by the hydraulic pressure imposed by the geologic layer and the waste exothermicity. This apparatus, based on triaxial cell functioning, allows applying on samples pressure drop between 2 and 10 MPa and

  12. Micro-crack detection in high-performance cementitious materials

    DEFF Research Database (Denmark)

    Lura, Pietro; Guang, Ye; Tanaka, Kyoji

    2005-01-01

    aggregate size. Gallium intrusion of the cracks and subsequent examination by electron probe micro analysis, EPMA, are used to identify the cracks. The gallium intrusion technique allows controllable impregnation of cracks in the cement paste. A distinct contrast between gallium and the surrounding material...

  13. COMBS: open source python library for RVE generation - Application to microscale diffusion simulations in cementitious materials

    International Nuclear Information System (INIS)

    Bourcier, C.; Laucoin, E.; Dridi, W.; Chomat, L.; Bary, B.; Adam, E.

    2013-01-01

    In the context of radioactive waste storage and disposal, the knowledge of the concrete diffusivity is primordial in the numerical simulations of the long term behavior of these materials. COMBS is an open source python library, it is used to define the shapes of the inclusions, to insert them in the box featuring the representative volume element (RVE) of the cementitious medium, and to assess their diffusive properties. The algorithms developed in COMBS target a fast placement of the inclusions and a fast generation of the RVE shape and mesh. Two application cases are considered: the unaltered material diffusivity and the degraded material diffusivity. The first case of application focuses on the description of the capillary porosity. The second application case focuses on the description of the degradation of cementitious material (mineral and porosity) and the diffusive properties associated. The reliability of the analytical effective medium approximations (MT and SC) is confirmed from 3D finite elements (FE) calculations performed on a matrix-inclusions microstructure obtained by RVE generation with Combs. The results also show the need to take into account the percolation behavior

  14. Mesoscopic analysis of drying shrinkage damage in a cementitious material

    DEFF Research Database (Denmark)

    Moonen, P.; Pedersen, R.R.; Simone, A.

    2008-01-01

    Concrete and cement-based materials exhibit shrinkage when exposed to drying. Structural effects and inhomogeneity of material properties adverse free shrinkage, hereby inducing stress concentrations and possibly damage. In this contribution, the magnitude of shrinkage- induced damage during...... a typical sample preparation procedure is assessed. To this extent, a coupled hygro-thermo-mechanical model, incorporating rate-effects, is developed. The constitutive model is applied at a mesoscopic level where the aggregates and the interfacial transition zone (ITZ) are explicitly modelled. Two drying...... temperatures are considered: 35 °C and 50 °C. Significantly more micro-damage and higher internal stresses are found for the latter, revealing the importance of drying shrinkage damage, even at laboratory scale....

  15. Low to high performance recycled cementitious materials: case studies

    OpenAIRE

    Etxeberria Larrañaga, Miren

    2015-01-01

    In this work, four real case studies using concrete produced with recycled aggregates are described. The four real cases carried out in Barcelona are: 1) Pavement filling with control low strength material (CLSM) employing fine recycled aggregates, 2) pervious recycled aggregate concrete employing coarse mixed recycled aggregates in the works undertaken at Cervantes park; 3) Concrete blocks produced employing recycled and slag aggregates as well as sea water for a new breakwater dyke and 4) R...

  16. Review of the potential effects of alkaline plume migration from a cementitious repository for radioactive waste

    International Nuclear Information System (INIS)

    Savage, D.

    1997-01-01

    Extensive use of cement and concrete is envisaged in the construction of geological repositories for low and intermediate-level radioactive wastes, both for structural, and encapsulation and backfilling purposes. Saturation of these materials with groundwater may occur in the post-closure period of disposal, producing a hyperalkaline pore fluid with a pH in the range 10-13.5. These pore fluids have the potential to migrate from the repository according to local groundwater flow conditions and react chemically with the host rock. These chemical reactions may affect the rock's capacity to retard the migration of radionuclides released from the repository after the degradation of the waste packages. The effects of these chemical reactions on the behaviour of the repository rock as a barrier to waste migration need to be investigated for the purposes of assessing the safety of the repository design (so-called 'safety assessment' or 'performance assessment'). The objectives of the work reported here were to: identify those processes influencing radionuclide mobility in the geosphere which could be affected by plume migration; review literature relevant to alkali-rock reaction; contact organisations carrying out relevant research and summarise their current and future activities; and make recommendations how the effects of plume migration can be incorporated into models of repository performance assessment. (author)

  17. A new pozzolan for high performance cementitious materials

    Directory of Open Access Journals (Sweden)

    de Gutiérrez, R. M.

    2000-12-01

    Full Text Available This paper presents results on the physical and chemical properties of metakaolinite, MK which is prepared by dehydroxylation of high quality kaolinite. The properties of Portland cement mortars blended with MK additions up to 50% are investigated. These properties are compressive strength, pore size distribution, resistance to the penetration of water and chloride ions and corrosion performance of steels embedded in the mortar. The optimum replacement of ordinary Portland cement (OPC with MK to obtain high strength concrete is about 20%, but it is possible to use a higher percent in order to achieve the best durability properties and strength similar to the control mixture. There is a significant decrease in average pore size with an increase in MK replacement. Metakaolinite is able to bind chloride ions to produce Friedel's salt (SF, which can be considered as the main cause of the lower chloride penetration in portland cement mortars blended with MK addition. This chemical binding capacity was proved by XRD. In general, the test results indicate that the MK is a highly pozzolanic material and can be used as a supplementary cementing material in order to produce a high-performance concrete especially for use in aggressive environments. Such as, thawing salts and dew of the sea.

    Este artículo reporta los resultados de las propiedades físicas y químicas de un producto denominado metacaolín, MK; que fue preparado a partir del tratamiento térmico controlado de una caolinita de alta pureza. Se discuten las propiedades de morteros de cemento adicionados con MK en porcentajes hasta del 50%. Las propiedades investigadas corresponden a la resistencia a la compresión, la distribución del tamaño de poros, la resistencia a la penetración del agua y los iones cloruro y el comportamiento a la corrosión de barras de acero de refuerzo embebidas en este material. Se concluye que para alcanzar un hormigón de alta resistencia se requiere un

  18. A poly-dispersed particle system representation of the porosity for non-saturated cementitious materials

    International Nuclear Information System (INIS)

    Bary, B.

    2006-01-01

    In this paper, the porosity of cementitious materials is described in terms of pore size distribution by means of a 3-dimensional overlapping sphere system with poly-dispersivity in size. On the basis of results established by Lu and Torquato [B. Lu, S. Torquato, Nearest-surface distribution functions for poly-dispersed particle systems, Phys. Rev. A 45(8) (1992) 5530-5544] and Torquato [S. Torquato, Random Heterogeneous Media: Microstructure and Macroscopic Properties. Springer-Verlag: New York, 2001] providing relations for nearest-neighbor distribution functions, the volume fraction of pores having a radius larger than a prescribed value is explicitly expressed. By adopting an appropriate size distribution function for the sphere system, it is shown that the pore size distribution of cementitious materials as detected for instance by mercury intrusion porosimetry (MIP), which generally points out several pore classes, can be well approached. On the basis of this porosity representation, the evaluation of the capillary pressure in function of the saturation degree is provided. The model is then applied to the simulation of the saturation degree versus relative humidity adsorption curves. The impact of the pore size distribution, the temperature and the thickness of the adsorbed water layer on these parameters are assessed and analyzed for three model materials having different pore characteristics. (author)

  19. The Effectiveness of High Quality Supplementary Cementitious Materials for Mitigating ASR Expansion in Concrete with High Alkali Content

    Directory of Open Access Journals (Sweden)

    I. Prasetia

    2015-10-01

    Full Text Available Alkali silica reaction (ASR is influenced by external factors such as the surrounding environment of high alkalinity. Countries with cold climate have a high probability to be exposed to high concentrations of NaCl solution by the deicing salt. This condition will lead to serious ASR problems in concrete, if the aggregates contain reactive silica. The main research work in this paper is to investigate the effect of 15% replacement ratio of high quality fine fly ash (FA15% and 42% replacement ratio of blast furnace slag (BFS42% on the ASR mitigation in concrete with different alkali amount inside the pore solution. The experiments were conducted according to the accelerated mortar bars experiment following the JIS A1146 mortar bar test method. In addition, post-analysis such as observation of ASR gel formation by the Uranyl Acetate Fluorescence Method and observation of thin sections using a Polarizing Microscope were also conducted. The mortar bar tests show a very good mitigation effect of supplementary cementitious materials (SCMs. The results show that only small ASR expansions, which can be categorized as “innocuous”, occurred for specimens with 1.2% Na2Oeq using FA15% and BFS42%. However, larger alkali amount inside the system will require more SCMs amount.

  20. Measurement of volume change in cementitious materials at early ages - Review of testing protocols and interpretation of results

    DEFF Research Database (Denmark)

    Sant, Gaurav; Lura, Pietro; Weiss, Jason

    2006-01-01

    Early-age cracking in concrete bridge decks, pavements, and superstructure elements has served as the impetus for substantial research on early-age shrinkage in cementitious materials. Much of this research has indicated how mixture proportions, constituent materials, and construction operations ...

  1. Electrokinetic decontamination of porous media. Experimental study and modeling of the cesium transport through cementitious materials

    International Nuclear Information System (INIS)

    Frizon, F.

    2003-01-01

    The aim of this work is to study the nuclear decontamination of cementitious materials by an electrokinetic method. Special attention is given to the understanding of the mechanisms leading to the removal of radioelements from the material. First, a bibliographic research allowed us to reduce the study to a normalized mortar and to cesium ions. This choice was confirmed by the experimental study of interactions between the contaminant and the material. Next, the efficiency of the electrokinetic decontamination was experimentally shown in laboratory conditions and electromigration was identified as the main transport phenomenon. Then, a numerical model was implemented in order to describe the ionic transport by electromigration. The results obtained were compared to experiments. Finally, some applications and developments of the electrokinetic process were proposed. (author)

  2. Non-destructive ultrasonic evaluation of thermal damage in cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Masse, S.; Vetter, G.; Boch, P. [Ecole Superieure de Physique et de Chimie Industrielles, Paris (France). Lab. of Ceramics and Minerals

    2002-07-01

    Thermal damage in cementitious materials (cement paste and microconcretes) subjected to high temperatures (T) up to 1000 C was monitored using a non-destructive, ultrasonic method of measurement of Young's modulus (E). Four cements were used: a Portland cement, two slag cements, and a ternary blend cement. Microconcretes were made by mixing cement, silica fume, quartz sand, and superplasticizer. Heat treating the materials at increasing T results in a decrease in E, more pronounced in microconcretes than in pastes. For a given sort of material (i.e. pastes or microconcretes) the curves of E/E{sub 0} = f[T] follow the same trend, whatever the kind of cement. (orig.)

  3. Significance of Shrinkage Induced Clamping Pressure in Fiber-Matrix Bonding in Cementitious Composite Materials

    DEFF Research Database (Denmark)

    Stang, Henrik

    1996-01-01

    used in high performance cementitious composite materials.Assuming a Coulomb type of friction on the fiber/matrix interface andusing typical values for the frictional coefficient it is shownthat the shrinkage induced clamping pressure could be one of the mostimportant factors determining the frictional......The present paper accesses the significance of shrinkage inducedclamping pressure in fiber/matrix bonding mechanisms incementitious composite materials. The paper contains a description of an experimental setup whichallows mbox{measurement} of the clamping pressure which develops on anelastic...... inhomogeneity embedded in a matrix consisting of acementitious material undergoing shrinkage during hydration(autogenous shrinkage). Furthermore, the paperpresents the analysis necessary to perform an interpretation of the experimental results and which allows for thedetermination of the clamping pressure...

  4. Selection of Nutrient Used in Biogenic Healing Agent for Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Eirini Tziviloglou

    2017-06-01

    Full Text Available Biogenic self-healing cementitious materials target on the closure of micro-cracks with precipitated inorganic minerals originating from bacterial metabolic activity. Dormant bacterial spores and organic mineral compounds often constitute a biogenic healing agent. The current paper focuses on the investigation of the most appropriate organic carbon source to be used as component of a biogenic healing agent. It is of great importance to use an appropriate organic source, since it will first ensure an optimal bacterial performance in terms of metabolic activity, while it should, second, affect the least the properties of the cementitious matrix. The selection is made among three different organic compounds, namely calcium lactate (CaL, calcium acetate (CaA, and sodium gluconate (NaG. The methodology that was used for the research was based on continuous and non-continuous oxygen consumption measurements of washed bacterial cultures and on compressive strength tests on mortar cubes. The oxygen consumption investigation revealed a preference for CaL and CaA, but an indifferent behavior for NaG. The compressive strength on mortar cubes with different amounts of either CaL or CaA (up to 2.24% per cement weight was not or it was positively affected when the compounds were dissolved in the mixing water. In fact, for CaL, the increase in compressive strength reached 8%, while for CaA, the maximum strength increase was 13.4%.

  5. Recent IAEA activities to support utilisation of cementitious materials in radioactive waste management

    International Nuclear Information System (INIS)

    Ojowan, M.I.; Samanta, S.K.

    2015-01-01

    The International Atomic Energy Agency promotes a safe and effective management of radioactive waste and has suitable programmes in place to serve the needs of Member States in this area. In support of these programmes the Waste Technology Section fosters technology transfer, promotes information exchange and cooperative research, as well as builds capacity in Member States to manage radioactive wastes, resulting both from the nuclear fuel cycle and nuclear applications. Technical assistance in pre disposal area covers all of these activities and is delivered through established Agency mechanisms including publication of technical documents. While the Agency does not conduct any in-house research activities, its Coordinated Research Projects (CRPs) foster research in Member States. There are 2 CRPs concerning cementitious materials: a CRP on cements and an on-going CRP on irradiated graphite waste. The CRP on cements has resulted in the recent IAEA publication TECDOC-1701. An important activity concerned with characterisation of cementitious waste forms is the LABONET network of laboratory-based centres of expertise involved in the characterization of low and intermediate level radioactive wastes. The Waste Technology Section is preparing a series of comprehensive state of the art technical handbooks

  6. Selection of nutrient used in biogenic healing agent for cementitious materials

    Science.gov (United States)

    Tziviloglou, Eirini; Wiktor, Virginie; Jonkers, Henk M.; Schlangen, Erik

    2017-06-01

    Biogenic self-healing cementitious materials target on the closure of micro-cracks with precipitated inorganic minerals originating from bacterial metabolic activity. Dormant bacterial spores and organic mineral compounds often constitute a biogenic healing agent. The current paper focuses on the investigation of the most appropriate organic carbon source to be used as component of a biogenic healing agent. It is of great importance to use an appropriate organic source, since it will firstly ensure an optimal bacterial performance in terms of metabolic activity, while it should secondly affect the least the properties of the cementitious matrix. The selection is made among three different organic compounds, namely calcium lactate, calcium acetate and sodium gluconate. The methodology that was used for the research was based on continuous and non-continuous oxygen consumption measurements of washed bacterial cultures and on compressive strength tests on mortar cubes. The oxygen consumption investigation revealed a preference for calcium lactate and acetate, but an indifferent behaviour for sodium gluconate. The compressive strength on mortar cubes with different amounts of either calcium lactate or acetate (up to 2.24% per cement weight) was not or it was positively affected when the compounds were dissolved in the mixing water. In fact, for calcium lactate the increase in compressive strength reached 8%, while for calcium acetate the maximum strength increase was 13.4%.

  7. Alkaline Material Effects on Roots of Teeth

    Directory of Open Access Journals (Sweden)

    Sowmya Shetty

    2017-12-01

    Full Text Available The aim of this review was to identify and analyse all studies related to the effects of alkaline materials used in dentistry on roots of teeth. The first part of the review focused on mechanical property alterations of root dentine due to sodium hypochlorite (SH used as an irrigant solution based on MeSH (Medical Subject Heading terms from a previous study by Pascon et al in 2009. The second part reviewed literature on calcium hydroxide (CH, mineral trioxide aggregate (MTA and other alkaline materials used as root canal dressings or filling materials. Additional MeSH terms used included “compressive strength”, “elastic modulus” “flexural strength”, “fracture strength” and “fracture resistance”. The language filter was English. Of the initial 205 articles identified, 49 were included in this review, of which 29 were on SH, 21 on CH/MTA, and 1 relating to both. Many in vitro studies indicated a strong link between reduced mechanical properties of roots of teeth or radicular dentine treated with SH, and when sealers or root fillings with CH- or MTA-based materials were placed in contact with roots or radicular dentine. Recent literature indicates that the association between reduced mechanical properties and alkaline sealers and/or root-filling materials is not as straightforward as previously assumed, and requires further investigation using more valid experimental models.

  8. Contribution to the study of multi-physical phenomena in cementitious materials

    International Nuclear Information System (INIS)

    Bary, B.

    2010-09-01

    This document is a synthesis of the applied research studies undertaken by the author during ten years, first at the University of Marne-La-Vallee during the period 1999-2002, then at the CEA. These studies concern the modeling and the numerical simulations of the cementitious materials behavior subjected on the one hand to moderate thermomechanical and hydric loadings, and on the other hand to chemical attacks due to the migration of calcium, carbonate and sulfate ions. The developed approaches may be viewed as multi-physical in the sense that the models used for describing the behavior couple various fields and phenomena such as mechanics, thermal, hydric and ionic transfers, and chemistry. In addition, analytical up-scaling techniques are applied to estimate the physical properties associated with these phenomena (mechanical, hydraulic and diffusive parameters) as a function of the microstructure and the hydric state of the material. (author)

  9. Determination of Chloride Content in Cementitious Materials : From Fundamental Aspects to Application of Ag/AgCl Chloride Sensors

    NARCIS (Netherlands)

    Pargar, F.; Koleva, D.A.; van Breugel, K.

    2017-01-01

    This paper reports on the advantages and drawbacks of available test methods for the determination of chloride content in cementitious materials in general, and the application of Ag/AgCl chloride sensors in particular. The main factors that affect the reliability of a chloride sensor are presented.

  10. The influence of superabsorbent polymers on the autogenous shrinkage properties of cement pastes with supplementary cementitious materials

    DEFF Research Database (Denmark)

    Snoeck, D.; Jensen, Ole Mejlhede; De Belie, N.

    2015-01-01

    shrinkage was determined by manual and automated shrinkage measurements. Autogenous shrinkage was reduced in cement pastes with the supplementary cementitious materials versus Portland cement pastes. At later ages, the rate of autogenous shrinkage is higher due to the pozzolanic activity. Internal curing...

  11. Titanium dioxide coated cementitious materials for air purifying purposes: Preparation, characterization and toluene removal potential

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, Anibal Maury; De Belie, Nele [Magnel Laboratory for Concrete Research, Department of Structural Engineering, Engineering Faculty, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Ghent (Belgium); Demeestere, Kristof [Research Group EnVOC, Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653. B-9000 Ghent (Belgium); Maentylae, Tapio; Levaenen, Erkki [Department of Materials Science, Tampere University of Technology, Korkeakoulunkatu 6, FIN-33720 Tampere (Finland)

    2010-04-15

    This work presents promising results for air purification by heterogeneous photocatalysis on new titanium dioxide loaded cementitious materials. A set of eight concretes and plasters is enriched with TiO{sub 2} photocatalyst by dip-coating and/or sol-gel methods. First, the macro-structural features of the cementitious materials have been studied in terms of porosity and roughness. The first parameter has been determined using mercury intrusion porosimetry or by vacuum saturation, and ranged between 9 and 75%, with the highest values obtained for autoclaved aerated white concrete. Surface roughness, determined by laser profilometry, has been characterized by the R{sub a} factor. This expresses the mean deviation of the profile from the centre line and ranged between 0.7 and 252 {mu}m, with the highest value obtained for conventional grey concrete finished with surface brush. Secondly, the weathering resistance of the TiO{sub 2} coatings has been determined by exposing them to different abrasive conditions and by performing SEM-Edax analyses to measure quantitatively the coating's titanium content. Hereby, it is shown that high porosity and roughness are favourable for TiO{sub 2} particles retention. Finally, the preliminary air purification potential of both dip-coated and sol-gel coated TiO{sub 2} enriched concrete samples has been investigated on lab-scale using toluene as a model pollutant. High removal efficiencies (up to 86%) were obtained with the dip-coated samples, indicating their attractive photocatalytic properties for future application as air purifying building materials. (author)

  12. Determination of Acidity and Alkalinity of Food Materials

    OpenAIRE

    三浦,芳助; 福永,祐子; 瀧川,裕里子; 津田,真美; 渡辺,陽子; 瀨山,一正

    2006-01-01

    The acidity and alkalinity of food materials in various menus was determined to clarify the influence of food on physiological functions. Menus mainly containing alkaline food materials (alkaline menu) and acid ones (acid menu) were compared. Determination of acidity and alkalinity was performed for each food material in the alkaline menu and acid menu, and acidity and alkalinity of one meal and a day's one were estimated. 1. Most of food materials in acid menu were assessed to be...

  13. Wet-Treated MSWI Fly Ash Used as Supplementary Cementitious Material

    Directory of Open Access Journals (Sweden)

    Martin Keppert

    2015-01-01

    Full Text Available Municipal solid waste incineration (MSWI is a common technique in treatment of domestic waste. This technique annually produces approximately 25 Mt solid residues (i.e., bottom and fly ash worldwide which is also a major issue in current research. In this research we are concerned with reusing the fly ash (FA as supplementary cementitious material (SCM in concrete. Such application solves the problem with heavy metal immobilization as well. To remove the high content of undesired soluble salts, number of washing treatments has been applied. Chemical composition of FA has been examined before and after treatments. The impact of cement substitution by FA in concrete was evaluated by measurement of its compressive strength and durability.

  14. Development of low-pH cementitious materials for HLRW repositories

    International Nuclear Information System (INIS)

    Garcia Calvo, J.L.; Hidalgo, A.; Alonso, C.; Fernandez Luco, L.

    2010-01-01

    One of the most accepted engineering construction concepts of underground repositories for high radioactive waste considers the use of low-pH cementitious materials. This paper deals with the design of those based on Ordinary Portland Cements with high contents of silica fume and/or fly ashes that modify most of the concrete 'standard' properties, the pore fluid composition and the microstructure of the hydrated products. Their resistance to long-term groundwater aggression is also evaluated. The results show that the use of OPC cement binders with high silica content produces low-pH pore waters and the microstructure of these cement pastes is different from the conventional OPC ones, generating C-S-H gels with lower CaO/SiO 2 ratios that possibly bind alkali ions. Leaching tests show a good resistance of low-pH concretes against groundwater aggression although an altered front can be observed.

  15. Use of Cementitious Materials for SRS Reactor Facility In-Situ Decommissioning

    International Nuclear Information System (INIS)

    Langton, C.A.; Stefanko, D.B.; Serrato, M.G.; Blankenship, J.K.; Griffin, W.G.; Long, J.T.

    2013-01-01

    The United States Department of Energy (US DOE) concept for facility in-situ decommissioning (ISD) is to physically stabilize and isolate intact, structurally sound facilities that are no longer needed for their original purpose of producing (reactor facilities), processing (isotope separation facilities) or storing radioactive materials. The Savannah River Site 105-P and 105-R Reactor Facility ISD project requires approximately 250000 cubic yards of cementitious materials to fill the below-grade structure. The fills are designed to prevent subsidence, reduce water infiltration, and isolate contaminated materials. This work is being performed as a Comprehensive Environmental Response, Compensations and Liability Act (CERCLA) action and is part of the overall soil and groundwater completion projects for P- and R-Areas. Funding is being provided under the American Recovery and Reinvestment Act (ARRA). Cementitious materials were designed for the following applications: (A) Below-grade massive voids / rooms: Portland cement-based structural flowable fills for: (A.1) Bulk filling; (A.2) Restricted placement and (A.3) Underwater placement. (B) Special below-grade applications for reduced load bearing capacity needs: (B.1) Cellular portland cement lightweight fill. (C) Reactor vessel fills that are compatible with reactive metal (aluminum metal) components in the reactor vessels (C.1) Blended calcium aluminate - calcium sulfate based flowable fill; (C.2) Magnesium potassium phosphate flowable fill. (D) Caps to prevent water infiltration and intrusion into areas with the highest levels of radionuclides: (D.1) Portland cement based shrinkage compensating concrete. A system engineering approach was used to identify functions and requirements of the fill and capping materials. Laboratory testing was performed to identify candidate formulations and develop final design mixes. Scale-up testing was performed to verify material production and placement as well as fresh and cured

  16. Measurement of volume change in cementitious materials at early ages - Review of testing protocols and interpretation of results

    DEFF Research Database (Denmark)

    Sant, Gaurav; Lura, Pietro; Weiss, Jason

    2006-01-01

    Early-age cracking in concrete bridge decks, pavements, and superstructure elements has served as the impetus for substantial research on early-age shrinkage in cementitious materials. Much of this research has indicated how mixture proportions, constituent materials, and construction operations...... can be altered to reduce the risk of cracking. Unfortunately, many unrestrained shrinkage-testing protocols do not provide a comprehensive picture of the early-age shrinkage exhibited by cementitious materials, especially those used in higher-strength concrete. In this paper, the authors review...... correlated with one another. This can provide the end user with reliable test procedures to compare different paste compositions and different admixtures and can provide inputs for models that quantify cracking potential....

  17. The influence of rainwater composition on the conservation state of cementitious building materials

    Energy Technology Data Exchange (ETDEWEB)

    Morillas, Héctor, E-mail: hector.morillas@ehu.es [Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080 Bilbao, Basque Country (Spain); Marcaida, Iker [Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080 Bilbao, Basque Country (Spain); Maguregui, Maite [Department of Analytical Chemistry, Faculty of Pharmacy, University of the Basque Country UPV/EHU, P.O. Box 450, 01080 Vitoria-Gasteiz, Basque Country (Spain); Carrero, Jose Antonio; Madariaga, Juan Manuel [Department of Analytical Chemistry, Faculty of Science and Technology, University of the Basque Country UPV/EHU, P.O. Box 644, 48080 Bilbao, Basque Country (Spain)

    2016-01-15

    Rainwater is one of the main pollution tracers around the world. There are many reasons that can explain the presence of high concentrations of certain hazardous elements (HEs) in the rainwater (traffic, marine port activities, industry, etc.). In this work, rainwater samples were collected at six different locations in the Metropolitan Bilbao (Basque Country, north of Spain) during November 2014. HE concentrations were determined by means of inductively coupled plasma mass spectrometry (ICP-MS) and anions by ion chromatography. The pH and redox potential values on these samples were also assessed. According to the obtained results, different trends along the estuary of Bilbao have been observed. To corroborate some hypothesis, thermodynamic simulations and correlation analyses were also carried out using quantitative data. These trends are closely related to the surrounding pollution and marine influence. Finally, in order to ascertain the influence of the Metropolitan Bilbao rainwater on buildings materials, a recent construction was characterized. Using techniques such as Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM–EDS) and Raman Spectroscopy, different types of sulfates and nitrates were observed. - Highlights: • Rainwater from six sampling points along Nervion River (Bilbao, Spain) were analyzed. • Ion chromatography, ICP-MS and chemometrics were used for the rainwater analyses. • The interaction between wet depositions and building materials was studied. • Cementitious materials were analyzed using µ-Raman spectroscopy and SEM–EDS.

  18. Effect of Different Supplementary Cementitious Materials on Mechanical and Durability Properties of Concrete

    Directory of Open Access Journals (Sweden)

    Rahul Sharma

    2016-09-01

    Full Text Available Concrete is the most widely used composite in the world. Ordinary Portland cement (OPC is the most commonly used binding material but the energy required for its production is large and its production leads to release of green house gases in the atmosphere therefore, the need for supplementary cementitious material is real. The utilization of Fly Ash (FA, Silica Fume (SF,Metakaolin (MK and Ground Granulated Blast Furnace Slag (GGBS, as a pozzolanic material for concrete has received considerable attention in the recent years. This interest is a part of the widely spread attention directed towards the utilization of wastes and industrial byproducts in order to minimize the Portland cement consumption, the manufacture of which is being environment damaging. The paper reviews were carried out on the use of FA, SF, MK and GGBS as partial pozzolanic replacement for cement in concrete. The literature demonstrates that GGBS was found to increase the mechanical and durability properties at later age depending upon replacement level. Silica fume concrete performed better than OPC concrete even at early period for production of high strength concrete and high performance concrete. Fly ash increases the later age strength due to slow rate of pozzlanic reaction. Metakaolin was found to improve early age strength as well as long term strength but had poor workability.

  19. Overview of recent work on self-healing in cementitious materials

    Directory of Open Access Journals (Sweden)

    Lv, Z.

    2014-12-01

    Full Text Available Cracks, especially microcracks, in concrete are of paramount importance to the durability and the service life of cementitious composite. However, the self-healing technology, including autogenous healing and autonomous healing, is expected to be one of effective tools to overcome this boring problem. In this paper, we focus on the autogenous healing of concrete material and a few of recent works of autonomous healing are also mentioned. The durability and the mechanical properties improved by the self-healing phenomenon are reviewed from experimental investigation and practical experience. Several aspects of researches, such as autogenous healing capability of an innovative concrete incorporated geo-materials, self-healing of engineered cementitious composite and fire-damaged concrete, effect of mineral and admixtures on mechanism and efficiency of self-healing concrete are summarized to evaluate the presented progresses in the past several years and to outline the perspective for the further developments. Moreover, a special emphasis is given on the analytical models and computer simulation method of the researches of self-healing in cementitious materials.Las fisuras, y sobre todo las microfisuras, tienen una gran repercusión en la durabilidad y en la vida útil de los materiales cementantes. Ante este problema, la tecnología de la autorreparación, tanto autógena como autónoma, se presenta como una solución eficaz. El artículo se centra en la reparación autógena del hormigón, así como en algunos trabajos recientes sobre la reparación autónoma. Se describen las mejoras de las propiedades de durabilidad y de resistencia que proporciona la técnica del hormigón autorreparable, tanto desde el punto de vista de la investigación experimental como del de la experiencia práctica. A fin de evaluar los avances logrados en los últimos años y de trazar las grandes líneas de desarrollo futuro, se resumen varios de los aspectos

  20. Properties of cathode materials in alkaline cells

    International Nuclear Information System (INIS)

    Salkind, A.J.; McBreen, J.; Freeman, R.; Parkhurst, W.A.

    1985-01-01

    Conventional and new cathode materials in primary and secondary alkaline cells were investigated for stability, structure, electrochemical reversibility and efficiency. Included were various forms of AgO for reserve-type silver-zinc batteries, a new material - AgNiO/sub 2/ - and several nickel electrodes for nickel-cadmium and nickel-hydrogen cells for aerospace applications. A comparative study was made of the stability of electroformed and chemically prepared AgO. Stability was correlated with impurities detected by XPS and SAM. After the first discharge AgNiO/sub 2/ can be recharged to the monovalent level. The discharge product is predominantly silver. Plastic-bonded nickel electrodes display a second plateau on discharge. Additions of Co(OH)/sub 2/ largely eliminate this

  1. Properties of cathode materials in alkaline cells

    Science.gov (United States)

    Salkind, A. J.; McBreen, J.; Freeman, R.; Parkhurst, W. A.

    1984-04-01

    Conventional and new cathode materials in primary and secondary alkaline cells were investigated for stability, structure, electrochemical reversibility and efficiency. Included were various forms of AgO for reserve type silver zinc batteries, a new material - AgNiO2 and several nickel electrodes for nickel cadmium and nickel hydrogen cells for aerospace applications. A comparative study was made of the stability of electroformed and chemically prepared AgO. Stability was correlated with impurities. After the first discharge AgNiO2 can be recharged to the monovalent level. The discharge product is predominantly silver. Plastic bonded nickel electrodes display a second plateau on discharge. Additions of Co(OH)2 largely eliminate this.

  2. Formulation of portland composite cement using waste glass as a supplementary cementitious material

    Science.gov (United States)

    Manullang, Ria Julyana; Samadhi, Tjokorde Walmiki; Purbasari, Aprilina

    2017-09-01

    Utilization of waste glass in cement is an attractive options because of its pozzolanic behaviour and the market of glass-composite cement is potentially available. The objective of this research is to evaluate the formulation of waste glass as supplementary cementitious material (SCM) by an extreme vertices mixture experiment, in which clinker, waste glass and gypsum proportions are chosen as experimental variables. The composite cements were synthesized by mixing all of powder materials in jar mill. The compressive strength of the composite cement mortars after being cured for 28 days ranges between 229 to 268 kg/cm2. Composite cement mortars exhibit lower compressive strength than ordinary Portland cement (OPC) mortars but is still capable of meeting the SNI 15-7064-2004 standards. The highest compressive strength is obtained by shifting the cement blend composition to the direction of increasing clinker and gypsum proportions as well as reducing glass proportion. The lower compressive strength of composite cement is caused by expansion due to ettringite and ASR gel. Based on the experimental result, the composite cement containing 80% clinker, 15% glass and 5% gypsum has the highest compressive strength. As such, the preliminary technical feasibility of reuse of waste glass as SCM has been confirmed.

  3. Specimen preparation for nano-scale investigation of cementitious repair material.

    Science.gov (United States)

    Azarsa, Pejman; Gupta, Rishi

    2018-04-01

    Cementitious Repair Materials (CRMs) in the construction industry have been used for many decades now and has become a very important part of activities in cement world. The performance of some of these CRMs when applied to retrofitting concrete structural elements is also well documented. However, the characterization of some of the CRMs at the micro- and nano level is not fully documented. The first step to studying materials at the microscopic level is to be able to fabricate proper specimens for microscopy. In this study, a special and newly developed class of CRM was selected and fabricated by Focused Ion Beam (FIB) using well-known "Lift-out" technique. The prepared specimen was later examined using various analytical techniques such as energy dispersive x-ray analysis using one of the highest and most stable Scanning Transmission Electron Holography Microscopy (STEHM) around the world. This process enabled understanding of the composition, morphology, and spatial distribution of various phases of the CRM. It was observed that the microstructure consisted of a very fine, compact, and homogenous amorphous structure. X-ray analysis indicated that there was considerable deviation between the Si/Ca ratios for the hydrated product. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Integrated modelling approach to simulate the long-term chemical evolution of cementitious materials in radioactive waste repository environment

    International Nuclear Information System (INIS)

    Elakneswaran, Y.; Ishida, T.

    2015-01-01

    A multi-scale chemo-physics model called Durability Concrete Model (DuCOM) and the geochemical transport code PHREEQC were coupled to predict the long-term performance of cementitious materials in nuclear waste repository environment. The coupled model retains all the capability of each model and allows the prediction of the spatio-temporal variation of cement hydrate composition, pore water concentration, other hydration and pore structure properties, etc. simultaneously. In contrast to existing models, DuCOM-PHREEQC does not require physical or chemical properties of cementitious materials in advance as input parameters because these are calculated automatically in the model. The simulation result from DuCOM-PHREEQC system was verified with reported experimental data for total calcium content in cement paste exposed to pure water. The good agreement between the calculation and the experimental data indicates that the important features and processes have been included in the model for the assessment of cementitious materials in radioactive waste repository environment. Finally, the importance of the strong coupling among various processes and mechanisms in the DuCOM-PHREEQC system is discussed

  5. The Behaviours of Cementitious Materials in Long Term Storage and Disposal of Radioactive Waste. Results of a Coordinated Research Project

    International Nuclear Information System (INIS)

    2013-09-01

    Radioactive waste with widely varying characteristics is generated from the operation and maintenance of nuclear power plants, nuclear fuel cycle facilities, research laboratories and medical facilities. This waste must be treated and conditioned, as necessary, to provide waste forms acceptable for safe storage and disposal. Many countries use cementitious materials (concrete, mortar, etc.) as a containment matrix for immobilization, as well as for engineered structures of disposal facilities. Radionuclide release is dependent on the physicochemical properties of the waste forms and packages, and on environmental conditions. In the use of cement, the diffusion process and metallic corrosion can induce radionuclide release. The advantage of cementitious materials is the added stability and mechanical support during storage and disposal of waste. Long interim storage is becoming an important issue in countries where it is difficult to implement low level waste and intermediate level waste disposal facilities, and in countries where cement is used in the packaging of waste that is not suitable for shallow land disposal. This coordinated research project (CRP), involving 24 research organizations from 21 Member States, investigated the behaviour and performance of cementitious materials used in an overall waste conditioning system based on the use of cement - including waste packaging (containers), waste immobilization (waste form) and waste backfilling - during long term storage and disposal. It also considered the interactions and interdependencies of these individual elements (containers, waste, form, backfill) to understand the processes that may result in degradation of their physical and chemical properties. The main research outcomes of the CRP are summarized in this report under four topical sections: (i) conventional cementitious systems; (ii) novel cementitious materials and technologies; (iii) testing and waste acceptance criteria; and (iv) modelling long

  6. Durability of mortars modified by the effect of combining SPA polymers and supplementary cementitious materials

    Directory of Open Access Journals (Sweden)

    Belbachir B.

    2018-01-01

    Full Text Available Nowadays, the major concern of professionals in the field of building materials is to improve the properties induced by the addition of different additives (polymers and mineral additions (Supplementary Cement Materials SCMs and to eventually adapt them to a particular application. This race towards performance has resulted in mortar formulations that are increasingly complex and rich in diversified additions. This is an industry-friendly practice since it generally yields a mortar modified by the combination of a polymer and SCMs, at low cost and low environmental impact, with an improved sustainability in the long term. In order to improve the durability of SCM-modified repair mortars, it seemed interesting to evaluate the influence of adding the styrene polyacrylic (SPA Latex on the properties of these mortars when exposed to aggressive media such as acids. Composite mortars based on pozzolanic mineral additions, containing different levels of 0.5%, 1% and 2%w latex, were stored in acid solutions, for various periods of immersion. The analysis of the microstructure of these mortars, after exposure to acid attack, was carried out by FTIR spectroscopy. The results obtained allowed to demonstrate the beneficial effect of adding the SPA polymer and the pozzolanic additions to the modified materials and to show their improved resistance to acid attacks, such as HNO3 and H3PO4 solutions at 8%. The best durability properties of the mortars modified by the combination of the polymer and the additional cementitious materials observed in this study indicate a longer service life of the repaired structure when using this type of Latex-modified repair materials.

  7. Preparation of Silica Nanoparticles and Its Beneficial Role in Cementitious Materials

    Directory of Open Access Journals (Sweden)

    S. Ahalawat

    2011-07-01

    Full Text Available Spherical silica nanoparticles (n‐SiO2 with controllable size have been synthesized using tetraethoxysilane as starting material and ethanol as solvent by sol‐gel method. Morphology and size of the particles was controlled through surfactants. Sorbitan monolaurate, sorbitain monopalmitate and sorbitain monostearate produced silica nanoparticles of varying sizes (80‐150 nm, indicating the effect of chain length of the surfactant. Increase in chain length of non‐ionic surfactant resulted in decreasing particle size of silica nanoparticles. Further, the size of silica particles was also controlled using NH3 as base catalyst. These silica nanoparticles were incorporated into cement paste and their role in accelerating the cementitious reactions was investigated. Addition of silica nanoparticles into cement paste improved the microstructure of the paste and calcium leaching is significantly reduced as n‐SiO2 reacts with calcium hydroxide and form additional calcium‐ silicate‐hydrate (C‐S‐H gel. It was found that calcium hydroxide content in silica nanoparticles incorporated cement paste reduced ~89% at 1 day and up to ~60% at 28 days of hydration process. Synthesized silica particles and cement paste samples were characterized using scanning electron microscopy (SEM, powder X‐ray diffraction (XRD, infrared spectroscopy (IR and thermogravimetric analysis (TGA.

  8. The mechanisms of heavy metal immobilization by cementitious material treatments and thermal treatments: A review.

    Science.gov (United States)

    Guo, Bin; Liu, Bo; Yang, Jian; Zhang, Shengen

    2017-05-15

    Safe disposal of solid wastes containing heavy metals is a significant task for environment protection. Immobilization treatment is an effective technology to achieve this task. Cementitious material treatments and thermal treatments are two types of attractive immobilization treatments due to that the heavy metals could be encapsulated in their dense and durable wasteforms. This paper discusses the heavy metal immobilization mechanisms of these methods in detail. Physical encapsulation and chemical stabilization are two fundamental mechanisms that occur simultaneously during the immobilization processes. After immobilization treatments, the wasteforms build up a low permeable barrier for the contaminations. This reduces the exposed surface of wastes. Chemical stabilization occurs when the heavy metals transform into more stable and less soluble metal bearing phases. The heavy metal bearing phases in the wasteforms are also reviewed in this paper. If the heavy metals are incorporated into more stable and less soluble metal bearing phases, the potential hazards of heavy metals will be lower. Thus, converting heavy metals into more stable phases during immobilization processes should be a common way to enhance the immobilization effect of these immobilization methods. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Penetration of corrosion products and corrosion-induced cracking in reinforced cementitious materials

    DEFF Research Database (Denmark)

    Michel, Alexander; Pease, Brad J.; Peterova, Adela

    2014-01-01

    -dependent concentrations of corrosion products averaged through the specimen thickness. Digital image correlation (DIC) was used to measure corrosion-induced deformations including deformations between steel and cementitious matrix as well as formation and propagation of corrosion-induced cracks. Based on experimental...... observations, a conceptual model was developed to describe the penetration of solid corrosion products into capillary pores of the cementitious matrix. Only capillary pores within a corrosion accommodating region (CAR), i.e. in close proximity of the steel reinforcement, were considered accessible...

  10. Numerical estimation of transport properties of cementitious materials using 3D digital images

    NARCIS (Netherlands)

    Ukrainczyk, N.; Koenders, E.A.B.; Van Breugel, K.

    2012-01-01

    A multi-scale characterisation of the transport process within cementitious microstructure possesses a great challenge in terms of modelling and schematization. In this paper a numerical method is proposed to mitigate the resolution problems in numerical methods for calculating effective transport

  11. Self-healing behavior of strain hardening cementitious composites incorporating local waste materials

    NARCIS (Netherlands)

    Qian, S.; Zhou, J.; Rooij, M.R. de; Schlangen, E.; Ye, G.; Breugel, K. van

    2009-01-01

    The self-healing behavior of a series of pre-cracked fiber reinforced strain hardening cementitious composites incorporating blast furnace slag (BFS) and limestone powder (LP) with relatively high water/binder ratio is investigated in this paper, focusing on the recovery of its deflection capacity.

  12. Overview of recent and future work on material development and usage of cementitious materials in salt repositories

    International Nuclear Information System (INIS)

    Mauke, Ralf; Wollrath, Juergen; Mueller-Hoeppe, Nina; Becker, Dirk-Alexander; Noseck, Ulrich

    2012-01-01

    Juergen Wollrath from BfS, Germany, presented work on cementitious materials developed and used in salt repositories. The presentation focussed on the ERAM low-level waste repository, which has been developed in a former salt mine. The closure concept includes extensive backfilling of the mine and sealing of the waste emplacement areas. With this objective, a concrete with a salt aggregate has been developed and the feasibility of using this material for backfilling has been demonstrated. One concern has been the level of naturally occurring long-lived radionuclides (radium and thorium) in the backfill materials. Assessments of the potential impacts of radionuclides in the backfill indicate that they do not compromise the long-term safety of the facility. A test of drift seal performance will take place during the next few years. In conclusion, the salt concrete developed for backfilling and sealing of repositories in salt formations has proven to satisfy all requirements from pre- and post-closure considerations

  13. Development of an accurate pH measurement methodology for the pore fluids of low pH cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, M. C.; Garcia Calvo, J. L. [The Spanish National Research Council (CSIC), Madrid (Spain); Walker, C. [Japan Atomic Energy Agency (JAEA), Ibaraki (Japan)] [and others

    2012-08-15

    The main objective of this project has been the development of an agreed set of protocols for the pH measurement of the pore fluid of a low pH cementitious material. Three protocols have been developed (Chapter 2), a reference method, based on pore fluid expression (PFE), and two routine methods with and without filtering, based on Ex Situ Leaching (ESL) procedures. Templates have been designed on which to record details of the pH measurement for the reference (PFE) method (Appendix C) and the routine (ESL) methods without and with filtering (Appendix D). Preliminary protocols were based on a broad review of the literature (Appendix A) and refined through a series of test experiments of the more critical parameters (Appendix B). After definition of the preliminary protocols, two phases of interlaboratory tests were performed. The first phase (Chapter 3) used the same low pH cement paste and enabled the nine participating laboratories to use, become familiar with and to identify any problems/uncertainties in the preliminary protocols. The reported pH values were subjected to a statistical analysis of the (within laboratory) repeatability and (between-laboratory) reproducibility and so provided a reliability test of the preliminary protocols. The second phase (Chapter 4) of interlaboratory tests used four different candidate low pH cementitious materials in the same nine laboratories, which allowed testing, validation and comparison of the reported pH values, which were obtained using the final protocols for the reference (PFE) and routine (ESL) methods by statistical analysis. The proposed final protocols (Chapter 2) have resulted in the reported pH values having low deviation and high reproducibility and repeatability. This will allow confidence in the pH value when selecting a candidate low pH cementitious material to be used in the engineered component of a high-level nuclear waste repository.

  14. Development of an accurate pH measurement methodology for the pore fluids of low pH cementitious materials

    International Nuclear Information System (INIS)

    Alonso, M. C.; Garcia Calvo, J. L.; Walker, C.

    2012-08-01

    The main objective of this project has been the development of an agreed set of protocols for the pH measurement of the pore fluid of a low pH cementitious material. Three protocols have been developed (Chapter 2), a reference method, based on pore fluid expression (PFE), and two routine methods with and without filtering, based on Ex Situ Leaching (ESL) procedures. Templates have been designed on which to record details of the pH measurement for the reference (PFE) method (Appendix C) and the routine (ESL) methods without and with filtering (Appendix D). Preliminary protocols were based on a broad review of the literature (Appendix A) and refined through a series of test experiments of the more critical parameters (Appendix B). After definition of the preliminary protocols, two phases of interlaboratory tests were performed. The first phase (Chapter 3) used the same low pH cement paste and enabled the nine participating laboratories to use, become familiar with and to identify any problems/uncertainties in the preliminary protocols. The reported pH values were subjected to a statistical analysis of the (within laboratory) repeatability and (between-laboratory) reproducibility and so provided a reliability test of the preliminary protocols. The second phase (Chapter 4) of interlaboratory tests used four different candidate low pH cementitious materials in the same nine laboratories, which allowed testing, validation and comparison of the reported pH values, which were obtained using the final protocols for the reference (PFE) and routine (ESL) methods by statistical analysis. The proposed final protocols (Chapter 2) have resulted in the reported pH values having low deviation and high reproducibility and repeatability. This will allow confidence in the pH value when selecting a candidate low pH cementitious material to be used in the engineered component of a high-level nuclear waste repository

  15. ANDRA - Referential Materials. Volume 1: Context and scope; Volume 2: Argillaceous materials; Volume 3: Cementitious materials; Volume 4: The corrosion of metallic materials

    International Nuclear Information System (INIS)

    2001-01-01

    This huge document gathers four volumes. The first volume presents some generalities about materials used in the storage of radioactive materials (definition, design principle, current choices and corresponding storage components, general properties of materials and functions of the corresponding storage components, physical and chemical solicitations experienced by materials in a storage), and the structure and content of the other documents. The second volume addresses argillaceous materials. It presents some generalities about these materials in the context of a deep geological storage, and about their design. It presents and comments the crystalline and chemical, and physical and chemical characteristics of swelling argillaceous materials and minerals, describes how these swelling argillaceous materials are shaped and set up, presents and comments physical properties (hydraulic, mechanical and thermal properties) of these materials, comments and discusses the modelling of the geo-chemical behaviour, and their behaviour in terms of containment and transport of radionuclides. The third volume addresses cementitious materials. It presents some generalities about these materials in the context of a deep geological storage, and about their definition and specifications. It presents some more detailed generalities (cement definition and composition, hydration, microstructure of hydrated cements, adjuvants), presents and comments their physical properties (fresh concrete structure and influence of composition, main aimed properties in the hardened status, transfer, mechanical, and thermal properties, shaping and setting up of these materials, technical solutions for hydraulic works). The fourth volume addresses the corrosion of metallic materials. It presents some generalities about these materials in the context of a deep geological storage of radioactive materials. It presents metallic materials and discusses their corrosion behaviour. It describes the peculiarities

  16. Guidelines for assessing the valorization of a waste into cementitious material: dredged sediment for production of self compacting concrete

    Directory of Open Access Journals (Sweden)

    Rozas, F.

    2015-09-01

    Full Text Available This article presents some guidelines in order to analyse the feasibility of including a waste material in the production of a structural cementitious material. First of all, the compatibility of the waste with a cementitious material has to be assured; then, if necessary, a decontamination step will be carried out; after, decision on the type of material has to be taken based on different aspects, with special emphasis on the granulometry. As a last step, mechanical, environmental and durability properties have to be evaluated. Then the procedure is illustrated with a full example, obtaining a self compacting concrete (SCC including dredged sediment taken from a Spanish harbour.Este artículo presenta algunas directrices con el fin de analizar la posibilidad de incluir un material de desecho en la producción de un material base cemento estructural. En primer lugar, debe asegurarse la compatibilidad de los residuos con el material base cemento. Tras ello, si es necesario, se llevará a cabo la etapa de descontaminación del residuo. Después debe tomarse la decisión sobre el tipo de material a utilizar en base a diferentes aspectos, haciendo especial énfasis en la granulometría. Como último paso, deben evaluarse las propiedades mecánicas, ambientales y de durabilidad del producto final. El procedimiento a seguir se ilustra con un ejemplo concreto basado en la obtención de un hormigón autocompactante (SCC incluyendo en su fabricación sedimentos dragados tomados de un puerto español.

  17. Cementitious Materials in Safety Cases for Geological Repositories for Radioactive Waste: Role, Evolution and Interactions. A Workshop organised by the OECD/NEA Integration Group for the Safety Case and hosted by ONDRAF/NIRAS. Cementitious materials in safety cases for radioactive waste: role, evolution and interactions

    International Nuclear Information System (INIS)

    2012-01-01

    The OECD Nuclear Energy Agency (NEA) Integration Group for the Safety Case (IGSC) organised a workshop to assess current understanding on the use of cementitious materials in radioactive waste disposal. The workshop was hosted by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (Ondraf/Niras), in Brussels, Belgium on 17-19 November 2009. The workshop brought together a wide range of people involved in supporting safety case development and having an interest in cementitious materials: namely, cement and concrete experts, repository designers, scientists, safety assessors, disposal programme managers and regulators. The workshop was designed primarily to consider issues relevant to the post-closure safety of radioactive waste disposal, but also addressed some related operational issues, such as cementitious barrier emplacement. Where relevant, information on cementitious materials from analogous natural and anthropogenic systems was also considered. This report provides a synthesis of the workshop, and summarises its main results and findings. The structure of this report follows the workshop agenda: - Section 2 summarises plenary and working group discussions on the uses, functions and evolution of cementitious materials in geological disposal, and highlights key aspects and discussions points. - Section 3 summarises plenary and working group discussions on interactions of cementitious materials with other disposal system components, and highlights key aspects and discussions points. - Section 4 summarises the workshop session on the integration of issues related to cementitious materials using the safety case. - Section 5 presents the main conclusions from the workshop. - Section 6 contains a list of references. - Appendix A presents the workshop agenda. - Appendix B contains the abstracts and, where provided, technical papers supporting oral presentations at the workshop. - Appendix C contains the abstracts and, where provided, technical

  18. Use of X-ray diffraction to quantify amorphous supplementary cementitious materials in anhydrous and hydrated blended cements

    International Nuclear Information System (INIS)

    Snellings, R.; Salze, A.; Scrivener, K.L.

    2014-01-01

    The content of individual amorphous supplementary cementitious materials (SCMs) in anhydrous and hydrated blended cements was quantified by the PONKCS [1] X-ray diffraction (XRD) method. The analytical precision and accuracy of the method were assessed through comparison to a series of mixes of known phase composition and of increasing complexity. A 2σ precision smaller than 2–3 wt.% and an accuracy better than 2 wt.% were achieved for SCMs in mixes with quartz, anhydrous Portland cement, and hydrated Portland cement. The extent of reaction of SCMs in hydrating binders measured by XRD was 1) internally consistent as confirmed through the standard addition method and 2) showed a linear correlation to the cumulative heat release as measured independently by isothermal conduction calorimetry. The advantages, limitations and applicability of the method are discussed with reference to existing methods that measure the degree of reaction of SCMs in blended cements

  19. Characterization of Structural Rebuilding and Shear Migration in Cementitious Materials in Consideration of Thixotropy

    Science.gov (United States)

    Qian, Ye

    Characterization of structural rebuilding and shear migration in cementitious materials in consideration of thixotropy Ye Qian From initial contact with water until hardening, and deterioration, cement and concrete materials are subjected to various chemical and physical transformations and environmental impacts. This thesis focuses on the properties during the fresh state, shortly after mixing until the induction period. During this period flow history, including shearing and resting, and hydration both play big roles in determining the rheological properties. The rheological properties of cement and concrete not only affect the casting and pumping process, but also very critical for harden properties and durability properties. Compared with conventional concrete, self-consolidating concrete (SCC) can introduce many advantages in construction application. These include readiness to apply, decreasing labor necessary for casting, and enhancing hardened properties. However, challenges still remain, such as issues relating to formwork pressure and multi-layer casting. Each of these issues is closely related to the property of thixotropy. From the microstructural point of view, thixotropy is described as structural buildup (flocculation) under rest and breakdown (deflocculation) under flow. For SCC, as well as other concrete systems, it is about balancing sufficient flowability during casting and rate of structural buildup after placement for the application at hand. For instance, relating to the issue of SCC formwork, it is ideal for the material to be highly flowable to achieve rapid casting, but then exhibit high rate of structural buildup to reduce formwork pressure. This can reduce the cost of formwork and reduce the risk of formwork failure. It is apparent that accurately quantifying the two aspects of thixotropy, i.e. structuration and destructuration, is key to tackling these challenges in field application. Thus, the overall objective of my doctoral study is

  20. Alkaline Materials and Regenerative Endodontics: A Review

    Directory of Open Access Journals (Sweden)

    Bill Kahler

    2017-12-01

    Full Text Available Periapical health is the primary goal of endodontic treatment in mature and immature teeth. In addition, the goals of treatment of immature teeth with arrested root development include root growth to length and maturation of the apex, as well as thickening of the canal wall. These goals are valid for immature teeth that have been subjected to trauma and dental caries or that are the result of developmental anomalies that expose the tooth to the risk of pulp necrosis and consequently result in the cessation of root maturation. Regenerative endodontic procedures (REPs have been described as a “paradigm shift” in the treatment of immature teeth with pulp necrosis and underdeveloped roots, as there is the potential for further root maturation and return of vitality. Treatment with REPs is advocated as the treatment of choice for immature teeth with pulp necrosis. REP protocols involve the use of alkaline biomaterials, primarily sodium hypochlorite, calcium hydroxide, mineral trioxide aggregates and Biodentine, and are the essential components of a successful treatment regimen.

  1. Alkaline and ultrasound assisted alkaline pretreatment for intensification of delignification process from sustainable raw-material.

    Science.gov (United States)

    Subhedar, Preeti B; Gogate, Parag R

    2014-01-01

    Alkaline and ultrasound-assisted alkaline pretreatment under mild operating conditions have been investigated for intensification of delignification. The effect of NaOH concentration, biomass loading, temperature, ultrasonic power and duty cycle on the delignification has been studied. Most favorable conditions for only alkaline pretreatment were alkali concentration of 1.75 N, solid loading of 0.8% (w/v), temperature of 353 K and pretreatment time of 6 h and under these conditions, 40.2% delignification was obtained. In case of ultrasound-assisted alkaline approach, most favorable conditions obtained were alkali concentration of 1N, paper loading of 0.5% (w/v), sonication power of 100 W, duty cycle of 80% and pretreatment time of 70 min and the delignification obtained in ultrasound-assisted alkaline approach under these conditions was 80%. The material samples were characterized by FTIR, SEM, XRD and TGA technique. The lignin was recovered from solution by precipitation method and was characterized by FTIR, GPC and TGA technique. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Performance and mechanism on a high durable silica alumina based cementitious material composed of coal refuse and coal combustion byproducts

    Science.gov (United States)

    Yao, Yuan

    Coal refuse and combustion byproducts as industrial solid waste stockpiles have become great threats to the environment. Recycling is one practical solution to utilize this huge amount of solid waste through activation as substitute for ordinary Portland cement. The central goal of this dissertation is to investigate and develop a new silica-alumina based cementitious material largely using coal refuse as a constituent that will be ideal for durable construction, mine backfill, mine sealing and waste disposal stabilization applications. This new material is an environment-friendly alternative to ordinary Portland cement. The main constituents of the new material are coal refuse and other coal wastes including coal sludge and coal combustion products (CCPs). Compared with conventional cement production, successful development of this new technology could potentially save energy and reduce greenhouse gas emissions, recycle vast amount of coal wastes, and significantly reduce production cost. A systematic research has been conducted to seek for an optimal solution for enhancing pozzolanic reactivity of the relatively inert solid waste-coal refuse in order to improve the utilization efficiency and economy benefit for construction and building materials. The results show that thermal activation temperature ranging from 20°C to 950°C significantly increases the workability and pozzolanic property of the coal refuse. The optimal activation condition is between 700°C to 800°C within a period of 30 to 60 minutes. Microanalysis illustrates that the improved pozzolanic reactivity contributes to the generated amorphous materials from parts of inert aluminosilicate minerals by destroying the crystallize structure during the thermal activation. In the coal refuse, kaolinite begins to transfer into metakaol in at 550°C, the chlorite minerals disappear at 750°C, and muscovite 2M1 gradually dehydroxylates to muscovite HT. Furthermore, this research examines the environmental

  3. State of the art of TiO2 containing cementitious materials: self-cleaning properties

    Directory of Open Access Journals (Sweden)

    Maury, A.

    2010-06-01

    Full Text Available Due to the physico-chemical characteristics of cementitious materials the aesthetic quality of these materials tend to decrease easily. On the other hand, the photocatalytic activity produced by TiO2 loaded cementitious materials have recently allowed them to include self-cleaning and air-purifying properties. However, because a better understanding of these properties is still needed, only a limited number of these materials is present in the construction market. As a strategy to improve this situation, non standards tests based on photodegradation of organic dyes have become widely used to evaluate the photocatalytic action of the different materials. Today, a wide spectrum of non easily comparable results have been produced. In order to improve this situation, this paper focuses on the description of the developed laboratory tests as well as on the evaluation of the self-cleaning potential of the first buildings containing TiO2. Finally, future research challenges in this field are identified.

    Debido a las características físico-químicas de los materiales a base de cemento, la calidad estética de estos materiales tiende a disminuir con facilidad. Por otra parte, la actividad fotocatalítica producida por los materiales a base de cemento que contienen TiO2, ha permitido incorporar recientemente en estos materiales propiedades de auto-limpieza y purificación del aire. Sin embargo, actualmente sólo existe en el mercado un número limitado de dichos materiales, dado que aún se necesita conocer mejor las mencionadas propiedades. Para mejorar esta situación, se vienen desarrollando ensayos no estandarizados donde se evalúa la foto-degradación de colorantes orgánicos producida por los diferentes materiales. Por tanto, se han producido una gran cantidad de resultados no fácilmente comparables entre sí. Este artículo presenta una descripción de los diferentes ensayos de laboratorio desarrollados

  4. Micro-structural characterization of the hydration products of bauxite-calcination-method red mud-coal gangue based cementitious materials

    International Nuclear Information System (INIS)

    Liu, Xiaoming; Zhang, Na; Yao, Yuan; Sun, Henghu; Feng, Huan

    2013-01-01

    Highlights: • Al IV and Al VI both exist in the hydration products. • Increase of Ca/Si ratio promotes the conversion from [AlO 4 ] to [AlO 6 ]. • Polymerization degree of [SiO 4 ] in the hydration products declines. -- Abstract: In this research, the micro-structural characterization of the hydration products of red mud-coal gangue based cementitious materials has been investigated through SEM-EDS, 27 Al MAS NMR and 29 Si MAS NMR techniques, in which the used red mud was derived from the bauxite calcination method. The results show that the red mud-coal gangue based cementitious materials mainly form fibrous C-A-S-H gel, needle-shaped/rod-like AFt in the early hydration period. With increasing of the hydration period, densification of the pastes were promoted resulting in the development of strength. EDS analysis shows that with the Ca/Si of red mud-coal gangue based cementitious materials increases, the average Ca/Si and Ca/(Si + Al) atomic ratio of C-A-S-H gel increases, while the average Al/Si atomic ratio of C-A-S-H gel decreases. MAS NMR analysis reveals that Al in the hydration products of red mud-coal gangue based cementitious materials exists in the forms of Al IV and Al VI , but mainly in the form of Al VI . Increasing the Ca/Si ratio of raw material promotes the conversion of [AlO 4 ] to [AlO 6 ] and inhibits the combination between [AlO 4 ] and [SiO 4 ] to form C-A-S-H gel. Meanwhile, the polymerization degree of [SiO 4 ] in the hydration products declines

  5. Shrinkage behaviour and related corrosion performance of low-pH cementitious materials based on OPC or CAC

    Directory of Open Access Journals (Sweden)

    García-Calvo, J. L.

    2016-03-01

    Full Text Available Prior to using low-pH cementitious materials in underground repositories for high level waste, the characteristics determining their long-term durability must be analysed in depth. In this sense, different shrinkage tests have been made on mortar and concrete specimens using low-pH cement formulations based on ordinary portland cement (OPC or calcium aluminate cement (CAC, with high mineral admixtures contents. They showed similar autogenous shrinkage than samples without mineral admixtures but higher drying shrinkage when materials based on OPC with high silica fume contents were considered. Besides, as the use of reinforced concrete could be required in underground repositories, the susceptibility of reinforcement to corrosion when using low-pH cementitious materials based on OPC was analyzed, considering carbon steel and galvanized steel. In the formers corrosion was detected due to the low pore solution pH but any problem was detected when galvanized reinforcement were used.Previo al empleo de materiales con cementos de bajo pH en almacenamientos geológicos profundos (AGP de residuos radiactivos de alta actividad, características relacionadas con su durabilidad a largo plazo deben ser verificadas. Así, su estabilidad volumétrica se ha analizado en morteros y hormigones de bajo pH basados en OPC o CAC, con elevados contenidos de adiciones minerales. Estos presentaron retracciones autógenas similares a las medidas en materiales convencionales, pero retracciones por secado mayores en los basados en OPC y altos contenidos de humo de sílice. Dado que en zonas de los AGP podría emplearse hormigón armado, también se evaluó la susceptibilidad a la corrosión de aceros al carbono y aceros galvanizados en materiales de bajo pH basados en OPC. Se detectó un inicio temprano de corrosión en los primeros debido al bajo pH presente en el fluido de los poros de estos materiales, sin detectarse problemas al emplear aceros galvanizados.

  6. Implications of cementitious evolution for solubility and retention of radionuclides over long timescales

    International Nuclear Information System (INIS)

    Williams, Steve; Norris, Simon

    2012-01-01

    Simon Norris of the NDA described the current status of understanding of radionuclide solubility and retention in cementitious materials based on experience in the United Kingdom. Cementitious materials play a number of roles in the long-term management and disposal of radioactive wastes. One of these roles is to contribute to the post-closure containment and retention of radionuclides within a disposal facility by imposing conditions that minimise radionuclide solubility and provide sites for radionuclide sorption. The chemical containment provided by the highly-alkaline, chemically reducing environment imposed by cementitious materials plays an important role in the long-term retention of many radionuclides. However, the mineralogy and other properties of cementitious materials that contribute to their physical and chemical barrier performance within the engineered barrier system will evolve due to several processes, including: - Leaching. - Reaction with groundwater solutes. - Hydration and crystallisation. - Reaction with wastes, their degradation products, and with non-cementitious waste forms. - Cracking. Some of these processes are better understood than others. For example, the evolution of pH within a homogeneous repository near field can be modelled based on knowledge of cement dissolution combined with expected groundwater compositions and flow rates. The calculated changes in pH can then be coupled to radionuclide solubility and sorption in safety assessment models. Other processes are not as well constrained. Reaction of cementitious materials with groundwater will lead to changes in the mineralogical composition of the cements, accompanied by changes in porosity and permeability, and cracking can lead to localised water flow along the cracks and preferential leaching or deposition of reaction products. These processes can also alter the sorption properties of the cementitious materials. Additional complexities result from the heterogeneous

  7. Evaluation of the suitability of tin slag in cementitious materials: Mechanical properties and Leaching behaviour

    Science.gov (United States)

    Rustandi, Andi; Wafa’ Nawawi, Fuad; Pratesa, Yudha; Cahyadi, Agung

    2018-01-01

    Tin slag, a by-product of tin production has been used in cementitious application. The present investigation focuses on the suitability of tin slag as primary component in cement and as component that substitute some amount of Portland Cement. The tin slags studied were taken from Bangka, Indonesia. The main contents of the tin slag are SiO2, Al2O3, and Fe2O3 according to the XRF investigation. The aim of this article was to study the mechanical behaviour (compressive strength), microstructure and leaching behaviour of tin slag blended cement. This study used air-cooled tin slag that had been passed through 400# sieve to replace Portland Cement with ratio 0, 10, 20, 30, 40 by weight. Cement pastes and tin slag blended cement pastes were prepared by using water/cement ratio (W/C) of 0.40 by weight and hydrated for various curing ages of 3, 7, 14 days The microstructure of the raw tin slag was investigated using Scanning Electron Microscope (SEM). The phase composition of each cement paste was investigated using X-ray Diffraction (XRD). The aim of the leachability test was to investigate the environmental impacts of tin slag blended cement product in the range 4-8 pH by using static pH-dependent leaching test. The result show that the increase of the tin slag content decreasing the mortar compressive strength at early ages. The use of tin slag in cement provide economic benefits for all related industries.

  8. Influence of aggregate and supplementary cementitious materials on the properties of hydrated lime (CL90s mortars

    Directory of Open Access Journals (Sweden)

    S. Pavía

    2016-11-01

    Full Text Available Hydrated lime is a historic material currently used in conservation. It hardens slowly by carbonation slowing construction however, supplementary cementitious materials accelerate hardening enhancing strength. Hydrated-lime mortars with rice husk ash–RHA-; ground granulated blastfurnace slag–GGBS- and increasing amounts of two aggregates were studied. Increasing aggregate lowered strength as interfacial zones proliferate; it lowered hygric properties and raised water demand. Aggregate content/composition didn’t affect the high water retention. For the higher aggregate contents (90 days, limestone mortars are c.20% stronger than silica mortars while the (1:1 silica sand mortars are 56% stronger in flexion. Additions increased strength with little impact on hygric properties. GGBS increased strength c.six times. RHA increased strength with little impact on hygric properties due to its great specific surface and high water-demand increasing porosity. GGBS and RHA properties ruling hydrate production and the kinetics of the pozzolanic reaction are considered partially responsible for the mortar property variation.

  9. Utilization of red mud and Pb/Zn smelter waste for the synthesis of a red mud-based cementitious material.

    Science.gov (United States)

    Li, Yuan-Cheng; Min, Xiao-Bo; Ke, Yong; Chai, Li-Yuan; Shi, Mei-Qing; Tang, Chong-Jian; Wang, Qing-Wei; Liang, Yan-Jie; Lei, Jie; Liu, De-Gang

    2018-02-15

    A new method in which Pb/Zn smelter waste containing arsenic and heavy metals (arsenic sludge), red mud and lime are utilized to prepare red mud-based cementitious material (RCM) is proposed in this study. XRD, SEM, FTIR and unconfined compressive strength (UCS) tests were employed to assess the physicochemical properties of RCM. In addition, ettringite and iron oxide-containing ettringite were used to study the hydration mechanism of RCM. The results show that the UCS of the RCM (red mud+arsenic sludge+lime) was higher than that of the binder (red mud+arsenic sludge). When the mass ratio of m (binder): m (lime) was 94:6 and then maintained 28days at ambient temperature, the UCS reached 12.05MPa. The red mud has potential cementitious characteristics, and the major source of those characteristics was the aluminium oxide. In the red mud-arsenic sludge-lime system, aluminium oxide was effectively activated by lime and gypsum to form complex hydration products. Some of the aluminium in ettringite was replaced by iron to form calcium sulfoferrite hydrate. The BCR and leaching toxicity results show that the leaching concentration was strongly dependent on the chemical speciation of arsenic and the hydration products. Therefore, the investigated red mud and arsenic sludge can be successfully utilized in cement composites to create a red mud-based cementitious material. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Experimental Investigation and Prediction of Compressive Strength of Ultra-High Performance Concrete Containing Supplementary Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Jisong Zhang

    2017-01-01

    Full Text Available Ultra-high performance concrete (UHPC has superior mechanical properties and durability to normal strength concrete. However, the high amount of cement, high environmental impact, and initial cost are regarded as disadvantages, restricting its wider application. Incorporation of supplementary cementitious materials (SCMs in UHPC is an effective way to reduce the amount of cement needed while contributing to the sustainability and cost. This paper investigates the mechanical properties and microstructure of UHPC containing fly ash (FA and silica fume (SF with the aim of contributing to this issue. The results indicate that, on the basis of 30% FA replacement, the incorporation of 10% and 20% SF showed equivalent or higher mechanical properties compared to the reference samples. The microstructure and pore volume of the UHPCs were also examined. Furthermore, to minimise the experimental workload of future studies, a prediction model is developed to predict the compressive strength of the UHPC using artificial neural networks (ANNs. The results indicate that the developed ANN model has high accuracy and can be used for the prediction of the compressive strength of UHPC with these SCMs.

  11. Production, characterization, and mechanical behavior of cementitious materials incorporating carbon nanofibers.

    Science.gov (United States)

    2012-08-01

    Carbon nanotubes (CNTs) and carbon nanofirbers (CNFs) have excellent properties : (mechanical, electrical, magnetic, etc.), which can make them effective : nanoreinforcements for improving the properties of materials. The incorporation of : CNT/Fs in...

  12. Magnesium alloy and graphite wastes encapsulated in cementitious materials - Experimental approach

    International Nuclear Information System (INIS)

    Chartier, D.; Sanchez-Canet, J.; Muzeau, B.; Monguillon, C.; Stefan, L.

    2015-01-01

    Magnesium alloys (Mg-0.8%Zr and Mg-1.2%Mn) and graphite from spent nuclear fuel, that have been used in the former French gas cooled reactors, have been stored together in AREVA La Hague plant. The recovery and packaging of these wastes is currently studied and several solutions are under consideration. One of the developed solutions would be to mix these wastes in a grout composed of industrially available cement, e.g. OPC (Ordinary Portland Cement), OPC blended with blast furnace slag or aluminous cement. Within the alkaline pore solution of these matrixes, magnesium alloys are imperfectly protected by a layer of magnesium hydroxide (Mg(OH) 2 , Brucite) resulting in a slow process of corrosion releasing hydrogen. As the production of this gas must be considered for the storage safety, it is important to select a cement matrix capable of lowering the corrosion kinetics of magnesium alloys. This is especially true when magnesium alloys are conditioned together with graphite wastes. Indeed, galvanic coupling phenomena may increase early age corrosion of the mixed waste, as magnesium and graphite will be found in electrical contact in the same electrolyte. Many types of common cements have been tested. All of them have shown strong hydrogen production when magnesium alloys and graphite are conditioned together into such cement pastes. Corrosion patterns, observed and analyzed by SEM/EDS, at the metal-binder interfaces, reveal important corrosion products layers as well as bubbles and cracks in the binder. Attempts to reduce corrosion by lowering water to cement ratio have been performed. W/C ratios as low as 0.2 have been tested but galvanic corrosion is not significantly reduced at early age when compared to a common ratio of 0.4. Best results were obtained by the use of laboratory synthesized tricalcium silicate (C 3 S) with an ordinary W/C ratio of 0.4 and also with white Portland clinker ground without additives such as gypsum and grinding agent. (authors)

  13. Cementitious Spray Dryer Ash-Tire Fiber Material for Maximizing Waste Diversion

    OpenAIRE

    Riley, Charles E.; Atadero, Rebecca A.; van de Lindt, John W.; Heyliger, Paul R.

    2011-01-01

    Spray dryer absorber (SDA) material, also known as spray dryer ash, is a byproduct of coal combustion and flue gas scrubbing processes that has self-cementing properties similar to those of class C fly ash. SDA material does not usually meet the existing standards for use as a pozzolan in Portland cement concrete due to its characteristically high sulfur content, and thus unlike fly ash, it is rarely put to beneficial use. This paper presents the results of a study with the objective of devel...

  14. Micro-level Porosimetry of Virtual Cementitious Materials : Structural Impact on Mechanical and Durability Evolution

    NARCIS (Netherlands)

    Le, L.B.N.

    2015-01-01

    Understanding the microstructure of cement paste is the basis of a study towards properties and behaviour of cementi¬tious materials. It is attractive exploit¬ing modern computer facilities for this purpose, favourably competing with time-consuming and laborious experimental approaches. This study

  15. Cementitious Spray Dryer Ash-Tire Fiber Material for Maximizing Waste Diversion

    Directory of Open Access Journals (Sweden)

    Charles E. Riley

    2011-01-01

    Full Text Available Spray dryer absorber (SDA material, also known as spray dryer ash, is a byproduct of coal combustion and flue gas scrubbing processes that has self-cementing properties similar to those of class C fly ash. SDA material does not usually meet the existing standards for use as a pozzolan in Portland cement concrete due to its characteristically high sulfur content, and thus unlike fly ash, it is rarely put to beneficial use. This paper presents the results of a study with the objective of developing beneficial uses for SDA material in building materials when combined with tire fiber reinforcement originating from a recycling process. Specifically, spray dryer ash was investigated for use as the primary or even the sole binding component in a mortar or concrete. This study differs from previous research in that it focuses on very high contents of spray dryer ash (80 to 100 percent in a hardened product. The overarching objective is to divert products that are normally sent to landfills and provide benefit to society in beneficial applications.

  16. Synthesis of a Cementitious Material Nanocement Using Bottom-Up Nanotechnology Concept: An Alternative Approach to Avoid CO2 Emission during Production of Cement

    Directory of Open Access Journals (Sweden)

    Byung Wan Jo

    2014-01-01

    Full Text Available The world’s increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic properties of the chemically synthesized nanocement were verified by the chemical composition analysis, setting time measurement, particle size distribution, fineness analysis, and SEM and XRD analyses. Finally, the performance of the nanocement was ensured by the fabrication and characterization of the nanocement based mortar. Comparing the results with the commercially available cement product, it is demonstrated that the chemically synthesized nanocement not only shows better physical and mechanical performance, but also brings several encouraging impacts to the society, including the reduction of CO2 emission and the development of sustainable construction material. A plausible reaction scheme has been proposed to explain the synthesis and the overall performances of the nanocement.

  17. Non-Destructive Testing for the In Situ Assessment of the Ionic Flux in Cementitious Materials

    Science.gov (United States)

    Tittarelli, Francesca; Pierpaoli, Mattia; Giosuè, Chiara; Ruello, M. Letizia

    2017-08-01

    The study deals with the design, calibration and testing of a diffusive sampling probe for in situ assessment of ion mobility in binder-based matrix. In parallel, leaching texts were conducted to compare the ions release obtained under equilibrium condition with the dynamic flux induced by the diffusive sampling probe. The probe contains an ionic exchange resin that acts as sink, causing a re-supply of ions from the solid to the solution phase, and inducing diffusion fluxes from the mortar through a thin diffusion chamber. The flux depends on the quantity of mobile ions in the solid phase and on the exchanging rate from solid phase to solution. By means of the in situ sampling with this diffusive probe, information about the interaction of materials with the environment can be obtained. This information is very useful for the environmental impact assessment of the material and its durability.

  18. Influence of the binder nature and the temperature on the chloride transport through cementitious materials

    International Nuclear Information System (INIS)

    Nguyen, Th.S.

    2006-09-01

    The objective of this work is to document the effect of the temperature on the chloride diffusion through cement-based materials. The chloride diffusion coefficient, the penetration profiles and the chloride interactions with the solid phase were highlighted. The materials were CEM I and CEM V/A mortars and pastes. They were cured in wet room (21 ± 2 C, 90% relative humidity) for 1 month in the case of CEM I and 3 months in the case of CEM V before the experiments started. The temperature levels were 5, 21, 35 and 80 C.In addition, microstructure analyses were carried on using X-rays diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The experimental results were then used to continue to develop the numerical code, MsDiff, developed in our research group. A good agreement between the numerical concentration profiles and the experimental ones was found. (author)

  19. Impact of carbonation on the durability of cementitious materials: water transport properties characterization

    Directory of Open Access Journals (Sweden)

    Le Bescop P.

    2013-07-01

    Full Text Available Within the context of long-lived intermediate level radioactive waste geological disposal, reinforced concrete would be used. In service life conditions, the concrete structures would be subjected to drying and carbonation. Carbonation relates to the reaction between carbon dioxide (CO2 and the main hydrates of the cement paste (portlandite and C-S-H. Beyond the fall of the pore solution pH, indicative of steel depassivation, carbonation induces mineralogical and microstructural changes (due to portlandite and C-S-H dissolution and calcium carbonate precipitation. This results in the modification of the transport properties, which can impact the structure durability. Because concrete durability depends on water transport, this study focuses on the influence of carbonation on water transport properties. In fact, the transport properties of sound materials are known but they still remain to be assessed for carbonated ones. An experimental program has been designed to investigate the transport properties in carbonated materials. Four hardened cement pastes, differing in mineralogy, are carbonated in an accelerated carbonation device (in controlled environmental conditions at CO2 partial pressure of about 3%. Once fully carbonated, all the data needed to describe water transport, using a simplified approach, will be evaluated.

  20. Temperature impact on cementitious materials carbonation - description of water transport influence

    International Nuclear Information System (INIS)

    Drouet, E.

    2010-11-01

    Carbonation is the major cause of degradation of reinforced concrete structures. It leads to rebar corrosion and cracking of the concrete cover. In the framework of radioactive waste management, cement-based materials used as building material for structures or containers would be simultaneously submitted to heating (due to the waste thermal output), subsequent drying and atmospheric carbon dioxide. Such environmental conditions are expected to modify the carbonation mechanisms (with respect to temperature). In order to describe their long-term evolution of material, a double approach was developed, combining the description of carbonation and drying for temperatures up to 80 C to complement available data at ambient temperature. The present work focuses on the durability study of four hardened cement pastes; two of them are derived from the reference formulations selected by Andra (CEM I and CEM V) and a low-pH mix. The first experimental campaign focuses on moisture transfer. The effect of temperature on drying is investigated through water vapour desorption experiments. The first desorption isotherms of four hardened cement pastes was characterized at 20, 50 and 80 C. The results show a significant influence of the temperature. For a given relative humidity (RH) the water content equilibrium is always reduced temperature is increased and the starting point of capillary condensation is shifted towards higher RHs. The experimental campaign is complemented through modelling activities. The impact of temperature on the first desorption isotherms is effectively described using the Clausius-Clapeyron equation (characterization of the isosteric heat of adsorption). The intrinsic permeability to water is evaluated through inverse analysis by reprocessing the experimental weight loss of initially saturated samples submitted to constant environmental conditions. The intrinsic permeability appears to increase with temperature in relation to the observed microstructure

  1. Electrical resistance tomography to monitor unsaturated moisture flow in cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Hallaji, Milad [Department of Civil Construction and Environmental Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Seppänen, Aku [Department of Applied Physics, University of Eastern Finland, Kuopio (Finland); Pour-Ghaz, Mohammad, E-mail: mpourghaz@ncsu.edu [Department of Civil Construction and Environmental Engineering, North Carolina State University, Raleigh, NC 27695 (United States)

    2015-03-15

    Traditionally the electrically-based assessment of the moisture flow in cement-based materials relies on two- or four-point measurements. In this paper, imaging of moisture distribution with electrical resistance tomography (ERT) is considered. Especially, the aim is to study whether ERT could give information on unsaturated moisture flows in cases where the flow is non-uniform. In the experiment, the specimens are monitored with ERT during the water ingress. The ERT reconstructions are compared with neutron radiographs, which provide high resolution information on the 2D distribution of the moisture. The results indicate that ERT is able to detect the moisture movement and to show approximately the shape and position of the water front even if the flow is nonuniform.

  2. CEM V based special cementitious materials investigated by means of SANS method. Preliminary results

    Science.gov (United States)

    Dragolici, A. C.; Balasoiu, M.; Orelovich, O. L.; Ionascu, L.; Nicu, M.; Soloviov, D. V.; Kuklin, A. I.; Lizunov, E. I.; Dragolici, F.

    2017-05-01

    The management of the radioactive waste assume the conditioning in a cement matrix as an embedding, stable, disposal material. Cement matrix is the first and most important engineering barrier against the migration in the environment of the radionuclides contained in the waste packages. Knowing how the microstructure develops is therefore desirable in order to assess the compatibility of radioactive streams with cement and predict waste form performance during storage and disposal. For conditioning wastes containing radioactive aluminum new formulas of low basicity cements, using coatings as a barrier between the metal and the conditioning environment or introducing a corrosion inhibitor in the matrix system are required. Preliminary microstructure investigation of such improved CEM V based cement matrix is reported.

  3. Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Eileen Hao Yu

    2010-08-01

    Full Text Available Direct alkaline alcohol fuel cells (DAAFCs have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of DAAFCs in alcohol oxidation and oxygen reduction are discussed. Despite the high energy densities available during the oxidation of polycarbon alcohols they are difficult to oxidise. Apart from methanol, the complete oxidation of other polycarbon alcohols to CO2 has not been achieved with current catalysts. Different types of catalysts, from conventional precious metal catalyst of Pt and Pt alloys to other lower cost Pd, Au and Ag metal catalysts are compared. Non precious metal catalysts, and lanthanum, strontium oxides and perovskite-type oxides are also discussed. Membranes like the ones used as polymer electrolytes and developed for DAAFCs are reviewed. Unlike conventional proton exchange membrane fuel cells, anion exchange membranes are used in present DAAFCs. Fuel cell performance with DAAFCs using different alcohols, catalysts and membranes, as well as operating parameters are summarised. In order to improve the power output of the DAAFCs, further developments in catalysts, membrane materials and fuel cell systems are essential.

  4. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Ince, C.

    2015-06-01

    Full Text Available The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs on water transport kinetics and mechanical properties of hydrated lime (CL90 and Portland cement (PC mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.El objetivo de este artículo es investigar el papel de los materiales cementantes suplementarios (SCMs en la cinética de transporte del agua y en las propiedades mecánicas de los morteros de cal hidratada (CL90 y cemento Portland. Las propiedades de la cal hidratada son significativamente diferentes a las del cemento y por lo tanto el control de las propiedades de los morteros frescos y endurecidos es fundamental en la optimización mortero/substrato en albañilería. Los parámetros estudiados en este trabajo son a menudo las principales barreras para el uso de la cal hidratada en la práctica de la construcción. Los resultados indican que la absortividad y el tiempo necesario para deshidratar morteros de cal hidratada recién mezclados pueden ser controlados cuando el conglomerante es parcialmente remplazado por SCMs. La resistencia a compresión de los morteros CL90 aumenta sistem

  5. The influence of rainwater composition on the conservation state of cementitious building materials.

    Science.gov (United States)

    Morillas, Héctor; Marcaida, Iker; Maguregui, Maite; Carrero, Jose Antonio; Madariaga, Juan Manuel

    2016-01-15

    Rainwater is one of the main pollution tracers around the world. There are many reasons that can explain the presence of high concentrations of certain hazardous elements (HEs) in the rainwater (traffic, marine port activities, industry, etc.). In this work, rainwater samples were collected at six different locations in the Metropolitan Bilbao (Basque Country, north of Spain) during November 2014. HE concentrations were determined by means of inductively coupled plasma mass spectrometry (ICP-MS) and anions by ion chromatography. The pH and redox potential values on these samples were also assessed. According to the obtained results, different trends along the estuary of Bilbao have been observed. To corroborate some hypothesis, thermodynamic simulations and correlation analyses were also carried out using quantitative data. These trends are closely related to the surrounding pollution and marine influence. Finally, in order to ascertain the influence of the Metropolitan Bilbao rainwater on buildings materials, a recent construction was characterized. Using techniques such as Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM–EDS) and Raman Spectroscopy, different types of sulfates and nitrates were observed.

  6. Hybrid Alkaline Cements: Bentonite-Opc Binders

    Directory of Open Access Journals (Sweden)

    Ines Garcia-Lodeiro

    2018-03-01

    Full Text Available Moderately alkaline activators can be used to formulate cementitious binders with a high Supplemetary Cementitious Materials (SCMs and a low portland cement content (hybrid alkaline cements. This study aimed to prepare hybrid alkaline cements containing large percentages of dehydroxylated bentonite (BT and small Portland cement (OPC fractions, with 5% Na2SO4 as a solid alkaline activator. The hydration kinetics of the pastes hydrated in water in the presence and absence of the solid activator were assessed by isothermal conduction calorimetry, whilst the reaction products were characterised with X-Ray Powder Diffraction (XRD and Fourier-transform Infrared Spectroscopy (FTIR. The presence of the alkaline activator hastened OPC and BT/OPC hydration: more heat of hydration was released, favouring greater initial bentonite reactivity. The portlandite forming during cement hydration reacted readily with the Na2SO4, raising medium alkalinity and enhancing bentonite dissolution and with it reaction product precipitation (primarily (N,C-A-S-H-like gels that co-exist with C-S-H- or C-A-S-H-like gels. The presence of sulfate ions favoured the formation of AFm-like phases. Preceding aspects accelerated the hydration reactions, with the formation of more reaction product and matrix densification. As a result, the 28 days Na2SO4 activated systems developed greater mechanical strength than the water-hydrated systems, with the 60% BT/40% OPC blends exhibiting higher compressive strength than the 100% OPC pastes.

  7. Evaluation of blends bauxite-calcination-method red mud with other industrial wastes as a cementitious material: Properties and hydration characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Na, E-mail: zhangna06@mails.tsinghua.edu.cn [State Key Lab of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu Xiaoming [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Sun Henghu [School of Engineering and Computer Science, University of the Pacific, Stockton, CA 95211 (United States); Li Longtu [State Key Lab of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2011-01-15

    Red mud is generated from alumina production, and its disposal is currently a worldwide problem. In China, large quantities of red mud derived from bauxite calcination method are being discharged annually, and its utilization has been an urgent topic. This experimental research was to evaluate the feasibility of blends red mud derived from bauxite calcination method with other industrial wastes for use as a cementitious material. The developed cementitious material containing 30% of the bauxite-calcination-method red mud possessed compressive strength properties at a level similar to normal Portland cement, in the range of 45.3-49.5 MPa. Best compressive strength values were demonstrated by the specimen RSFC2 containing 30% bauxite-calcination-method red mud, 21% blast-furnace slag, 10% fly ash, 30% clinker, 8% gypsum and 1% compound agent. The mechanical and physical properties confirm the usefulness of RSFC2. The hydration characteristics of RSFC2 were characterized by XRD, FTIR, {sup 27}Al MAS-NMR and SEM. As predominant hydration products, ettringite and amorphous C-S-H gel are principally responsible for the strength development of RSFC2. Comparing with the traditional production for ordinary Portland cement, this green technology is easier to be implemented and energy saving. This paper provides a key solution to effectively utilize bauxite-calcination-method red mud.

  8. Experimental studies on the inventory of cement-derived colloids in the pore water of a cementitious backfill material

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E

    2001-06-01

    The potential role of near-field colloids for the colloid-facilitated migration of radionuclides has stimulated investigations concerning the generation and presence of colloids in the near-field of a repository for low- and intermediate level waste (L/ILW). The highly gas permeable mortar (Nagra designation: mortar M1) is currently favoured as backfill material for the engineered barrier of the planned Swiss L/ILW repository. The cementitious backfill is considered to be a chemical environment with some potential for colloid generation. In a series of batch-style laboratory experiments the physico-chemical processes controlling the inventory of colloids in cement pore water of the backfill were assessed for chemical conditions prevailing in the initial stage of the cement degradation. In these experiments, backfill mortar M1 or quartz, respectively, which may be used as aggregate material for the backfill, were immersed in artificial cement pore water (a NaOH/KOH rich cement fluid). Colloid concentrations in the cement pore water were recorded as a function of time for different experimental settings. The results indicate that a colloid-colloid interaction process (coagulation) controlled the colloid inventory. The mass concentration of dispersed colloids was found to be typically lower than 0.02 ppm in undisturbed batch systems. An upper-bound value was estimated to be 0.1 ppm taking into account uncertainties on the measurements. To assess the potential for colloid generation in a dynamic system, colloid concentrations were determined in the pore water of a column filled with backfill mortar. The chemical conditions established in the mortar column corresponded to conditions observed in the second stage of the cement degradation (a Ca(OH){sub 2{sup -}} controlled cement system). In this dynamic system, the upper-bound value for the colloid mass concentration was estimated to be 0.1 ppm. Implications for radionuclide mobility were deduced taking into account the

  9. Ultrafine cementitious grout

    Science.gov (United States)

    Ahrens, Ernst H.

    1999-01-01

    An ultrafine cementitious grout in three particle grades containing Portland cement, pumice as a pozzolanic material and superplasticizer in the amounts of about 30 wt. % to about 70 wt. % Portland cement; from about 30 wt. % to about 70 wt. % pumice containing at least 70% amorphous silicon dioxide; and from 1.2 wt. % to about 5.0 wt. % superplasticizer. The superplasticizer is dispersed in the mixing water prior to the addition of dry grout and the W/CM ratio is about 0.4 to 1/1. The grout has very high strength and very low permeability with good workability. The ultrafine particle sizes allow for sealing of microfractures below 10 .mu.m in width.

  10. Radon exhalation of cementitious materials made with coal fly ash: Part 1 - scientific background and testing of the cement and fly ash emanation

    International Nuclear Information System (INIS)

    Kovler, K.; Perevalov, A.; Steiner, V.; Metzger, L.A.

    2005-01-01

    Increased interest in measuring radionuclides and radon concentrations in fly ash, cement and other components of building products is due to the concern of health hazards of naturally occurring radioactive materials (NORM). The current work focuses on studying the influence of fly ash (FA) on radon-exhalation rate (radon flux) from cementitious materials. The tests were carried out on cement paste specimens with different FA contents. The first part of the paper presents the scientific background and describes the experiments, which we designed for testing the radon emanation of the raw materials used in the preparation of the cement-FA pastes. It is found that despite the higher 226 Ra content in FA (more than 3 times, compared with Portland cement) the radon emanation is significantly lower in FA (7.65% for cement vs. 0.52% only for FA)

  11. Adhesives in Building--Lamination of Structural Timber Beams, Bonding of Cementitious Materials, Bonding of Gypsum Drywall Construction. Proceedings of a Conference of the Building Research Institute, Division of Engineering and Industrial Research (Spring 1960).

    Science.gov (United States)

    National Academy of Sciences - National Research Council, Washington, DC.

    The role of adhesives in building design is discussed. Three major areas are as follows--(1) lamination of structural timber beams, (2) bonding of cementitious materials, and (3) bonding of gypsum drywall construction. Topical coverage includes--(1) structural lamination today, (2) adhesives in use today, (3) new adhesives needed, (4) production…

  12. Information on Coordinated Research Project: Behaviours of Cementitious Materials in Multipurpose Packaging for Transportation, Long Term Storage and Disposal

    International Nuclear Information System (INIS)

    Meyer, W.

    2013-01-01

    The durability of concrete is an important issue and the imaging thereof plays a major part in the understanding of the characteristics of concrete. The ability of concrete to withstand the penetration of liquid and oxygen contribute to the durability of concrete. The durability of concrete, can in turn, be quantified by certain characteristics such as the porosity, sorptivity and permeability. For non-destructive analytical quantification of these parameters, neutron radiography was developed and validated against conventional measurements. Results indicated that because the neutron attenuation of the concrete and water differs to a significant degree, the movement of water in concrete (sorptivity) could be visualized. The neutron radiography results were validated against conventional measurements and excellent correlation was found. To improve the characteristics of current grout/cement matrixes used for the encapsulation of radioactive waste, different cement mixtures Cem 1 (96% OPC) and Cem 5 (mixture of 20% fly ash, 20% blast furnace slag and 60% cement powder) with the addition of different admixtures, inert fibre material and plasticizers were investigated. With no formal guidance from the WAC of the disposal site, it was decided that the following matrix requirements have to be met in order to qualify a possible matrix for radioactive waste immobilisation research: -Total porosity less than 10% (Implies a compression strength higher than 50 MPa) and -Sorptivity rate lower than 2.5 g/h (Implies pore structure not interlinked). Results with radioactive waste (excluding organic waste) indicated an admixture of bitumen or asphalt in CEM 1 (96% OPC cement) has the best characteristics and comply with the specified requirement. Treatment of contaminated organic waste which is a non standard waste stream proved to be difficult and direct disposal is also not an option because many organic liquids are immiscible. Cementation is generally not an option as the

  13. PARTNERSHIP FOR THE DEVELOPMENT OF NEXT GENERATION SIMULATION TOOLS TO EVALUATE CEMENTITIOUS BARRIERS AND MATERIALS USED IN NUCLEAR APPLICATION - 8388

    International Nuclear Information System (INIS)

    Langton, C; Richard Dimenna, R

    2008-01-01

    The US DOE has initiated a multidisciplinary cross cutting project to develop a reasonable and credible set of tools to predict the structural, hydraulic and chemical performance of cement barriers used in nuclear applications over extended time frames (e.g., > 100 years for operating facilities and > 1000 years for waste management). A partnership that combines DOE, NRC, academia, private sector, and international expertise has been formed to accomplish the project objectives by integrating existing information and realizing advancements where necessary. The set of simulation tools and data developed under this project will be used to evaluate and predict the behavior of cementitious barriers used in near surface engineered waste disposal systems, e.g., waste forms, containment structures, entombments and environmental remediation, including decontamination and decommissioning (D and D) activities. The simulation tools will also support analysis of structural concrete components of nuclear facilities (spent fuel pools, dry spent fuel storage units, and recycling facilities, e.g., fuel fabrication, separations processes). Simulation parameters will be obtained from prior literature and will be experimentally measured under this project, as necessary, to demonstrate application of the simulation tools for three prototype applications (waste form in concrete vault, high level waste tank grouting, and spent fuel pool). Test methods and data needs to support use of the simulation tools for future applications will be defined. This is a national issue that affects all waste disposal sites that use cementitious waste forms and structures, decontamination and decommissioning activities, service life determination of existing structures, and design of future public and private nuclear facilities. The problem is difficult because it requires projecting conditions and responses over extremely long times. Current performance assessment analyses show that engineered barriers

  14. Review of durability of cementitious engineered barriers in repository environments

    International Nuclear Information System (INIS)

    Parrott, L.J.; Lawrence, C.D.

    1992-01-01

    This report is concerned with the durability of cementitious engineered barriers in a repository for low and intermediate level nuclear waste. Following the introduction the second section of the review identifies the environmental conditions associated with a deep, hard rock repository for ILW and LLW that are relevant to the durability of cementitious barriers. Section three examines the microstructure and macrostructure of cementitious materials and considers the physical and chemical processes of radionuclide immobilization. Potential repository applications and compositions of cementitious materials are reviewed in Section four. The main analysis of durability is dealt with in Section five. The different types of cementitious barrier are considered separately and their most probable modes of degradation are analysed. Concluding remarks that highlight critical technical matters are given in Section six. (author)

  15. Modeling aging of cementitious pore structure

    NARCIS (Netherlands)

    Ukrainczyk, N.; Koenders, E.A.B.

    2014-01-01

    Coupled reactive-transport processes in cementitious materials play a crucial role in the aging process pf building materials. Up to now, the effect of aging on microstructure and evolution of it’s properties, in three dimensions, was studied only by dissolution of certain phases at random

  16. Disassembly Properties of Cementitious Finish Joints Using an Induction Heating Method

    Science.gov (United States)

    Ahn, Jaecheol; Noguchi, Takafumi; Kitagaki, Ryoma

    2015-01-01

    Efficient maintenance and upgrading of a building during its lifecycle are difficult because a cementitious finish uses materials and parts with low disassembly properties. Additionally, the reuse and recycling processes during building demolition also present numerous problems from the perspective of environmental technology. In this study, an induction heating (IH) method was used to disassemble cementitious finish joints, which are widely used to join building members and materials. The IH rapidly and selectively heated and weakened these joints. The temperature elevation characteristics of the cementitious joint materials were measured as a function of several resistor types, including wire meshes and punching metals, which are usually used for cementitious finishing. The disassembly properties were evaluated through various tests using conductive resistors in cementitious joints such as mortar. When steel fiber, punching metal, and wire mesh were used as conductive resistors, the cementitious modifiers could be weakened within 30 s. Cementitious joints with conductive resistors also showed complete disassembly with little residual bond strength.

  17. Adesão em materiais cimentícios: "In-built nanotechnology" Adhesion in cementitious materials: In-built nanotechnology

    Directory of Open Access Journals (Sweden)

    H. L. Rossetto

    2009-06-01

    Full Text Available A Engenharia de Materiais propiciou os avanços mais notáveis em termos do desempenho mecânico dos materiais cimentícios nas últimas décadas, por meio das técnicas de conformação e do projeto da microestrutura. Com isso foi demonstrada ser equivocada a idéia de que baixas resistências mecânicas seriam inerentes aos materiais cimentícios. No entanto, pouco ainda se sabe a respeito de um parâmetro físico-químico que poderá nos conduzir a novos avanços: a adesão entre as fases hidratadas. Logo, o objetivo do presente trabalho é investigar a adesão com o intuito de ampliar o entendimento sobre seu papel na resistência mecânica dos materiais cimentícios. Os resultados indicaram que a resistência mecânica desses materiais é governada por moléculas de água confinadas em películas nanométricas entre as superfícies das fases cimentícias hidratadas. Em outras palavras, essa pode ser uma contribuição para tornar viável a nanotecnologia desses materiais por meio de um tema até então pouco explorado: a adesão por água confinada.The Materials Engineering afforded the greatest known advances on the mechanical performance of cementitious materials in the latest decades, by casting techniques and microstructural design. Therewith, it was demonstrated to be inadequate the idea that low mechanical strengths should be inherent to cement-based materials. Nevertheless, another promising parameter still remains in the early stages of understanding: the adhesion. Thus, this paper aims to investigate adhesion in order to get an in-depth understanding about its role on the mechanical strength of cementitious materials. According to the experimental evidences, the mechanical strength of such materials is ruled by water molecules which are confined in nanolayers by the hydrated surfaces. These results provided helpful insights on in-built nanotechnology able to render high performance materials through a so far little explored subject

  18. Research and Development of a New Silica-Alumina Based Cementitious Material Largely Using Coal Refuse for Mine Backfill, Mine Sealing and Waste Disposal Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Henghu Sun; Yuan Yao

    2012-06-29

    Coal refuse and coal combustion byproducts as industrial solid waste stockpiles have become great threats to the environment. To activate coal refuse is one practical solution to recycle this huge amount of solid waste as substitute for Ordinary Portland Cement (OPC). The central goal of this project is to investigate and develop a new silica-alumina based cementitious material largely using coal refuse as a constituent that will be ideal for durable construction, mine backfill, mine sealing and waste disposal stabilization applications. This new material is an environment-friendly alternative to Ordinary Portland Cement. The main constituents of the new material are coal refuse and other coal wastes including coal sludge and coal combustion products (CCPs). Compared with conventional cement production, successful development of this new technology could potentially save energy and reduce greenhouse gas emissions, recycle vast amount of coal wastes, and significantly reduce production cost. A systematic research has been conducted to seek for an optimal solution for enhancing pozzolanic reactivity of the relatively inert solid waste-coal refuse in order to improve the utilization efficiency and economic benefit as a construction and building material.

  19. Contribution to the study of cementitious and clayey materials behaviour in the context of deep geological disposal: transport aspect, durability and thermo-hydro-mechanical behaviour

    International Nuclear Information System (INIS)

    Galle, C.

    2011-07-01

    Deep geological formation disposal is the reference solution in France for the management of medium and high activities radioactive waste. In this context, to demonstrate the feasibility of such a disposal, it is necessary to evaluate the long-term performances and the behaviour of the materials engaged in the elaboration of engineered barrier systems (EBS) and waste package elements. The studies mentioned and synthesized in this HDR thesis focused mainly on the convective transport of gas (under pressure gradient) in cementitious matrices, by coupling microstructure aspect (porosity/pores sizes distribution) and hydric environment (water saturation). Works on physico-chemical durability allowed the description of the chemical degradation of cement-based materials in extreme conditions using ammonium nitrate, to increase the materials damaging processes in order to identify functional margins. In relationship with the interim storage management phase, studies related to the behaviour and characterization of concrete submitted to high temperatures (up to 400 C) were also described. Finally, results concerning the gas (H 2 ) overpressure resistance of engineered barriers made of compacted clays were summarized. (author)

  20. Development of rock bolt grout and shotcrete for rock support and corrosion of steel in low-pH cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    Boden, Anders (Vattenfall Power Consultant AB, Vaellingby (Sweden)); Pettersson, Stig (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2011-04-15

    It is foreseen that cementitious products will be utilized in the construction of the final repository. The use of conventional cementitious material creates pulses in the magnitude of pH 12.13 in the leachates and release alkalis. Such a high pH is detrimental mainly to impairment of bentonite functioning, but also to possibly enhanced dissolution of spent fuel and alteration of fracture filling materials. It also complicates the safety analysis of the repository, as the effect of a high pH-plume should be considered in the evaluation. As no reliable pH-plume models exist, the use of products giving a pH below 11 in the leachates facilitates the safety analysis, although limiting the amount of low-pH cement is recommended. In earlier studies it was found that shotcreting, standard casting and rock bolting with low-pH cement (pH . 11 in the leachate) should be possible without any major development work. This report summarizes the results of development work done during 2008 and 2009 in the fields of low-pH rock bolt grout, low-pH shotcrete and steel corrosion in low-pH concrete. Development of low-pH rock bolt grout mixes and laboratory testing of the selected grout was followed by installation of twenty rock bolts for rock support at Aspo HRL using the chosen low-pH grout. The operation was successful and the bolts and grout are subject to follow up the next ten years. Low-pH shotcrete for rock support was initially developed within the ESDRED project, which was an Integrated Project within the European Commission sixth framework for research and technological development. ESDRED is an abbreviation for Engineering Studies and Demonstrations of Repository Designs. ESDRED was executed from 1st February 2004 to 31st January 2009. The development of the mix design described in this report was based on the results from ESDRED. After laboratory testing of the chosen mix, it was field tested in niche NASA 0408A at Aspo HRL. Further, some areas in the TASS-tunnel were

  1. Alkaline degradation of organic materials contained in TRU wastes under repository conditions

    International Nuclear Information System (INIS)

    Otsuka, Yoshiki; Banba, Tsunetaka

    2007-09-01

    Alkaline degradation tests for 9 organic materials were conducted under the conditions of TRU waste disposal: anaerobic alkaline conditions. The tests were carried out at 90degC for 91 days. The sample materials for the tests were selected from the standpoint of constituent organic materials of TRU wastes. It has been found that cellulose and plastic solidified products are degraded relatively easily and that rubbers are difficult to degrade. It could be presumed that the alkaline degradation of organic materials occurs starting from the functional group in the material. Therefore, the degree of degradation difficulty is expected to be dependent on the kinds of functional group contained in the organic material. (author)

  2. Recycling of cementitious scrap inert in the manufacture of fiber composite materials; Riciclo dei materiali inerti cementizi per la produzione di materiali compositi fibrosi

    Energy Technology Data Exchange (ETDEWEB)

    Buccolieri, G. [Lecce Univ. (Italy). Dipt. Scienza dei Materiali; De Luca, F.; De Stefano, L. [Ente Nazionale per l' Energia Elettrica, Brindisi (Italy). Area Ambiente; Paglietti, F. [ECOTEC Srl, Rome (Italy); Plescia, P. [Consiglio Nazionale delle Ricerche, Rome (Italy). Istituto Trattamento Minerali

    1999-04-01

    The disposal of cementitious scrap materials, coming from demolition and construction actives, it is a problem of enormous environmental impact, either for the quantities in play, either for the lack of the fit sites to receive them. In the present work is described a recycling technology of such residual for the production of fiber composites, as thermo acoustical insulating materials or fiber-reinforced, that could be applied also to the cement-asbestos like the eter nit. In this case, inertization and re-use of refusal, also otherwise classified like special or dangerous according to his state of preservation, is archived. [Italian] Lo smaltimento dei materiali inerti cementizi, derivanti da attivita' di demolizione e costruzione, e' un problema di enorme rilevanza ambientale, sia per i quantitativi in gioco sia per la mancanza di siti a riceverli. Nel presente lavoro e' descritta una metodologia di riciclo di tali residui per la produzione di materiali compositi fibrosi, come isolanti termoacustici e fibrorinforzanti, che puo' essere applicata anche al cemento animato tipo eternit. In questo caso si ottiene anche l'inertizzazione ed il riutilizzo di un rifiuto altrimenti classificato come speciale o pericoloso a seconda del suo stato di conservazione.

  3. Laboratory evaluation of 100% fly ash cementitious systems containing Ekkomaxx.

    Science.gov (United States)

    2013-09-01

    Long-lasting, durable concrete is a must have for DOTs in todays construction : and economic climate. Many entities are turning to alternative concrete : mixtures, such as ternary mixtures, lower w/cm ratios, lower cementitious : materials cont...

  4. Temporary Cementitious Sealers in Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Butcher, T.; Brothers, L.; Bour, D.

    2011-12-31

    Unlike conventional hydrothennal geothermal technology that utilizes hot water as the energy conversion resources tapped from natural hydrothermal reservoir located at {approx}10 km below the ground surface, Enhanced Geothermal System (EGS) must create a hydrothermal reservoir in a hot rock stratum at temperatures {ge}200 C, present in {approx}5 km deep underground by employing hydraulic fracturing. This is the process of initiating and propagating a fracture as well as opening pre-existing fractures in a rock layer. In this operation, a considerable attention is paid to the pre-existing fractures and pressure-generated ones made in the underground foundation during drilling and logging. These fractures in terms of lost circulation zones often cause the wastage of a substantial amount of the circulated water-based drilling fluid or mud. Thus, such lost circulation zones must be plugged by sealing materials, so that the drilling operation can resume and continue. Next, one important consideration is the fact that the sealers must be disintegrated by highly pressured water to reopen the plugged fractures and to promote the propagation of reopened fractures. In response to this need, the objective of this phase I project in FYs 2009-2011 was to develop temporary cementitious fracture sealing materials possessing self-degradable properties generating when {ge} 200 C-heated scalers came in contact with water. At BNL, we formulated two types of non-Portland cementitious systems using inexpensive industrial by-products with pozzolanic properties, such as granulated blast-furnace slag from the steel industries, and fly ashes from coal-combustion power plants. These byproducts were activated by sodium silicate to initiate their pozzolanic reactions, and to create a cemetitious structure. One developed system was sodium silicate alkali-activated slag/Class C fly ash (AASC); the other was sodium silicate alkali-activated slag/Class F fly ash (AASF) as the binder of temper

  5. Mobile colloid generation induced by a cementitious plume: mineral surface-charge controls on mobilization.

    Science.gov (United States)

    Li, Dien; Kaplan, Daniel I; Roberts, Kimberly A; Seaman, John C

    2012-03-06

    Cementitious materials are increasingly used as engineered barriers and waste forms for radiological waste disposal. Yet their potential effect on mobile colloid generation is not well-known, especially as it may influence colloid-facilitated contaminant transport. Whereas previous papers have studied the introduction of cement colloids into sediments, this study examined the influence of cement leachate chemistry on the mobilization of colloids from a subsurface sediment collected from the Savannah River Site, USA. A sharp mobile colloid plume formed with the introduction of a cement leachate simulant. Colloid concentrations decreased to background concentrations even though the aqueous chemical conditions (pH and ionic strength) remained unchanged. Mobile colloids were mainly goethite and to a lesser extent kaolinite. The released colloids had negative surface charges and the mean particle sizes ranged primarily from 200 to 470 nm. Inherent mineralogical electrostatic forces appeared to be the controlling colloid removal mechanism in this system. In the background pH of ~6.0, goethite had a positive surface charge, whereas quartz (the dominant mineral in the immobile sediment) and kaolinite had negative surface charges. Goethite acted as a cementing agent, holding kaolinite and itself onto the quartz surfaces due to the electrostatic attraction. Once the pH of the system was elevated, as in the cementitious high pH plume front, the goethite reversed to a negative charge, along with quartz and kaolinite, then goethite and kaolinite colloids were mobilized and a sharp spike in turbidity was observed. Simulating conditions away from the cementitious source, essentially no colloids were mobilized at 1:1000 dilution of the cement leachate or when the leachate pH was ≤ 8. Extreme alkaline pH environments of cementitious leachate may change mineral surface charges, temporarily promoting the formation of mobile colloids.

  6. Characterization and application of automated in-vacuum PIXE/EBS system for direct analysis of chloride and sulfate ions attack in cementitious materials

    Science.gov (United States)

    Rihawy, M. S.; Alwazzeh, M.; Abbas, K.

    2018-01-01

    Ion beam analysis (IBA) techniques (Particle Induced X-ray Emission, PIXE and Elastic Backscattering Spectrometry, EBS), were applied to investigate chloride and sulfate ions diffusion into laboratory prepared mortar samples. Development and characterization of an automated in-vacuum macro PIXE/EBS system is thoroughly discussed. Depth profile information of both chloride and sulfate ions in laboratory prepared mortar samples, after immersion in sea water for nine months, was rapidly and easily obtained at fairly low cost and with standardless analysis, demonstrating the value of the application of IBA to elemental depth profiling in cementitious materials. Chloride and sulfate depth profiles were obtained for two sets of mortar samples, one prepared with different water/cement (W/C) ratios and the other with different sand/cement (S/C) ratios. Results showed higher diffusion rates of both chloride and sulfate ions when both ratios are increased. Additionally, the W/C ratio has a stronger influence in both sulfate and chloride penetration than the S/C ratio, and chloride ions penetrate faster than sulfates. Advantages and limitations of applying IBA techniques in this investigation are discussed. The comparison between PIXE and other X-ray based analytical techniques, namely X-ray fluorescence (XRF) and energy and wavelength dispersive X-rays (EDX/WDX), as well as other traditional wet chemical methods is reviewed, and industrial applications are discussed.

  7. High-Performance Cementitious Matrix using Carbon Nanofibers

    Directory of Open Access Journals (Sweden)

    Muhammad Maqbool Sadiq Awan

    2017-03-01

    Full Text Available Graphite nanomaterials would realize their reinforcement potential within cement-based materials when they are thoroughly dispersed and effectively bonded to cement hydrates. Thorough dispersion of graphite nanomaterials in the fresh cementitious matrix encounters challenges associated with the hydrophobic nature of nanomaterial surfaces and their strong tendency towards agglomeration via attractive van der Waals forces. Effective interfacial interactions with cement hydrates are further challenged by the relatively inert nature of nanomaterial surfaces. An experimental program was conducted with the objective of effectively utilizing both acid-oxidized and pristine carbon nanofibers towards reinforcement of high-performance cementitious pastes. Hybrid reinforcement systems comprising optimum volume fraction of carbon nanofibers and micro-scale fibers were also evaluated in cementitious matrices. The improvements in nanofiber dispersion and interfacial interactions resulting from acid-oxidation and use of proper dispersion techniques were found to bring about significant gains in the engineering properties of high-performance cementitious materials.

  8. The solubility of nickel and its migration through the cementitious backfill of a geological disposal facility for nuclear waste.

    Science.gov (United States)

    Felipe-Sotelo, M; Hinchliff, J; Field, L P; Milodowski, A E; Holt, J D; Taylor, S E; Read, D

    2016-08-15

    This work describes the solubility of nickel under the alkaline conditions anticipated in the near field of a cementitious repository for intermediate level nuclear waste. The measured solubility of Ni in 95%-saturated Ca(OH)2 solution is similar to values obtained in water equilibrated with a bespoke cementitious backfill material, on the order of 5×10(-7)M. Solubility in 0.02M NaOH is one order of magnitude lower. For all solutions, the solubility limiting phase is Ni(OH)2; powder X-ray diffraction and scanning transmission electron microscopy indicate that differences in crystallinity are the likely cause of the lower solubility observed in NaOH. The presence of cellulose degradation products causes an increase in the solubility of Ni by approximately one order of magnitude. The organic compounds significantly increase the rate of Ni transport under advective conditions and show measurable diffusive transport through intact monoliths of the cementitious backfill material. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Cementitious yttria products

    Energy Technology Data Exchange (ETDEWEB)

    Holcombe, C.E.

    1978-03-01

    An investigation has been made of the physical properties and formation conditions of cements formed in the yttria/salt/water system. Cementitious binders were of the nominal Y/sub 2/(OH)/sub 5/X.H/sub 2/O type (where X represents the Cl/sup -/ or NO/sub 3//sup -/). An ammonium nitrate-produced yttria cement was shown to be sinterable and was demonstrated to form very refractory castable concretes with zirconia or alumina aggregates.

  10. Cementitious yttria products

    International Nuclear Information System (INIS)

    Holcombe, C.E.

    1978-03-01

    An investigation has been made of the physical properties and formation conditions of cements formed in the yttria/salt/water system. Cementitious binders were of the nominal Y 2 (OH) 5 X.H 2 O type (where X represents the Cl - or NO 3 - ). An ammonium nitrate-produced yttria cement was shown to be sinterable and was demonstrated to form very refractory castable concretes with zirconia or alumina aggregates

  11. Magnesium alloys and graphite wastes encapsulated in cementitious materials: Reduction of galvanic corrosion using alkali hydroxide activated blast furnace slag

    International Nuclear Information System (INIS)

    Chartier, D.; Muzeau, B.; Stefan, L.; Sanchez-Canet, J.; Monguillon, C.

    2017-01-01

    Highlights: • Embedded in cement, magnesium is corroded by residual water present in porosity of the matrix. • Corrosion is enhanced by galvanic phenomenon when magnesium is in contact with graphite. • Galvanic corrosion of magnesium in contact with graphite debris is shown to be severe with ordinary Portland cement. • Galvanic corrosion is significantly lowered in high alkali medium such as sodium hydroxide. • Sodium hydroxide activated blast furnace slag is a convenient binder to embed magnesium. - Abstract: Magnesium alloys and graphite from spent nuclear fuel have been stored together in La Hague plant. The packaging of these wastes is under consideration. These wastes could be mixed in a grout composed of industrially available cement (Portland, calcium aluminate…). Within the alkaline pore solution of these matrixes, magnesium alloys are imperfectly protected by a layer of Brucite resulting in a slow corrosion releasing hydrogen. As the production of this gas must be considered for the storage safety, and the quality of wasteform, it is important to select a cement matrix capable of lowering the corrosion kinetics. Many types of calcium based cements have been tested and most of them have caused strong hydrogen production when magnesium alloys and graphite are conditioned together because of galvanic corrosion. Exceptions are binders based on alkali hydroxide activated ground granulated blast furnace slag (BFS) which are presented in this article.

  12. Magnesium alloys and graphite wastes encapsulated in cementitious materials: Reduction of galvanic corrosion using alkali hydroxide activated blast furnace slag

    Energy Technology Data Exchange (ETDEWEB)

    Chartier, D., E-mail: david.chartier@cea.fr [Commissariat à l' Energie Atomique et aux Energies Alternatives, CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze (France); Muzeau, B. [DEN-Service d’Etude du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Stefan, L. [AREVA NC/D& S - France/Technical Department, 1 place Jean Millier 92084 Paris La Défense (France); Sanchez-Canet, J. [Commissariat à l' Energie Atomique et aux Energies Alternatives, CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze (France); Monguillon, C. [DEN-Service d’Etude du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France)

    2017-03-15

    Highlights: • Embedded in cement, magnesium is corroded by residual water present in porosity of the matrix. • Corrosion is enhanced by galvanic phenomenon when magnesium is in contact with graphite. • Galvanic corrosion of magnesium in contact with graphite debris is shown to be severe with ordinary Portland cement. • Galvanic corrosion is significantly lowered in high alkali medium such as sodium hydroxide. • Sodium hydroxide activated blast furnace slag is a convenient binder to embed magnesium. - Abstract: Magnesium alloys and graphite from spent nuclear fuel have been stored together in La Hague plant. The packaging of these wastes is under consideration. These wastes could be mixed in a grout composed of industrially available cement (Portland, calcium aluminate…). Within the alkaline pore solution of these matrixes, magnesium alloys are imperfectly protected by a layer of Brucite resulting in a slow corrosion releasing hydrogen. As the production of this gas must be considered for the storage safety, and the quality of wasteform, it is important to select a cement matrix capable of lowering the corrosion kinetics. Many types of calcium based cements have been tested and most of them have caused strong hydrogen production when magnesium alloys and graphite are conditioned together because of galvanic corrosion. Exceptions are binders based on alkali hydroxide activated ground granulated blast furnace slag (BFS) which are presented in this article.

  13. Self-Healing Efficiency of Cementitious Materials Containing Microcapsules Filled with Healing Adhesive: Mechanical Restoration and Healing Process Monitored by Water Absorption

    Science.gov (United States)

    Li, Wenting; Jiang, Zhengwu; Yang, Zhenghong; Zhao, Nan; Yuan, Weizhong

    2013-01-01

    Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks. PMID:24312328

  14. Self-healing efficiency of cementitious materials containing microcapsules filled with healing adhesive: mechanical restoration and healing process monitored by water absorption.

    Directory of Open Access Journals (Sweden)

    Wenting Li

    Full Text Available Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.

  15. Impact of cementitious materials decalcification on transfer properties: application to radioactive waste deep repository; Influence de la decalcification de materiaux cimentaires sur les proprietes de transfert: application au stockage profond de dechets radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Perlot, C

    2005-09-15

    Cementitious materials have been selected to compose the engineering barrier system (EBS) of the French radioactive waste deep repository, because of concrete physico-chemical properties: the hydrates of the cementitious matrix and the pH of the pore solution contribute to radionuclides retention; furthermore the compactness of these materials limits elements transport. The confinement capacity of the system has to be assessed while a period at least equivalent to waste activity (up to 100.000 years). His durability was sustained by the evolution of transfer properties in accordance with cementitious materials decalcification, alteration that expresses structure long-term behavior. Then, two degradation modes were carried out, taking into account the different physical and chemical solicitations imposed by the host formation. The first mode, a static one, was an accelerated decalcification test using nitrate ammonium solution. It replicates the EBS alteration dues to underground water. Degradation kinetic was estimated by the amount of calcium leached and the measurement of the calcium hydroxide dissolution front. To evaluate the decalcification impact, samples were characterized before and after degradation in term of microstructure (porosity, pores size distribution) and of transfer properties (diffusivity, gas and water permeability). The influence of cement nature (ordinary Portland cement, blended cement) and aggregates type (lime or siliceous) was observed: experiments were repeated on different mortars mixes. On this occasion, an essential reflection on this test metrology was led. The second mode, a dynamical degradation, was performed with an environmental permeameter. It recreates the EBS solicitations ensured during the re-saturation period, distinguished by the hydraulic pressure imposed by the geologic layer and the waste exothermicity. This apparatus, based on triaxial cell functioning, allows applying on samples pressure drop between 2 and 10 MPa and

  16. Effect of root canal filling materials containing calcium hydroxide on the alkalinity of root dentin.

    Science.gov (United States)

    Staehle, H J; Spiess, V; Heinecke, A; Müller, H P

    1995-08-01

    The effect of root canal filling pastes containing calcium oxide resp. calcium hydroxide on the alkalinity of extracted human teeth was investigated using a colour indicator (cresol red). An aqueous suspension of calcium hydroxide (Pulpdent), which is normally used for temporary root canal filling, most consistently produced alkalinity. Removal of the smear layer following instrumentation of the root canal led to increased proportion of alkaline-positive spots in dentinal locations distant from the canal. A clearly smaller effect was found with a calcium salicylate cement (Sealapex) and an oil-paste (Gangraena Merz), both of which are available for definite root canal fillings. Following removal of the smear layer, these hard-setting preparations caused moderate alkalinity in dentin adjacent to the canal but no effect was observed in locations more distant from the canal. Neither at locations adjacent to nor distant from the root canal was alkalinity found when another calcium salicylate cement (Apexit) was used. Apparently the release of hydroxyl ions into root dentin from calcium hydroxide containing root canal filling materials is not solely influenced by the absolute amount of calcium hydroxide, but also depends on other ingredients which variably inhibit the release of these ions.

  17. Investigation of Self Consolidating Concrete Containing High Volume of Supplementary Cementitious Materials and Recycled Asphalt Pavement Aggregates

    Science.gov (United States)

    Patibandla, Varun chowdary

    The use of sustainable technologies such as supplementary cementitiuous materials (SCMs), and/or recycled materials is expected to positively affect the performance of concrete mixtures. However, it is important to study and qualify such mixtures and check if the required specifications of their intended application are met before they can be implemented in practice. This study presents the results of a laboratory investigation of Self Consolidating concrete (SCC) containing sustainable technologies. A total of twelve concrete mixtures were prepared with various combinations of fly ash, slag, and recycled asphalt pavement (RAP). The mixtures were divided into three groups with constant water to cementitiuous materials ratio of 0.37, and based on the RAP content; 0, 25, and 50% of coarse aggregate replaced by RAP. All mixtures were prepared to achieve a target slump flow equal to or higher than 500 mm (24in). A control mixture for each group was prepared with 100% Portland cement whereas all other mixtures were designed to have up to 70% of portland cement replaced by a combination of supplementary cementitiuous materials (SCMs) such as class C fly ash and granulated blast furnace slag. The properties of fresh concrete investigated in this study include flowability, deformability; filling capacity, and resistance to segregation. In addition, the compressive strength at 3, 14, and 28 days, the tensile strength, and the unrestrained shrinkage up to 80 days was also investigated. As expected the inclusion of the sustainable technologies affected both fresh and hardened concrete properties. Analysis of the experimental data indicated that inclusion of RAP not only reduces the ultimate strength, but it also affected the compressive strength development rate. Moreover, several mixes satisfied compressive strength requirements for pavements and bridges; those mixes included relatively high percentages of SCMs and RAP. Based on the results obtained in this study, it is not

  18. Evaluation of Microstructure and Transport Properties of Deteriorated Cementitious Materials from Their X-ray Computed Tomography (CT) Images.

    Science.gov (United States)

    Promentilla, Michael Angelo B; Cortez, Shermaine M; Papel, Regina Anne Dc; Tablada, Bernadette M; Sugiyama, Takafumi

    2016-05-19

    Pore structure, tortuosity and permeability are considered key properties of porous materials such as cement pastes to understand their long-term durability performance. Three-dimensional image analysis techniques were used in this study to quantify pore size, effective porosity, tortuosity, and permeability from the X-ray computed tomography (CT) images of deteriorated pastes that were subjected to accelerated leaching test. X-ray microtomography is a noninvasive three-dimensional (3D) imaging technique which has been recently gaining attention for material characterization. Coupled with 3D image analysis, the digitized pore can be extracted and computational simulation can be applied to the pore network to measure relevant microstructure and transport properties. At a spatial resolution of 0.50 μm, the effective porosity (ψ e ) was found to be in the range of 0.04 to 0.33. The characteristic pore size ( d ) using a local thickness algorithm was found to be in the range of 3 to 7 μm. The geometric tortuosity (τ g ) based on a 3D random walk simulation in the percolating pore space was found to be in the range of 2.00 to 7.45. The water permeability values ( K ) using US NIST Permeability Stokes Solver range from an order of magnitudes of 10 -14 to 10 -17 m². Indications suggest that as effective porosity increases, the geometric tortuosity increases and the permeability decreases. Correlation among these microstructure and transport parameters is also presented in this study.

  19. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions

    International Nuclear Information System (INIS)

    Iriya, K.; Fujii, K.; Kubo, H.

    2002-02-01

    The chemical conditions of TRU waste repository were estimated as alkaline conditions effected by cementitious materials. And, some TRU wastes include soluble nitrate salt, we have to consider the repository conditions might be high ionic strength condition leaching of nitrate salt. In this study, experimental studies were carried out to evaluate hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions. The followings results were obtained for bentonite. 1) In the immersion experiments of bentonite in hyper alkaline fluids with and without nitrate, the disappearance of montmorillonite of bentonite was observed and CSH formation was found after 30 days. In hyper alkaline fluid with nitrate, minerals at θ=37 nm by XRD was identified. 2) Significant effects of hyper alkaline on hydraulic conductivity of compacted bentonite were not observed. However, hydraulic conductivities of hyper alkaline fluid with nitrate and ion exchanged bentonite increased. In hyper alkaline with nitrate, more higher hydraulic conductivities of exchanged bentonite were measured. The followings results were obtained for rock. 1) In the immersion experiments of crushed tuff in hyper alkaline fluids with and without nitrate, CSH and CASH phases were observed. 2) The hydraulic conductivity of tuff in hyper alkaline fluids decreased gradually. Finally, hyper alkaline flow in tuff stopped after 2 months and hyper alkaline flow with nitrate stopped shorter than without nitrate. In the results of analysis of tuff after experiment, we could identified secondary minerals, but we couldn't find the clogging evidence of pores in tuff by secondary minerals. (author)

  20. Large-scale Experiment for Water and Gas Transport in Cementitious Backfill Materials (Phase 1 ): COLEX I

    International Nuclear Information System (INIS)

    Mayer, G.; Wittmann, F.H.; Moetsch, H.A.

    1998-05-01

    In the planned Swiss repository for low- and intermediate-level radioactive waste, the voids between the waste containers will be backfilled with a highly permeable mortar (NAGRA designation: mortar M1 ). As well as providing mechanical stability through filling of voids and sorbing radionuclides, the mortar must divert gases formed in the repository as a result of corrosion into the neighbouring host rock. This will prevent damage which could be caused by excess pressure on the repository structures. Water transport, which is coupled to gas transport, is also of interest. The former is responsible for the migration of radionuclides. Up till now, numerical simulations for a repository situation were carried out using transport parameters determined for small samples in the laboratory. However, the numerical simulations still had to be validated by a large-scale experiment. The investigations presented here should close this gap. Investigations into gas and water transport were carried out using a column (up to 5.4 m high) filled with backfill mortar. The column has a modular construction and can be sealed at the top end with a material of defined permeability (plug or top plug). The possibility to vary the material of the plug allows the influence of the more impermeable cavern lining or possible gas escape vents in the cavern roof to be investigated. A gas supply is connected to the bottom end and is used to simulate different gas generation rates from the waste. A total of 5 experiments were carried out in which the gas generation rate, the column height and the permeability of the plug were varied. Before the start of the experiments, the mortar in the column and the plug were saturated with water to approx. 95 %. In all the experiments, an increase in pressure with time could be observed. The higher the gas generation rate and the lower the permeability of the plug, the more quickly this occurred. At the beginning, only water flow out of the top of the column

  1. Neutron Radiography Based Visualization and Profiling of Water Uptake in (Un)cracked and Autonomously Healed Cementitious Materials.

    Science.gov (United States)

    Van den Heede, Philip; Van Belleghem, Bjorn; Alderete, Natalia; Van Tittelboom, Kim; De Belie, Nele

    2016-04-26

    Given their low tensile strength, cement-based materials are very susceptible to cracking. These cracks serve as preferential pathways for corrosion inducing substances. For large concrete infrastructure works, currently available time-consuming manual repair techniques are not always an option. Often, one simply cannot reach the damaged areas and when making those areas accessible anyway (e.g., by redirecting traffic), the economic impacts involved would be enormous. Under those circumstances, it might be useful to have concrete with an embedded autonomous healing mechanism. In this paper, the effectiveness of incorporating encapsulated high and low viscosity polyurethane-based healing agents to ensure (multiple) crack healing has been investigated by means of capillary absorption tests on mortar while monitoring the time-dependent water ingress with neutron radiography. Overall visual interpretation and water front/sample cross-section area ratios as well as water profiles representing the area around the crack and their integrals do not show a preference for the high or low viscosity healing agent. Another observation is that in presence of two cracks, only one is properly healed, especially when using the latter healing agent. Exposure to water immediately after release of the healing agent stimulates the foaming reaction of the polyurethane and ensures a better crack closure.

  2. Ancient analogues concerning stability and durability of cementitious wasteform

    International Nuclear Information System (INIS)

    Jiang, W.; Roy, D.M.

    1994-01-01

    The history of cementitious materials goes back to ancient times. The Greeks and Romans used calcined limestone and later developed pozzolanic cement by grinding together lime and volcanic ash called open-quotes pozzolanclose quotes which was first found near Port Pozzuoli, Italy. The ancient Chinese used lime-pozzolanic mixes to build the Great Wall. The ancient Egyptians used calcined impure gypsum to build the Great Pyramid of Cheops. The extraordinary stability and durability of these materials has impressed us, when so much dramatically damaged infrastructure restored by using modern portland cement now requires rebuilding. Stability and durability of cementitious materials have attracted intensive research interest and contractors' concerns, as does immobilization of radioactive and hazardous industrial waste in cementitious materials. Nuclear waste pollution of the environment and an acceptable solution for waste management and disposal constitute among the most important public concerns. The analogy of ancient cementitious materials to modern Portland cement could give us some clues to study their stability and durability. This present study examines selected results of studies of ancient building materials from France, Italy, China, and Egypt, combined with knowledge obtained from the behavior of modern portland cement to evaluate the potential for stability and durability of such materials in nuclear waste forms

  3. Determination of the OH- Content in the aqueous phase of hardened cementitious materials by an empirical Leaching method

    Directory of Open Access Journals (Sweden)

    Castellote, M.

    2002-03-01

    Full Text Available The most reliable method to determine the concentration of hydroxyl ions in the aqueous phase of hardened cementitious materials is the squeezing of concrete at high pressures. However, this method needs special equipment as well as a relatively high amount of sample to be carried out. In present research, the determination of the OH concentration in the concrete pore solution is undertaken by a leaching method in granulated samples. The experimental program has been made using mortars with 5 different binders and three different leaching solutions. In the treatment of the results, different phenomena (dilution + dissolution of solid phases occurring during leaching have been taken into account until reaching the target values validated by comparison with those obtained by means of the high pressure technique. The agreement found is good enough, for every binder tested, in spite of the fact that fully understanding of the leaching mechanism is not achieved and that concentrations and not activities of the ions are taken into account in the calculations. Therefore, the method suggested is empirical at present stage.

    El método más fiable de determinación de iones hidroxilo en una fase acuosa de materiales cementantes es la extracción de la misma mediante aplicación de presión (pore-pressing. Sin embargo, este método necesita un equipo especial además de una cantidad de muestra relativamente alta. En la presente investigación, se propone la determinación de la concentración de OH' en la fase acuosa del hormigón mediante un método de lixiviación en muestra granulada. El programa experimental se ha realizado a partir de morteros con 5 diferentes materiales cementantes y tres disoluciones de lixiviado distintas. En el tratamiento de los resultados, se han considerado diferentes fenómenos (dilución + disolución de las fases sólidas que tienen lugar durante la lixiviación, hasta llegar a obtener los resultados obtenidos por la

  4. Extrusion of ECC-Material

    DEFF Research Database (Denmark)

    Stang, Henrik; Li, Victor C.

    1999-01-01

    An extrusion process especially designed for extrusion of pipes made from fiber reinforced cementitious materials has been developed at Department of Structural Engineering and Materials at the Technical University of DenmarkEngineered Cementitious Composite (ECC) materials have been developed...

  5. The Cementitious Barriers Partnership (CBP) Software Toolbox Capabilities In Assessing The Degradation Of Cementitious Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States); Burns, H. H. [Savannah River Site (SRS), Aiken, SC (United States); Langton, C. [Savannah River Site (SRS), Aiken, SC (United States); Smith, F. G. III [Savannah River Site (SRS), Aiken, SC (United States); Brown, K. G. [Vanderbilt University, Nashville, TN (United States); Kosson, D. S. [Vanderbilt University, Nashville, TN (United States); Garrabrants, A. C. [Vanderbilt University, Nashville, TN (United States); Sarkar, S. [Vanderbilt University, Nashville, TN (United States); van der Sloot, H. [Hans van der Sloot Consultancy (The Netherlands); Meeussen, J. C.L. [Nuclear Research and Consultancy Group, Petten (The Netherlands); Samson, E. [SIMCO Technologies Inc. , 1400, boul. du Parc - Technologique , Suite 203, Quebec (Canada); Mallick, P. [United States Department of Energy, 1000 Independence Ave. SW , Washington, DC (United States); Suttora, L. [United States Department of Energy, 1000 Independence Ave. SW , Washington, DC (United States); Esh, D. W. [U .S. Nuclear Regulatory Commission , Washington, DC (United States); Fuhrmann, M. J. [U .S. Nuclear Regulatory Commission , Washington, DC (United States); Philip, J. [U .S. Nuclear Regulatory Commission , Washington, DC (United States)

    2013-01-11

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste and Nuclear Materials Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to 100 years and longer for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox has produced tangible benefits to the DOE Performance Assessment (PA) community. A review of prior DOE PAs has provided a list of potential opportunities for improving cementitious barrier performance predictions through the use of the CBP software tools. These opportunities include: 1) impact of atmospheric exposure to concrete and grout before closure, such as accelerated slag and Tc-99 oxidation, 2) prediction of changes in Kd/mobility as a function of time that result from changing pH and redox conditions, 3) concrete degradation from rebar corrosion due to carbonation, 4) early age cracking from drying and/or thermal shrinkage and 5) degradation due to sulfate attack. The CBP has already had opportunity to provide near-term, tangible support to ongoing DOE-EM PAs such as the Savannah River Saltstone Disposal Facility (SDF) by providing a sulfate attack analysis that predicts the extent and damage that sulfate ingress will have on the concrete vaults over extended time (i.e., > 1000 years). This analysis is one of the many technical opportunities in cementitious barrier performance that can be addressed by the DOE-EM sponsored CBP software

  6. Cementitious Barriers Partnership Accomplishments And Relevance To The DOE Complex

    International Nuclear Information System (INIS)

    Burns, H.; Langton, C.; Flach, G.; Kosson, D.

    2010-01-01

    The Cementitious Barriers Partnership (CBP) was initiated to reduce risk and uncertainties in the performance assessments that directly impact U.S. Department of Energy (DOE) environmental cleanup and closure programs. The CBP is supported by the DOE Office of Environmental Management (DOE-EM) and has been specifically addressing the following critical EM program needs: (i) the long-term performance of cementitious barriers and materials in nuclear waste disposal facilities and (ii) increased understanding of contaminant transport behavior within cementitious barrier systems to support the development and deployment of adequate closure technologies. To accomplish this, the CBP has two initiatives: (1) an experimental initiative to increase understanding of changes in cementitious materials over long times (> 1000 years) over changing conditions and (2) a modeling initiative to enhance and integrate a set of computational tools validated by laboratory and field experimental data to improve understanding and prediction of the long-term performance of cementitious barriers and waste forms used in nuclear applications. In FY10, the CBP developed the initial phase of an integrated modeling tool that would serve as a screening tool which could help in making decisions concerning disposal and tank closure. The CBP experimental programs are underway to validate this tool and provide increased understanding of how CM changes over time and under changing conditions. These initial CBP products that will eventually be enhanced are anticipated to reduce the uncertainties of current methodologies for assessing cementitious barrier performance and increase the consistency and transparency of the DOE assessment process. These tools have application to low activity waste forms, high level waste tank closure, D and D and entombment of major nuclear facilities, landfill waste acceptance criteria, and in-situ grouting and immobilization of vadose zone contamination. This paper

  7. Method for the production of cementitious compositions and aggregate derivatives from said compositions

    Science.gov (United States)

    Minnick, L. John

    1981-01-01

    Method for the production of cementitious compositions and aggregate derivatives of said compositions, and cementitious compositions and aggregates produced by said method, wherein fluidized bed combustion residue and pozzolanic material, such as pulverized coal combustion system fly ash, are incorporated in a cementitious mix. The mix is cast into desired shape and cured. If desired, the shape may then be crushed so as to result in a fluidized bed combustion residue-fly ash aggregate material or the shape may be used by itself.

  8. A Plastic Damage Mechanics Model for Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2007-01-01

    This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides...

  9. Disassembly Properties of Cementitious Finish Joints Using an Induction Heating Method

    Directory of Open Access Journals (Sweden)

    Jaecheol Ahn

    2015-05-01

    Full Text Available Efficient maintenance and upgrading of a building during its lifecycle are difficult because a cementitious finish uses materials and parts with low disassembly properties. Additionally, the reuse and recycling processes during building demolition also present numerous problems from the perspective of environmental technology. In this study, an induction heating (IH method was used to disassemble cementitious finish joints, which are widely used to join building members and materials. The IH rapidly and selectively heated and weakened these joints. The temperature elevation characteristics of the cementitious joint materials were measured as a function of several resistor types, including wire meshes and punching metals, which are usually used for cementitious finishing. The disassembly properties were evaluated through various tests using conductive resistors in cementitious joints such as mortar. When steel fiber, punching metal, and wire mesh were used as conductive resistors, the cementitious modifiers could be weakened within 30 s. Cementitious joints with conductive resistors also showed complete disassembly with little residual bond strength.

  10. Detection of metal fibres in cementitious composites based on signal and image processing approaches

    Czech Academy of Sciences Publication Activity Database

    Vala, J.; Hobst, L.; Kozák, Vladislav

    2015-01-01

    Roč. 10, č. 1 (2015), s. 39-46 ISSN 1991-8747 Institutional support: RVO:68081723 Keywords : Cementitious composites * Computational simulation * Non-destructive testing Subject RIV: JI - Composite Materials

  11. Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes

    Science.gov (United States)

    Narayan, Sri R.; Yen, Shiao-Ping S.; Reddy, Prakash V.; Nair, Nanditha

    2012-01-01

    Polymer electrolyte membranes that conduct hydroxide ions have potential use in fuel cells. A variety of polystyrene-based quaternary ammonium hydroxides have been reported as anion exchange fuel cell membranes. However, the hydrolytic stability and conductivity of the commercially available membranes are not adequate to meet the requirements of fuel cell applications. When compared with commercially available membranes, polystyrene-imidazolium alkaline membrane electrolytes are more stable and more highly conducting. At the time of this reporting, this has been the first such usage for imidazolium-based polymeric materials for fuel cells. Imidazolium salts are known to be electrochemically stable over wide potential ranges. By controlling the relative ratio of imidazolium groups in polystyrene-imidazolium salts, their physiochemical properties could be modulated. Alkaline anion exchange membranes based on polystyrene-imidazolium hydroxide materials have been developed. The first step was to synthesize the poly(styrene-co-(1-((4-vinyl)methyl)-3- methylimidazolium) chloride through a free-radical polymerization. Casting of this material followed by in situ treatment of the membranes with sodium hydroxide solutions provided the corresponding hydroxide salts. Various ratios of the monomers 4-chloromoethylvinylbenzine (CMVB) and vinylbenzine (VB) provided various compositions of the polymer. The preferred material, due to the relative ease of casting the film, and its relatively low hygroscopic nature, was a 2:1 ratio of CMVB to VB. Testing confirmed that at room temperature, the new membranes outperformed commercially available membranes by a large margin. With fuel cells now in use at NASA and in transportation, and with defense potential, any improvement to fuel cell efficiency is a significant development.

  12. Desarrollo de hormigones con aglomerante cal-puzolana fina como material cementicio suplementario Development of concrete mixtures with fine lime-pozzolan binder as supplementary cementitious material

    Directory of Open Access Journals (Sweden)

    Juan José Dopico

    2008-01-01

    Full Text Available La alta resistencia y durabilidad alcanzada en los hormigones de alta y ultra alta resistencia está asociada a la obtención de una matriz muy densa, definida a partir del uso de altos volúmenes de adiciones minerales muy finas, tales como las cenizas volantes, microsílice, metacaolín y polvos finos de cuarzo. El trabajo muestra un estudio sobre el uso del aglomerante cal- puzolana (ACP de alta finura, como adición mineral activa en el hormigón. Las partículas muy finas de la cal, de tamaños entre las 0.1-lOum pueden llenar los vacíos entre los granos de cemento, mientras las partículas más grandes de la puzolana, entre 10-100 [jm, pueden llenar los vacíos entre los granos más finos del agregado, resultando en una matriz más densa. La adición de hidróxido de calcio (HC durante el mezclado del hormigón, también incrementa la concentración de iones Ca+2 y OH", lo cual resulta en una mejor y mas rápida hidratación del Cemento Portland Ordinario (CPO y de la reacción puzolánica. El uso de la ACP como adición mineral activa en hormigones de alta resistencia (HAR, podría contribuir a disminuir los costos del producto sin afectar su resistencia mecánica y durabilidad usando menos cemento, con lo cual se estaría mejorando el perfil ecológico de este material. Resultados iniciales son mostrados en este trabajo, requiriéndose de ensayos adicionales para establecer los beneficios del uso de la ACP en los HAR. Un ejemplo de aplicación de este trabajo en hormigones son también presentados.The very high concrete strength and durability achieved in high and ultra-high-performance concrete is associated with a very dense matrix, accomplished through the use of high volumes of very fine mineral additions, such as fly ash, silica-fume, metakaolin and ground quartz sand. The paper reports on a study where a finely ground lime-pozzolan binder (LPB is used as active mineral addition in concrete. The very fine lime particles, having

  13. Assessment of commercially available ion exchange materials for cesium removal from highly alkaline wastes

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, K.P.; Kim, A.Y.; Kurath, D.E.

    1996-04-01

    Approximately 61 million gallons of nuclear waste generated in plutonium production, radionuclide removal campaigns, and research and development activities is stored on the Department of Energy`s Hanford Site, near Richland, Washington. Although the pretreatment process and disposal requirements are still being defined, most pretreatment scenarios include removal of cesium from the aqueous streams. In many cases, after cesium is removed, the dissolved salt cakes and supernates can be disposed of as LLW. Ion exchange has been a leading candidate for this separation. Ion exchange systems have the advantage of simplicity of equipment and operation and provide many theoretical stages in a small space. The organic ion exchange material Duolite{trademark} CS-100 has been selected as the baseline exchanger for conceptual design of the Initial Pretreatment Module (IPM). Use of CS-100 was chosen because it is considered a conservative, technologically feasible approach. During FY 96, final resin down-selection will occur for IPM Title 1 design. Alternate ion exchange materials for cesium exchange will be considered at that time. The purpose of this report is to conduct a search for commercially available ion exchange materials which could potentially replace CS-100. This report will provide where possible a comparison of these resin in their ability to remove low concentrations of cesium from highly alkaline solutions. Materials which show promise can be studied further, while less encouraging resins can be eliminated from consideration.

  14. Assessment of commercially available ion exchange materials for cesium removal from highly alkaline wastes

    International Nuclear Information System (INIS)

    Brooks, K.P.; Kim, A.Y.; Kurath, D.E.

    1996-04-01

    Approximately 61 million gallons of nuclear waste generated in plutonium production, radionuclide removal campaigns, and research and development activities is stored on the Department of Energy's Hanford Site, near Richland, Washington. Although the pretreatment process and disposal requirements are still being defined, most pretreatment scenarios include removal of cesium from the aqueous streams. In many cases, after cesium is removed, the dissolved salt cakes and supernates can be disposed of as LLW. Ion exchange has been a leading candidate for this separation. Ion exchange systems have the advantage of simplicity of equipment and operation and provide many theoretical stages in a small space. The organic ion exchange material Duolite trademark CS-100 has been selected as the baseline exchanger for conceptual design of the Initial Pretreatment Module (IPM). Use of CS-100 was chosen because it is considered a conservative, technologically feasible approach. During FY 96, final resin down-selection will occur for IPM Title 1 design. Alternate ion exchange materials for cesium exchange will be considered at that time. The purpose of this report is to conduct a search for commercially available ion exchange materials which could potentially replace CS-100. This report will provide where possible a comparison of these resin in their ability to remove low concentrations of cesium from highly alkaline solutions. Materials which show promise can be studied further, while less encouraging resins can be eliminated from consideration

  15. Modeling of Cementitious Representative Volume Element with Additives

    Science.gov (United States)

    Shahzamanian, M. M.; Basirun, W. J.

    CEMHYD3D has been employed to simulate the representative volume element (RVE) of cementitious systems (Type I cement) containing fly ash (Class F) through a voxel-based finite element analysis (FEA) approach. Three-dimensional microstructures composed of voxels are generated for a heterogeneous cementitious material consisting of various constituent phases. The primary focus is to simulate a cementitious RVE containing fly ash and to present the homogenized macromechanical properties obtained from its analysis. Simple kinematic uniform boundary conditions as well as periodic boundary conditions were imposed on the RVE to obtain the principal and shear moduli. Our current work considers the effect of fly ash percentage on the elastic properties based on the mass and volume replacements. RVEs with lengths of 50, 100 and 200μm at different degrees of hydration are generated, and the elastic properties are modeled and simulated. In general, the elastic properties of a cementitious RVE with fly ash replacement for cement based on mass and volume differ from each other. Moreover, the finite element (FE) mesh density effect is studied. Results indicate that mechanical properties decrease with increasing mesh density.

  16. REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C

    2009-01-06

    The Cementitious Barriers Project (CBP) is a multidisciplinary cross cutting project initiated by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (1) a common set of system configurations to illustrate the methods and tools developed by the CBP, (2) a common basis for evaluating methodology for uncertainty characterization, (3) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, and (4) a basis for experiments and model validation, and (5) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (1) a cementitious low activity waste form in a reinforced concrete disposal vault, (2) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (3) a spent nuclear fuel basin during operation. Each case provides a different set of desired performance characteristics and interfaces between materials and with the environment. Examples of concretes, grout fills and a cementitious waste form are identified for the relevant reference case configurations.

  17. Cementitious Barriers Partnership FY2013 End-Year Report

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States); Langton, C. A. [Savannah River Site (SRS), Aiken, SC (United States); Burns, H. H. [Savannah River Site (SRS), Aiken, SC (United States); Smith, F. G. [Savannah River Site (SRS), Aiken, SC (United States); Kosson, D. S. [Vanderbilt University, School of Engineering, Nashville, TN (United States); Brown, K. G. [Vanderbilt University, School of Engineering, Nashville, TN (United States); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Meeussen, J. C.L. [Nuclear Research and Consultancy Group (NRG), Petten (The Netherlands); van der Sloot, H. A. [Hans van der Sloot Consultancy, Langedijk (The Netherlands); Garboczi, E. J. [Materials & Construction Research Division, National Institute of Standards and Technology, Gaithersburg, MD (United States)

    2013-11-01

    In FY2013, the Cementitious Barriers Partnership (CBP) demonstrated continued tangible progress toward fulfilling the objective of developing a set of software tools to improve understanding and prediction of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In November 2012, the CBP released “Version 1.0” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. In addition, the CBP completed development of new software for the “Version 2.0” Toolbox to be released in early FY2014 and demonstrated use of the Version 1.0 Toolbox on DOE applications. The current primary software components in both Versions 1.0 and 2.0 are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. The CBP Software Toolbox Version 1.0 supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. Version 2.0 includes the additional analysis of chloride attack and dual regime flow and contaminant migration in fractured and non-fractured cementitious material. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). THAMES is a planned future CBP Toolbox component focused on simulation of the microstructure of cementitious materials and calculation of resultant

  18. Rapid determination of methanol content in paper materials by alkaline extraction, coupled with headspace analysis.

    Science.gov (United States)

    Zhang, Chun-Yun; Li, Ling-Ling; Chai, Xin-Sheng; Barnes, Donald G

    2014-07-11

    This study reports on a rapid method for the determination of methanol in paper-based materials by alkaline extraction, coupled with headspace analysis. Methanol partition equilibria between solid-liquid phases and vapor-liquid phases were conducted in two separate containers, from which an equation for calculating the total methanol content in the original paper sample was derived. It was found that the extraction equilibrium of methanol from solid sample could be achieved within 5min at room temperature using a high-speed disintegrator, and a subsequent neutralization step is an effective way to prevent methanol from being regenerated at high temperature during headspace equilibration. The results showed that the relative standard deviations for reproducibility tests were in the range of 1.86-6.03%, and the recoveries were in the range of 92.3-107%. The present method is simple and practical; it can be an efficient tool for quantifying the methanol content in paper-based materials and thus play an important role in the investigation of methanol migration behavior in food and beverage packaging. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Review of high and ultrahigh performance cementitious composites incorporating various combinations of fibers and ultrafines

    Directory of Open Access Journals (Sweden)

    M.I. Khan

    2017-10-01

    Full Text Available The outcomes of the research in modern cementitious composites have paved the way for their wide use in construction industry. The introduction of short, discontinuous and randomly distributed fibers to these composites has altered their inherent brittleness. Extensive research has been carried out on the effects of using of mono-fibers in a cementitious composite. However, limited reports in the approachable references on the use of hybrid fibers are available. The synergetic interaction between hybrid fibers have beneficial impact on cementitious composites. The incorporation of micro- and nano-pozzolanic materials, such as fly ash and silica fume have been used to develop high performance cementitious composites such as reactive powder concrete, DUCTAL and CEMTEC multiscale. Further developments were recently achieved by the development of ultra-high performance cementitious composites. The matter of developing high and ultrahigh cementitious composites using various kinds of fibers and particles has received enormous attention from the scientific community. This paper presents a comprehensive critical literature review on the area of high and ultra-high performance cement-based materials.

  20. Evaluation of micro-mechanical properties of nonlinear cementitious ...

    Indian Academy of Sciences (India)

    B S Sindu

    2018-03-10

    Mar 10, 2018 ... phases is between 125 and 145 GPa. It was also reported that the hardness of C3A is around 10 GPa and that of silicates around 8–9 GPa. Constantinides et al [4] carried out nanoindentation tests on intact and calcium-leached cementitious material and confirmed the presence of two forms of C-S-H, i.e., ...

  1. Modelling the interaction of the alkaline plume with Boom Clay at different scales

    International Nuclear Information System (INIS)

    Jacques, Diederik; Wang, Lian

    2012-01-01

    In Belgium, Boom Clay is studied as a potential host formation for geological disposal of high-level radioactive waste. The current reference design of the engineered barrier system ('supercontainer design') plans to use a considerable amount of cementitious materials as construction material, buffer and backfill. Diffusion of the alkaline pore fluids from the concrete engineered barriers to the Boom Clay may change the retention properties of the Boom Clay in the vicinity of the engineered barriers - Boom Clay interface. The objectives of this work are to (i) model the breakthrough curves obtained from leaching small undisturbed Boom Clay cores with young concrete water (high Na and K content, pH 13.5), and (ii) simulate the possible extent of Boom Clay alterations owing to interactions with alkaline fluids for a period of 100,000 years. For both objectives, the reactive transport code PHREEQC is used

  2. Corrosion of copper in alkaline chloride environments

    International Nuclear Information System (INIS)

    King, F.

    2002-08-01

    The available literature information on the corrosion and electrochemical behaviour of copper in alkaline environments has been reviewed. The purpose of the review was to assess the impact of an alkaline plume from cementitious material on the corrosion behaviour of a copper canister in an SKB-3 type repository. The effect of the evolution of the environmental conditions within the repository have been considered, including the effects of temperature, redox conditions, pore-water salinity and pH. If the pore-water pH increases prior to the establishment of anoxic conditions, the canister surface will passivate as the pore-water pH exceeds a value of ∼ pH 9. Passivation will result from the formation of a duplex Cu 2 O/Cu(OH) 2 film. The corrosion potential will be determined by the equilibrium potential for the Cu 2 O/Cu(OH) 2 couple under oxic conditions, or by the Cu/Cu 2 O redox couple under anoxic conditions (in the absence of sulphide). Pitting corrosion is only likely to occur early in the evolution of the repository environment, whilst the canister is still relatively cool ( 2 available to support localised corrosion, and prior to the increase in pore-water pH and salinity. The subsequent increase in canister surface temperature, pore-water pH and salinity, and decrease in O 2 will make pit initiation less likely, although the canister will remain passive provided the pore-water pH is maintained above pH 9. The higher the pore-water pH, the more strongly the canister is passivated and the less likely the surface is to undergo localised attack. If the pore-water salinity increases prior to the increase in pH, there could be a period of active canister corrosion before passivation occurs.Under these circumstances, the corrosion potential will be a true mixed potential, determine by the relative kinetics of Cu dissolution as CuCl 2 - and of the reduction of O 2 . The development of anoxic conditions and an increase in pore-water sulphide concentration will

  3. REVIEW OF MECHANISTIC UNDERSTANDING AND MODELING AND UNCERTAINTY ANALYSIS METHODS FOR PREDICTING CEMENTITIOUS BARRIER PERFORMANCE

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Kosson, D.

    2009-11-30

    Cementitious barriers for nuclear applications are one of the primary controls for preventing or limiting radionuclide release into the environment. At the present time, performance and risk assessments do not fully incorporate the effectiveness of engineered barriers because the processes that influence performance are coupled and complicated. Better understanding the behavior of cementitious barriers is necessary to evaluate and improve the design of materials and structures used for radioactive waste containment, life extension of current nuclear facilities, and design of future nuclear facilities, including those needed for nuclear fuel storage and processing, nuclear power production and waste management. The focus of the Cementitious Barriers Partnership (CBP) literature review is to document the current level of knowledge with respect to: (1) mechanisms and processes that directly influence the performance of cementitious materials (2) methodologies for modeling the performance of these mechanisms and processes and (3) approaches to addressing and quantifying uncertainties associated with performance predictions. This will serve as an important reference document for the professional community responsible for the design and performance assessment of cementitious materials in nuclear applications. This review also provides a multi-disciplinary foundation for identification, research, development and demonstration of improvements in conceptual understanding, measurements and performance modeling that would be lead to significant reductions in the uncertainties and improved confidence in the estimating the long-term performance of cementitious materials in nuclear applications. This report identifies: (1) technology gaps that may be filled by the CBP project and also (2) information and computational methods that are in currently being applied in related fields but have not yet been incorporated into performance assessments of cementitious barriers. The various

  4. Graphene-cobaltite-Pd hybrid materials for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells.

    Science.gov (United States)

    Sharma, Chandra Shekhar; Awasthi, Rahul; Singh, Ravindra Nath; Sinha, Akhoury Sudhir Kumar

    2013-12-14

    Hybrid materials comprising of Pd, MCo2O4 (where M = Mn, Co or Ni) and graphene have been prepared for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells. Structural and electrochemical characterizations were carried out using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, chronoamperometry and cyclic, CO stripping, and linear sweep voltammetries. The study revealed that all the three hybrid materials are active for both methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1 M KOH. However, the Pd-MnCo2O4/GNS hybrid electrode exhibited the greatest MOR and ORR activities. This active hybrid electrode has also outstanding stability under both MOR and ORR conditions, while Pt- and other Pd-based catalysts undergo degradation under similar experimental conditions. The Pd-MnCo2O4/GNS hybrid catalyst exhibited superior ORR activity and stability compared to even Pt in alkaline solutions.

  5. Enhancement Experiment on Cementitious Activity of Copper-Mine Tailings in a Geopolymer System

    Directory of Open Access Journals (Sweden)

    Lin Yu

    2017-12-01

    Full Text Available Copper-mine tailings are the residual products after the extraction of precious copper metal from copper ores, and their storage can create numerous environmental problems. Many researchers have used copper-mine tailings for the preparation of geopolymers. This paper studies the enhancement of the cementitious activity of copper-mine tailings in geopolymer systems. First, copper-mine tailings are activated through mechanical grinding activation. Then, the mechanically activated copper-mine tailings are further processed through thermal activation and alkaline-roasting activation. The cementitious activity index of copper-mine tailings is characterized through the degree of leaching concentration of Si and Al. It was observed that the Si and Al leaching concentration of mechanically activated tailings was increased by 26.03% and 93.33%, respectively. The concentration of Si and Al was increased by 54.19% and 119.92%, respectively. For alkaline-roasting activation, roasting time, temperature and the mass ratio of copper-mine tailings to NaOH (C/N ratio were evaluated through orthogonal tests, and the best condition for activation was 120 min at 600 °C with a C/N ratio of 5:1. In this study, scanning electron microscopy (SEM, X-ray diffraction (XRD and infra-red (IR analysis show that mechanical, thermal and alkaline-roasting activation could be used to improve the cementitious activity index of copper-mine tailings.

  6. Anodes for alkaline electrolysis

    Science.gov (United States)

    Soloveichik, Grigorii Lev [Latham, NY

    2011-02-01

    A method of making an anode for alkaline electrolysis cells includes adsorption of precursor material on a carbonaceous material, conversion of the precursor material to hydroxide form and conversion of precursor material from hydroxide form to oxy-hydroxide form within the alkaline electrolysis cell.

  7. Development of geopolymers as candidate materials for low/intermediate level highly alkaline nuclear waste

    International Nuclear Information System (INIS)

    Perera, D.S.; Vance, E.R.; Kiyama, S.; Aly, Z.; Yee, P.

    2006-01-01

    Full text: Geopolymers have been studied for many years as a possible improvement on cement in respect of compressive strength, resistance to fire, heat and acidity, and as a medium for the encapsulation of hazardous or low/ intermediate level radioactive waste. They are made by adding aluminosilicates to concentrated alkali solutions and the application of heat at 0 Cfor subsequent polymerisation. In this work we studied them as suitable candidate materials to incorporate NaOH/NaA10 2 containing waste with low levels of Cs, Sr and Nd. Geopolymers were produced by incorporating the highly alkaline solution as part of the composition with added metakaolinite, fumed silica and extra NaOH, such that the overall geopolymer composition was of molar ratios Si/Al = 2 and Na/Al = 1. The simulated waste contained Na2SO 4 , therefore Ba(OH) 2 was also added to precipitate the SO 4 x 2 as BaSO 4 . Three geoplymers of the same composition containing simulated wastes were leach tested in triplicate after heating at 400 0 Cfor 1 h (to remove -98% of free and interstitial water) under the PCT-B test protocol at 90 0 Cfor 7 days and their results are listed in Table 1. The Cs, Sr and Nd normalised leach rates were low. The Na leach rate was ∼ 4 g/L thus passing the PCT-B test protocol value of 13.5 g/L for EA glass. The X-ray diffraction and scanning electron microscopy showed that BaS04 did precipitate, however all the S did not appear to have precipitated. The ANSI/ANS-16.1-2003 test was carried out on the above geopolymer composition for 5 days. The ANSI Leachability Index D (diffusivity of 10''cm sec'') for the elements released are listed in Table 2. A Portland cement was also tested for comparison and the Leachability index values are 11, 8 and 10 for Al, Na and Ca respectively. Both passed the test protocol insofar as they were > 6. Geopolymers thus passing the tests for high level nuclear waste glass (PCT-B) and for low level nuclear waste (ANSI) show promising potential

  8. Thin fiber and textile reinforced cementitious systems

    National Research Council Canada - National Science Library

    Aldea, Corina-Maria

    2007-01-01

    This Special Publication (SP) contains ten papers which provide insight on the topics of state of the art of thin fiber and textile-reinforced cementitious systems both in academia and the industry...

  9. Description of near-tip fracture processes in strain hardening cementitious composites using image-based analysis and the compact tension test

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2013-01-01

    The cracking mechanisms assume a key role in the composite behavior of Strain Hardening Cementitious Composites (SHCCs). Due to their importance, in previous studies the mechanical behavior of SHCC materials, as well as of other strain softening fiber reinforced cementitious composites, was chara......The cracking mechanisms assume a key role in the composite behavior of Strain Hardening Cementitious Composites (SHCCs). Due to their importance, in previous studies the mechanical behavior of SHCC materials, as well as of other strain softening fiber reinforced cementitious composites......, was characterized under eccentric tensile loading using the Compact Tension Test (CTT). The present research further extends this investigation, with particular emphasis on cementitious composites reinforced with multiple types of fibers. The experimental tensile load-displacement results are discussed and compared...

  10. Concrete mixture characterization. Cementitious barriers partnership

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Protiere, Yannick [SIMCO Technologies, Inc., Quebec (Canada)

    2014-12-01

    This report summarizes the characterization study performed on two concrete mixtures used for radioactive waste storage. Both mixtures were prepared with approximately 425 kg of binder. The testing protocol mostly focused on determining the transport properties of the mixtures; volume of permeable voids (porosity), diffusion coefficients, and water permeability were evaluated. Tests were performed after different curing durations. In order to obtain data on the statistical distribution of transport properties, the measurements after 2 years of curing were performed on 10+ samples. Overall, both mixtures exhibited very low tortuosities and permeabilities, a direct consequence of their low water-to-binder ratio and the use of supplementary cementitious materials. The data generated on 2-year old samples showed that porosity, tortuosity and permeability follow a normal distribution. Chloride ponding tests were also performed on test samples. They showed limited chloride ingress, in line with measured transport properties. These test results also showed that both materials react differently with chloride, a consequence of the differences in the binder chemical compositions.

  11. Ultrastable α phase nickel hydroxide as energy storage materials for alkaline secondary batteries

    Science.gov (United States)

    Huang, Haili; Guo, Yinjian; Cheng, Yuanhui

    2018-03-01

    α Phase nickel hydroxide (α-Ni(OH)2) has higher theoretical capacity than that of commercial β phase Ni(OH)2. But the low stability inhibits its wide application in alkaline rechargeable batteries. Here, we propose a totally new idea to stabilize α phase Ni(OH)2 by introducing large organic molecule into the interlayer spacing together with doping multivalent cobalt into the layered Ni(OH)2 host. Ethylene glycol is served as neutral stabilizer in the interlayer spacing. Nickel is substituted by cobalt to increase the electrostatic attraction between layered Ni(OH)2 host and anion ions in the interlayer spacing. Polyethylene glycol (PEG-200) is utilized to design a three-dimensional network structure. This prepared α-Ni(OH)2-20 exhibits specific capacity as high as 334 mAh g-1and good structural stability even after immersing into strong alkaline zincate solution for 20 days. Ni(OH)2 electrode with a specific capacity of 35 mAh cm-2 is fabricated and used as positive electrode in zinc-nickel single flow batteries, which also shows good cycling stability. This result can provide an important guideline for the rational design and preparation of highly active and stable α phase Ni(OH)2 for alkaline secondary battery.

  12. Using Cementitious Materials Such as Fly Ash to Replace a Part of Cement in Producing High Strength Concrete in Hot Weather

    Science.gov (United States)

    Turuallo, Gidion; Mallisa, Harun

    2018-03-01

    The use of waste materials in concrete gave many advantages to prove the properties of concrete such as its workability, strength and durability; as well to support sustaianable development programs. Fly ash was a waste material produced from coal combustion. This research was conducted to find out the effect of fly ash as a part replacement of cement to produce high strength concrete. The fly ash, which was used in this research, was taken from PLTU Mpanau Palu, Central Sulawesi. The water-binder ratio used in this research was 0.3 selected from trial mixes done before. The results of this research showed that the strength of fly ash concretes were higher than concrete with PCC only. The replacement of cement with fly ash concrete could be up to 20% to produce high strength concrete.

  13. Impact of alkaline alterations to a Brazilian soil on cesium retention under low temperature conditions.

    Science.gov (United States)

    Calábria, Jaqueline Alves de Almeida; Cota, Stela Dalva Santos; de Morais, Gustavo Ferrari; Ladeira, Ana Cláudia Queiroz

    2017-11-01

    , demonstrated that the adsorbent surface became more homogenous as a consequence of the alkaline alteration. Together these results suggest that cementitious leachate has a profound effect on Cs retention and should be accounted for estimating radionuclide retention in radioactive waste disposal systems containing cementitious materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Solubility constraints affecting the migration of selenium through the cementitious backfill of a geological disposal facility

    Energy Technology Data Exchange (ETDEWEB)

    Felipe-Sotelo, M., E-mail: m.felipe-sotelo@lboro.ac.uk; Hinchliff, J.; Evans, N.D.M.; Read, D.

    2016-03-15

    Highlights: • The availability of Ca controls the concentration of SeO{sub 3}{sup 2−} in solution. • Cellulose degradation products increase the solubility of SeO{sub 3}{sup 2−} at alkaline pH. • Selenite diffuses faster through the backfill NRVB than through fly ash cements. - Abstract: This work presents the study of the solubility of selenium under cementitious conditions and its diffusion, as SeO{sub 3}{sup 2−}, through monolithic cement samples. The solubility studies were carried out under alkaline conditions similar to those anticipated in the near-field of a cement-based repository for low- and intermediate-level radioactive waste. Experiments were conducted in NaOH solution, 95%-saturated Ca(OH){sub 2}, water equilibrated with a potential backfill material (Nirex reference vault backfill, NRVB) and in solutions containing cellulose degradation products, with and without reducing agents. The highest selenium concentrations were found in NaOH solution. In the calcium-containing solutions, analysis of the precipitates suggests that the solubility controlling phase is Ca{sub 2}SeO{sub 3}(OH){sub 2}·2H{sub 2}O, which appears as euhedral rhombic crystals. The presence of cellulose degradation products caused an increase in selenium concentration, possibly due to competitive complexation, thereby, limiting the amount of calcium available for precipitation. Iron coupons had a minor effect on selenium solubility in contrast to Na{sub 2}S{sub 2}O{sub 4}, suggesting that effective reduction of Se(IV) occurs only at E{sub h} values below −300 mV. Radial through-diffusion experiments on NRVB and in a fly ash cement showed no evidence of selenium breakthrough after one year. However, autoradiography of the exposed surfaces indicated that some migration had occurred and that selenium was more mobile in the higher porosity backfill than in the fly ash cement.

  15. CEMENTITIOUS BARRIERS PARTNERSHIP FY13 MID-YEAR REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Burns, H.; Flach, G.; Langton, C.; KOSSON, D.; BROWN, K.; SAMSON, E.; MEEUSSEN, J.; SLOOT, H.; GARBOCZI, E.

    2013-05-01

    In FY2013, the Cementitious Barriers Partnership (CBP) is continuing in its effort to develop and enhance software tools demonstrating tangible progress toward fulfilling the objective of developing a set of tools to improve understanding and prediction of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. In FY2012, the CBP released the initial inhouse “Beta-version” of the CBP Software Toolbox, a suite of software for simulating reactive transport in cementitious materials and important degradation phenomena. The current primary software components are LeachXS/ORCHESTRA, STADIUM, and a GoldSim interface for probabilistic analysis of selected degradation scenarios. THAMES is a planned future CBP Toolbox component (FY13/14) focused on simulation of the microstructure of cementitious materials and calculation of resultant hydraulic and constituent mass transfer parameters needed in modeling. This past November, the CBP Software Toolbox Version 1.0 was released that supports analysis of external sulfate attack (including damage mechanics), carbonation, and primary constituent leaching. The LeachXS component embodies an extensive material property measurements database along with chemical speciation and reactive mass transport simulation cases with emphasis on leaching of major, trace and radionuclide constituents from cementitious materials used in DOE facilities, such as Saltstone (Savannah River) and Cast Stone (Hanford), tank closure grouts, and barrier concretes. STADIUM focuses on the physical and structural service life of materials and components based on chemical speciation and reactive mass transport of major cement constituents and aggressive species (e.g., chloride, sulfate, etc.). The CBP issued numerous reports and other documentation that accompanied the “Version 1.0” release including a CBP Software Toolbox User Guide and Installation Guide. These documents, as well as, the

  16. Study on cementitious properties of steel slag

    Directory of Open Access Journals (Sweden)

    Zhu G.

    2013-01-01

    Full Text Available The converter steel slag chemical and mineral components in China’s main steel plants have been analysed in the present paper. The electronic microscope, energy spectrum analysis, X-ray diffraction analysis confirmed the main mineral compositions in the converter slag. Converter slag of different components were grounded to obtain a powder with specific surface area over 400m2/kg, making them to take place some part of the cement in the concrete as the admixture and carry out the standard tests. The results indicate that the converter slag can be used as cementitious materials for construction. Furthermore, physical mechanic and durability tests on the concrete that certain amount of cement be substituted by converter steel slag powder from different steel plants are carried out, the results show that the concrete with partial substitution of steel slag powder has the advantages of higher later period strength, better frost resistance, good wear resistance and lower hydration heat, etc. This study can be used as the technical basis for “Steel Slag Powder Used For Cement And Concrete”, “Steel Slag Portland Cement”, “Low Heat Portland Steel Slag Cement”, “Steel Slag Road Cement” in China, as well as a driving force to the works of steel slag utilization with high-value addition, circular economy, energy conservation and discharge reduction in the iron and steel industry.

  17. Confirmation of the applicability of low alkaline cement-based material in the Horonobe Underground Research Laboratory

    International Nuclear Information System (INIS)

    Nakayama, Masashi; Niunoya, Sumio; Minamide, Masashi

    2016-01-01

    In Japan, high-level radioactive waste repository will be constructed in a stable host rock formation more than 300 m underground. Tunnel support is used for safety during the construction and operation, so, shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement, water and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed the low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silicafume (SF) and Fly-ash (FA). JAEA is presently constructing the underground research laboratory (URL) at Horonobe for research and development in the geosciences and repository engineering technology. HFSC was used experimentally as the shotcrete material in construction of part of the 350 m deep gallery in the Horonobe URL in 2013. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel constructed using HFSC shotcrete is about 112 m at 350 m deep drift. The workability of HFSC shotcrete was confirmed by this experimental construction. In this report, we present detailed results of the in-situ construction test. (author)

  18. Rigid-body-spring model numerical analysis of joint performance of engineered cementitious composites and concrete

    Science.gov (United States)

    Khmurovska, Y.; Štemberk, P.; Křístek, V.

    2017-09-01

    This paper presents a numerical investigation of effectiveness of using engineered cementitious composites with polyvinyl alcohol fibers for concrete cover layer repair. A numerical model of a monolithic concaved L-shaped concrete structural detail which is strengthened with an engineered cementitious composite layer with polyvinyl alcohol fibers is created and loaded with bending moment. The numerical analysis employs nonlinear 3-D Rigid-Body-Spring Model. The proposed material model shows reliable results and can be used in further studies. The engineered cementitious composite shows extremely good performance in tension due to the strain-hardening effect. Since durability of the bond can be decreased significantly by its degradation due to the thermal loading, this effect should be also taken into account in the future work, as well as the experimental investigation, which should be performed for validation of the proposed numerical model.

  19. Service life prediction and fibre reinforced cementitious composites

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    The present Ph.D.thesis addresses the service life concept on the fibre reinforced cementitious composites. The advantages and problems of adding fibre to a cementitious matrix and the influence on service life are described. In SBI Report 221, Service life prediction and cementitious somposites,...

  20. A Plastic Damage Mechanics Model for Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2007-01-01

    This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides in...... information about crack opening and spacing, which makes it possible to assess the condition of a structure in the serviceability state. A simulation of a four point bending beam is performed to demonstrate the capability of the model....

  1. Engineered cementitious composites for strengthening masonry infilled reinforced concrete frames

    DEFF Research Database (Denmark)

    Dehghani, Ayoub; Nateghi-Alahi, Fariborz; Fischer, Gregor

    2015-01-01

    The results of the second part of a comprehensive experimental program, aimed at investigating the behavior of masonry infilled reinforced concrete (RC) frames strengthened with fiber reinforced engineered cementitious composites (ECC) used as an overlay on the masonry wall, are presented...... in this paper. The proposed strengthening technique aims at increasing the lateral strength of infilled RC frames and maintaining the integrity of masonry infills during loading, which is an important seismic parameter for these elements. Material tests were conducted first for ECC in order to assess its...

  2. Investigations on cementitious composites based on rubber particle waste additions

    Directory of Open Access Journals (Sweden)

    Glaucio Laun Nacif

    2013-04-01

    Full Text Available The amount of waste rubber has gradually increased over recent years because of over-growing use of rubber products. The disposal of waste rubber has caused serious environmental problems. The incorporation of recycled materials into cementitious composites is a feasible alternative that has gained ground in civil construction. The performance of such materials is much affected not only by the rubber addition, but also the particle size which has been controversially reported in the literature. In order to investigate the single effect of rubber particles into cement based materials, rubber cementitious composites were prepared with no silica particle additions. A full factorial design has been conducted to assess the influence of the rubber particle size (0.84/0.58 mm and 0.28/0.18 mm; mass fraction used (5, 15 and 30%; and water/cement ratio (0.35 and 0.50 on the physic-mechanical properties of the composites. The materials were characterized through apparent density, porosity, compressive strength, flexural strength, modulus of elasticity and microstructural analysis. The interactions of rubber particle size, rubber fraction and water/cement ratio affected significantly the density and compressive strength of the composites. The apparent porosity was influenced mainly by the rubber particle size. The flexural strength was affected by the main factors and the modulus of elasticity was affected by the interaction factors rubber particle size and fraction, and rubber fraction and w/c ratio.

  3. Alkaline earth lead and tin compounds Ae2 Pb, Ae2 Sn, Ae =Ca,Sr,Ba, as thermoelectric materials

    Science.gov (United States)

    Parker, David; Singh, David

    2014-03-01

    We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli - roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  4. Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae = Ca, Sr, Ba, as thermoelectric materials

    Directory of Open Access Journals (Sweden)

    David Parker and David J Singh

    2013-01-01

    Full Text Available We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli—roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature.

  5. Characterization of potassic materials of Pocos de Caldas alkaline massif, Southeastern Brazil

    International Nuclear Information System (INIS)

    Goncalves, P.; Navarro, F.C.; Roveri, C.D.; Bergerman, M.G.

    2016-01-01

    Potassium, which has featured in Brazil's agricultural sector and in the world's in the application of fertilizers, is present in magmatic rocks, such as nepheline syenite and phonolite, found in the Alkaline Massif of Pocos de Caldas (AMPC). The rare earth elements (REE), in turn, also occur in this region and have important uses in various industrial fields. The aim of this study was to investigate the potential of potassic rocks of AMPC in the fertilizer and rare earths industry. Five samples were collected and characterized. It was observed that there was no preferential concentration by granulometric range of potassium oxide, alumina, silica and iron oxide. Feldspathic mass, potash feldspar, and muscovite were found in all samples. The samples show REE with amounts greater than those found in the earth's crust, except for lutetium and scandium and possessed average content of potassium oxide from 8.70 to 14.40%. (author)

  6. Cementitious Barriers Partnership - FY2015 End-Year Report

    Energy Technology Data Exchange (ETDEWEB)

    Burns, H. H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Langton, C. A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, F. G. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Kosson, D. S. [Vanderbilt Univ., Nashville, TN (United States). School of Engineering; Brown, K. G. [Vanderbilt Univ., Nashville, TN (United States). School of Engineering; Samson, E. [SIMCO Technologies, Inc., QC (Canada); Meeussen, J. C. L. [Nuclear Research and Consultancy Group (NRG); Seignette, Paul [Energy Research Center of the Netherlands; van der Sloot, H. A. [Hans van der Sloot Consultancy

    2015-09-17

    The DOE-EM Office of Tank Waste Management Cementitious Barriers Partnership (CBP) is chartered with providing the technical basis for implementing cement-based waste forms and radioactive waste containment structures for long-term disposal. Therefore, the CBP ultimate purpose is to support progress in final treatment and disposal of legacy waste and closure of High-Level Waste (HLW) tanks in the DOE complex. This status report highlights the CBP 2015 Software and Experimental Program efforts and accomplishments that support DOE needs in environmental cleanup and waste disposal. DOE needs in this area include: Long-term performance predictions to provide credibility (i.e., a defensible technical basis) for regulator and DOE review and approvals, Facility flow sheet development/enhancements, and Conceptual designs for new disposal facilities. In 2015, the CBP developed a beta release of the CBP Software Toolbox – “Version 3.0”, which includes new STADIUM carbonation and damage models, a new SRNL module for estimating hydraulic properties and flow in fractured and intact cementitious materials, and a new LeachXS/ORCHESTRA (LXO) oxidation module. In addition, the STADIUM sulfate attack and chloride models have been improved as well as the LXO modules for sulfate attack, carbonation, constituent leaching, and percolation with radial diffusion (for leaching and transport in cracked cementitious materials). These STADIUM and LXO models are applicable to and can be used by both DOE and the Nuclear Regulatory Commission (NRC) end-users for service life prediction and long-term leaching evaluations of radioactive waste containment structures across the DOE complex.

  7. Effects of the material composition in the TL curves of alkaline halides with Eu2+ exposed to β radiation

    International Nuclear Information System (INIS)

    Perez S, R.; Piters, T.; Aceves, R.; Rodriguez M, R.

    2006-01-01

    The solid state dosemeters plays a very important paper in the growing use of the ionizing radiation. When being increased the use of the radioactive isotopes in the medicine and in the industry, the necessity to have materials but adapted in each case it has increased. To synthesize such materials, it is necessary to enlarge the knowledge on the paper that its play the physical characteristics of the crystals such as the crystalline structure, the lattice constant, imbibed nano structures, dislocations, ions size, electronic states of the ions, etc., on the effects of the ionizing radiation. In the past its have been carried out many studies approaching these problems in some materials, but we consider that its are insufficient before the challenges of the applications. To contribute to the understanding of these effects, we present a study focused to alkaline halide crystals impurified with Eu 2+ ions, making an analysis on the paper that its play a) the ions concentration of Eu 2+ in KBr: Eu 2+ , b) the different sites of trapping of electrons and holes in KBr: Eu 2+ , KCl: Eu 2+ , RbBr:Eu 2+ , RbCl: Eu 2+ and c) the composition of the crystalline solid solutions KCl x Br 1-X : Eu 2+ and RbCI x KBr 1-x : Eu 2+ on the thermoluminescence curve when these materials are exposed to small dose of β irradiation. The increase in the concentration of Eu 2+ ions produces a smaller relative intensity of the emissions of high temperature for a given dose and it is found that in a RbCl x KBr 1-x : Eu 2+ with the greater/smaller concentration of Cl - ions, the temperature of the characteristic emission is near to the 453/373 K. The composition x of halogenous ions and not the one of alkaline in the crystalline solid solution dominates the landslide of the temperature of the emission. (Author)

  8. Modelling of water permeability in cementitious materials

    DEFF Research Database (Denmark)

    Guang, Ye; Lura, Pietro; van Breugel, K.

    2006-01-01

    This paper presents a network model to predict the permeability of cement paste from a numerical simulation of its microstructure. Based on a linked list pore network structure, the effective hydraulic conductivity is estimated and the fluid flow is calculated according to the Hagen-Poiseuille la...

  9. Dissolution rates of amorphous silica in highly alkaline solution

    International Nuclear Information System (INIS)

    Niibori, Yuichi; Tochiyama, Osamu; Kunita, Masahisa; Chida, Tadashi

    2000-01-01

    Cement is an essential materials to construct the subsurface radioactive waste disposal system. However, cementitious materials alter the groundwater pH to highly alkaline condition about 13. To comprehend the effect of such a hyperalkaline condition on the repository surroundings, this study focused on the dissolution rates of amorphous silica at [NaOH]=10 -1 mol·dm -3 . The used samples were three kinds of pure commercial silica and a natural silica scale which was obtained from inside wall of the hot-water pipe of a geothermal power plant. The observed dissolution rates were interpreted with using the model, which assumed that the particle sizes decrease with the progress of dissolution. Moreover, due to the particle size distribution anticipated in the natural silica scale, this analysis assumed it contained particles with various initial diameters. In the results, (1) all pure silica samples and at least 60 wt% of the silica scale showed good agreement of the activation energy of the dissolution in the range of 77 through 88 kJ·mol -1 in the highly alkaline solution, (2) these rate constants were of the order of 10 -8 - 10 -7 mol·m -2 ·s -1 at around 310 K and were definitely larger than those already reported for quartz, (3) the specific surface area based on BET method was revealed to be an important factor to give the main difference in the dissolution rates between the synthetic silica and the natural silica. (author)

  10. Effect of different dispersants in compressive strength of carbon fiber cementitious composites

    Science.gov (United States)

    Lestari, Yulinda; Bahri, Saiful; Sugiarti, Eni; Ramadhan, Gilang; Akbar, Ari Yustisia; Martides, Erie; Khaerudini, Deni S.

    2013-09-01

    Carbon Fiber Cementitious Composites (CFCC) is one of the most important materials in smart concrete applications. CFCC should be able to have the piezoresistivity properties where its resistivity changes when there is applied a stress/strain. It must also have the compressive strength qualification. One of the important additives in carbon fiber cementitious composites is dispersant. Dispersion of carbon fiber is one of the key problems in fabricating piezoresistive carbon fiber cementitious composites. In this research, the uses of dispersants are methylcellulose, mixture of defoamer and methylcellulose and superplasticizer based polycarboxylate. The preparation of composite samples is similar as in the mortar technique according to the ASTM C 109/109M standard. The additives material are PAN type carbon fibers, methylcellulose, defoamer and superplasticizer (as water reducer and dispersant). The experimental testing conducts the compressive strength and resistivity at various curing time, i.e. 3, 7 and 28 days. The results obtained that the highest compressive strength value in is for the mortar using superplasticizer based polycarboxylate dispersant. This also shown that the distribution of carbon fiber with superplasticizer is more effective, since not reacting with the cementitious material which was different from the methylcellulose that creates the cement hydration reaction. The research also found that the CFCC require the proper water cement ratio otherwise the compressive strength becomes lower.

  11. Alkaline-earth metal (Mg) polynitrides at high pressure as possible high-energy materials.

    Science.gov (United States)

    Wei, Shuli; Li, Da; Liu, Zhao; Li, Xin; Tian, Fubo; Duan, Defang; Liu, Bingbing; Cui, Tian

    2017-03-29

    The high-pressure structural evolutionary behaviors of magnesium polynitrides were studied up to 100 GPa using first-principles calculations. Using the unbiased structure searching method, five stable chemical stoichiometries of magnesium polynitrides (MgN, Mg 2 N 3 , MgN 2 , MgN 3 , and MgN 4 ) were theoretically predicted at high pressures. The predicted MgN x compounds contain a rich variety of polynitrogen forms ranging from charged molecules (one-dimensional bent molecules N 3 , planar triangle N 4 to benzene-like rings N 6 ) to extended polymeric chains (N ∞ ). To the best of our knowledge, this is the first time that stable bent molecules N 3 , planar triangle N 4 , and polymeric chains (N ∞ ) were predicted in alkaline-earth metal polynitrides. The decomposition of P1[combining macron]-MgN 3 and P1[combining macron]-MgN 4 are expected to be highly exothermic, releasing an energy of approximately 2.83 kJ g -1 and 2.01 kJ g -1 , respectively. Furthermore, P1[combining macron]-MgN 4 can be synthesized at several GPa. The results of the present study suggest that it is possible to obtain energetic polynitrogen in main-group nitrides under high pressure.

  12. Inclined Fiber Pullout from a Cementitious Matrix: A Numerical Study

    Directory of Open Access Journals (Sweden)

    Hui Zhang

    2016-09-01

    Full Text Available It is well known that fibers improve the performance of cementitious composites by acting as bridging ligaments in cracks. Such bridging behavior is often studied through fiber pullout tests. The relation between the pullout force vs. slip end displacement is characteristic of the fiber-matrix interface. However, such a relation varies significantly with the fiber inclination angle. In the current work, we establish a numerical model to simulate the entire pullout process by explicitly representing the fiber, matrix and the interface for arbitrary fiber orientations. Cohesive elements endorsed with mixed-mode fracture capacities are implemented to represent the bond-slip behavior at the interface. Contact elements with Coulomb’s friction are placed at the interface to simulate frictional contact. The bond-slip behavior is first calibrated through pull-out curves for fibers aligned with the loading direction, then validated against experimental results for steel fibers oriented at 30 ∘ and 60 ∘ . Parametric studies are then performed to explore the influences of both material properties (fiber yield strength, matrix tensile strength, interfacial bond and geometric factors (fiber diameter, embedment length and inclination angle on the overall pullout behavior, in particular on the maximum pullout load. The proposed methodology provides the necessary pull-out curves for a fiber oriented at a given angle for multi-scale models to study fracture in fiber-reinforced cementitious materials. The novelty lies in its capacity to capture the entire pullout process for a fiber with an arbitrary inclination angle.

  13. Interaction of low pH cementitious concretes with groundwaters

    International Nuclear Information System (INIS)

    Garcia Calvo, Jose Luis; Alonso, Maria Cruz; Hidalgo, Ana; Fernandez Luco, Luis

    2012-01-01

    Some engineering construction concepts for high level radioactive waste underground repositories consider the use of a bentonite barrier in contact with cementitious materials with a pore fluid pH value inferior or equal to 11 (based on low-pH cements) to maintain the bentonite stability. The research on low-pH cementitious materials is mainly addressed from two different approaches, one with Calcium Silicate Cements (OPC, Ordinary Portland Cement based), the other with Calcium Aluminates Cements (CAC based). The use of these both types of cements (OPC based or CAC based) implies the use of high mineral additions contents in the binder that should significantly modify most of the concrete 'standard' properties. Taking into account the long life expected in this type of repositories, parameters related to the durability of the low-pH concretes must be analyzed. This work shows some recent studies that deal with the evaluation of the resistance of low-pH concretes to long term groundwater aggression. After a presentation of the accelerated leaching test (based on a percolation method), results are given for the characterization of the leaching solution evolution and the evaluation of the modifications generated in the solid phases. Results show that the low-pH concretes evaluated have good resistance against groundwater interaction, although an altered front can be observed from the surface in all the tested samples

  14. Electrochemical behavior of NixW1−x materials as catalyst for hydrogen evolution reaction in alkaline media

    International Nuclear Information System (INIS)

    Oliver-Tolentino, Miguel A.; Arce-Estrada, Elsa M.; Cortés-Escobedo, Claudia A.; Bolarín-Miro, Ana M.; Sánchez-De Jesús, Félix; González-Huerta, Rosa de G.; Manzo-Robledo, Arturo

    2012-01-01

    Highlights: ► The electrochemical techniques used in this study elucidated the Ni–W surface state. ► The Ni–W materials were effective for the hydrogen evolution reaction. ► The prepared alloys exhibited higher catalytic activity than their precursors. ► The preparation method is relatively simple and effective procedure. - Abstract: In the present work, results of electrochemical evaluation, as well as morphological and structural characterization of Ni x W 1−x materials with x = 0.77, 0.64, 0.4, 0.19 and 0.07 processed by means of high energy ball milling from high purity powders are presented. Also, the electrocatalytic performance on the hydrogen evolution reaction (HER) of the Ni x W 1−x materials evaluated by linear polarization and cyclic voltammetry techniques in alkaline media at room temperature is discussed. The structural and morphological characterization of the as-prepared materials was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results indicated a small-particle clusters and solid solution formation. According to the kinetics parameters the best electrocatalytic activity was observed at Ni 64 W 36 .

  15. Alkaline "Permanent" Paper.

    Science.gov (United States)

    Pacey, Antony

    1991-01-01

    Discussion of paper manufacturing processes and their effects on library materials focuses on the promotion of alkaline "permanent" paper, with less acid, by Canadian library preservation specialists. Standards for paper acidity are explained; advantages of alkaline paper are described, including decreased manufacturing costs; and…

  16. Service life prediction and cementitious composites

    DEFF Research Database (Denmark)

    Stoklund Larsen, E.

    The present Ph.D.thesis describes and discusses the applicability of a systematic methodology recommended by CIB W80/RILEM-PSL for sevice life prediction. The report describes the most important inherent and environmental factors affecting the service life of structures of cementitious composites...

  17. Synthesis and Sintering Behavior of Cordierite Prepared from Multi-Component Materials Including Alkaline-Earth Minerals

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Suk-In; Kim, Nam-Il; Lee, Sang-Jin [Mokpo National University, Muan (Korea, Republic of)

    2016-10-15

    Cordierite was synthesized using multi-component materials based on a talc-alumina-clay system. The cordierite sintered at 1360 °C showed a high relative density of 98.8% and a low thermal expansion coefficient of 1.59×10{sup -}6/°C. To study the effect of adding alkaline-earth minerals on the cordierite properties, petalite, potash-feldspar, and dicalcium phosphate were added to the synthesized cordierite. In the case of 9 wt% petalite or potash-feldspar addition, the cordierite was more densified; however, the thermal expansion coefficient and the pyroplasticity index were increased. In particular, a 5 μm thick self-glazed coating was formed with the addition of 9 wt% potash-feldspar. In the case of adding dicalcium phosphate, a glass phase was formed at low temperature and gas bubbles formed at high temperature above 1320 ℃. The cordierite synthesized using multi-component materials is expected to be employed as a material for high thermal shock, dense-microstructure flameware.

  18. Gel-like properties of MCM-41 material and its transformation to MCM-50 in a caustic alkaline surround

    International Nuclear Information System (INIS)

    Saputra, Hens; Othman, Raihan; Sutjipto, A.G.E.; Muhida, R.; Ani, M.H.

    2012-01-01

    Highlights: ► MCM-41 material transforms gradually into MCM-50 lamellar gel upon controlled exposure to 6 M KOH. ► The formation of MCM-50 ordered gel structure occurs at KOH weight content of 40–70 wt. %. ► MCM gel phase shows pseudoplastic behavior and possesses homogeneous matrix texture. -- Abstract: MCM-41 material, prepared by sol–gel method, reveals gel-like properties in a caustic alkaline environment, i.e., 6 M potassium hydroxide (KOH) electrolyte. The gellation of MCM-41 starts at a KOH weight ratio of 40 wt.%. The structural change of the material is verified with X-Ray diffractograms and supported by observation using Scanning Electron Microscope (SEM). As the KOH weight ratio increases, the MCM-41 hexagonal arrays structure gradually transforms into MCM-50 lamellar structure before disappearing completely at 80 wt.% KOH. The MCM gel phase is further characterized by rotational viscometry and texture analysis. The gel phase shows shear thinning or pseudoplastic behavior and possesses homogeneous matrix structure.

  19. Gel-like properties of MCM-41 material and its transformation to MCM-50 in a caustic alkaline surround

    Energy Technology Data Exchange (ETDEWEB)

    Saputra, Hens [Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728 Kuala Lumpur (Malaysia); Othman, Raihan, E-mail: raihan@iium.edu.my [Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728 Kuala Lumpur (Malaysia); Sutjipto, A.G.E.; Muhida, R.; Ani, M.H. [Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728 Kuala Lumpur (Malaysia)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer MCM-41 material transforms gradually into MCM-50 lamellar gel upon controlled exposure to 6 M KOH. Black-Right-Pointing-Pointer The formation of MCM-50 ordered gel structure occurs at KOH weight content of 40-70 wt. %. Black-Right-Pointing-Pointer MCM gel phase shows pseudoplastic behavior and possesses homogeneous matrix texture. -- Abstract: MCM-41 material, prepared by sol-gel method, reveals gel-like properties in a caustic alkaline environment, i.e., 6 M potassium hydroxide (KOH) electrolyte. The gellation of MCM-41 starts at a KOH weight ratio of 40 wt.%. The structural change of the material is verified with X-Ray diffractograms and supported by observation using Scanning Electron Microscope (SEM). As the KOH weight ratio increases, the MCM-41 hexagonal arrays structure gradually transforms into MCM-50 lamellar structure before disappearing completely at 80 wt.% KOH. The MCM gel phase is further characterized by rotational viscometry and texture analysis. The gel phase shows shear thinning or pseudoplastic behavior and possesses homogeneous matrix structure.

  20. Strengthening masonry infill panels using engineered cementitious composites

    DEFF Research Database (Denmark)

    Dehghani, Ayoub; Fischer, Gregor; Nateghi Alahi, Fariborz

    2015-01-01

    This comprehensive experimental study aims at investigating the behavior of masonry infill panels strengthened by fiber reinforced engineered cementitious composites (ECC). The experimental program included testing of materials, masonry elements and panels. Material tests were carried out first...... for ECC in order to assess its distinctive mechanical properties such as tensile stress–strain behavior and multiple cracking. To investigate the influence of a thin layer of ECC on plain masonry in terms of changes in stiffness, strength, and deformability, small scale tests have been conducted...... on masonry elements. Finally, a total of 10 brick panels including two control specimens and eight specimens with different ECC-strengthening configuration were selected. The specimens were subjected to diagonal compression loading under displacement control to evaluate their in-plane deformation...

  1. High-Tc superconducting materials in Y-Ba-Cu-O system with the dopants of alkaline metals

    International Nuclear Information System (INIS)

    Kuznetsov, M.V.

    1996-01-01

    The dopants of alkaline metals being introduced into the system Y-Ba-Cu-O do not greatly effect the value of T c . The dopants of alkaline metals lead to the formation of new super-conducting structures o the solid solutions types incorporating an alkaline metal; however, the region of homogeneity of these solutions are different due to the variety of conditions and methods of synthesis. Super-conducting structures, containing an alkaline metal, are characterized by the lowered content of oxygen in comparison with the system YBa 2 Cu 3 O 7-y . Probably, the presence of an alkaline metal in the structure of super-conducting system Y-Ba-Cu-O promotes the retaining of an orthorhombic nature of the crystalline lattice of the product at any dopant concentration. 49 refs

  2. An investigation of zincite from spent anodic portions of alkaline batteries: An industrial mineral approach for evaluating stock material for recycling potential

    Science.gov (United States)

    Barrett, Heather A.; Borkiewicz, Olaf; Krekeler, Mark P. S.

    The mineralogy of anodic portions of spent alkaline batteries from a leading brand (Duracell) that had been equilibrated in ambient air for approximately 4 months was investigated to determine if material generated from this low energy process may be suitable stock material for recycling. Powder X-ray diffraction (XRD) identified the bulk of the ambient air oxidized anodic material as zincite (ZnO). Scanning electron microscopy investigation indicates a variety of textures of zincite are present with euhedral hexagonal prisms being the most common crystal form. Energy dispersive spectroscopy (EDS) analysis indicates that there are no minor amounts of Mn within the zincite. Transmission electron microscopy investigation indicates a variety of textures exist in the zinc oxide. Impurities in the batteries. A promising applications of zincite are numerous, including the development of new solar cell materials. The spent alkaline battery waste stream may serve as promising resource for driving further development of this sector of the economy.

  3. Electrodeposited gold nanoparticles on carbon nanotube-textile: Anode material for glucose alkaline fuel cells

    KAUST Repository

    Pasta, Mauro

    2012-06-01

    In the present paper we propose a new anode material for glucose-gluconate direct oxidation fuel cells prepared by electrodepositing gold nanoparticles onto a conductive textile made by conformally coating single walled carbon nanotubes (SWNT) on a polyester textile substrate. The electrodeposition conditions were optimized in order to achieve a uniform distribution of gold nanoparticles in the 3D porous structure of the textile. On the basis of previously reported studies, the reaction conditions (pH, electrolyte composition and glucose concentration) were tuned in order to achieve the highest oxidation rate, selectively oxidizing glucose to gluconate. The electrochemical characterization was carried out by means of cyclic voltammetry. © 2012 Elsevier B.V. All rights reserved.

  4. Towards more sustainable construction–application of superabsorbent polymers in cementitious matrices with reduced carbon footprint

    Directory of Open Access Journals (Sweden)

    Klemm Agnieszka J.

    2018-01-01

    Full Text Available Construction industry is constantly searching for sustainable innovations to mitigate negative environmental impacts. Ground granulated blast-furnace slag (GGBS is a well-known supplementary cementitious material which contributes to reduction of energy and CO2 emissions from cement industry. However, its use in cementitious systems leads to materials with high cracking susceptibility due to their greater autogenous shrinkage triggered by self-desiccation processes. This problem is even more pronounced when concrete is exposed to severe dry-hot weather conditions, such as in North Africa. In order to mitigate this negative effect of cracking, internal curing agents in the form of Superabsorbent polymers (SAP can be successfully used. This approach leads to more durable cement based materials and in turn more sustainable constructions.

  5. OVERVIEW OF THE U.S. DEPARTMENT OF ENERGY AND NUCLEAR REGULATORY COMMISSION PERFORMANCE ASSESSMENT APPROACHES: CEMENTITIOUS BARRIERS PARTNERSHIP

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Burns, H.

    2009-05-29

    Engineered barriers including cementitious barriers are used at sites disposing or contaminated with low-level radioactive waste to enhance performance of the natural environment with respect to controlling the potential spread of contaminants. Drivers for using cementitious barriers include: high radionuclide inventory, radionuclide characteristics (e.g., long half-live, high mobility due to chemical form/speciation, waste matrix properties, shallow water table, and humid climate that provides water for leaching the waste). This document comprises the first in a series of reports being prepared for the Cementitious Barriers Partnership. The document is divided into two parts which provide a summary of: (1) existing experience in the assessment of performance of cementitious materials used for radioactive waste management and disposal and (2) sensitivity and uncertainty analysis approaches that have been applied for assessments. Each chapter is organized into five parts: Introduction, Regulatory Considerations, Specific Examples, Summary of Modeling Approaches and Conclusions and Needs. The objective of the report is to provide perspective on the state of the practice for conducting assessments for facilities involving cementitious barriers and to identify opportunities for improvements to the existing approaches. Examples are provided in two contexts: (1) performance assessments conducted for waste disposal facilities and (2) performance assessment-like analyses (e.g., risk assessments) conducted under other regulatory regimes. The introductory sections of each section provide a perspective on the purpose of performance assessments and different roles of cementitious materials for radioactive waste management. Significant experience with assessments of cementitious materials associated with radioactive waste disposal concepts exists in the US Department of Energy Complex and the commercial nuclear sector. Recently, the desire to close legacy facilities has created

  6. Novel Co(OH)2 with cotton-like structure as anode material for alkaline secondary batteries

    Science.gov (United States)

    Zhao, W.; Liao, Y. L.; Qiu, S. J.; Chu, H. L.; Zou, Y. J.; Xiang, C. L.; Zhang, H. Z.; Xu, F.; Sun, L. X.

    2018-01-01

    The cotton-like Co(OH)2 (S-Co(OH)2) was successfully synthesized and its electrochemical performance was systematically investigated. S-Co(OH)2 was prepared through the “destruction” of the newly formed colloid Co(OH)2 by the reduction using sodium borohydride. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Used as an anode material for alkaline secondary batteries, S-Co(OH)2 sample exhibited better cycle stability, higher electrochemical capacity, and higher rate performance than those of conventional β-Co(OH)2. At a discharge current density of 100 mA/g, the initial discharge capacity of S-Co(OH)2 is 549.3 mAh/g and the discharge capacity is still sustained to be 329.2 mAh/g after 100 charge-discharge cycles with a capacity retention of 59.9%.

  7. Triboluminesence multifunctional cementitious composites with in situ damage sensing capability

    Science.gov (United States)

    Olawale, David O.; Dickens, Tarik; Uddin, Mohammed J.; Okoli, Okenwa O.

    2012-04-01

    Structural health monitoring of civil infrastructure systems like concrete bridges and dams has become critical because of the aging and overloading of these CIS. Most of the available SHM methods are not in-situ and can be very expensive. The triboluminescence multifunctional cementitious composites (TMCC) have in-built crack detection mechanism that can enable bridge engineers to monitor and detect abnormal crack formation in concrete structures so that timely corrective action can be taken to prevent costly or catastrophic failures. This article reports the fabrication process and test result of the flexural characterization of the TMCC. Accelerated durability test indicated that the 0.5 ZnS:Mn/Epoxy weight fraction ITOF sensor configuration to be more desirable in terms of durability. The alkaline environment at the highest temperature investigated (45 °C) resulted in significant reduction in the mean glass transition and storage moduli of the tested ITOF thin films. Further work is ongoing to correlate the TL response of the TMCC with damage, particularly crack opening.

  8. Effects of using silica fume and polycarboxylate-type superplasticizer on physical properties of cementitious grout mixtures for semiflexible pavement surfacing.

    Science.gov (United States)

    Koting, Suhana; Karim, Mohamed Rehan; Mahmud, Hilmi; Mashaan, Nuha S; Ibrahim, Mohd Rasdan; Katman, Herdayati; Husain, Nadiah Md

    2014-01-01

    Semi-flexible pavement surfacing is a composite pavement that utilizes the porous pavement structure of the flexible bituminous pavement, which is subsequently grouted with appropriate cementitious materials. This study aims to investigate the compressive strength, flexural strength, and workability performance of cementitious grout. The grout mixtures are designed to achieve high strength and maintain flow properties in order to allow the cement slurries to infiltrate easily through unfilled compacted skeletons. A paired-sample t-test was carried out to find out whether water/cement ratio, SP percentages, and use of silica fume influence the cementitious grout performance. The findings showed that the replacement of 5% silica fume with an adequate amount of superplasticizer and water/cement ratio was beneficial in improving the properties of the cementitious grout.

  9. Effects of Using Silica Fume and Polycarboxylate-Type Superplasticizer on Physical Properties of Cementitious Grout Mixtures for Semiflexible Pavement Surfacing

    Directory of Open Access Journals (Sweden)

    Suhana Koting

    2014-01-01

    Full Text Available Semi-flexible pavement surfacing is a composite pavement that utilizes the porous pavement structure of the flexible bituminous pavement, which is subsequently grouted with appropriate cementitious materials. This study aims to investigate the compressive strength, flexural strength, and workability performance of cementitious grout. The grout mixtures are designed to achieve high strength and maintain flow properties in order to allow the cement slurries to infiltrate easily through unfilled compacted skeletons. A paired-sample t-test was carried out to find out whether water/cement ratio, SP percentages, and use of silica fume influence the cementitious grout performance. The findings showed that the replacement of 5% silica fume with an adequate amount of superplasticizer and water/cement ratio was beneficial in improving the properties of the cementitious grout.

  10. Investigation on the Activity Activation and Cementitious Property of Coal Gangue with High Iron and Silica Contents

    Science.gov (United States)

    Wu, Hong; Li, Yu; Teng, Min; Yang, Yu

    2017-11-01

    The activity of coal gangue by thermal activation and composite activation technologies was investigated. The crystal composition, framework structure and morphology change were analyzed by XRD, FT-IR and SEM, respectively. The cementitious property of coal gangue was measured by strength test. The results showed that thermal activation decomposed kaolinite in coal gangue, and formed the metastable structure with a porous state, multiple internal broken bonds and large specific surface areas. Based on thermal activation, the added lime provided the alkaline environment, then this reduced the bond energy of reactant particles and the degree of crystallinity of quartz in coal gangue. The two activation methods could effectively improve the cementitious property of coal gangue based unburned bricks, and that the composite activation technology was superior performance.

  11. A Review on Nanomaterial Dispersion, Microstructure, and Mechanical Properties of Carbon Nanotube and Nanofiber Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Shama Parveen

    2013-01-01

    Full Text Available Excellent mechanical, thermal, and electrical properties of carbon nanotubes (CNTs and nanofibers (CNFs have motivated the development of advanced nanocomposites with outstanding and multifunctional properties. After achieving a considerable success in utilizing these unique materials in various polymeric matrices, recently tremendous interest is also being noticed on developing CNT and CNF reinforced cement-based composites. However, the problems related to nanomaterial dispersion also exist in case of cementitious composites, impairing successful transfer of nanomaterials' properties into the composites. Performance of cementitious composites also depends on their microstructure which is again strongly influenced by the presence of nanomaterials. In this context, the present paper reports a critical review of recent literature on the various strategies for dispersing CNTs and CNFs within cementitious matrices and the microstructure and mechanical properties of resulting nanocomposites.

  12. Mobility of as, Cu, Cr, and Zn from tailings covered with sealing materials using alkaline industrial residues: a comparison between two leaching methods.

    Science.gov (United States)

    Jia, Yu; Maurice, Christian; Öhlander, Björn

    2016-01-01

    Different alkaline residue materials (fly ash, green liquor dregs, and lime mud) generated from the pulp and paper industry as sealing materials were evaluated to cover aged mine waste tailings (<1% sulfur content, primarily pyrite). The mobility of four selected trace elements (Cr, Cu, Zn, and As) was compared based on batch and column leaching studies to assess the effectiveness of these alkaline materials as sealing agents. Based on the leaching results, Cr, Cu, and Zn were immobilized by the alkaline amendments. In the amended tailings in the batch system only As dramatically exceeded the limit values at L/S 10 L/kg. The leaching results showed similar patterns to the batch results, though leached Cr, Cu, and Zn showed higher levels in the column tests than in the batch tests. However, when the columns were compared with the batches, the trend for Cu was opposite for the unamended tailings. By contrast, both batch and column results showed that the amendment caused mobilization of As compared with the unamended tailings in the ash-amended tailings. The amount of As released was greatest in the ash column and decreased from the dregs to the lime columns. The leaching of As at high levels can be a potential problem whenever alkaline materials (especially for fly ash) are used as sealing materials over tailings. The column test was considered by the authors to be a more informative method in remediation of the aged tailings with low sulfur content, since it mimics better actual situation in a field.

  13. Non-cementitious compositions comprising vaterite and methods thereof

    Energy Technology Data Exchange (ETDEWEB)

    Devenney, Martin; Fernandez, Miguel; Morgan, Samuel O.

    2015-09-15

    Non-cementitious compositions and products are provided. The compositions of the invention include a carbonate additive comprising vaterite such as reactive vaterite. Additional aspects of the invention include methods of making and using the non-cementitious compositions and products.

  14. High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

    Energy Technology Data Exchange (ETDEWEB)

    Song, Ping; Barkholtz, Heather M.; Wang, Ying; Xu, Weilin; Liu, Dijia; Zhuang, Lin

    2017-12-01

    We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives of Pt-based catalysts with best performance/price.

  15. Mechanical interaction of Engineered Cementitious Composite (ECC) reinforced with Fiber Reinforced Polymer (FRP) rebar in tensile loading

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    2010-01-01

    This paper introduces a preliminary study of the composite interaction of Engineered Cementitious Composite (ECC), reinforced with Glass Fiber Reinforced Polymer (GFRP) rebar. The main topic of this paper will focus on the interaction of the two materials (ECC and GFRP) during axial loading...... distribution which in terms results in less mechanical deterioration during loading....

  16. Permeability Change of Crystalline Silicate Mineral-Packed Bed Column by Highly Alkaline Plume

    International Nuclear Information System (INIS)

    Hideo Usui; Yuichi Niibori; Hitoshi Mimura; Osamu Tochiyama

    2007-01-01

    For the construction of the geological disposal system, the use of the cementitious material may change the permeability of the natural barrier around the repository. Cementitious materials may alter the pH of ground water to highly alkaline. Also, the potential permeability change of the natural barrier is one of the notable factors for performance assessments of geological disposal systems. In the high pH region, the solubility of silica is very high compared to that in the natural pH (around 8). Therefore, highly alkaline groundwater would dissolve and alter a part of rock surface. Usui et al. (2005) reported that the change of mineral pore structure due to chemical reaction is the key factor to consider the change of the permeability [5-6]. Moreover, such a change of the pore structure was considered to be the result of the spatial heterogeneity of chemical composition. Since such spatial heterogeneity exists also in the sedimentary rocks consisting of crystalline minerals such as quartz and feldspar, we need to examine natural rock, in order to obtain more reliable understanding about the change of permeability induced by highly alkaline groundwater (plume). In this study, silica sand as crystalline mineral was packed in the column, and the effect of dissolution induced by the highly alkaline plume on the permeability-change was examined. The silica sand particles mainly consist of SiO 2 and include Al 2 O 3 , FeO, and K 2 O. The volumetric flow rate and the pressure difference between the inlet and outlet of the column were measured, and the permeability was calculated. At the same time, the concentrations of elements in the fluid were measured by ICP-AES. The experimental result showed that permeability decreased gradually, although the silica sand was continuously dissolved in the column. The behavior of the permeability is considered to be the result from the rearrangement of the particles, or precipitation of secondary mineral. In the column test using

  17. Contribution to the study of cementitious and clayey materials behaviour in the context of deep geological disposal: transport aspect, durability and thermo-hydro-mechanical behaviour; Contribution a l'etude du comportement des materiaux cimentaires et argileux en vue de leur utilisation dans le contexte du stockage geologique profond: aspect transport, durabilite et comportement thermo-hydro-mecanique

    Energy Technology Data Exchange (ETDEWEB)

    Galle, C.

    2011-07-15

    Deep geological formation disposal is the reference solution in France for the management of medium and high activities radioactive waste. In this context, to demonstrate the feasibility of such a disposal, it is necessary to evaluate the long-term performances and the behaviour of the materials engaged in the elaboration of engineered barrier systems (EBS) and waste package elements. The studies mentioned and synthesized in this HDR thesis focused mainly on the convective transport of gas (under pressure gradient) in cementitious matrices, by coupling microstructure aspect (porosity/pores sizes distribution) and hydric environment (water saturation). Works on physico-chemical durability allowed the description of the chemical degradation of cement-based materials in extreme conditions using ammonium nitrate, to increase the materials damaging processes in order to identify functional margins. In relationship with the interim storage management phase, studies related to the behaviour and characterization of concrete submitted to high temperatures (up to 400 C) were also described. Finally, results concerning the gas (H{sub 2}) overpressure resistance of engineered barriers made of compacted clays were summarized. (author)

  18. Relations between structure and material properties in earth alkaline silicate basing phosphors; Struktureigenschaftsbeziehungen in Erdalkalisilikat basierenden Leuchtstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Wolfgang

    2008-03-19

    This work is basing on the relation between structure and luminescence of Eu{sup 2+} doped Earth-Alkaline-Silicates. After an overview of Earth-Alkaline-Silicates silicates with an additional cation (Li{sup +}, Al{sup 3+}) and an additional anion (Cl{sup -}, N{sup 3-}) are examined in chapter 4 and 5. Basing on this data an relation between structural influence - like ion-radii, anion and coordination polyeder - and phosphor luminescence is set up. The ability of using as an industrial phosphor is made in the final chapter. (orig.)

  19. An alternative approach to the management of reactive metals: tolerant cementitious systems

    International Nuclear Information System (INIS)

    Swift, P.; Cox, J.; Wise, M.; McKinney, J.; Rhodes, C.

    2015-01-01

    In recent years research has focused on preventing or minimising corrosion of reactive metals to ensure long-term waste package integrity. An alternative approach to the encapsulation of reactive metals is being explored. The approach will identify a cementitious-based encapsulating material that will allow corrosion of reactive metals to occur in a controlled and predictable manner, rather than seeking to limit or prevent the corrosion, whilst retaining waste package integrity. A low strength grout will be developed that will be 'tolerant' to the expansive forces generated by the corrosion products of reactive metals. Novel cementitious systems (e.g. foamed cements, rubber composite cements, cenosphere composite cements, lime mortars, bentonite cements etc.) that may be tolerant to potentially expansive waste products, such as reactive metals will be considered and assessed in a series of small-scale preliminary trials (compressive strength, porosity, permeability, pore solution pH, etc.)

  20. Advances in alternative cementitious binders

    International Nuclear Information System (INIS)

    Juenger, M.C.G.; Winnefeld, F.; Provis, J.L.; Ideker, J.H.

    2011-01-01

    There is a burgeoning interest in the development, characterization, and implementation of alternatives to Portland cement as a binder in concrete. The construction materials industry is under increasing pressure to reduce the energy used in production of Portland cement clinker and the associated greenhouse gas emissions. Further, Portland cement is not the ideal binder for all construction applications, as it suffers from durability problems in particularly aggressive environments. Several alternative binders have been available for almost as long as Portland cement, yet have not been extensively used, and new ones are being developed. In this paper, four promising binders available as alternatives to Portland cement are discussed, namely calcium aluminate cement, calcium sulfoaluminate cement, alkali-activated binders, and supersulfated cements. The history of the binders, their compositions and reaction mechanisms, benefits and drawbacks, unanswered questions, and primary challenges are described.

  1. Modelling the carbonation of cementitious matrixes by means of the unreacted-core model, UR-CORE

    International Nuclear Information System (INIS)

    Castellote, M.; Andrade, C.

    2008-01-01

    This paper presents a model for the carbonation of cementitious matrixes (UR-CORE). The model is based on the principles of the 'unreacted-core' systems, typical of chemical engineering processes, in which the reacted product remains in the solid as a layer of inert ash, adapted for the specific case of carbonation. Development of the model has been undertaken in three steps: 1) Establishment of the controlling step in the global carbonation rate, by using data of fractional conversion of different phases of the cementitious matrixes, obtained by the authors through neutron diffraction data experiments, and reported in [M. Castellote, C. Andrade, X. Turrillas, J. Campo, G. Cuello, Accelerated carbonation of cement pastes in situ monitored by neutron diffraction, Cem. Concr. Res. (2008), doi:10.1016/j.cemconres.2008.07.002]. 2) Then, the model has been adapted and applied to the cementitious materials using different concentrations of CO 2 , with the introduction of the needed assumptions and factors. 3) Finally, the model has been validated with laboratory data at different concentrations (taken from literature) and for long term natural exposure of concretes. As a result, the model seems to be reliable enough to be applied to cementitious materials, being able to extrapolate the results from accelerated tests in any conditions to predict the rate of carbonation in natural exposure, being restricted, at present stage, to conditions with a constant relative humidity

  2. Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems

    Directory of Open Access Journals (Sweden)

    Alessandra Formia

    2015-04-01

    Full Text Available The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT having two different internal diameters (of 2 mm and 7.5 mm were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm. The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization.

  3. Cementitious Barriers Partnership (CBP): Training and Release of CBP Toolbox Software, Version 1.0 - 13480

    International Nuclear Information System (INIS)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S.; Flach, G.; Langton, C.; Smith, F.G. III; Burns, H.; Van der Sloot, H.; Meeussen, J.C.L.; Samson, E.; Mallick, P.; Suttora, L.; Esh, D.; Fuhrmann, M.; Philip, J.

    2013-01-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the Office of Tank Waste Management within the Office of Environmental Management of U.S. Department of Energy (US DOE). The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that improve understanding and predictions of the long-term hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program are intended to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1,000 years for waste management purposes. CBP software tools were made available to selected DOE Office of Environmental Management and field site users for training and evaluation based on a set of important degradation scenarios, including sulfate ingress/attack and carbonation of cementitious materials. The tools were presented at two-day training workshops held at U.S. National Institute of Standards and Technology (NIST), Savannah River, and Hanford included LeachXS TM /ORCHESTRA, STADIUM R , and a CBP-developed GoldSim Dashboard interface. Collectively, these components form the CBP Software Toolbox. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF) were also presented. The CBP Dashboard uses a custom Dynamic-link library developed by CBP to couple to the LeachXS TM /ORCHESTRA and STADIUM R codes to simulate reactive transport and degradation in cementitious materials for selected performance assessment scenarios. The first day of the workshop introduced participants to the software components via presentation materials, and the second day included hands-on tutorial exercises followed by discussions

  4. Cementitious Barriers Partnership (CBP): Training and Release of CBP Toolbox Software, Version 1.0 - 13480

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S. [Vanderbilt University, School of Engineering, CRESP, Nashville, TN 37235 (United States); Flach, G.; Langton, C.; Smith, F.G. III; Burns, H. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Van der Sloot, H. [Hans Van der Sloot Consultancy, Dorpsstraat 216, 1721BV Langedijk (Netherlands); Meeussen, J.C.L. [Nuclear Research and Consultancy Group, Westerduinweg 3, Petten (Netherlands); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Mallick, P.; Suttora, L. [U.S. Department of Energy, Washington, DC (United States); Esh, D.; Fuhrmann, M.; Philip, J. [U.S. Nuclear Regulatory Commission, Washington, DC (United States)

    2013-07-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the Office of Tank Waste Management within the Office of Environmental Management of U.S. Department of Energy (US DOE). The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that improve understanding and predictions of the long-term hydraulic and chemical performance of cementitious barriers used in nuclear applications. Tools selected for and developed under this program are intended to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1,000 years for waste management purposes. CBP software tools were made available to selected DOE Office of Environmental Management and field site users for training and evaluation based on a set of important degradation scenarios, including sulfate ingress/attack and carbonation of cementitious materials. The tools were presented at two-day training workshops held at U.S. National Institute of Standards and Technology (NIST), Savannah River, and Hanford included LeachXS{sup TM}/ORCHESTRA, STADIUM{sup R}, and a CBP-developed GoldSim Dashboard interface. Collectively, these components form the CBP Software Toolbox. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF) were also presented. The CBP Dashboard uses a custom Dynamic-link library developed by CBP to couple to the LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R} codes to simulate reactive transport and degradation in cementitious materials for selected performance assessment scenarios. The first day of the workshop introduced participants to the software components via presentation materials, and the second day included hands-on tutorial exercises followed

  5. Method of cleaning alkaline metal

    International Nuclear Information System (INIS)

    Kawakami, Yukio; Naito, Kesahiro; Iizawa, Katsuyuki; Nakasuji, Takashi

    1981-01-01

    Purpose: To prevent scattering of used sodium and aqueous alkaline solution when cleaning used sodium and metallic sodium adhering to equipment with an aqueous alkaline solution. Method: A sodium treating container is filled with an aqueous alkaline solution, and stainless steel gauze is sunk in the container. Equipment to be cleaned such as equipment with sodium adhering to it are retained under the gauze and are thus cleaned. On the other hand, the surface of the aqueous alkaline solution is covered with a fluid paraffin liquid covering material. Thus, the hydrogen produced by the reaction of the sodium and the aqueous alkaline solution will float up, pass through the liquid covering material and be discharged. The sodium will pass through the gauze and float upwardly while reacting with the aqueous alkaline solution in a partic ulate state to the boundary between the aqueous alkaline solution and up to the covering material, and thus the theratment reaction will continue. Thus, the cover material prevents the sodium and the aqueous alkaline solution from scattering. (Kamimura, M.)

  6. Stabilitas warna basis gigitiruan resin termoplastik nilon yang direndam dalam larutan pembersih gigitiruan peroksida alkalin Color stability of thermoplastic nylon denture base material immerse in alkaline peroxide denture cleanser

    Directory of Open Access Journals (Sweden)

    Melinda Maria Awing

    2013-06-01

    solution of alkaline peroxide every 8 hours, using 4 speciments for each solutions. Using ANOVA and independent ttest,it showed no significant color changes on thermoplastic nylon resin after immersed in alkaline peroxide solution  based on the time interval. However, there was significant color difference on the thermoplastic nylon resin immersed in alkaline peroxide and control solution at second to seventh interval of 8 hours immersed time with increase of time immersing. It was concluded that thermoplastic nylon resin have good stability although immerse in alkaline peroxide denture cleanser

  7. Design of rapid hardening engineered cementitious composites for sustainable construction

    Directory of Open Access Journals (Sweden)

    Marushchak Uliana

    2017-12-01

    Full Text Available This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica efficiency. A characterization of RHECC’s compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength – 84-95 MPa and parameter Rc2/Rc28 – 65–70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of “self-reinforcement” on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

  8. Design of rapid hardening engineered cementitious composites for sustainable construction

    Science.gov (United States)

    Marushchak, Uliana; Sanytsky, Myroslav; Sydor, Nazar

    2017-12-01

    This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC) nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica) efficiency. A characterization of RHECC's compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength - 84-95 MPa and parameter Rc2/Rc28 - 65-70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix) due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of "self-reinforcement" on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

  9. Image-based detection and analysis of crack propagation in cementitious composites

    DEFF Research Database (Denmark)

    Pereira, E.B.; Fischer, Gregor; Barros, J.A.O.

    2011-01-01

    The initiation and propagation of cracking in concrete and other cementitious materials is a governing mechanism for many physical and mechanical material properties. The observation of these cracking processes in concrete is typically taking place at discrete locations using destructive methods...... after the cracking process has occurred. The alternative nondestructive methods are often either not precise enough or experimentally too demanding. In this study, the use of an image analysis procedure to capture the crack initiation and propagation process is described, which utilizes digital images...

  10. Some properties of saline-alkaline soils of Aydin-Söke plain and activity of gypsum as amelioration material

    OpenAIRE

    Aydın, Gönül; Atatanır, Levent; Yorulmaz, Alper

    2008-01-01

    The study has been carried out in two different areas; a farmer area in Söke Plain and in experimental station of Adnan Menderes University. The aims of study, are to determine of some physical and chemical properties of the soils and to search of activity of gypsum (CaSO4) used in alkaline soils having high sodium. For this purpose, 50,100 and 150 kg/da gypsum were applied to the experimental soils besides control. These applications were made in autumn after harvest period and b...

  11. The effect of alkaline treatment and fiber orientation on impact resistant of bio-composites Sansevieria trifasciata fiber/polypropylene as automotive components material

    Science.gov (United States)

    Shieddieque, Apang Djafar; Mardiyati, Suratman, Rochim; Widyanto, Bambang

    2018-04-01

    The increasing amount of car usage is causing an escalated amount of fuel consumption and CO2 emission. It implicates demand for the automotive industry to increase the efficiency of their products, One of the most effective ways to solve the issue is to find green weight light material for the interior automotive component. The Aim of this research was to investigate the effect of alkaline treatment and fiber orientation on the impact resistant of material bio- composite sansevieiria trifasciata fiber/Polypropylene. In this research, bio-composites sansevieria trifasciata fiber/Polypropylene was prepared with random fiber orientation and unidirectional orientation by using a hot press method with pressure 140 Bar and temperature 240°C. Fiber was taken from Sansevieria trifasciata by using mechanical retting. In this study, Sansevieria fiber was given alkaline treatment (mercerization) with NaOH 3% (w/w) solution at temperature 100°C for an hour. The fraction of fiber volume that were used in this experiment are 0%, 5%, 10%, and 15%. The impact test was conducted based on ASTM D 6110 - 04, and the fracture analysis was investigated by scanning electron microscope (SEM). The best result of impact toughness and fracture analysis were achieved by bio composite untreated and unidirectional sansevieria trifasciata fiber/Polypropylene with fiber volume fraction of 15%, which was 48.092kJ/m2 for impact resistant. As compared to the impact toughness standard, which needed for interior automotive component, the impact toughness of sansevieria trifasciata fiber/Polypropylene has fulfilled the standard of the interior material automotive industry. Therefore, this material can be potentially used as materials on the car exterior component.

  12. Experimental Evaluation of Geopolymer and ‘Lunamer’ Binders as Radioactive Shielding Materials for Space Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — Geopolymers are inorganic cementitious binders produced by polymeric reaction between an aluminosilica rich material and an alkali metal hydroxide/silicate liquid,...

  13. Alkaline direct alcohol fuel cells

    Science.gov (United States)

    Antolini, E.; Gonzalez, E. R.

    The faster kinetics of the alcohol oxidation and oxygen reduction reactions in alkaline direct alcohol fuel cells (ADAFCs), opening up the possibility of using less expensive metal catalysts, as silver, nickel and palladium, makes the alkaline direct alcohol fuel cell a potentially low cost technology compared to acid direct alcohol fuel cell technology, which employs platinum catalysts. A boost in the research regarding alkaline fuel cells, fuelled with hydrogen or alcohols, was due to the development of alkaline anion-exchange membranes, which allows the overcoming of the problem of the progressive carbonation of the alkaline electrolyte. This paper presents an overview of catalysts and membranes for ADAFCs, and of testing of ADAFCs, fuelled with methanol, ethanol and ethylene glycol, formed by these materials.

  14. Cementitious waste option scoping study report

    Energy Technology Data Exchange (ETDEWEB)

    Lee, A.E.; Taylor, D.D.

    1998-02-01

    A Settlement Agreement between the Department of Energy (DOE) and the State of Idaho mandates that all high-level radioactive waste (HLW) now stored at the Idaho Chemical Processing Plant (ICPP) on the Idaho National Engineering and Environmental Laboratory (INEEL) will be treated so that it is ready to be moved out of Idaho for disposal by a target date of 2035. This study investigates the nonseparations Cementitious Waste Option (CWO) as a means to achieve this goal. Under this option all liquid sodium-bearing waste (SBW) and existing HLW calcine would be recalcined with sucrose, grouted, canisterized, and interim stored as a mixed-HLW for eventual preparation and shipment off-Site for disposal. The CWO waste would be transported to a Greater Confinement Disposal Facility (GCDF) located in the southwestern desert of the US on the Nevada Test Site (NTS). All transport preparation, shipment, and disposal facility activities are beyond the scope of this study. CWO waste processing, packaging, and interim storage would occur over a 5-year period between 2013 and 2017. Waste transport and disposal would occur during the same time period.

  15. Cementitious waste option scoping study report

    International Nuclear Information System (INIS)

    Lee, A.E.; Taylor, D.D.

    1998-02-01

    A Settlement Agreement between the Department of Energy (DOE) and the State of Idaho mandates that all high-level radioactive waste (HLW) now stored at the Idaho Chemical Processing Plant (ICPP) on the Idaho National Engineering and Environmental Laboratory (INEEL) will be treated so that it is ready to be moved out of Idaho for disposal by a target date of 2035. This study investigates the nonseparations Cementitious Waste Option (CWO) as a means to achieve this goal. Under this option all liquid sodium-bearing waste (SBW) and existing HLW calcine would be recalcined with sucrose, grouted, canisterized, and interim stored as a mixed-HLW for eventual preparation and shipment off-Site for disposal. The CWO waste would be transported to a Greater Confinement Disposal Facility (GCDF) located in the southwestern desert of the US on the Nevada Test Site (NTS). All transport preparation, shipment, and disposal facility activities are beyond the scope of this study. CWO waste processing, packaging, and interim storage would occur over a 5-year period between 2013 and 2017. Waste transport and disposal would occur during the same time period

  16. Properties of Calcium Acetate Manufactured with Etching Waste Solution and Limestone Sludge as a Cementitious High-Early-Strength Admixture

    OpenAIRE

    Kim, Deuck-Mo; Ryu, Hwa-Sung; Shin, Sang-Heon; Park, Won-Jun

    2016-01-01

    Concrete is one of the most widely used construction materials. There are several methods available to improve its performance, with one of them being the use of high-early-strength admixtures (HESAs). Typical HESAs include calcium nitrate, calcium chloride, and calcium formate (CF). Industrial by-products, such as acetic acid and lime stone sludge (LSS), can be used together to produce calcium acetate (CA), which can subsequently be used as a cementitious HESA. In this study, calcium carbona...

  17. Effect of Alkaline Solution with Varying Mix Proportion on Geopolymer Mortar

    Science.gov (United States)

    Karuppuchamy, K.; Ananthkumar, M.; Raghavapriya, S. M.

    2018-02-01

    Cement production is attributed by emission of carbon dioxide which causes severe environmental impacts. This has led to the invention of special construction materials which can replace cement. On the other hand, these construction materials (like Fly ash, Metakaolin) also need to be inexpensive and should possess all the characteristics of cementitious materials. In this project, the effect of geopolymerization on the properties of the end product were studied with varying distillation of NaOH solution (10M, 12M and 15M) for different mix proportion (1:1, 1:2 and 1:3). Curing was done for 1 day at a temperature of 60°C and 80°C respectively. The densities, compressive strength, alkalinity, co-efficient of absorption were determined. As a result, the experiments showed the effect of factors such as mix proportion, curing temperature and curing day on the physical and mechanical properties such as mix proportion of the geopolymer concrete. Results of NaOH concentration of 12M concentration cured for 24 hours at 80°C and 60°C showed better mechanical performance than the rest of the concentrations.

  18. Electrochemical behavior of Ni{sub x}W{sub 1-x} materials as catalyst for hydrogen evolution reaction in alkaline media

    Energy Technology Data Exchange (ETDEWEB)

    Oliver-Tolentino, Miguel A. [UPIBI-IPN, Departamento de Ciencias Basicas, Av. Acueducto s/n, Barrio La Laguna, Col. Ticoman, Mexico D.F. 07340 (Mexico); Arce-Estrada, Elsa M. [ESIQIE-IPN Departamento de Ingenieria en Metalurgia y Materiales, UPALM, UPALM, Mexico D.F. 07738 (Mexico); Cortes-Escobedo, Claudia A. [Centro de Investigacion e Innovacion Tecnologica del IPN, Cda. Cecati s/n, Col. Sta. Catarina, CP 02250 Azcapotzalco D.F. (Mexico); Bolarin-Miro, Ana M.; Sanchez-De Jesus, Felix [Area Academica de Ciencias de la Tierra y Materiales, Universidad Autonoma del Estado de Hidalgo, CU, Carr. Pachuca-Tulancingo Km. 4.5, Mineral de la Reforma, CP 42184 Hidalgo (Mexico); Gonzalez-Huerta, Rosa de G. [ESIQIE-IPN, Departamento de Ingenieria Quimica - Laboratorio de Electroquimica y Corrosion, Edif. Z-5 3er piso, UPALM, Mexico D.F. 07738 (Mexico); Manzo-Robledo, Arturo, E-mail: amanzor@ipn.mx [ESIQIE-IPN, Departamento de Ingenieria Quimica - Laboratorio de Electroquimica y Corrosion, Edif. Z-5 3er piso, UPALM, Mexico D.F. 07738 (Mexico)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer The electrochemical techniques used in this study elucidated the Ni-W surface state. Black-Right-Pointing-Pointer The Ni-W materials were effective for the hydrogen evolution reaction. Black-Right-Pointing-Pointer The prepared alloys exhibited higher catalytic activity than their precursors. Black-Right-Pointing-Pointer The preparation method is relatively simple and effective procedure. - Abstract: In the present work, results of electrochemical evaluation, as well as morphological and structural characterization of Ni{sub x}W{sub 1-x} materials with x = 0.77, 0.64, 0.4, 0.19 and 0.07 processed by means of high energy ball milling from high purity powders are presented. Also, the electrocatalytic performance on the hydrogen evolution reaction (HER) of the Ni{sub x}W{sub 1-x} materials evaluated by linear polarization and cyclic voltammetry techniques in alkaline media at room temperature is discussed. The structural and morphological characterization of the as-prepared materials was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results indicated a small-particle clusters and solid solution formation. According to the kinetics parameters the best electrocatalytic activity was observed at Ni{sub 64}W{sub 36}.

  19. Mechanical Properties and Shear Strengthening Capacity of High Volume Fly Ash-Cementitious Composite

    Science.gov (United States)

    Joseph, Aswin K.; Anand, K. B.

    2018-02-01

    This paper discusses development of Poly Vinyl Alcohol (PVA) fibre reinforced cementitious composites taking into account environmental sustainability. Composites with fly ash to cement ratios from 0 to 3 are investigated in this study. The mechanical properties of HVFA-cement composite are discussed in this paper at PVA fiber volume fraction maintained at 1% of total volume of composite. The optimum replacement of cement with fly ash was found to be 75%, i.e. fly ash to cement ratio (FA/C) of 3. The increase in fiber content from 1% to 2% showed better mechanical performance. A strain capacity of 2.38% was obtained for FA/C ratio of 3 with 2% volume fraction of fiber. With the objective of evaluating the performance of cementitious composites as a strengthening material in reinforced concrete beams, the beams deficient in shear capacity were strengthened with optimal mix having 2% volume fraction of fiber as the strengthening material and tested under four-point load. The reinforced concrete beams designed as shear deficient were loaded to failure and retrofitted with the composite in order to assess the efficiency as a repair material under shear.

  20. Direct assessment of tensile stress-crack opening behavior of Strain Hardening Cementitious Composites (SHCC)

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2012-01-01

    The process of designing Strain Hardening Cementitious Composites (SHCC) is driven by the need to achieve certain performance parameters in tension. These are typically the pseudo-strain hardening behavior and the ability to develop multiple cracks. The assessment of the tensile load-deformation ......The process of designing Strain Hardening Cementitious Composites (SHCC) is driven by the need to achieve certain performance parameters in tension. These are typically the pseudo-strain hardening behavior and the ability to develop multiple cracks. The assessment of the tensile load......-deformation behavior of these materials is therefore of great importance and is frequently carried out by characterizing the material tensile stress–strain behavior. In this paper an alternative approach to evaluate the tensile performance of SHCC is investigated. The behavior of the material in tension is studied...... at the level of a single crack. The derived tensile stress-crack opening behavior is utilized to analyze and compare the influence of various composite parameters on the resulting tensile behavior. The deformations occurring during tensile loading are furthermore examined using a digital image...

  1. Effect of total cementitious content on shear strength of high-volume fly ash concrete beams

    International Nuclear Information System (INIS)

    Arezoumandi, Mahdi; Volz, Jeffery S.; Ortega, Carlos A.; Myers, John J.

    2013-01-01

    Highlights: ► Existing design standards conservatively predicted the capacity of the HVFAC beams. ► In general, the HVFAC beams exceeded the code predicted shear strengths. ► The cementitious content did not have effect on the shear behavior of the HVFAC beams. - Abstract: The production of portland cement – the key ingredient in concrete – generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed manmade material on the planet. One method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. This paper compares two experimental studies that were conducted to investigate the shear strength of full-scale beams constructed with high-volume fly ash concrete (HVFAC) – concrete with at least 50% of the cement replaced with fly ash. The primary difference between the two studies involved the amount of cementitious material, with one mix having a relatively high total cementitious content (502 kg/m 3 ) and the other mix having a relatively low total cementitious content (337 kg/m 3 ). Both mixes utilized a 70% replacement of portland cement with a Class C fly ash. Each of these experimental programs consisted of eight beams (six without shear reinforcing and two with shear reinforcing in the form of stirrups) with three different longitudinal reinforcement ratios. The beams were tested under a simply supported four-point loading condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (US, Australia, Canada, Europe, and Japan) and a shear database of conventional concrete (CC) specimens. Furthermore, statistical data analyses (both parametric and nonparametric) were performed to evaluate whether or not there is any statistically significant difference between the shear strength of both mixes. Results of these

  2. SCM Paste Samples Exposed To Aggressive Solutions. Cementitious Barriers Partnership

    Energy Technology Data Exchange (ETDEWEB)

    Foster, T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-12-01

    This report summarizes experimental work performed by SIMCO Technologies Inc. (SIMCO) as part of the Cementitious Barriers Partnership (CBP) project. The test series followed an experimental program dedicated to the study of ordinary Portland cement (OPC) hydrated cement pastes exposed to aggressive solutions. In the present study, the scope is extended to hydrated cement pastes incorporating supplementary cementitious materials (SCM) such as fly ash and ground granulated blast furnace slag (GGBFS). Also, the range of aggressive contact solutions was expanded. The experimental program aimed at testing aggressive contact solutions that more closely mimic the chemical composition of saltstone pore solution. Five different solutions, some of which incorporated high levels of carbonate and nitrate, were placed in contact with four different hydrated cement paste mixes. In all solutions, 150 mmol/L of SO42– (14 400 ppm) were present. The solutions included different pH conditions and different sodium content. Two paste mixes were equivalent to Vault 1/4 and Vault 2 concrete mixes used at SRS in storage structures. Two additional paste mixes, cast at the same water-to-cement ratio and using the same cements but without SCMs, were also tested. The damage evolution in samples was monitored using ultrasonic pulse velocity (UPV) and mass measurements. After three and twelve months of exposure conditions, samples were taken out of solution containers and analyzed to perform migration tests and porosity measurements. Globally, results were in line with the previous study and confirmed that high pH may limit the formation of some deleterious phases like gypsum. In this case, ettringite may form but is not necessarily associated with damage. However, the high concentration of sodium may be associated with the formation of an AFm-like mineral called U-phase. The most significant evidences of damage were all associated with the Vault 2 paste analog. This

  3. Influence of the binder nature and the temperature on the chloride transport through cementitious materials; Influence de la nature du liant et de la temperature sur le transport des chlorures dans les materiaux cimentaires

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Th.S

    2006-09-15

    The objective of this work is to document the effect of the temperature on the chloride diffusion through cement-based materials. The chloride diffusion coefficient, the penetration profiles and the chloride interactions with the solid phase were highlighted. The materials were CEM I and CEM V/A mortars and pastes. They were cured in wet room (21 {+-} 2 C, 90% relative humidity) for 1 month in the case of CEM I and 3 months in the case of CEM V before the experiments started. The temperature levels were 5, 21, 35 and 80 C.In addition, microstructure analyses were carried on using X-rays diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The experimental results were then used to continue to develop the numerical code, MsDiff, developed in our research group. A good agreement between the numerical concentration profiles and the experimental ones was found. (author)

  4. Indications for Self-Sealing of a Cementitious L and ILW Repository

    Energy Technology Data Exchange (ETDEWEB)

    Pfingsten, W

    2001-07-01

    Repositories for low and intermediate level nuclear waste contain large amounts of cementitious material. As a consequence of the interaction with formation waters, the cement will be degraded forming secondary minerals. The amount of precipitating secondary minerals depends on the chemical composition of the formation water. Furthermore, in the vicinity of the repository the hydraulic conditions and the parameters describing mass (radionuclide) transport will change with time during the cement degradation phase. As a result, porosity changes due to mineral and cement reactions will influence permeability and diffusivity: formation water rich in CO{sub 2} will lead to calcite precipitation in the water conducting zones surrounding the cementitious waste repository and, therefore, will have an impact on the radionuclide release from the cementitious repository into the host rock environment. Laboratory column experiments showed concurrent porosity and permeability changes during degradation of porous cement discs. However, very different quantitative results have been observed when CO{sub 2}-rich or pure water were used. The sequentially coupled flow, transport and chemical reaction code, MCOTAC, is used to include such observations in the modelling. A porosity-permeability and a porosity-diffusivity relation are used for describing cement degradation and related secondary mineral precipitation. For these complex coupled processes one-dimensional modelling has reached its limits of applicability. Therefore, two-dimensional model calculations are used to predict the temporal evolution of transport parameters for radionuclides within a 'small scale' near-field of a cementitious waste repository. Mineral reactions influence hydraulic and transport parameters within such a near-field, causing reduced solute transport in the vicinity of the repository due to porosity and permeability changes at the rock-repository-interface. Also, the transport of radionuclides

  5. Experimental Study on Cementitious Composites Embedded with Organic Microcapsules

    NARCIS (Netherlands)

    Wang, X.; Xing, F.; Zhang, M.; Han, N.; Qian, Z.

    2013-01-01

    The recovery behavior for strength and impermeability of cementitious composites embedded with organic microcapsules was investigated in this study. Mortar specimens were formed by mixing the organic microcapsules and a catalyst with cement and sand. The mechanical behaviors of flexural and

  6. Crushing damage estimation for pavement with lightly cementitious bases

    CSIR Research Space (South Africa)

    De Beer, Morris

    2014-07-01

    Full Text Available the 1990s. Typically, crushing failure starts at the surface of the cementitious base layer, and could extend to 50 mm deep, depending on tyre load/stress conditions. Recently developed crushing damage relationships for 2, 5, 10, 15 and 20 mm level...

  7. Decorative application of strain-hardening cementitious composites

    NARCIS (Netherlands)

    Ibrovic, V.; Lukovic, M.; Schlangen, E.

    2014-01-01

    Strain hardening cementitious composites (SHCC) have been used in variety of structural applications. Apart from this, they are also suitable for non-structural applications. In this work, the application of SHCC for producing cover plates for light switches and power sockets is presented. For

  8. Cementitious Barriers Partnership (CBP): Using the CBP Software Toolbox to Simulate Sulfate Attack and Carbonation of Concrete Structures - 13481

    International Nuclear Information System (INIS)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S.; Flach, G.; Langton, C.; Smith, F.G.III; Burns, H.; Van der Sloot, H.; Meeussen, J.C.L.; Seignette, P.F.A.B.; Samson, E.; Mallick, P.; Suttora, L.; Esh, D.; Fuhrmann, M.; Philip, J.

    2013-01-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy Office of Tank Waste Management. The CBP project has developed a set of integrated modeling tools and leaching test methods to help improve understanding and prediction of the long-term hydraulic and chemical performance of cementitious materials used in nuclear applications. State-of-the-art modeling tools, including LeachXS TM /ORCHESTRA and STADIUM R , were selected for their demonstrated abilities to simulate reactive transport and degradation in cementitious materials. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF), now adopted as part of the SW-846 RCRA methods, have been used to help make the link between modeling and experiment. Although each of the CBP tools has demonstrated utility as a standalone product, coupling the models over relevant spatial and temporal solution domains can provide more accurate predictions of cementitious materials behavior over relevant periods of performance. The LeachXS TM /ORCHESTRA and STADIUM R models were first linked to the GoldSim Monte Carlo simulator to better and more easily characterize model uncertainties and as a means to coupling the models allowing linking to broader performance assessment evaluations that use CBP results for a source term. Two important degradation scenarios were selected for initial demonstration: sulfate ingress / attack and carbonation of cementitious materials. When sufficient sulfate is present in the pore solution external to a concrete barrier, sulfate can diffuse into the concrete, react with the concrete solid phases, and cause cracking that significantly changes the transport and structural properties of the concrete. The penetration of gaseous carbon dioxide within partially saturated concrete usually initiates a series of carbonation reactions with

  9. Cementitious Barriers Partnership (CBP): Using the CBP Software Toolbox to Simulate Sulfate Attack and Carbonation of Concrete Structures - 13481

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.G.; Kosson, D.S.; Garrabrants, A.C.; Sarkar, S. [Vanderbilt University, School of Engineering, CRESP, Nashville, TN 37235 (United States); Flach, G.; Langton, C.; Smith, F.G.III; Burns, H. [Savannah River National Laboratory, Aiken, SC 29808 (United States); Van der Sloot, H. [Hans Van der Sloot Consultancy, Dorpsstraat 216, 1721BV Langedijk (Netherlands); Meeussen, J.C.L. [Nuclear Research and Consultancy Group, Westerduinweg 3, Petten (Netherlands); Seignette, P.F.A.B. [Energy Research Center of The Netherlands, Petten (Netherlands); Samson, E. [SIMCO Technologies, Inc., Quebec (Canada); Mallick, P.; Suttora, L. [U.S. Department of Energy, Washington, DC (United States); Esh, D.; Fuhrmann, M.; Philip, J. [U.S. Nuclear Regulatory Commission, Washington, DC (United States)

    2013-07-01

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy Office of Tank Waste Management. The CBP project has developed a set of integrated modeling tools and leaching test methods to help improve understanding and prediction of the long-term hydraulic and chemical performance of cementitious materials used in nuclear applications. State-of-the-art modeling tools, including LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R}, were selected for their demonstrated abilities to simulate reactive transport and degradation in cementitious materials. The new U.S. Environmental Protection Agency leaching test methods based on the Leaching Environmental Assessment Framework (LEAF), now adopted as part of the SW-846 RCRA methods, have been used to help make the link between modeling and experiment. Although each of the CBP tools has demonstrated utility as a standalone product, coupling the models over relevant spatial and temporal solution domains can provide more accurate predictions of cementitious materials behavior over relevant periods of performance. The LeachXS{sup TM}/ORCHESTRA and STADIUM{sup R} models were first linked to the GoldSim Monte Carlo simulator to better and more easily characterize model uncertainties and as a means to coupling the models allowing linking to broader performance assessment evaluations that use CBP results for a source term. Two important degradation scenarios were selected for initial demonstration: sulfate ingress / attack and carbonation of cementitious materials. When sufficient sulfate is present in the pore solution external to a concrete barrier, sulfate can diffuse into the concrete, react with the concrete solid phases, and cause cracking that significantly changes the transport and structural properties of the concrete. The penetration of gaseous carbon dioxide within partially saturated concrete usually initiates a series of carbonation

  10. Review of the complexation of tetravalent actinides by ISA and gluconate under alkaline to hyperalkaline conditions.

    Science.gov (United States)

    Gaona, X; Montoya, V; Colàs, E; Grivé, M; Duro, L

    2008-12-12

    Isosaccharinic (ISA) and gluconic acids (GLU) are polyhydroxy carboxylic compounds showing a high affinity to metal complexation. Both organic ligands are expected in the cementitious environments usually considered for the disposal of low- and intermediate-level radioactive wastes. The hyperalkaline conditions imposed by cementitious materials contribute to the formation of ISA through cellulose degradation, whereas GLU is commonly used as a concrete additive. Despite the high stability attributed to ISA/GLU complexes of tetravalent actinides, the number and reliability of available experimental studies is still limited. This work aims at providing a general and comprehensive overview of the state of the art regarding Th, U(IV), Np(IV), and Pu(IV) complexes with ISA and GLU. In the presence of ISA/GLU concentrations in the range 10(-5)-10(-2) M and absence of calcium, An(IV)(OH)x(L)y complexes (An(IV)=Th, U(IV), Np(IV), Pu(IV); L=ISA, GLU) are expected to dominate the aqueous speciation of tetravalent actinides in the alkaline pH range. There is a moderate agreement among their stability, although the stoichiometry of certain An(IV)-GLU complexes is still ill-defined. Under hyperalkaline conditions and presence of calcium, the species CaTh(OH)4(L)2(aq) has been described for both ISA and GLU, and similar complexes may be expected to form with other tetravalent actinides. In the present work, the available thermodynamic data for An(IV)-ISA/GLU complexes have been reviewed and re-calculated to ensure the internal consistency of the stability constants assessed. Further modelling exercises, estimations based on Linear Free-Energy Relationships (LFER) among tetravalent actinides, as well as direct analogies between ISA and GLU complexes have also been performed. This approach has led to the definition of a speciation scheme for the complexes of Th, U(IV), Np(IV) and Pu(IV) with ISA and GLU forming in alkaline to hyperalkaline pH conditions, both in the absence and

  11. Method for the production of cementitious compositions and aggregate derivatives from said compositions, and cementitious compositions and aggregates produced thereby

    Science.gov (United States)

    Minnick, L. John

    1983-01-01

    The present invention relates to a method for preparing synthetic shaped cementitious compositions having high quality even without the addition of high energy binders, such as portland cement, through the use of the spent residue from a fluidized combustion bed of the type wherein limestone particles are suspended in a fluidized medium and sulfur oxides are captured, and pulverized coal fly ash.

  12. Protective or damage promoting effect of calcium carbonate layers on the surface of cement based materials in aqueous environments

    International Nuclear Information System (INIS)

    Schwotzer, M.; Scherer, T.; Gerdes, A.

    2010-01-01

    Cement based materials permanently exposed to aggressive aqueous environments are subject to chemical changes affecting their durability. However, this holds also for tap water that is considered to be not aggressive to cementitious materials, although in that case a formation of covering layers of CaCO 3 on the alkaline surfaces is commonly supposed to provide protection against reactive transport processes. Thus, investigations of the structural and chemical properties of the material/water interface were carried out in laboratory experiments and case studies to elucidate the consequences of surface reactions for the durability of cement based materials exposed to tap water. Focused Ion Beam investigations revealed that a protective effect of a CaCO 3 covering layer depends on its structural properties, which are in turn affected by the hydro-chemical conditions during crystallization. Surface precipitation of CaCO 3 can trigger further chemical degradation, if the required calcium is supplied by the pore solution of the material.

  13. Environmental friendly alkaline sulfite anthra quinone-methonal (ASAM) pulping with Rumex crispus plant extract of woody materials.

    Science.gov (United States)

    Mertoglu-Elmas, Gulnur; Gunaydin, Keriman; Ozden, Oznur

    2012-09-01

    ASAM with Rumex crispus extract organosolv pulping was developed by using 1,5-dihydroxy-3-methoxy-7-methyl-anthraquinone from Rumex crispus root, instead of anthraquinone. ASAM was also produced as a control pulping. Both pulps were made by handsheets from fast growing P. deltoides clone (Samsun p. clone), Robinia pseudoacacia L. and Pinus pinaster grown in Turkey for wood fibrous raw materials. The mechanical consisting tensile, bursting and tear values and optical values of ASAM handsheets yellowness, brightness and whiteness were compared to ASAM with Rumex crispus L. extracted. It is concluded that ASAM with Rumex crispus extract pulping suits well in the manufacturing of special papers.

  14. A review on alkaline activation: new analytical perspectives

    Directory of Open Access Journals (Sweden)

    Palomo, A.

    2014-09-01

    Full Text Available For many years now the idea of including alkalis in a Portland cement matrix has been regarded as a daft or inexcusably erroneous proposition: despite its absurdity, that opinion has been widely accepted as a basic premise by the scientific and technical community working in the area of the chemistry of cement. In 1957 Glukhovsky proposed a working hypothesis in which he established a close relationship between alkalis and cementitious materials. That hypothesis has become consolidated and has served as a basis for developing a new type of binders, initially called “alkaline cements”. The present paper reviews the most significant theoretical interpretations of the role played by alkalis in the formation of the “stony” structure of cement. It ends with a broad overview of the versatility of this type of materials for industrial applications and a discussion of the possibility of building on the existing legislation to meet the need for the future regulation of alkaline cement and concrete manufacture.Hace algunos años, la sola idea de la presencia de álcalis en una matriz de cemento Portland se consideraba casi como una aberración, o como un error imperdonable; convirtiéndose en un postulado básico (absurdo ampliamente aceptado por la comunidad científica y técnica vinculada a la química de los cementos. En 1957 Glukhovsky propuso una hipótesis en la que se establecía una estrecha relación entre los álcalis y los materiales cementantes. Hoy día nadie duda de que dicha hipótesis ha servido de base para el desarrollo de una nueva clase de materiales cementantes: “cementos alcalinos”. En el presente trabajo se hace una revisión sobre los aspectos teóricos más relevantes del papel de los álcalis en la formación de estos conglomerantes. También se da una visión genérica de su versatilidad, desarrollo industrial y estado de la normativa actual para regular en el futuro la fabricación de cementos y hormigones

  15. Cement technology for borehole plugging: an interim report on permeability measurements of cementitious solids

    International Nuclear Information System (INIS)

    McDaniel, E.W.

    1980-01-01

    The permeability of borehole plug solids and plug-wall rock junctions is a property of major interest in the Borehole Plugging Program. This report describes the equipment and techniques used to determine the permeabilities of possible borehole plugging materials and presents results from tests on various cementitious solids and plug-rock combinations. The cementitious solids were made from mixtures of cement, sand, salt, fly ash, and water. Three different types of cement and four different fly ashes were used. Permeabilities ranged from a high value of 3 x 10 -4 darcy for a neat cement paste to a low of 5 x 10 -8 darcy for a saltcrete containing 30 wt % sodium chloride. Miniature boreholes were made in the following four different types of rock: Westerly granite, Dresser basalt, Sioux quartzite, and St. Cloud granodiorite. These small holes were plugged with a mix consisting of 23 wt % Type I Portland cement, 20 wt % bituminous fy ash, 43.2 wt % sand, and 13.8 wt % water. After curing for 91 days at ambient temperature, the permeability of the plug-wall rock junctions ranged from 3 x 10 -5 to -8 darcy. Three of the four miniature plugged boreholes exhibited permeabilities of < 10 microdarcys

  16. RC beams shear-strengthened with fabric-reinforced-cementitious-matrix (FRCM) composite

    Science.gov (United States)

    Loreto, Giovanni; Babaeidarabad, Saman; Leardini, Lorenzo; Nanni, Antonio

    2015-12-01

    The interest in retrofit/rehabilitation of existing concrete structures has increased due to degradation and/or introduction of more stringent design requirements. Among the externally-bonded strengthening systems fiber-reinforced polymers is the most widely known technology. Despite its effectiveness as a material system, the presence of an organic binder has some drawbacks that could be addressed by using in its place a cementitious binder as in fabric-reinforced cementitious matrix (FRCM) systems. The purpose of this paper is to evaluate the behavior of reinforced concrete (RC) beams strengthened in shear with U-wraps made of FRCM. An extensive experimental program was undertaken in order to understand and characterize this composite when used as a strengthening system. The laboratory results demonstrate the technical viability of FRCM for shear strengthening of RC beams. Based on the experimental and analytical results, FRCM increases shear strength but not proportionally to the number of fabric plies installed. On the other hand, FRCM failure modes are related with a high consistency to the amount of external reinforcement applied. Design considerations based on the algorithms proposed by ACI guidelines are also provided.

  17. Optimisation of technical properties of low ph cementitious injection grout. Laboratory tests and pilot field test 3

    Energy Technology Data Exchange (ETDEWEB)

    Sievaenen, U. [Poeyry Infra Oy, Vantaa (Finland); Raivio, P. [Contesta Oy, Vantaa (Finland); Vuorinen, U. [VTT, Prosesses, Espoo (Finland); Hansen, J.; Norokallio, J. [Posiva Oy, Helsinki (Finland); Syrjaenen, P. [Gridpoint Finland Oy, Helsinki (Finland)

    2006-11-15

    Posiva, SKB and NUMO co-operated in developing low-pH (pH<11 in the leachate) grouts for deep repositories 2002 2005. The development of low-pH cementitious grouts for fractures > 100 {mu}m was done in Finland. The non-cementitious low-pH grouts for fractures < 100 {mu}m were studied in Sweden. Several cementitious binder material combinations were studied within the project. The most promising and suitable system was Portland cement + microsilica. The targets with regard to the main properties (pH and penetration ability) were reached, but all technical properties were not satisfying. Superplasticizers were avoided, but it turned out that in order to reach the acceptable technical properties together with low pH, superplasticizers were necessary to decrease water/dry material-ratio and fasten the early age strength development. Posiva continued the optimisation of Portland cement + microsilica + superplasticizer - mixes within the LPHTEK-project during 2005. The work comprised laboratory studies, two batch mixing tests in field conditions, the third pilot field test and monitoring of the test area. The objective of the laboratory tests was to improve the properties of the mix P3 developed in earlier stage. The superplasticizer was changed to one which is considered less harmful with respect to the long-term safety. The water/dry material-ratio and the contents of microsilica and superplasticizer were varied and the behaviour of the mixes was observed under cooled circumstances (12 deg C) and at room temperature. Several mixes showed promising results and one mix, P308B (SF/PC=0.69, naphtalene sulphonate SPL 4%) met the targets, except that set to yield stress. Technical tests indicated that cement consignment, age of the cement, age of the microsilica, mixer type and temperature affected on results, but it was not possible to study these in detail. The improved composition of the mix stabilised the leachate pH-values with time as well as somewhat lowered them; the

  18. New cementitious system: The case of glass frit

    Science.gov (United States)

    Fares, Galal

    Canada ranks as the world's third largest aluminium producer, and more than 80% of its aluminum industry is concentrated in Quebec. However, the spent pot-liner waste produced by the aluminium smelters accumulates with time into a considerable amount threatening the Canadian environment, especially that of Quebec. A new-engineered material, known as glass fit (GF) has been developed through the chemical treatment of such waste. GF shows potential hydraulic and pozzolanic properties. GF has been studied as a binder itself and as a supplementary cementitious material (SCM). The activation of industrial by-products into clinkerless binders is a novel trend that has attracted the attention of many researchers. The activation of GF into binder to produce paste, mortar and concrete was the first aim of this study. Potential activation of GF using different types and combinations of inorganic activators and temperatures of activation was successfully achieved and high strength concretes were obtained. Moreover, mortars with high compressive strength were obtained with well-formulated activators at ambient temperature. On the other hand, the utilization of industrial by-products as a partial replacement for cement in concrete is a widespread practice. As GF contains a high concentration of sodium in its structure, there is a concern as to the effect of sodium content on the development of alkali-silica reaction (ASR) expansion of concrete. Therefore, this study also aimed to investigate the effect of GF sodium content in the enhancement of ASR expansion and to find new synergistic mixtures that can effectively mitigate ASR expansion in the long term. We observed that ASR expansion decreases with the replacement level of GF. Different synergistic diagrams containing known SCM (silica fume, fly ash, and slag) were achieved from which different effective mixtures can effectively alleviate ASR expansion. In conclusion, the use of GF in the manufacture of concrete has great

  19. Characterization of cracking in Strain-Hardening Cementitious Composites using the compact tension test

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A. O.

    The characterization of the tensile behavior of strain hardening cementitious composites (SHCC) is of significant importance to the material design. In a previous work the tensile stress-crack opening response of different types of SHCC was characterized using notched specimens tested in direct...... tension, where a single crack was obtained and mechanically characterized by performing Single Crack Tension Test (SCTT). In this study the tensile behavior of SHCC materials is characterized under eccentric tensile load using the Compact Tension Test (CTT). The long edge notch placed in the rectangular...... results are discussed and compared to the numerically derived responses. The tensile load-displacement responses observed in the CTTs were simulated using the cohesive crack model. The tensile stress-crack opening behaviors previously obtained with the SCTT tests were utilized to derive the traction...

  20. Calcium aluminate cement hydration in a high alkalinity environment

    Directory of Open Access Journals (Sweden)

    Palomo, Á.

    2009-03-01

    Full Text Available The present paper forms part of a broader research project that aims primarily to devise new cementitious products via the alkali activation of silico-aluminous materials. This work addresses the possibility of using small percentages of calcium aluminate cement (CAC as a source of reactive aluminium. For this reason, a preliminary review was needed of the behaviour of CACs in highly alkaline media (2, 8 and 12M NaOH solutions. Two, 28- and 180-day mechanical strength was determined and the reaction products were characterized with XRD and FTIR. The water-hydrated CAC was used as the control.The results obtained showed that CAC hardening took place much more slowly in highly alkaline media than in water. Nonetheless, the 28-day compressive strength obtained, ≥80MPa. As main reaction products, to ambient temperature and from the two days of cured, cubic aluminate C3AH6, and AH3 polymorphs are formed, instead of the usual hexagonal aluminatos (CAH10 and C2AH8 that are formed in the normal hydrate with water.El presente trabajo forma parte de una amplia investigación cuyo objetivo principal es el de elaborar nuevos materiales con propiedades cementantes mediante la activación alcalina de materiales de naturaleza silito-aluminosa. En estos estudios se contempla la posibilidad de utilizar pequeños porcentajes de cemento de aluminato de calcio (CAC como fuente de aluminio reactivo. Por ello inicialmente se ha estudiado el comportamiento de los CAC en medios fuertemente alcalinos (disoluciones de NaOH 2M, 8M y 12M. Se determinaron las resistencias mecánicas a 2, 28 y 180 días y se realizó una caracterización de los productos de reacción formados por DRX, FTIR. Como sistema de referencia se consideró la hidratación del CAC con agua.Los resultados obtenidos muestran que en medios fuertemente alcalinos se retrasan los procesos de rápido endurecimiento de CAC con agua. No obstante a 28 días se obtienen valores de resistencia a compresión

  1. Air purification by cementitious materials : Evaluation of air purifying properties

    NARCIS (Netherlands)

    Hüsken, G.; Brouwers, H.J.H.; Al-Mattarneh, H.; Mustapha, K.N.; Nuruddin, M.F.

    2008-01-01

    This paper addresses the evaluation of the photocatalytic properties of concrete containing titanium dioxide (TiO2). Here, the assessment of the air purifying abilities of the hardened concrete regarding the degradation of nitric oxide (NO) is of major interest. A setup for measuring the performance

  2. Crystal chemistry of clinker relicts from aged cementitious materials

    Czech Academy of Sciences Publication Activity Database

    Secco, M.; Peruzzo, L.; Palasse, L.; Artioli, G.; Viani, Alberto; Gualtieri, A. F.

    2014-01-01

    Roč. 47, č. 5 (2014), s. 1626-1637 ISSN 0021-8898 R&D Projects: GA MŠk(CZ) LO1219 Keywords : aluminate * cement hydration * electron backscatter diffraction * electron microprobe analysis * ferrite Subject RIV: JN - Civil Engineering Impact factor: 3.720, year: 2014 http://scripts.iucr.org/cgi-bin/paper?S1600576714018287

  3. On the application of cohesive crack modeling in cementitious materials

    DEFF Research Database (Denmark)

    Stang, Henrik; Olesen, John Forbes; Poulsen, Peter Noe

    2007-01-01

    for a centrally cracked sheet is established applying semi-analytical, bridged and fictitious crack modeling. The semi-analytical crack model is compared with a FEM analysis and it is demonstrated, that the standard fictitious crack implementation in FEM packages (in this case DIANA) provides a good approximation...

  4. Acoustic Liners Utilizing A Cementitious Material, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this Phase I STTR project for NASA, Concrete Solutions Inc (CSI), together with the University of Texas at Austin (UTA), will develop a detailed research plan...

  5. Progress in Research on Carbon Nanotubes Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Qinghua Li

    2015-01-01

    Full Text Available As one-dimensional (1D nanofiber, carbon nanotubes (CNTs have been widely used to improve the performance of nanocomposites due to their high strength, small dimensions, and remarkable physical properties. Progress in the field of CNTs presents a potential opportunity to enhance cementitious composites at the nanoscale. In this review, current research activities and key advances on multiwalled carbon nanotubes (MWCNTs reinforced cementitious composites are summarized, including the effect of MWCNTs on modulus of elasticity, porosity, fracture, and mechanical and microstructure properties of cement-based composites. The issues about the improvement mechanisms, MWCNTs dispersion methods, and the major factors affecting the mechanical properties of composites are discussed. In addition, large-scale production methods of MWCNTs and the effects of CNTs on environment and health are also summarized.

  6. Multiscale characterization of chemical–mechanical interactions between polymer fibers and cementitious matrix

    Energy Technology Data Exchange (ETDEWEB)

    Hernández-Cruz, Daniel; Hargis, Craig W.; Bae, Sungchul; Itty, Pierre A.; Meral, Cagla; Dominowski, Jolee; Radler, Michael J.; Kilcoyne, David A.; Monteiro, Paulo J. M.

    2014-04-01

    Together with a series of mechanical tests, the interactions and potential bonding between polymeric fibers and cementitious materials were studied using scanning transmission X-ray microscopy (STXM) and microtomography (lCT). Experimental results showed that these techniques have great potential to characterize the polymer fiber-hydrated cement-paste matrix interface, as well as differentiating the chemistry of the two components of a bi-polymer (hybrid) fiber the polypropylene core and the ethylene acrylic acid copolymer sheath. Similarly, chemical interactions between the hybrid fiber and the cement hydration products were observed, indicating the chemical bonding between the sheath and the hardened cement paste matrix. Microtomography allowed visualization of the performance of the samples, and the distribution and orientation of the two types of fiber in mortar. Beam flexure tests confirmed improved tensile strength of mixes containing hybrid fibers, and expansion bar tests showed similar reductions in expansion for the polypropylene and hybrid fiber mortar bars.

  7. METHODOLOGY FOR POROSIMETRY IN VIRTUAL CEMENTITIOUS COMPOSITES TO ECONOMICALLY AND RELIABLY ESTIMATE PERMEABILITY

    Directory of Open Access Journals (Sweden)

    Kai Li

    2015-05-01

    Full Text Available A novel methodology is described for porosimetry as well as for water transport through the pore system in dynamic DEM-based virtual cementitious materials. The pore network topology, the pore size distribution and the pore connectivity are assessed on the basis of a robotics-inspired pore delineation method and star volume measurements. Permeability estimates are based on a tube network model that incorporates these parameters and a shape factor. Since concrete contains in practical situations a variable amount of water, permeability estimation is presented as a function of the state of saturation. Satisfactory agreement is found with experimental data, validating the methodology. Earlier, the various "building blocks" were separately validated. 

  8. Mechanical interaction of Engineered Cementitious Composite (ECC) reinforced with Fiber Reinforced Polymer (FRP) rebar in tensile loading

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    2010-01-01

    This paper introduces a preliminary study of the composite interaction of Engineered Cementitious Composite (ECC), reinforced with Glass Fiber Reinforced Polymer (GFRP) rebar. The main topic of this paper will focus on the interaction of the two materials (ECC and GFRP) during axial loading......, particularly in post cracking phase of the concrete matrix. The experimental program carried out in this study examined composite behavior under monotonic and cyclic loading of the specimens in the elastic and inelastic deformation phases. The stiffness development of the composite during loading was evaluated...... distribution which in terms results in less mechanical deterioration during loading....

  9. Thin fiber and textile reinforced cementitious systems

    National Research Council Canada - National Science Library

    Aldea, Corina-Maria

    2007-01-01

    .... The topics of the papers cover experimental and theoretical materials aspects, such as the effect of different input fibers, fabric type, and construction and matrix on mechanical and long-term...

  10. Methods to assess radioisotope migration in cementitious media using radial diffusion and advection

    International Nuclear Information System (INIS)

    Hinchliff, J.; Felipe-Sotero, M.; Evans, N.D.M.; Read, D.; Drury, D.

    2012-01-01

    One of the primary aims of this project is to understand how a range of isotopes associated with radioactive wastes, move through the cementitious media potentially present in a geological disposal facility (GDF). This paper describes the development of experimental methods that use radial flow from intact cylinders of cementitious material to evaluate the potential for diffusion and advection of relevant isotopes through Nirex reference vault backfill (NRVB). The small scale and cost effectiveness of the approach means that multiple experiments can be undertaken encompassing the full range of physical (and chemical) variations. The radial flow experimental method uses small pre-cast cylinders of the matrix under investigation. For diffusion an appropriate concentration of the isotope of interest ( 90 Sr in the present experiments) is introduced into a cavity in the centre of the cylinder, which is then sealed, and placed in a solution previously equilibrated with the matrix. The increase in concentration of the isotope in the external solution is then determined at defined time intervals. For advection 90 Sr is similarly introduced into the central core of the cylinder and then equilibrated water is forced under nitrogen pressure, from the central core to the outside of the cylinder where it is collected in a tray prior to analysis. Both experimental set ups and results have been modelled using conventional numerical solutions and the simulation package GoldSim. Concerning diffusion experiments the modelled data reproduces the observed data effectively with a right diffusivity value of 9*10 -11 m 2 /s. Concerning advection results are more mitigated and need further investigation

  11. Absorbency of Superabsorbent Polymers in Cementitious Environments

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Jensen, Ole Mejlhede

    2012-01-01

    Optimal use of superabsorbent polymers (SAP) in cement-based materials relies on knowledge on how SAP absorbency is influenced by different physical and chemical parameters. These parameters include salt concentration in the pore fluid, temperature of the system and SAP particle size. The present...... work shows experimental results on this and presents a new technique to measure the swelling of SAP particles. This new technique is compared with existing techniques that have been recently proposed for the measurement of pore fluid absorption by superabsorbent polymers. It is seen...

  12. Anion-selective materials with 1,4-diazabicyclo[2.2.2]octane functional groups for advanced alkaline water electrolysis

    Czech Academy of Sciences Publication Activity Database

    Hnát, J.; Plevová, M.; Žitka, Jan; Paidar, M.; Bouzek, K.

    2017-01-01

    Roč. 248, 10 September (2017), s. 547-555 ISSN 0013-4686 R&D Projects: GA ČR(CZ) GA16-20728S Institutional support: RVO:61389013 Keywords : water electrolysis * alkaline environment * anion-selective membrane Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cell s, batteries, fuel cell s, corrosion metals, electrolysis) Impact factor: 4.798, year: 2016

  13. Treatments of non-wood plant fibres used as reinforcement in composite materials

    Directory of Open Access Journals (Sweden)

    Marie-Ange Arsène

    2013-01-01

    Full Text Available This paper presents a summary of the knowledge on fibres and pulps of non wood tropical plants used as reinforcement in cementitious composites accumulated during the recent years by Guadeloupean and Brazilian teams participating in collaborative work. Vegetable fibres represent a good alternative as non-conventional materials for the construction of ecological and sustainable buildings. The use of such renewable resources contributes to the development of sustainable technologies. The main objective of the paper is to emphasize the use of agricultural wastes in the production of cement based composites. The botanical, chemical, physical, morphological and mechanical properties of fibres from various plants are described. The effects of different treatments on physical, chemical and mechanical properties of fibres are presented. The most effective treatments in influencing the mechanical and physical properties are pyrolysis and alkaline ones, according to the type of plant. The final choice will have to consider fibre availability, and treatment costs.

  14. Functional Cementitious Composites for Pyroelectric Applications

    Science.gov (United States)

    Srikanth, K. S.; Patel, Satyanarayan; Vaish, Rahul

    2018-04-01

    We have synthesized Ba0.85Ca0.15Zr0.10Ti0.88Sn0.02O3 (BCZT-Sn)-cement composites. They were prepared as BCZT-Sn to cement ratios of 90-10% and 85-15% by weight. The larger fraction of BCZT-Sn ceramic was used to minimize the losses in the composites. The open circuit voltage was found to be 0.75 V, 0.56 V and 0.4 V for pure, 10% and 15% cement composites, respectively. The voltage and current were also measured across resistances of 1 and 3 MΩ, and the obtained voltages were lower for composites compared to pure BCZT-Sn. Nonetheless, they remain promising candidates over traditional pyroelectric materials for device applications owing to their advantages, such as (1) these composites can be made without any sintering process and (2) they can be made in any shape and size. We also studied relative permittivity, which influences performance of pyroelectric devices.

  15. The evolution of clay rock/cement interfaces in a cementitious repository for low- and intermediate level radioactive waste

    Science.gov (United States)

    Kosakowski, Georg; Berner, Urs

    In Switzerland, deep geological storage in clay rich host rocks is the preferred option for low- and intermediate-level radioactive waste. For these waste types cementitious materials are used for tunnel support and backfill, waste containers and waste matrixes. The different geochemical characteristics of clay and cementitious materials may induce mineralogical and pore water changes which might affect the barrier functionality of host rocks and concretes. We present numerical reactive transport calculations that systematically compare the geochemical evolution at cement/clay interfaces for the proposed host rocks in Switzerland for different transport scenarios. We developed a consistent set of thermodynamic data, simultaneously valid for cementitious (concrete) and clay materials. With our setup we successfully reproduced mineralogies, water contents and pore water compositions of the proposed host rocks and of a reference concrete. Our calculations show that the effects of geochemical gradients between concrete and clay materials are very similar for all investigated host rocks. The mineralogical changes at material interfaces are restricted to narrow zones for all host rocks. The extent of strong pH increase in the host rocks is limited, although a slight increase of pH over greater distances seems possible in advective transport scenarios. Our diffusive and partially also the advective calculations show massive porosity changes due to precipitation/dissolution of mineral phases near the interface, in line with many other reported transport calculations on cement/clay interactions. For all investigated transport scenarios the degradation of concrete materials in emplacement caverns due to diffusive and advective transport of clay pore water into the caverns is limited to narrow zones. A specific effort has been made to improve the geochemical setup and the extensive use of solid solution phases demonstrated the successful application of a thermodynamically

  16. Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC.

    Science.gov (United States)

    Halim, Cheryl E; Short, Stephen A; Scott, Jason A; Amal, Rose; Low, Gary

    2005-10-17

    A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO4(2-) ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca3(AsO4)2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr.

  17. Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC

    International Nuclear Information System (INIS)

    Halim, Cheryl E.; Short, Stephen A.; Scott, Jason A.; Amal, Rose; Low, Gary

    2005-01-01

    A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6 M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO 4 2- ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca 3 (AsO 4 ) 2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr

  18. Using Converter Dust to Produce Low Cost Cementitious Composites by in situ Carbon Nanotube and Nanofiber Synthesis

    Directory of Open Access Journals (Sweden)

    Péter Ludvig

    2011-03-01

    Full Text Available Carbon nanotubes (CNTs and nanofibers (CNFs were synthesized on clinker and silica fume particles in order to create a low cost cementitious nanostructured material. The synthesis was carried out by an in situ chemical vapor deposition (CVD process using converter dust, an industrial byproduct, as iron precursor. The use of these materials reduces the cost, with the objective of application in large-scale nanostructured cement production. The resulting products were analyzed by scanning electron microscopy (SEM, transmission electron microscopy (TEM and thermogravimetric analysis (TGA and were found to be polydisperse in size and to have defective microstructure. Some enhancement in the mechanical behavior of cement mortars was observed due to the addition of these nano-size materials. The contribution of these CNTs/CNFs to the mechanical strength of mortar specimens is similar to that of high quality CNTs incorporated in mortars by physical mixture.

  19. DEMONSTRATION OF LEACHXS/ORCHESTRA CAPABILITIES BY SIMULATING CONSTITUENT RELEASE FROM A CEMENTITIOUS WASTE FORM IN A REINFORCED CONCRETE VAULT

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Meeussen, J.; Sloot, H.

    2010-03-31

    The objective of the work described in this report is to demonstrate the capabilities of the current version of LeachXS{trademark}/ORCHESTRA for simulating chemical behavior and constituent release processes in a range of applications that are relevant to the CBP. This report illustrates the use of LeachXS{trademark}/ORCHESTRA for the following applications: (1) Comparing model and experimental results for leaching tests for a range of cementitious materials including cement mortars, grout, stabilized waste, and concrete. The leaching test data includes liquid-solid partitioning as a function of pH and release rates based on laboratory column, monolith, and field testing. (2) Modeling chemical speciation of constituents in cementitious materials, including liquid-solid partitioning and release rates. (3) Evaluating uncertainty in model predictions based on uncertainty in underlying composition, thermodynamic, and transport characteristics. (4) Generating predominance diagrams to evaluate predicted chemical changes as a result of material aging using the example of exposure to atmospheric conditions. (5) Modeling coupled geochemical speciation and diffusion in a three layer system consisting of a layer of Saltstone, a concrete barrier, and a layer of soil in contact with air. The simulations show developing concentration fronts over a time period of 1000 years. (6) Modeling sulfate attack and cracking due to ettringite formation. A detailed example for this case is provided in a separate article by the authors (Sarkar et al. 2010). Finally, based on the computed results, the sensitive input parameters for this type of modeling are identified and discussed. The chemical speciation behavior of substances is calculated for a batch system and also in combination with transport and within a three layer system. This includes release from a barrier to the surrounding soil as a function of time. As input for the simulations, the physical and chemical properties of the

  20. Superhydrophobic engineered cementitious composites for highway bridge applications : technology transfer and implementation.

    Science.gov (United States)

    2013-09-01

    The strength and durability of highway bridges are two of the key components in maintaining a : high level of freight transportation capacity on the nations highways. Superhydrophobic : engineered cementitious composite (SECC) is a new advanced con...

  1. Development of alkaline fuel cells.

    Energy Technology Data Exchange (ETDEWEB)

    Hibbs, Michael R.; Jenkins, Janelle E.; Alam, Todd Michael; Janarthanan, Rajeswari; Horan, James L.; Caire, Benjamin R.; Ziegler, Zachary C.; Herring, Andrew M.; Yang, Yuan; Zuo, Xiaobing; Robson, Michael H.; Artyushkova, Kateryna; Patterson, Wendy; Atanassov, Plamen Borissov

    2013-09-01

    This project focuses on the development and demonstration of anion exchange membrane (AEM) fuel cells for portable power applications. Novel polymeric anion exchange membranes and ionomers with high chemical stabilities were prepared characterized by researchers at Sandia National Laboratories. Durable, non-precious metal catalysts were prepared by Dr. Plamen Atanassovs research group at the University of New Mexico by utilizing an aerosol-based process to prepare templated nano-structures. Dr. Andy Herrings group at the Colorado School of Mines combined all of these materials to fabricate and test membrane electrode assemblies for single cell testing in a methanol-fueled alkaline system. The highest power density achieved in this study was 54 mW/cm2 which was 90% of the project target and the highest reported power density for a direct methanol alkaline fuel cell.

  2. Cementitious Stabilization of Mixed Wastes with High Salt Loadings

    Energy Technology Data Exchange (ETDEWEB)

    Spence, R.D.; Burgess, M.W.; Fedorov, V.V.; Downing, D.J.

    1999-04-01

    Salt loadings approaching 50 wt % were tolerated in cementitious waste forms that still met leach and strength criteria, addressing a Technology Deficiency of low salt loadings previously identified by the Mixed Waste Focus Area. A statistical design quantified the effect of different stabilizing ingredients and salt loading on performance at lower loadings, allowing selection of the more effective ingredients for studying the higher salt loadings. In general, the final waste form needed to consist of 25 wt % of the dry stabilizing ingredients to meet the criteria used and 25 wt % water to form a workable paste, leaving 50 wt % for waste solids. The salt loading depends on the salt content of the waste solids but could be as high as 50 wt % if all the waste solids are salt.

  3. Using mixture experiments to develop cementitious waste forms

    International Nuclear Information System (INIS)

    Spence, R.D.; Anderson, C.M.; Piepel, G.F.

    1993-01-01

    Mixture experiments are presented as a means to develop cementitious waste forms. The steps of a mixture experiment are (1) identifying the waste form ingredients; (2) determining the compositional constraints of these ingredients; (3) determining the extreme vertices, edge midpoints, and face centroids of the constrained multidimensional volume (these points along with some interior points represent the set of possible compositions for testing); (4) picking a subset of these points for the experimental design; (5) measuring the properties of the selected subset; and (6) generating the response surface models. The models provide a means for predicting the properties within the constrained region. This article presents an example of this process for one property: unconfined compressive strength

  4. STEREOLOGICAL ESTIMATES FOR ROUGHNESS AND TORTUOSITY IN CEMENTITIOUS COMPOSITES

    Directory of Open Access Journals (Sweden)

    Piet Stroeven

    2011-05-01

    Full Text Available Relatively weak interfaces between aggregate grains and the cementitious matrix initiate the damage evolution process leading to fracture. Coalescence between nearby interface cracks is promoted by the small nearest neighbour distances in a dense random packing of the aggregate. The fracture surface is therefore modelled as a dividing plane from which particles protrude. Assuming spherical aggregate, roughness is obtained as the global geometrical-statistical expression for the increase in fracture surface area due to a multitude of dome-like caps of various sizes. Transport phenomena in concrete are equally influenced by the aggregate, because traversing water-born molecules or ions have to go around the dense grains. This route is additionally promoted by the relatively high porosity in the interfacial transition zone. The planar and linear concepts of tortuosity in the transport path are analogous to those of roughness.

  5. Calcium Sulfoaluminate, Geopolymeric, and Cementitious Mortars for Structural Applications

    Directory of Open Access Journals (Sweden)

    Alessandra Mobili

    2017-09-01

    Full Text Available This paper deals with the study of calcium sulfoaluminate (CSA and geopolymeric (GEO binders as alternatives to ordinary Portland cement (OPC for the production of more environmentally-friendly construction materials. For this reason, three types of mortar with the same mechanical strength class (R3 ≥ 25 MPa, according to EN 1504-3 were tested and compared; they were based on CSA cement, an alkaline activated coal fly ash, and OPC. Firstly, binder pastes were prepared and their hydration was studied by means of X-ray diffraction (XRD and differential thermal-thermogravimetric (DT-TG analyses. Afterwards, mortars were compared in terms of workability, dynamic modulus of elasticity, adhesion to red clay bricks, free and restrained drying shrinkage, water vapor permeability, capillary water absorption, and resistance to sulfate attack. DT-TG and XRD analyses evidenced the main reactive phases of the investigated binders involved in the hydration reactions. Moreover, the sulfoaluminate mortar showed the smallest free shrinkage and the highest restrained shrinkage, mainly due to its high dynamic modulus of elasticity. The pore size distribution of geopolymeric mortar was responsible for the lowest capillary water absorption at short times and for the highest permeability to water vapor and the greatest resistance to sulfate attack.

  6. Valorization of post-consumer waste plastic in cementitious concrete composites

    International Nuclear Information System (INIS)

    Marzouk, O. Yazoghli; Dheilly, R.M.; Queneudec, M.

    2007-01-01

    The sheer amount of disposable bottles being produced nowadays makes it imperative to identify alternative procedures for recycling them since they are non-biodegradable. This paper describes an innovative use of consumed plastic bottle waste as sand-substitution aggregate within composite materials for building application. Particularly, bottles made of polyethylene terephthalate (PET) have been used as partial and complete substitutes for sand in concrete composites. Various volume fractions of sand varying from 2% to 100% were substituted by the same volume of granulated plastic, and various sizes of PET aggregates were used. The bulk density and mechanical characteristics of the composites produced were evaluated. To study the relationship between mechanical properties and composite microstructure, scanning electron microscopy technique was employed. The results presented show that substituting sand at a level below 50% by volume with granulated PET, whose upper granular limit equals 5 mm, affects neither the compressive strength nor the flexural strength of composites. This study demonstrates that plastic bottles shredded into small PET particles may be used successfully as sand-substitution aggregates in cementitious concrete composites. These new composites would appear to offer an attractive low-cost material with consistent properties; moreover, they would help in resolving some of the solid waste problems created by plastics production and in saving energy

  7. Self-Healing of Microcracks in Engineered Cementitious Composites (ECC Under a Natural Environment

    Directory of Open Access Journals (Sweden)

    Victor C. Li

    2013-07-01

    Full Text Available This paper builds on previous self-healing engineered cementitious composites (ECC research by allowing ECC to heal outdoors, in the natural environment, under random and sometimes extreme environmental conditions. Development of an ECC material that can heal itself in the natural environment could lower infrastructure maintenance costs and allow for more sustainable development in the future by increasing service life and decreasing the amount of resources and energy needed for repairs. Determining to what extent current ECC materials self-heal in the natural environment is the first step in the development of an ECC that can completely heal itself when exposed to everyday environmental conditions. This study monitored outdoor ECC specimens for one year using resonant frequency (RF and mechanical reloading to determine the rate and extent of self-healing in the natural environment. It was found that the level of RF, stiffness, and first cracking strength recovery increased as the duration of natural environment exposure increased. For specimens that underwent multiple damage cycles, it was found that the level of recovery was highly dependent on the average temperature and amount of precipitation between each damage event. However, RF, stiffness, and first cracking strength recovery data for specimens that underwent multiple loading cycles suggest that self-healing functionality can be maintained under multiple damage events.

  8. Strength Properties and Micro-structure of Steel Slag Based Hardened Cementitious Composite with Graphene Oxide

    Directory of Open Access Journals (Sweden)

    Li Mao

    2017-01-01

    Full Text Available For the rapid hardening of concrete, various types of calcium aluminate composite have been used for special purpose as shotcrete or rapid repairing in construction field. However, high cost of calcium aluminates is demerit in the point of expanding usage. In recent years, a new binder for rapid hardening has been introduced as the pulverized ladle furnace slag (RC-LFS with main components of C12A7 and β-C2S. Like other traditional cementitious materials, it’s use will preserve natural resources and has high environmental advantage with economic efficiency, by transferring the industry byproducts into high value materials. Even though flake state, graphene oxide has high tensile strength and electric conductivity. Then, it can be used to increase strength and thermal properties of concrete and its efficiency depends on the dispersion in the cement matrix. In this paper, we used graphene oxide for increasing the engineering properties in RC-LFS concrete with GGBFS. Test results showed that the 0.05w% of graphene oxide increase the flexural strength to 26% and compressive strength to 16%.

  9. Alkaline and alkaline earth metal phosphate halides and phosphors

    Science.gov (United States)

    Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

    2012-11-13

    Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

  10. Alkaline battery operational methodology

    Science.gov (United States)

    Sholklapper, Tal; Gallaway, Joshua; Steingart, Daniel; Ingale, Nilesh; Nyce, Michael

    2016-08-16

    Methods of using specific operational charge and discharge parameters to extend the life of alkaline batteries are disclosed. The methods can be used with any commercial primary or secondary alkaline battery, as well as with newer alkaline battery designs, including batteries with flowing electrolyte. The methods include cycling batteries within a narrow operating voltage window, with minimum and maximum cut-off voltages that are set based on battery characteristics and environmental conditions. The narrow voltage window decreases available capacity but allows the batteries to be cycled for hundreds or thousands of times.

  11. Uranium in alkaline rocks

    International Nuclear Information System (INIS)

    Murphy, M.; Wollenberg, H.; Strisower, B.; Bowman, H.; Flexser, S.; Carmichael, I.

    1978-04-01

    Geologic and geochemical criteria were developed for the occurrence of economic uranium deposits in alkaline igneous rocks. A literature search, a limited chemical analytical program, and visits to three prominent alkaline-rock localities (Ilimaussaq, Greenland; Pocos de Caldas, Brazil; and Powderhorn, Colorado) were made to establish criteria to determine if a site had some uranium resource potential. From the literature, four alkaline-intrusive occurrences of differing character were identified as type-localities for uranium mineralization, and the important aspects of these localities were described. These characteristics were used to categorize and evaluate U.S. occurrences. The literature search disclosed 69 U.S. sites, encompassing nepheline syenite, alkaline granite, and carbonatite. It was possible to compare two-thirds of these sites to the type localities. A ranking system identified ten of the sites as most likely to have uranium resource potential

  12. Uranium in alkaline rocks

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M.; Wollenberg, H.; Strisower, B.; Bowman, H.; Flexser, S.; Carmichael, I.

    1978-04-01

    Geologic and geochemical criteria were developed for the occurrence of economic uranium deposits in alkaline igneous rocks. A literature search, a limited chemical analytical program, and visits to three prominent alkaline-rock localities (Ilimaussaq, Greenland; Pocos de Caldas, Brazil; and Powderhorn, Colorado) were made to establish criteria to determine if a site had some uranium resource potential. From the literature, four alkaline-intrusive occurrences of differing character were identified as type-localities for uranium mineralization, and the important aspects of these localities were described. These characteristics were used to categorize and evaluate U.S. occurrences. The literature search disclosed 69 U.S. sites, encompassing nepheline syenite, alkaline granite, and carbonatite. It was possible to compare two-thirds of these sites to the type localities. A ranking system identified ten of the sites as most likely to have uranium resource potential.

  13. The Cementitious Barriers Partnership Experimental Programs and Software Advancing DOE’s Waste Disposal/Tank Closure Efforts – 15436

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Heather [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, Greg [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Smith, Frank [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Langton, Christine [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Brown, Kevin [Vanderbilt Univ./CRESP, Nashville, TN (United States); Kosson, David [Vanderbilt Univ./CRESP, Nashville, TN (United States); Samson, Eric [SIMCO Technologies, Inc. (United States); Mallick, Pramod [US DOE, Washington, DC (United States)

    2015-01-27

    The U.S. Department of Energy Environmental Management (DOE-EM) Office of Tank Waste Management-sponsored Cementitious Barriers Partnership (CBP) is chartered with providing the technical basis for implementing cement-based waste forms and radioactive waste containment structures for long-term disposal. DOE needs in this area include the following to support progress in final treatment and disposal of legacy waste and closure of High-Level Waste (HLW) tanks in the DOE complex: long-term performance predictions, flow sheet development and flow sheet enhancements, and conceptual designs for new disposal facilities. The DOE-EM Cementitious Barriers Partnership is producing software and experimental programs resulting in new methods and data needed for end-users involved with environmental cleanup and waste disposal. Both the modeling tools and the experimental data have already benefited the DOE sites in the areas of performance assessments by increasing confidence backed up with modeling support, leaching methods, and transport properties developed for actual DOE materials. In 2014, the CBP Partnership released the CBP Software Toolbox –“Version 2.0” which provides concrete degradation models for 1) sulfate attack, 2) carbonation, and 3) chloride initiated rebar corrosion, and includes constituent leaching. These models are applicable and can be used by both DOE and the Nuclear Regulatory Commission (NRC) for service life and long-term performance evaluations and predictions of nuclear and radioactive waste containment structures across the DOE complex, including future SRS Saltstone and HLW tank performance assessments and special analyses, Hanford site HLW tank closure projects and other projects in which cementitious barriers are required, the Advanced Simulation Capability for Environmental Management (ASCEM) project which requires source terms from cementitious containment structures as input to their flow simulations, regulatory reviews of DOE performance

  14. The influence of alkalinity of portland cement on the absorption characteristics of superabsorbent polymers (SAP) for use in internally cured concrete

    Science.gov (United States)

    Tabares Tamayo, Juan D.

    The concrete industry increasingly emphasizes advances in novel materials that promote construction of more resilient infrastructure. Due to its potential to improve concrete durability, internal curing (IC) of concrete by means of superabsorbent polymers (SAP) has been identified as one of the most promising technologies of the 21st century. The addition of superabsorbent polymers into a cementitious system promotes further hydration of cement by providing internal moisture during the hardening and strength development periods, and thus limits self-desiccation, shrinkage, and cracking. This thesis presents the work performed on the series of cement pastes with varying alkalinity of their pore solutions to provide a better understanding of: (1) the influence of the chemistry of the pore solution (i.e. its level of alkalinity and the type of ionic species present) on the absorption capacity of SAP, and (2) the effectiveness of SAP with different absorption capacities as an internal curing agent. This research work was divided into three stages: (a) materials characterization, (b) measurement of absorption capacity of SAP in synthetic pore solutions, and (c) evaluation of the internal curing effectiveness of SAP. During the first stage (Materials Characterization), pore solutions were extracted from the fresh (5 minutes old) cement pastes prepared using cements with three different levels of alkalinity. The pH values of the extracted solutions were determined (using the pH meter) and their chemical analysis was performed by means of titration (concentration of hydroxyl), ion chromatography (sulfates and chlorides), atomic absorption (AA) and inductively coupled plasma optical emission spectrometry (ICP) (sodium, potassium and calcium). The commercial SAP adopted for this study was used with "as-supplied" gradation and with the finer gradation obtained by grinding the original polymer in the 6850 Cryomilling Freezer/Mill. The physical properties of these SAP's, such

  15. Utilization of Local Ingredients for the Production of High-Early-Strength Engineered Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Hanwen Deng

    2018-01-01

    Full Text Available The rapid repair and retrofitting of existing transportation infrastructure requires dimensional stability and ductile repair material that can obtain sufficiently high strength in a few hours to accommodate the large loading and deformation at an early age. Engineering cementitious composites (ECCs is a class representative of the new generation of high-performance fiber-reinforced cement-based composites (HPFRCC with medium fiber content. The unique properties of tremendous ductility and tight multiple crack behavior indicate that ECC can be used as an effective retrofit material. The wide application of this material in China will require the use of all local ingredients. In this study, based on Chinese domestic ingredients, including matrix materials and all fibers, high-early-strength ECC (HES-ECC was designed under the guidance of strain-hardening criterion of ECC. The matrix properties and fiber/matrix interfacial micromechanics properties were obtained from three-point-bending test and single-fiber pullout test. The mechanical properties of HES-ECC were achieved by direct tensile test. The experimental results show that HES-ECC was successfully developed by using all Chinese materials. When using the domestic PVA fiber at 2%, the strength requirement can be achieved but only a low ductility. When using the domestic PE fiber at 0.8%, the strength and deformation requirement both can be obtained. The HES-ECC developed in this study exhibited compressive strength of more than 25 MPa within 6 hours, and an ultimate tensile strength of 5-6 MPa and tensile strain capacity of 3-4% after 60 days. Moreover, the cost of using domestic fiber can be largely reduced compared with using imported fiber, up to 70%; it is beneficial to the promotion of these high-early-strength ECCs in the Chinese market.

  16. Structural Performance of Polymer Fiber Reinforced Engineered Cementitious Composites Subjected to Static and Fatigue Flexural Loading

    Directory of Open Access Journals (Sweden)

    Mohamed A.A. Sherir

    2015-07-01

    Full Text Available This paper presents the influence of silica sand, local crushed sand and different supplementary cementing materials (SCMs to Portland cement (C ratio (SCM/C on the flexural fatigue performance of engineered cementitious composites (ECCs. ECC is a micromechanically-based designed high-performance polymer fiber reinforced concrete with high ductility which exhibits strain-hardening and micro-cracking behavior in tension and flexure. The relative high cost remains an obstacle for wider commercial use of ECC. The replacement of cement by SCMs, and the use of local sand aggregates can lower cost and enhance greenness of the ECC. The main variables of this study were: type and size of aggregates (local crushed or standard silica sand, type of SCMs (fly ash “FA” or slag, SCM/cement ratio of 1.2 or 2.2, three fatigue stress levels and number of fatigue cycles up to 1 million. The study showed that ECC mixtures produced with crushed sand (with high volume of fly ash and slag exhibited strain hardening behavior (under static loading with deformation capacities comparable with those made with silica sand. Class F-fly ash combined with crushed sand was the best choice (compared to class CI fly ash and slag in order to enhance the ECC ductility with slag–ECC mixtures producing lowest deflection capacity. FA–ECC mixtures with silica sand developed more damage under fatigue loading due to higher deflection evolution than FA–ECC mixtures with crushed sand.

  17. Effect of Carbon Nanotube Size on Compressive Strengths of Nanotube Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Tanvir Manzur

    2014-01-01

    Full Text Available Application of nanoscale science to construction material has already begun. In recent times, various nanofibers have raised the interest of researchers due to their exceptional mechanical properties and high potential to be used as reinforcement within cement matrix. Carbon nanotube (CNT is one of the most important areas of research in the field of nanotechnology. The size and exceptional mechanical properties of CNT show their high potential to be used to produce high performance next generation cementitious composites. In this study, an attempt has been made to investigate the effect of size of CNTs on compressive strengths of CNT reinforced cement composites. Seven different sizes of multiwalled nanotubes (MWNTs were used to produce MWNT-cement composites. A trend was observed regarding the effect of nanotube size on compressive strength of composites in most cases. MWNT with outside diameter (OD of 20 nm or less exhibited relatively better performance. Smaller MWNT can be distributed at much finer scale and consequently filling the nanopore space within the cement matrix more efficiently. This in turn resulted in stronger composites.

  18. Long-term degradation (or improvement?) of cementitious grout/concrete for waste disposal at Hanford

    International Nuclear Information System (INIS)

    Piepho, M.G.

    1997-01-01

    If grout and/or concrete barriers and containments are considered for long-term (500 yrs to 100,000 ) waste disposal, then long-term degradation of grout/cement materials (and others) need to be studied. Long-term degradations of a cementitious grout monolith (15.4mW x 10.4mH x 37.6mL) and its containment concrete shell and asphalt shell (each 1-m thick) were analyzed. The main degradation process of the concrete shell was believed to be fractures due to construction joints, shrinkage, thermal stress, settlement, and seismic events. A scenario with fractures was modeled (flow and transport model) for long-term risk performance (out to a million yrs). Even though the concrete/grout is expected to fracture, the concrete/grout chemistry, which has high Ph value, is very beneficial in causing calcite deposits from calcium in the water precipitating in the fractures. These calcite deposits will tend to plug the fracture and keep water from entering. The effectiveness of such plugging needs to be studied more. It's possible that the plugged fractures are more impermeable than the original concrete/grout. The long-term performance of concrete/grout barriers will be determined by its chemistry, not its mechanical properties

  19. Developing Connections for Longitudinal Joints between Deck Bulb Tees - Development of UHPC Mixes with Local Materials

    Science.gov (United States)

    2016-10-30

    In past decades, many state DOTs and the Federal Highway Administration (FHWA) have begun : working with ultra-high performance concrete (UHPC), an advanced cementitious material. The Washington State Department of Transportation (WSDOT) has not empl...

  20. Alkaline phosphatase: an overview.

    Science.gov (United States)

    Sharma, Ujjawal; Pal, Deeksha; Prasad, Rajendra

    2014-07-01

    Alkaline phosphatase (ALP; E.C.3.I.3.1.) is an ubiquitous membrane-bound glycoprotein that catalyzes the hydrolysis of phosphate monoesters at basic pH values. Alkaline phosphatase is divided into four isozymes depending upon the site of tissue expression that are Intestinal ALP, Placental ALP, Germ cell ALP and tissue nonspecific alkaline phosphatase or liver/bone/kidney (L/B/K) ALP. The intestinal and placental ALP loci are located near the end of long arm of chromosome 2 and L/B/K ALP is located near the end of the short arm of chromosome 1. Although ALPs are present in many mammalian tissues and have been studied for the last several years still little is known about them. The bone isoenzyme may be involved in mammalian bone calcification and the intestinal isoenzyme is thought to play a role in the transport of phosphate into epithelial cells of the intestine. In this review, we tried to provide an overview about the various forms, structure and functions of alkaline phosphatase with special focus on liver/bone/kidney alkaline phosphatase.

  1. Advanced alkaline water electrolysis

    International Nuclear Information System (INIS)

    Marini, Stefania; Salvi, Paolo; Nelli, Paolo; Pesenti, Rachele; Villa, Marco; Berrettoni, Mario; Zangari, Giovanni; Kiros, Yohannes

    2012-01-01

    A short review on the fundamental and technological issues relevant to water electrolysis in alkaline and proton exchange membrane (PEM) devices is given. Due to price and limited availability of the platinum group metal (PGM) catalysts they currently employ, PEM electrolyzers have scant possibilities of being employed in large-scale hydrogen production. The importance and recent advancements in the development of catalysts without PGMs are poised to benefit more the field of alkaline electrolysis rather than that of PEM devices. This paper presents our original data which demonstrate that an advanced alkaline electrolyzer with performances rivaling those of PEM electrolyzers can be made without PGM and with catalysts of high stability and durability. Studies on the advantages/limitations of electrolyzers with different architectures do show how a judicious application of pressure differentials in a recirculating electrolyte scheme helps reduce mass transport limitations, increasing efficiency and power density.

  2. Alkaline Plume in the Aptian Sand Aquifer in the Context of Low-Level Radioactive Waste Surface Disposal

    Science.gov (United States)

    Cochepin, B.; Munier, I.; MADE, B.

    2017-12-01

    The storage vaults for low and intermediate-level short-lived radioactive waste in the East of France are settled on the Aptian sand layer. In the context of the periodic examination by the nuclear regulators, it has been recommended to assess more precisely the chemical conditions for a potential release of radionuclides in the underlying water table. In particular, this study aims at assessing the eventuality of spreading an alkaline plume in the Aptian sand pore water by the chemical degradation of the vault cementitious materials. The numerical approach developed for this purpose is supported by both experimental characterizations of tracers in the water table and results from preliminary numerical studies on the hydrology of the site and the hydraulic evolution of the storage. The results from these specific simulations were simplified in the reactive transport model to focus on the mechanistic description of the chemical processes taking place in the waste and vaults and on their consequences on the underlying water table. During the operating period of the disposal, the reactive transport modelling shows that the low water saturation in the vaults material and in the vadose zone prevents the aquifer from a significant increase of the water pH under the cement-based vaults. These results are in reasonable agreement with the pH regularly measured in the underlying water table. After storage closure, during the few hundred years of the monitoring period and furthermore beyond, the reactive transport modelling shows a noticeable release of hydroxyls and alkali ions under the disposal vaults and their spread downstream the storage site leading to pH values above 10. It is noteworthy that the pH is not buffered in the Aptian sands because of their low amount in clayey minerals. This effect is now considered for pH-sensitive radionuclide solutes in safety assessment calculations by weighting correspondingly their retention parameters.

  3. Lightweight Heat Resistant Geopolymer-based Materials Synthesized from Red Mud and Rice Husk Ash Using Sodium Silicate Solution as Alkaline Activator

    Directory of Open Access Journals (Sweden)

    Hoc Thang Nguyen

    2017-01-01

    Full Text Available Geopolymer is an inorganic polymer composite with potentials to replace Ordinary Portland Cement (OPC-based materials in the future because of its lower energy consumption, minimal CO2 emissions and lower production cost as it utilizes industrial waste resources. Hence, geopolymerization and the process to produce geopolymers for various applications like building materials can be considered as green industry. Moreover, in our study, the raw materials we used are red mud and rice husk ash, which are are industrial and agricultural wastes that need to be managed to reduce their impact to the environment. The red mud and rice husk ash combined with sodium silicate (water glass solution were mixed to form geopolymer materials. Moreover, the geopolymer specimens were also tested for heat resistance at a temperature of 1000°C for 2 hours. Results suggest high heat resistance with an increase of compressive strength after exposed at high temperature.

  4. [Advances of alkaline amylase production and applications].

    Science.gov (United States)

    Yang, Haiquan; Liu, Long; Li, Jianghua; Du, Guocheng; Chen, Jian

    2012-04-01

    Alkaline amylase is one of alkaline enzymes with optimum pH in the alkaline range, and it could keep stability and efficiently hydrolyze starch under alkaline conditions. Alkaline amylase finds wide applications in textile, detergent, pharmaceutical, food and other fields. Alkaline amylases could be produced by alkaliphilic microorganisms. In this work, the advances of alkaline amylase production and applications were reviewed.

  5. Alkaline Activator Impact on the Geopolymer Binders

    Science.gov (United States)

    Błaszczyński, Tomasz Z.; Król, Maciej R.

    2017-10-01

    Concrete structures are constantly moving in the direction of improving the durability. Durability depends on many factors, which are the composition of concrete mix, the usage of additives and admixtures and the place, where material will work and carry the load. The introduction of new geopolymer binders for geopolymer structures adds a new aspect that is type of used activator. This substance with strongly alkaline reaction is divided because of the physical state, the alkaline degree and above all the chemical composition. Taking into account, that at present the geopolymer binders are made essentially from waste materials or by-products from the combustion of coal or iron ore smelting, unambiguous determination of the effect of the activator on the properties of the geopolymer material requires a number of trials, researches and observation. This paper shows the influence of the most alkaline activators on the basic parameters of the durability of geopolymer binders. In this study there were used highly alkaline hydroxides, water glasses and granules, which are waste materials in a variety of processes taking place in chemical plants. As the substrate of geopolymer binders there were used fly ash which came from coal and high calcareous ash from the burning of lignite.

  6. Carbonation of ternary cementitious concrete systems containing fly ash and silica fume

    Directory of Open Access Journals (Sweden)

    Eehab Ahmed Badreldin Khalil

    2015-04-01

    Full Text Available Carbonation is quite a complex physical negative effect phenomenon on concrete especially in the ones containing ternary blends of Portland Cement, fly ash, and silica fume. Nine selected concrete mixtures were prepared with various water to cementitious materials’ ratios and various cementitious contents. The concrete mixtures were adapted in such a way to have the same workability and air content. The fresh concrete properties were kept near identical in slump, air content, and unit weight. The variation was in the hardened concrete mechanical properties of compression and tension strength. The carbonation phenomenon was studied for these mixes showing at which mixes of ternary cementitious content heavy carbonation attacks maybe produced. The main components of such mixes that do affect the carbonation process with time were presented.

  7. Effect of hybrid fiber reinforcement on the cracking process in fiber reinforced cementitious composites

    DEFF Research Database (Denmark)

    Pereira, Eduardo B.; Fischer, Gregor; Barros, Joaquim A.O.

    2012-01-01

    tensile deformations in the composite, the fibers with different geometrical and mechanical properties restrain the propagation and further development of cracking at different scales from the micro- to the macro-scale. The optimized design of the fiber reinforcing systems requires the objective......The simultaneous use of different types of fibers as reinforcement in cementitious matrix composites is typically motivated by the underlying principle of a multi-scale nature of the cracking processes in fiber reinforced cementitious composites. It has been hypothesized that while undergoing...... assessment of the contribution of each type of fiber to the overall tensile response. Possible synergistic effects resulting from particular combinations of fibers need to be clearly identified. In the present study, the evaluation of the response of different fiber reinforced cementitious composite...

  8. EIS and adjunct electrical modeling for material selection by evaluating two mild steels for use in super-alkaline mineral processing

    DEFF Research Database (Denmark)

    Bakhtiyari, Leila; Moghimi, Fereshteh; Mansouri, Seyed Soheil

    2012-01-01

    The production of metal concentrates during mineral processing of ferrous and non-ferrous metals involves a variety of highly corrosive chemicals which deteriorate common mild steel as the material of choice in the construction of such lines, through rapid propagation of localized pitting...... in susceptible parts, often in sensitive areas. This requires unscheduled maintenance and plant shut down. In order to test the corrosion resistance of different available materials as replacement materials, polarization and electrochemical impedance spectroscopy (EIS) tests were carried out. The EIS numerical...... software-enhanced polarization resistance, and reduced capacitance added to much diminished current densities, verified the acceptable performance of CK45 compared with high priced stainless steel substitutes with comparable operational life. Therefore, CK45 can be a suitable alternative in steel...

  9. Alkaline earth filled nickel skutterudite antimonide thermoelectrics

    Science.gov (United States)

    Singh, David Joseph

    2013-07-16

    A thermoelectric material including a body centered cubic filled skutterudite having the formula A.sub.xFe.sub.yNi.sub.zSb.sub.12, where A is an alkaline earth element, x is no more than approximately 1.0, and the sum of y and z is approximately equal to 4.0. The alkaline earth element includes guest atoms selected from the group consisting of Be, Mb, Ca, Sr, Ba, Ra and combinations thereof. The filled skutterudite is shown to have properties suitable for a wide variety of thermoelectric applications.

  10. Bentonite reactivity in alkaline solutions: results of the Cyprus natural analogue project (CNAP)

    International Nuclear Information System (INIS)

    Alexander, W.R.; Milodowski, A.E.; Pitty, A.F.; Hardie, S.M.L.; Korkeakoski, P.; Norris, S.; Puigdomenech, I.; Sellin, P.; Rigas, M.

    2012-01-01

    Document available in extended abstract form only. Bentonite is one of the most safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. Bentonite is used due to its favourable properties (including plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides) and its stability in relevant geological environments. However, bentonite is unstable under alkaline conditions and, due to the fact that cementitious materials react with groundwater to produce initial leachates with pH >13 (later falling to around pH 12.5), this has driven recent interest in low alkali cements, because the pH of the leachate is somewhat lower than standard OPC (Ordinary Portland Cement), lying around pH 10-11. It is hoped that this lower pH will reduce bentonite reaction, so allowing the use of low alkali cements in close proximity with bentonite. Assuring the long-term stability of bentonite in contact with such alkaline fluids under conditions representative of a deep geological repository requires complementary laboratory, modelling and in situ studies. In particular, to build a robust safety case, it is important to have supporting natural analogue data to confirm understanding - and validate models - of the likely long-term performance of bentonite. As a result of a review of the available literature and recent geological investigations by the authors, several sites in Cyprus were selected as particularly promising for this purpose. All alkaline groundwaters studied so far in Cyprus originate from ophiolite host rocks which are wide-spread across the island. The alkaline pH values (generally between pH 10 and 11, but a maximum of 12 has been observed) reported in the groundwaters are a product of the serpentinization of the ophiolites. The presence of bentonite and other clay-rich rocks in close proximity to the natural alkaline groundwaters permits the

  11. Micro-mechanical Analysis of Fiber Reinforced Cementitious Composites using Cohesive Crack Modeling

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2006-01-01

    This paper discusses the mechanism appearing during fiber debonding in fiber reinforced cementitious composite. The investigation is performed on the micro scale by use of a Finite Element Model. The model is 3 dimensional and the fictitious crack model and a mixed mode stress formulation...... are implemented. It is shown that the cohesive law for a unidirectional fiber reinforced cementitious composite can be found through superposition of the cohesive law for mortar and the fiber bridging curve. A comparison between the numerical and an analytical model for fiber pull-out is performed....

  12. Interface Properties in Extruded FRC-Materials

    DEFF Research Database (Denmark)

    Stang, Henrik

    1997-01-01

    reinforced cementitious material extruded by the developed process. It is further more shown that the fiber-matrix bond is highly dependent on the relative slip at the interface and a bond-slip relationship is suggested for the extruded material. The observed very high fiber-matrix bond is explained...

  13. Bond strength of cementitious borehole plugs in welded tuff

    International Nuclear Information System (INIS)

    Akgun, H.; Daemen, J.J.K.

    1991-02-01

    Axial loads on plugs or seals in an underground repository due to gas, water pressures and temperature changes induced subsequent to waste and plug emplacement lead to shear stresses at the plug/rock contact. Therefore, the bond between the plug and rock is a critical element for the design and effectiveness of plugs in boreholes, shafts or tunnels. This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young's modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. The main conclusion is a strong recommendation to design friction plugs in shafts, drifts, tunnels or boreholes with a minimum length to diameter ratio of four. Such a geometrical design will reduce tensile stresses in the plug and in the host rock to a level which should minimize the risk of long-term deterioration caused by excessive tensile stresses. Push-out tests have been used to determine the bond strength by applying an axial load to cement plugs emplaced in boreholes in welded tuff cylinders. A total of 130 push-out tests have been performed as a function of borehole size, plug length, temperature, and degree of saturation of the host tuff. The use of four different borehole radii enables evaluation of size effects. 119 refs., 42 figs., 20 tabs

  14. Mechanical resilience and cementitious processes in Imperial Roman architectural mortar.

    Science.gov (United States)

    Jackson, Marie D; Landis, Eric N; Brune, Philip F; Vitti, Massimo; Chen, Heng; Li, Qinfei; Kunz, Martin; Wenk, Hans-Rudolf; Monteiro, Paulo J M; Ingraffea, Anthony R

    2014-12-30

    The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥ 90 d, after pozzolanic consumption of hydrated lime was complete. Platey strätlingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2- to 30-µm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clast-supported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.

  15. Viscosity of Molten Alkaline-Earth Fluorides

    Science.gov (United States)

    Takeda, Osamu; Hoshino, Yosuke; Anbo, Yusuke; Yanagase, Kei-ichi; Aono, Masahiro; Sato, Yuzuru

    2015-04-01

    The viscosities of molten alkaline-earth fluorides were measured using the oscillating crucible method, which is especially suitable for measuring molten salts with low viscosity. The results showed a good Arrhenius linearity over a wide temperature range. The measured viscosities and activation energies increased in the following order: . Judging by the charge density, the viscosity of alkaline-earth fluorides should increase from molten to . However, the results indicate a different tendency, which may be explained by a Coulomb force that is very strong. The low viscosity of can be attributed to a decreased cohesive force, due to a partial loss of the Coulomb force caused by a higher charge density of the material. The viscosities were also compared to those of molten alkali fluorides and alkaline-earth chlorides. The viscosities of molten alkaline-earth fluorides were higher than those of molten alkali fluorides and alkaline-earth chlorides. The viscosity determined in this study was compared to literature values and showed a reasonable value in the relatively low-viscosity region.

  16. Avaliação da resistência a fadiga dos Engineered Cementitious Composites (ecc), reforçados com fibra de polipropileno e produzidos com adição de cinza de casca de arroz

    OpenAIRE

    Alceu Lopes de Freitas Júnior; Monica Regina Garcez

    2017-01-01

    O Engineered Cementitious Composites - ECC – é um tipo especial de compósito cimentício de alto desempenho reforçado com fibra, cuja principal característica é a alta ductilidade. O traço de ECC é composto por cimento, material pozolânico, agregado miúdo e fibras. Este estudo avaliou a resistência à fadiga de traços de Engineered Cementitious Composites reforçados com fibras de polipropileno - PPECC – e cuja composição da matriz cimentícia tenha a incorporação de cinza de casca de arroz como ...

  17. Seismic resistant repair and reinforcement materials; Shiyo zairyo ni miru taishin hokyo to hoshu gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, E.; Daimon, M. [Tokyo Industral Univ. (Japan)

    1997-08-10

    Seismic resistant repair and reinforcement materials are outlined with emphasis on relation between main components and characteristics of cements, polymers and composite materials referring to recent domestic reports and guidelines. First, types and required performance of polymer and specialized cementitious repair and reinforcement materials are summarized. Among the polymer repair and reinforcement materials, grouting materials for cracks, adhesives and carbon fiber FRP are taken up, and the following items are specifically explained; use of injection property and adhesiveness; use of reinforcement effect. On the cementitious repair and reinforcement materials, the following items are explained; use of rapid adhesion and rapid hardening; use of injection and filling properties; use of low contraction; use of adhesion; use of densification and chemical resistance. Finally, the following future problems are shown; new material development based on the user demand on existing materials; performance improvement of cementitious composite materials as durable materials; warranty of construction and quality. 25 refs., 5 figs., 8 tabs.

  18. Kinetics of the Fading of Phenolphthalein in Alkaline Solution.

    Science.gov (United States)

    Nicholson, Lois

    1989-01-01

    Described is an experiment which illustrates pseudo-first-order kinetics in the fading of a common indicator in an alkaline solution. Included are background information, details of materials used, laboratory procedures, and sample results. (CW)

  19. Metal Distribution and Mobility under alkaline conditions

    International Nuclear Information System (INIS)

    Dario, Maarten

    2004-01-01

    colloidal matter (clays and an iron hydroxide) was measured by photon correlation spectroscopy. In the absence of large amounts of organic material, the present colloids will, in most cases, not enhance metal migration in a cementitious environment due to agglomeration of the colloidal phase at high pH and salinities

  20. Understanding of bonding and mechanical characteristics of cementitious mineral tobermorite from first principles.

    Science.gov (United States)

    Tunega, Daniel; Zaoui, Ali

    2011-01-30

    This paper reports density functional theory study of the structural and mechanical properties of tobermorite mineral (9 Å phase) as one of the main component of cementitious materials in a concrete chemistry. Calculated bulk modulus and elastic constants reflect a relatively high resistance of the tobermorite structure with respect to external isostatic compression. Moreover, the elastic constants proved the anisotropic character of the tobermorite structure. The directions parallel to the axb plane are more resistant to the compression than the perpendicular direction. The largest contribution to this resistance comes from the "dreierketten" silicate chains. The bonding analysis linked macroscopic mechanical properties and the atomic structure of the tobermorite. It was found that polar covalent Si-O bonds are stiffer than iono-covalent Ca-O bonds. The SiO(4) tetrahedra are resistant with respect to the compression and the effect of external pressure is reflected by the large mutual tilting of these tetrahedra as it is shown by changes of the Si-O-Si bridging angles. Polyhedra with the seven-fold coordinated Ca(2+) cations undergo large structural changes. Especially, axial Ca-O bonds perpendicular to the axb plane are significantly shortened. Besides, it was shown that structural parameters, more or less in parallel orientation to the axb plane, are mainly responsible for the high resistance of the tobermorite structure to external pressure. The main mechanism of a dissipation of energy entered to the structure through the compression is proceeded by the tilting of the tetrahedra of the silicate chains and by large shortening of the axial Ca-O distances. Copyright © 2010 Wiley Periodicals, Inc.

  1. Corrosion resistance and development length of steel reinforcement with cementitious coatings

    Science.gov (United States)

    Pei, Xiaofei

    This research program focused on the corrosion resistance and development length of reinforcing steel coated with Cementitious Capillary Crystalline Waterproofing (CCCW) materials. The first part of this research program involved using the half-cell potential method to evaluate the corrosion resistance of CCCW coating materials. One hundred and two steel bars were embedded in concrete cylinders and monitored. In total, 64 steel reinforcing bars were coated with CCCW prior to embedment, 16 mortar cylinders were externally coated with CCCW, and 22 control (uncoated) samples were tested. All the samples were immersed in a 3.5% concentration chloride solution for a period of one year. Three coating types were studied: CCCW-B, CCCW-B+ C and CCCW-C+D. The test results showed that the CCCW coating materials delayed the corrosion activity to varying degrees. In particular, CCCW-C+D applied on the reinforcing steel surface dramatically delayed the corrosion activity when compared to the control samples. After being exposed to the chloride solution for a period of one year, no sign of corrosion was observed for the cylinders where the concrete surface was coated. The second part of this research evaluated the bond strength and development length of reinforcing steel coated with two types of CCCW coating materials (CCCW-B+C and CCCW-C+D) using a modified pull-out test method. A self-reacting inverted T-shaped beam was designed to avoid compression in the concrete surrounding the reinforcing steel. Steel reinforcing bars were embedded along the web portion of the T-beam with various embedded lengths and were staggered side by side. In total, six T-beams were fabricated and each beam contained 8 samples. Both short-term (7 days) and long-term (3 months) effects of water curing were evaluated. The reinforcing steel bars coated with CCCW-B+C demonstrated a higher bond strength than did samples coated with CCCW-C+D. However, the bond strengths of samples with coating materials

  2. THERMALLY CONDUCTIVE CEMENTITIOUS GROUTS FOR GEOTHERMAL HEAT PUMPS. PROGRESS REPORT BY 1998

    Energy Technology Data Exchange (ETDEWEB)

    ALLAN,M.L.; PHILIPPACOPOULOS,A.J.

    1998-11-01

    Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98.

  3. Glass science tutorial: Lecture No. 8, introduction cementitious systems for Low-Level Waste immobilization

    International Nuclear Information System (INIS)

    Young, J.F.; Kirkpatrick, R.J.; Mason, T.O.; Brough, A.

    1995-07-01

    This report presents details about cementitious systems for low-level waste immobilization. Topics discussed include: composition and properties of portland cement; hydration properties; microstructure of concrete; pozzolans; slags; zeolites; transport properties; and geological aspects of long-term durability of concrete

  4. Cementitious Composites Engineered with Embedded Carbon Nanotube Thin Films for Enhanced Sensing Performance

    International Nuclear Information System (INIS)

    Loh, Kenneth J; Gonzalez, Jesus

    2015-01-01

    Cementitious composites such as concrete pavements are susceptible to different damage modes, which are primarily caused by repeated loading and long-term deterioration. There is even greater concern that damage could worsen and occur more frequently with the use of heavier vehicles or new aircraft carrying greater payloads. Thus, the objective of this research is to engineer cementitious composites with capabilities of self-sensing or detecting damage. The approach was to enhance the damage sensitivity of cementitious composites by incorporating multi-walled carbon nanotubes (MWNT) as part of the mix design and during casting. However, as opposed to directly dispersing MWNTs in the cement matrix, which is the current state-of-art, MWNT-based thin films were airbrushed and coated onto sand particles. The film-coated sand was then used as part of the mix design for casting mortar specimens. Mortar specimens were subjected to compressive cyclic loading tests while their electrical properties were recorded simultaneously. The results showed that the electrical properties of these cementitious composites designed with film-coated sand exhibited extremely high strain sensitivities. The electrical response was also stable and consistent between specimens. (paper)

  5. Cementitious Composites Engineered with Embedded Carbon Nanotube Thin Films for Enhanced Sensing Performance

    Science.gov (United States)

    Loh, Kenneth J.; Gonzalez, Jesus

    2015-07-01

    Cementitious composites such as concrete pavements are susceptible to different damage modes, which are primarily caused by repeated loading and long-term deterioration. There is even greater concern that damage could worsen and occur more frequently with the use of heavier vehicles or new aircraft carrying greater payloads. Thus, the objective of this research is to engineer cementitious composites with capabilities of self-sensing or detecting damage. The approach was to enhance the damage sensitivity of cementitious composites by incorporating multi-walled carbon nanotubes (MWNT) as part of the mix design and during casting. However, as opposed to directly dispersing MWNTs in the cement matrix, which is the current state-of-art, MWNT-based thin films were airbrushed and coated onto sand particles. The film-coated sand was then used as part of the mix design for casting mortar specimens. Mortar specimens were subjected to compressive cyclic loading tests while their electrical properties were recorded simultaneously. The results showed that the electrical properties of these cementitious composites designed with film-coated sand exhibited extremely high strain sensitivities. The electrical response was also stable and consistent between specimens.

  6. Glass science tutorial: Lecture No. 8, introduction cementitious systems for Low-Level Waste immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Young, J.F.; Kirkpatrick, R.J.; Mason, T.O.; Brough, A.

    1995-07-01

    This report presents details about cementitious systems for low-level waste immobilization. Topics discussed include: composition and properties of portland cement; hydration properties; microstructure of concrete; pozzolans; slags; zeolites; transport properties; and geological aspects of long-term durability of concrete.

  7. Treatment of Alkaline Cr(VI)-Contaminated Leachate with an Alkaliphilic Metal-Reducing Bacterium.

    Science.gov (United States)

    Watts, Mathew P; Khijniak, Tatiana V; Boothman, Christopher; Lloyd, Jonathan R

    2015-08-15

    Chromium in its toxic Cr(VI) valence state is a common contaminant particularly associated with alkaline environments. A well-publicized case of this occurred in Glasgow, United Kingdom, where poorly controlled disposal of a cementitious industrial by-product, chromite ore processing residue (COPR), has resulted in extensive contamination by Cr(VI)-contaminated alkaline leachates. In the search for viable bioremediation treatments for Cr(VI), a variety of bacteria that are capable of reduction of the toxic and highly soluble Cr(VI) to the relatively nontoxic and less mobile Cr(III) oxidation state, predominantly under circumneutral pH conditions, have been isolated. Recently, however, alkaliphilic bacteria that have the potential to reduce Cr(VI) under alkaline conditions have been identified. This study focuses on the application of a metal-reducing bacterium to the remediation of alkaline Cr(VI)-contaminated leachates from COPR. This bacterium, belonging to the Halomonas genus, was found to exhibit growth concomitant to Cr(VI) reduction under alkaline conditions (pH 10). Bacterial cells were able to rapidly remove high concentrations of aqueous Cr(VI) (2.5 mM) under anaerobic conditions, up to a starting pH of 11. Cr(VI) reduction rates were controlled by pH, with slower removal observed at pH 11, compared to pH 10, while no removal was observed at pH 12. The reduction of aqueous Cr(VI) resulted in the precipitation of Cr(III) biominerals, which were characterized using transmission electron microscopy and energy-dispersive X-ray analysis (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The effectiveness of this haloalkaliphilic bacterium for Cr(VI) reduction at high pH suggests potential for its use as an in situ treatment of COPR and other alkaline Cr(VI)-contaminated environments. Copyright © 2015, Watts et al.

  8. Reclaiming the spent alkaline zinc manganese dioxide batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} materials

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Ya; Cui, Yan; Zuo, Xiaoxi; Huang, Shanna; Hu, Keshui; Xiao, Xin; Nan, Junmin, E-mail: jmnan@scnu.edu.cn

    2014-10-15

    Highlights: • The spent Zn–Mn batteries collected from manufacturers is the target waste. • A facile reclaiming process is presented. • The zinc is reclaimed to valuable electrolytic zinc by electrodepositing method. • The manganese elements are to produce valuable LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} battery material. • The reclamation process features environmental friendliness and saving resource. - Abstract: A process for reclaiming the materials in spent alkaline zinc manganese dioxide (Zn–Mn) batteries collected from the manufacturers to prepare valuable electrolytic zinc and LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} materials is presented. After dismantling battery cans, the iron cans, covers, electric rods, organic separator, label, sealing materials, and electrolyte are separated through the washing, magnetic separation, filtrating, and sieving operations. Then, the powder residues react with H{sub 2}SO{sub 4} (2 mol L{sup −1}) solution to dissolve zinc under a liquid/solid ratio of 3:1 at room temperature, and subsequently, the electrolytic Zn with purity of ⩾99.8% is recovered in an electrolytic cell with a cathode efficiency of ⩾85% under the conditions of 37–40 °C and 300 A m{sup −2}. The most of MnO{sub 2} and a small quantity of electrolytic MnO{sub 2} are recovered from the filtration residue and the electrodeposit on the anode of electrolytic cell, respectively. The recovered manganese oxides are used to synthesize LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} material of lithium-ion battery. The as-synthesized LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} discharges 118.3 mAh g{sup −1} capacity and 4.7 V voltage plateau, which is comparable to the sample synthesized using commercial electrolytic MnO{sub 2}. This process can recover the substances in the spent Zn–Mn batteries and innocuously treat the wastewaters, indicating that it is environmentally acceptable and applicable.

  9. Phosphatidylinositol anchor of HeLa cell alkaline phosphatase

    International Nuclear Information System (INIS)

    Jemmerson, R.; Low, M.G.

    1987-01-01

    Alkaline phosphatase from cancer cells, HeLa TCRC-1, was biosynthetically labeled with either 3 H-fatty acids or [ 3 H]ethanolamine as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography of immunoprecipitated material. Phosphatidylinositol-specific phospholipase C (PI-PLC) released a substantial proportion of the 3 H-fatty acid label from immunoaffinity-purified alkaline phosphatase but had no effect on the radioactivity of [ 3 H]ethanolamine-labeled material. PI-PLC also liberated catalytically active alkaline phosphatase from viable cells, and this could be selectively blocked by monoclonal antibodies to alkaline phosphatase. However, the alkaline phosphatase released from 3 H-fatty acid labeled cells by PI-PLC was not radioactive. By contrast, treatment with bromelain removed both the 3 H-fatty acid and the [ 3 H]ethanolamine label from purified alkaline phosphatase. Subtilisin was also able to remove the [ 3 H]ethanolamine label from the purified alkaline phosphatase. The 3 H radioactivity in alkaline phosphatase purified from [ 3 H]ethanolamine-labeled cells comigrated with authentic [ 3 H]ethanolamine by anion-exchange chromatography after acid hydrolysis. The data suggest that the 3 H-fatty acid and [ 3 H]ethanolamine are covalently attached to the carboxyl-terminal segment since bromelain and subtilisin both release alkaline phosphatase from the membrane by cleavage at that end of the polypeptide chain. The data are consistent with findings for other proteins recently shown to be anchored in the membrane through a glycosylphosphatidylinositol structure and indicate that a similar structure contributes to the membrane anchoring of alkaline phosphatase

  10. INTERNATIONAL PROGRAM: SUMMARY REPORT ON THE PROPERTIES OF CEMENTITIOUS WASTE FORMS

    Energy Technology Data Exchange (ETDEWEB)

    Harbour, J

    2007-03-02

    effective diffusivity of {approx}5 x 10{sup -9} cm{sup 2}/sec and a corresponding leaching index of {approx}8.2. Leaching tests at the lower bound of concentration and the leaching tests to determine the impact of redox (selenium exists in two oxidation states, selenite (SeO{sub 3}{sup -2}) and selenate (SeO{sub 4}{sup -2})) on Se-79 release were not completed due to lack of funding. The heat of hydration of a Saltstone mix limits the processing rate at the Saltstone Production Facility. Therefore, reduction in the heat of hydration of a Saltstone formulation that still complies with the remaining property requirements would provide for a greater rate of production. Initial testing for this task was completed. There was good agreement between the isothermal measurements of heat of hydration performed as part of this task with previous measurements of heat of hydration of Saltstone obtained adiabatically over the same 80 hour time period. The slightly higher heat of hydration per gram of cementitious material measured adiabatically can be explained by the higher temperatures achieved during the adiabatic measurements. The isothermal measurements reveal additional details of the heat generation process that were not evident in the adiabatic measurements. An initial heat release in the first minutes was observed isothermally. A second peak at about 5 hours was also observed isothermally that was not detected adiabatically. The major heat releases in the 10 to 30 hour period were observed by both techniques but at slightly different times and ratios of the two major peaks that comprise that region. The degree of reaction was calculated from these measurements based upon the value assigned to maximum hydration. Using the Schmidt method, the degree of reaction after 80 hours was 36% complete by isothermal calorimetry and 46% complete by adiabatic calorimetry. Using the theoretical maximum wherein the fly ash and slag are hydraulically equivalent to the portland cement, the degree

  11. INTERNATIONAL PROGRAM: SUMMARY REPORT ON THE PROPERTIES OF CEMENTITIOUS WASTE FORMS

    International Nuclear Information System (INIS)

    Harbour, J

    2007-01-01

    -9 cm 2 /sec and a corresponding leaching index of ∼8.2. Leaching tests at the lower bound of concentration and the leaching tests to determine the impact of redox (selenium exists in two oxidation states, selenite (SeO 3 -2 ) and selenate (SeO 4 -2 )) on Se-79 release were not completed due to lack of funding. The heat of hydration of a Saltstone mix limits the processing rate at the Saltstone Production Facility. Therefore, reduction in the heat of hydration of a Saltstone formulation that still complies with the remaining property requirements would provide for a greater rate of production. Initial testing for this task was completed. There was good agreement between the isothermal measurements of heat of hydration performed as part of this task with previous measurements of heat of hydration of Saltstone obtained adiabatically over the same 80 hour time period. The slightly higher heat of hydration per gram of cementitious material measured adiabatically can be explained by the higher temperatures achieved during the adiabatic measurements. The isothermal measurements reveal additional details of the heat generation process that were not evident in the adiabatic measurements. An initial heat release in the first minutes was observed isothermally. A second peak at about 5 hours was also observed isothermally that was not detected adiabatically. The major heat releases in the 10 to 30 hour period were observed by both techniques but at slightly different times and ratios of the two major peaks that comprise that region. The degree of reaction was calculated from these measurements based upon the value assigned to maximum hydration. Using the Schmidt method, the degree of reaction after 80 hours was 36% complete by isothermal calorimetry and 46% complete by adiabatic calorimetry. Using the theoretical maximum wherein the fly ash and slag are hydraulically equivalent to the portland cement, the degree of reaction after 80 hours was 20% complete by isothermal

  12. Injection grout for deep repositories - Low-pH cementitious grout for larger fractures. Field testing in Finland, Pilot tests

    International Nuclear Information System (INIS)

    Sievaeen, U.; Syrjaenen, P.; Ranta-aho, S.

    2005-10-01

    Posiva, SKB and NUMO have cooperated for developing a low pH injection grout for sealing of the deep repositories for spent nuclear fuel. A project 'Injection grout for deep repositories' was divided into four subprojects. The development of low pH cementitious grout for > 100 μm fractures was carried out in Finland. The development of non-cementitious low pH grout for < 100 μm fractures was carried out in Sweden. This report concerns the cementitious grout. Requirements for pH and penetration ability were set for the grouts to be developed. Besides these, the grouts were desired to fulfil certain targets set for viscosity, bleeding, shear strength, yield value, compressive strength and open time. Also durability, availability of the components and known history in practical engineering were given as requirements. The object of the work presented here was to test if the grout properties developed in laboratory can be met in field conditions. Only the most promising binder material combinations, which have fulfilled the main requirements in laboratory, were tested in field. Evaluations of environmental aspects are included in this report. In the pilot test 1, carried out in a multi-purpose tunnel in Helsinki, Portland cement-cilicasystem and blast furnace slag-based system were chosen to be tested. In field conditions, mixed with ordinary mixer, all grout properties achieved in laboratory, were not verified. Penetration ability was typically good, but fluidity and strength development were not satisfying. The main conclusion was that water to dry material ratio should be diminished. In order to get better rheological properties at the same time, superplastizicer was needed in further development of the mixes. Also accurate dosing and mixing seemed to be very important. Blast furnace slag - system was after this pilot test ruled out due to high leaching of sulphide from the product, not due to the bad technical properties. The development work continued with

  13. Alkaline carbonates in blast furnace process

    Directory of Open Access Journals (Sweden)

    P. Besta

    2014-10-01

    Full Text Available The production of iron in blast furnaces is a complex of physical, chemical and mechanical processes. The input raw materials contain not only metallic components, but also a number of negative elements. The most important negative elements include alkaline carbonates. They can significantly affect the course of the blast furnace process and thus the overall performance of the furnace. As a result of that, it is essential to accurately monitor the alkali content in the blast furnace raw materials. The article analyzes the alkali content in input and output raw materials and their impact on the blast furnace process.

  14. Alkaline fuel cells applications

    Science.gov (United States)

    Kordesch, Karl; Hacker, Viktor; Gsellmann, Josef; Cifrain, Martin; Faleschini, Gottfried; Enzinger, Peter; Fankhauser, Robert; Ortner, Markus; Muhr, Michael; Aronson, Robert R.

    On the world-wide automobile market technical developments are increasingly determined by the dramatic restriction on emissions as well as the regimentation of fuel consumption by legislation. Therefore there is an increasing chance of a completely new technology breakthrough if it offers new opportunities, meeting the requirements of resource preservation and emission restrictions. Fuel cell technology offers the possibility to excel in today's motive power techniques in terms of environmental compatibility, consumer's profit, costs of maintenance and efficiency. The key question is economy. This will be decided by the costs of fuel cell systems if they are to be used as power generators for future electric vehicles. The alkaline hydrogen-air fuel cell system with circulating KOH electrolyte and low-cost catalysed carbon electrodes could be a promising alternative. Based on the experiences of Kordesch [K. Kordesch, Brennstoffbatterien, Springer, Wien, 1984, ISBN 3-387-81819-7; K. Kordesch, City car with H 2-air fuel cell and lead-battery, SAE Paper No. 719015, 6th IECEC, 1971], who operated a city car hybrid vehicle on public roads for 3 years in the early 1970s, improved air electrodes plus new variations of the bipolar stack assembly developed in Graz are investigated. Primary fuel choice will be a major issue until such time as cost-effective, on-board hydrogen storage is developed. Ammonia is an interesting option. The whole system, ammonia dissociator plus alkaline fuel cell (AFC), is characterised by a simple design and high efficiency.

  15. Effect of Undensified Silica Fume on the Dispersion of Carbon Nanotubes within a Cementitious Composite

    Science.gov (United States)

    Alrekabi, S.; Cundy, A.; Whitby, Raymond L. D.; Lampropoulos, A.; Savina, I.

    2017-04-01

    The synergistic effect of multi-walled carbon nanotubes (MWCNTs) and Undensified Silica Fume (USF) on the microstructure of cementitious composites has been studied. In the current work, USF was used to enhance the dispersion of nanotubes throughout the composite and prevent the re-agglomeration of nanotubes by providing a physical barrier of particles of small size. Ultrasonication was employed to disperse MWCNTs in water in the presence of polycarboxylate-based superplasticizer (PCE) as a dispersion agent. The results indicate that incorporation of USF considerably improves the dispersion of nanotubes in the composites, with subsequent enhancement of composite packing density. This enhancement can be attributed to the synergistic effect of MWCNTs and USF in reducing the volume of pores through the cementitious composites.

  16. Secondary Waste Cementitious Waste Form Data Package for the Integrated Disposal Facility Performance Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Westsik, Joseph H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Serne, R Jeffrey [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Um, Wooyong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cozzi, Alex D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-05-16

    A review of the most up-to-date and relevant data currently available was conducted to develop a set of recommended values for use in the Integrated Disposal Facility (IDF) performance assessment (PA) to model contaminant release from a cementitious waste form for aqueous wastes treated at the Hanford Effluent Treatment Facility (ETF). This data package relies primarily upon recent data collected on Cast Stone formulations fabricated with simulants of low-activity waste (LAW) and liquid secondary wastes expected to be produced at Hanford. These data were supplemented, when necessary, with data developed for saltstone (a similar grout waste form used at the Savannah River Site). Work is currently underway to collect data on cementitious waste forms that are similar to Cast Stone and saltstone but are tailored to the characteristics of ETF-treated liquid secondary wastes. Recommended values for key parameters to conduct PA modeling of contaminant release from ETF-treated liquid waste are provided.

  17. Hydrogen gas generation from the corrosion of iron in cementitious environments

    International Nuclear Information System (INIS)

    Kreis, P.; Simpson, J.P.

    1992-01-01

    Then production of hydrogen from the anaerobic corrosion of iron or steel is an important issue in low/intermediate level nuclear waste repositories where large quantities of iron and steel (e.g. as drums and reinforcing steel) accompany the waste. Most of the iron in intermediate level repositories is in a cementitious environment. The literature on the corrosion of iron and steel at high pH values, in particular in cementitious environments, points to hydrogen evolution rates between 22 and 220 mmol (Hsub(2)).msup(-2) per year. In the present work a volumetric method was used to measure hydrogen evolution rates over several thousand hours under conditions relevant to intermediate level waste repositories. The sensitivity of this method (0.4 mmol (Hsub(2))/(msup(2).year) is sufficient to detect hydrogen evolution rates lower than those predicted for iron and steel in concrete. (author)

  18. Applications of Titanium Dioxide Photocatalysis to Construction Materials

    CERN Document Server

    Ohama, Yoshihiko

    2011-01-01

    Titanium dioxide photocatalysis is based on the semiconducting nature of its anatase crystal type. Construction materials with titanium photocatalyst show performances of air purification, self-cleaning, water purification, antibacterial action. This book describes principles of titanium dioxide photocatalysis, its applications to cementitious and noncementitious materials, as well as an overview of standardization of testing methods.

  19. Repair of Impact-Damaged Prestressed Bridge Girders Using Strand Splices and Fabric Reinforced Cementitious Matrix

    OpenAIRE

    Jones, Mark Stevens

    2017-01-01

    This thesis investigates the repair of impact-damaged prestressed concrete bridge girders with strand splices and fabric-reinforced cementitious matrix systems, specifically for repair of structural damage to the underside of an overpass bridge girder due to an overheight vehicle collision. Collision damage to bridges can range from minor to catastrophic, potentially requiring repair or replacement of a bridge girder. This thesis investigates the performance of two different types of repair...

  20. Caracterização de cinza do bagaço de cana-de-açúcar para emprego como pozolana em materiais cimentícios Characterization of sugar cane bagasse ash for use as pozzolan in cementitious materials

    Directory of Open Access Journals (Sweden)

    Guilherme Chagas Cordeiro

    2009-01-01

    Full Text Available This work presents the results of morphological and physical-chemical characteristics of a sugar cane bagasse ash material sample produced under controlled burning conditions. The investigation was carried out by analyzing chemical composition, X-ray diffraction, 29Si nuclear magnetic resonance, morphology, thermal analysis, particle size, specific surface, and density. Moreover, the pozzolanic activity of the ash was evaluated by pozzolanic activity index and Chapelle's method. The results suggest that the sugar cane bagasse ash has adequate properties to be used as pozzolan in construction materials.

  1. Degradation of polymers in an alkaline environment

    Energy Technology Data Exchange (ETDEWEB)

    Borges, P. G.; Thorpe, S. J.; Venter, R. D. [Toronto Univ., Toronto, ON (Canada)

    1999-10-01

    To introduce widespread use of hydrogen as a source of fuel, it is essential to significantly reduce the cost of electrolysers and fuel cells, preferably by substituting degradation-resistant low cost alternatives for traditional materials. An experimental apparatus for evaluating short-term degradation characteristics of polymers in 25 per cent potassium hydroxide aqueous solution at 70 and at 85 degrees C was constructed to determine changes in physical appearance, weight, volume and dimensions as a function of immersion time from 0 to 670 hours. Polymers that were part of this test included chlorinated polyvinyl chloride (CPVC), polypropylene (PP),and a polyurethane/polyester blend. Polypropylene demonstrated the greatest degradation resistance to the alkaline environment at both temperatures. CPVC discolored and the polyurethane/polyester blend deteriorated into smaller pieces when subjected to identical conditions. Resistance to degradation in an alkaline environment is a primary requirement for the selection of polymers for use as structural materials in alkaline water analyzers, which in turn is fundamental to the widespread adoption of a hydrogen economy. 6 refs., 13 figs.

  2. In situ measurement of the rheological properties and agglomeration on cementitious pastes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Hong [School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, 50 UNIST-gil, Ulsan 44919 (Korea, Republic of); Yim, Hong Jae, E-mail: yimhj@knu.ac.kr [Department of Construction and Disaster Prevention Engineering, Kyungpook National University, 2559 Gyeongsang-daero, Sangju, Gyeongsangbuk-do 742-711 (Korea, Republic of); Ferron, Raissa Douglas [Department of Civil, Architectural and Environmental Engineering, University of Texas at Austin, 301 East Dean Keeton Street, C1748, Austin, Texas 78712 (United States)

    2016-07-15

    Various factors influence the rheology of cementitious pastes, with the most important being the mixing protocol, mixture proportions, and mixture composition. This study investigated the influence of ground-granulated blast-furnace slag, on the rheological behavior of cementitious pastes. In tandem with the rheological measurements, fresh state microstructural measurements were conducted using three different techniques: A coupled stroboscope-rheometer, a coupled laser backscattering-rheometer, and a conventional laser diffraction technique. Laser diffraction and the coupled stroboscope-rheometer were not good measures of the in situ state of flocculation of a sample. Rather, only the laser backscattering technique allowed for in situ measurement on a highly concentrated suspension (cementitious paste). Using the coupled laser backscattering-rheometer technique, a link between the particle system and rheological behavior was determined through a modeling approach that takes into account agglomeration properties. A higher degree of agglomeration was seen in the ordinary Portland cement paste than pastes containing the slag and this was related to the degree of capillary pressure in the paste systems.

  3. Bond Characteristics of Macro Polypropylene Fiber in Cementitious Composites Containing Nanosilica and Styrene Butadiene Latex Polymer

    Directory of Open Access Journals (Sweden)

    Jae-Woong Han

    2015-01-01

    Full Text Available This study evaluated the bond properties of polypropylene (PP fiber in plain cementitious composites (PCCs and styrene butadiene latex polymer cementitious composites (LCCs at different nanosilica contents. The bond tests were evaluated according to JCI SF-8, in which the contents of nanosilica in the cement were 0, 2, 4, 6, 8, and 10 wt%, based on cement weight. The addition of nanosilica significantly affected the bond properties between macro PP fiber and cementitious composites. For PCCs, the addition of 0–2 wt% nanosilica enhanced bond strength and interface toughness, whereas the addition of 4 wt% or more reduced bond strength and interface toughness. The bond strength and interfacial toughness of LCCs also increased with the addition of up to 6% nanosilica. The analysis of the relative bond strength showed that the addition of nanosilica affects the bond properties of both PCC and LCC. This result was confirmed via microstructural analysis of the macro PP fiber surface after the bond tests, which revealed an increase in scratches due to frictional forces and fiber tearing.

  4. Utilize Cementitious High Carbon Fly Ash (CHCFA) to Stabilize Cold In-Place Recycled (CIR) Asphalt Pavement as Base Coarse

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haifang; Li, Xiaojun; Edil, Tuncer; O' Donnell, Jonathan; Danda, Swapna

    2011-02-05

    The purpose of this study was to evaluate the performance of cementitious high carbon fly ash (CHCFA) stabilized recycled asphalt pavement as a base course material in a real world setting. Three test road cells were built at MnROAD facility in Minnesota. These cells have the same asphalt surface layers, subbases, and subgrades, but three different base courses: conventional crushed aggregates, untreated recycled pavement materials (RPM), and CHCFA stabilized RPM materials. During and after the construction of the three cells, laboratory and field tests were carried out to characterize the material properties. The test results were used in the mechanistic-empirical pavement design guide (MEPDG) to predict the pavement performance. Based on the performance prediction, the life cycle analyses of cost, energy consumption, and greenhouse gasses were performed. The leaching impacts of these three types of base materials were compared. The laboratory and field tests showed that fly ash stabilized RPM had higher modulus than crushed aggregate and RPM did. Based on the MEPDG performance prediction, the service life of the Cell 79 containing fly ash stabilized RPM, is 23.5 years, which is about twice the service life (11 years) of the Cell 77 with RPM base, and about three times the service life (7.5 years) of the Cell 78 with crushed aggregate base. The life cycle analysis indicated that the usage of the fly ash stabilized RPM as the base of the flexible pavement can significantly reduce the life cycle cost, the energy consumption, the greenhouse gases emission. Concentrations of many trace elements, particularly those with relatively low water quality standards, diminish over time as water flows through the pavement profile. For many elements, concentrations below US water drinking water quality standards are attained at the bottom of the pavement profile within 2-4 pore volumes of flow.

  5. Screening of Alkaline Protease-Producing Streptomyces diastaticus and Optimization of Enzyme Production

    Directory of Open Access Journals (Sweden)

    Elham Dawoodi

    2014-12-01

    Full Text Available Background and Aim: Alkaline proteases are used in pharmaceutical, film and photography, silk production and food, leather and detergent industries. Actinomycetes are gram positive bacteria that produce different enzymes such as proteases. The aims of this research were isolation of native alkaline protease-producing Actinomycete spp. from different soil samples as well as optimizing the conditions for enzyme production. Materials and Methods: The different soil samples were collected from different locations of the provinces of Khouzestan, Chahar Mahalo Bakhtiari and Isfahan, Iran. After determining of the best alkaline protease producing species using Lowry method, the optimization of alkaline protease was performed. Results: The alkaline protease producing Actinomycete spp. was isolated from soil. The most enzyme activity was measured in S.diastaticus. The best concentration of sucrose as the carbon source for the highest production of alkaline protease was 10 g/l. The optimum pH and temperature for the alkaline protease production by S. diastaticus were 10 and 30°C respectively. The maximum activity of alkaline protease was measured at 200 rpm as the best aeration speed. Conclusions: This is the first report of alkaline protease production by Streptomyces diastaticus in Iran. The accomplished examinations in this research confirmed the previous theories of alkaline protease production by Actinomycetes relatively. Regarding the immense applications of alkaline proteases in several industries and isolation of a native alkaline protease producing Actinomycete, The production potential of this enzyme in our country could be accessible in the near future.

  6. Properties of Calcium Acetate Manufactured with Etching Waste Solution and Limestone Sludge as a Cementitious High-Early-Strength Admixture

    Directory of Open Access Journals (Sweden)

    Deuck-Mo Kim

    2016-01-01

    Full Text Available Concrete is one of the most widely used construction materials. There are several methods available to improve its performance, with one of them being the use of high-early-strength admixtures (HESAs. Typical HESAs include calcium nitrate, calcium chloride, and calcium formate (CF. Industrial by-products, such as acetic acid and lime stone sludge (LSS, can be used together to produce calcium acetate (CA, which can subsequently be used as a cementitious HESA. In this study, calcium carbonate and LSS were mixed with cement in weight ratios of 1 : 1, 1 : 1.5, and 1 : 2, and the properties of the as-produced CA were evaluated. CA and CF were mixed with cement in different weight ratios (0, 1, 2, and 3 wt% to obtain CA- and CF-mortars, respectively. The flow behavior, setting time, pH, and compressive strength of these mortars were evaluated, and their X-ray diffraction patterns were also analyzed. It was found that as the CF content in the CF-mortar increased, the initial strength of the mortar also increased. However, it impaired its long-term strength. On the other hand, when 1% CA was mixed with cement, satisfactory early and long-term strengths were achieved. Thus, CA, which is obtained from industrial by-products, can be an effective HESA.

  7. Feasibility investigation of self-healing cementitious composite using oil core/silica gel shell passive smart microcapsules

    Science.gov (United States)

    Yang, Zhengxian; Hollar, John; He, Xiaodong; Shi, Xianming

    2009-07-01

    This paper presents our work in the concept exploration of a new family of self-healing materials that hold promise for "crack-free" cementitious composites. This innovative system features the design of passive smart microcapsules with oil core and silica gel shell, prepared through an interfacial self-assembly process and sol-gel reaction. Methylmethacrylate monomer and triethylborane were chosen as the healing agent and the catalyst, and were microencapsulated respectively. The microcapsules were dispersed in fresh cement mortar along with carbon microfibers. For the hardened mortar, self-healing can be triggered by crack propagation through the microcapsules, which then releases the healing agent and the catalyst into the microcracks. Polymerization of the healing agent is initiated by contact with the catalyst, bonding the crack faces. Surface analytical tools such as optical microscope and field emission scanning electron microscope were used to examine the localized morphology and encapsulation of the passive smart microcapsules. The self-healing effect was evaluated using gas permeability and electrochemical impedance measurements.

  8. Efficient utilization of licorice root by alkaline extraction.

    Science.gov (United States)

    Ohno, Hirokazu; Miyoshi, Shozo; Araho, Daisuke; Kanamoto, Taisei; Terakubo, Shigemi; Nakashima, Hideki; Tsuda, Tadashi; Sunaga, Katsuyoshi; Amano, Shigeru; Ohkoshi, Emika; Sakagami, Hiroshi; Satoh, Kazue; Yamamoto, Masaji

    2014-01-01

    Compared to studies of water extracts of plants, those utilising alkaline extracts are limited. Both water and alkaline extracts from licorice root were compared regarding their biological activities. Licorice root was successively extracted first with water or alkaline solution (pH 9 or 12), and the alkaline (pH 12.0) extract was further separated into 50% ethanol-soluble and -insoluble fractions. Viable cell number was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Antibacterial activity against Porphyromonas gingivalis 381 was determined by turbidity assay. Cytochrome P-450 (CYP)3A4 activity was measured by β-hydroxylation of testosterone using human recombinant CYP3A4. Radical intensity of superoxide and hydroxyl radicals was determined by electron spin resonance spectroscopy. Alkaline extraction yielded slightly higher amounts of dried materials compared to water extraction. Alkaline extract showed higher anti-HIV and antibacterial activities, and similar magnitudes of CYP3A4 inhibitory and superoxide and hydroxyl radical-scavenging activities, compared to water extract. When alkaline extract was fractionated by 50% ethanol, anti-HIV activity was recovered from the insoluble fraction representing approximately 3% of the alkaline extract, whereas antibacterial activity was concentrated in the soluble fraction rich in glycyrrhizid acid, flavanones and chalcones. All extracts and sub-fractions led to bimodal hormetic dose-response (maximum hormetic response=238%) on the bacterial growth. The present study demonstrated the superiority of alkaline extraction over water extraction for preparing anti-HIV and antibacterial agents at higher yield from licorice root. Copyright © 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  9. The Estimation Formation Alkaline In The Proses Desalination MSF

    International Nuclear Information System (INIS)

    Latiffah, Siti Nurul

    2000-01-01

    Already to go on estimation phenomena formation alkaline scale of a seawater. In desalination system seawater on MSF to go on scale by a thermal decomposition HCO sub.3- ion and hydrolysis carbonate ion with water on the temperature operation. The varieties alkaline scale in attached on tube surface, while reduced efficiency heat transfer and to raise corrosion attack to structure material is caused all this high cost. Estimation to take please which a sum step by step decomposition ion bicarbonate from then information scale which carbonate and hydroxyl ion. The various scale maximal is alkaline form is a calcium carbonate = 116,5 gram per meter cubic the various sedimentation is alkaline and magnesium hydroxide = 67,57 gram per meter cubic

  10. Effects of an iron-silicon material, a synthetic zeolite and an alkaline clay on vegetable uptake of As and Cd from a polluted agricultural soil and proposed remediation mechanisms.

    Science.gov (United States)

    Yao, Aijun; Wang, Yani; Ling, Xiaodan; Chen, Zhe; Tang, Yetao; Qiu, Hao; Ying, Rongrong; Qiu, Rongliang

    2017-04-01

    Economic and highly effective methods of in situ remediation of Cd and As polluted farmland in mining areas are urgently needed. Pot experiments with Brassica chinensis L. were carried out to determine the effects of three soil amendments [a novel iron-silicon material (ISM), a synthetic zeolite (SZ) and an alkaline clay (AC)] on vegetable uptake of As and Cd. SEM-EDS and XRD analyses were used to investigate the remediation mechanisms involved. Amendment with ISM significantly reduced the concentrations of As and Cd in edible parts of B. chinensis (by 84-94 % and 38-87 %, respectively), to levels that met food safety regulations and was much lower than those achieved by SZ and AC. ISM also significantly increased fresh biomass by 169-1412 % and 436-731 % in two consecutive growing seasons, while SZ and AC did not significantly affect vegetable growth. Correlation analysis suggested that it was the mitigating effects of ISM on soil acidity and on As and Cd toxicity, rather than nutrient amelioration, that contributed to the improvement in plant growth. SEM-EDS analysis showed that ISM contained far more Ca, Fe and Mn than did SZ or AC, and XRD analysis showed that in the ISM these elements were primarily in the form of silicates, oxides and phosphates that had high capacities for chemisorption of metal(loid)s. After incubation with solutions containing 800 mg L -1 AsO 4 2- or Cd 2+ , ISM bound distinctly higher levels of As (6.18 % in relative mass percent by EDS analysis) and Cd (7.21 % in relative mass percent by EDS analysis) compared to SZ and AC. XRD analysis also showed that ISM facilitated the precipitation of Cd 2+ as silicates, phosphates and hydroxides, and that arsenate combined with Fe, Al, Ca and Mg to form insoluble arsenate compounds. These precipitation mechanisms were much more active in ISM than in SZ or AC. Due to the greater pH elevation caused by the abundant calcium silicate, chemisorption and precipitation mechanisms in ISM treatments

  11. Effects of the material composition in the TL curves of alkaline halides with Eu{sup 2+} exposed to {beta} radiation; Efectos de la composicion del material en las curvas de TL de halogenuros alcalinos con Eu{sup 2+} expuestos a radiacion {beta}

    Energy Technology Data Exchange (ETDEWEB)

    Perez S, R.; Piters, T.; Aceves, R.; Rodriguez M, R. [Dpto. de Investigacion en Fisica, Universidad de Sonora, 83190 Hermosillo, Sonora (Mexico)

    2006-07-01

    The solid state dosemeters plays a very important paper in the growing use of the ionizing radiation. When being increased the use of the radioactive isotopes in the medicine and in the industry, the necessity to have materials but adapted in each case it has increased. To synthesize such materials, it is necessary to enlarge the knowledge on the paper that its play the physical characteristics of the crystals such as the crystalline structure, the lattice constant, imbibed nano structures, dislocations, ions size, electronic states of the ions, etc., on the effects of the ionizing radiation. In the past its have been carried out many studies approaching these problems in some materials, but we consider that its are insufficient before the challenges of the applications. To contribute to the understanding of these effects, we present a study focused to alkaline halide crystals impurified with Eu{sup 2+} ions, making an analysis on the paper that its play a) the ions concentration of Eu{sup 2+} in KBr: Eu{sup 2+}, b) the different sites of trapping of electrons and holes in KBr: Eu{sup 2+}, KCl: Eu{sup 2+}, RbBr:Eu{sup 2+}, RbCl: Eu{sup 2+} and c) the composition of the crystalline solid solutions KCl{sub x}Br{sub 1-X}: Eu{sup 2+} and RbCI{sub x}KBr{sub 1-x}: Eu{sup 2+} on the thermoluminescence curve when these materials are exposed to small dose of {beta} irradiation. The increase in the concentration of Eu{sup 2+} ions produces a smaller relative intensity of the emissions of high temperature for a given dose and it is found that in a RbCl{sub x}KBr{sub 1-x}: Eu{sup 2+} with the greater/smaller concentration of Cl{sup -} ions, the temperature of the characteristic emission is near to the 453/373 K. The composition x of halogenous ions and not the one of alkaline in the crystalline solid solution dominates the landslide of the temperature of the emission. (Author)

  12. Mechanical Properties of High Cementitious Grout (I)

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.

     The present report describes tests carried out on the high performance grout MASTERFLOW 9500, marked WMG 7145 FP, developed by BASF Construction Materials and designed for use in grouted connections of offshore windmill foundations....... The present report describes tests carried out on the high performance grout MASTERFLOW 9500, marked WMG 7145 FP, developed by BASF Construction Materials and designed for use in grouted connections of offshore windmill foundations....

  13. Effect of Alkaline Water on the Lipid Profile in Wistar Rats

    Directory of Open Access Journals (Sweden)

    Z. Salemi

    2015-08-01

    Full Text Available Backgrounds: Alkaline water could be prepared through both electro-chemical and natural ways and previous studies have shown that alkaline water scavenges oxygen radicals in cell culture. It’s expected that alkaline water has positive and preventive effects on diseases related to stress oxidative like atherosclerosis and cardiovascular disease. In recent study, we showed the effects of alkaline water on serum lipid profile in wistar rats. Materials and Methods: In this study 32 male wistar rats weighing 250-200 g were used. Rats divided randomly into four groups, namely control group, alkaline group 1, alkaline group 2 by adding sodium bicarbonate, and acidic group by adding acetic acid to their drinking water. After 32 weeks, blood samples were obtained and lipid profile was measured in all groups, the data was analyzed with SPSS statistical software. Results: Relay on obtained results, cholesterol and triglyceride concentrations in alkaline water group1 and 2 to control group and LDL concentrations in alkaline water group1 have been reduced significantly (p<0.5. While LDL concentration in alkaline water group2 and HDL concentrations in alkaline water group1 and 2 to control group have not significant changes. Conclusion: Results of this study declare that daily administration of alkaline water can improve serum lipid profile and maybe reduced risk of oxidative stress diseases.

  14. Leaching results in the assessement of slag and rock materials as construction material

    OpenAIRE

    Tossavainen, Mia

    2005-01-01

    Extraction of rock material and ore for construction and metal production involves large quantities of wastes and by-products. Iron- and steelmaking slag has durability qualities and latent cementitious properties which are positive in construction. The leaching of so-called hazardous metals is important in the evaluation of secondary materials for utilization, while knowledge of the leaching behaviour is not required for rock materials used in road making. Iron- and steelmaking slags have va...

  15. High temperature and pressure alkaline electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Ganley, Jason C. [Department of Chemical Engineering, Howard University, 2013 Lewis K. Downing Hall, 2300 6th Street NW, Washington, DC 20059 (United States)

    2009-05-15

    This paper describes experimental work involving the direct-current electrolysis of highly concentrated potassium hydroxide solutions at high temperatures (up to 400 C) and under various pressures. A high-temperature alkaline electrolysis cell resistant to chemical attack from the highly corrosive electrolyte solution and capable of high-pressure operation was designed and tested. The cell was constructed with a Monel {sup registered} alloy housing and cathode, while various anode materials were compared. The anode materials tested included nickel, Monel alloy, lithiated nickel, and cobalt-plated nickel. The advantages of operating an alkaline electrolysis cell at high temperatures include increasing the ionic conductivity of the electrolyte and enhancing the rates of electrochemical reactions at the electrode surfaces. Cell operation with increasing steam partial pressure over the solution is also shown to enhance cell performance. The prudent selection of anode material also impacts the required terminal potential for a given current density, and consequently the cell's electric power efficiency. The best cell performance was achieved using a cobalt-plated nickel anode at a temperature of 400 C and a steam partial pressure of 8.7 MPa. (author)

  16. Selection and durability of seal materials for a bedded salt repository: preliminary studies

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Grutzeck, M.W.; Wakeley, L.D.

    1983-11-01

    This report details preliminary results of both experimental and theoretical studies of cementitious seal materials for use in a proposed nuclear waste repository in bedded salt. Effects of changes in bulk composition and environment upon phase stability and physical/mechanical properties have been evaluated for more than 25 formulations. Bonding and interfacial characteristics of the region between host rock and seal material or concrete aggregate and cementitious matrix for selected formulations have been studied. Compatibilities of clays and zeolites in brines typical of the SE New Mexico region have been investigated, and their stabilities reviewed. Results of these studies have led to the conclusion that cementitious materials can be formulated which are compatible with the major rock types in a bedded salt repository environment. Strengths are more than adequate, permeabilities are consistently very low, and elastic moduli generally increase only very slightly with time. Seal formulation guidelines and recommendations for present and future work are presented. 73 references, 25 figures, 61 tables.

  17. Selection and durability of seal materials for a bedded salt repository: preliminary studies

    International Nuclear Information System (INIS)

    Roy, D.M.; Grutzeck, M.W.; Wakeley, L.D.

    1983-11-01

    This report details preliminary results of both experimental and theoretical studies of cementitious seal materials for use in a proposed nuclear waste repository in bedded salt. Effects of changes in bulk composition and environment upon phase stability and physical/mechanical properties have been evaluated for more than 25 formulations. Bonding and interfacial characteristics of the region between host rock and seal material or concrete aggregate and cementitious matrix for selected formulations have been studied. Compatibilities of clays and zeolites in brines typical of the SE New Mexico region have been investigated, and their stabilities reviewed. Results of these studies have led to the conclusion that cementitious materials can be formulated which are compatible with the major rock types in a bedded salt repository environment. Strengths are more than adequate, permeabilities are consistently very low, and elastic moduli generally increase only very slightly with time. Seal formulation guidelines and recommendations for present and future work are presented. 73 references, 25 figures, 61 tables

  18. Reactive transport simulations of the evolution of a cementitious repository in clay-rich host rocks

    Science.gov (United States)

    Kosakowski, Georg; Berner, Urs; Kulik, Dmitrii A.

    2010-05-01

    In Switzerland, the deep geological disposal in clay-rich rocks is foreseen not only for high-level radioactive waste, but also for intermediate-level (ILW) and low-level (LLW) radioactive waste. Typically, ILW and LLW repositories contain huge amounts of cementitious materials used for waste conditioning, confinement, and as backfill for the emplacement caverns. We are investigating the interactions of such a repository with the surrounding clay rocks and with other clay-rich materials such as sand/bentonite mixtures that are foreseen for backfilling the access tunnels. With the help of a numerical reactive transport model, we are comparing the evolution of cement/clay interfaces for different geochemical and transport conditions. In this work, the reactive transport of chemical components is simulated with the multi-component reactive transport code OpenGeoSys-GEM. It employs the sequential non-iterative approach to couple the mass transport code OpenGeoSys (http://www.ufz.de/index.php?en=18345) with the GEMIPM2K (http://gems.web.psi.ch/) code for thermodynamic modeling of aquatic geochemical systems which is using the Gibbs Energy Minimization (GEM) method. Details regarding code development and verification can be found in Shao et al. (2009). The mineral composition and the pore solution of a CEM I 52.5 N HTS hydrated cement as described by Lothenbach & Wieland (2006) are used as an initial state of the cement compartment. The setup is based on the most recent CEMDATA07 thermodynamic database which includes several ideal solid solutions for hydrated cement minerals and is consistent with the Nagra/PSI thermodynamic database 01/01. The smectite/montmorillonite model includes cation exchange processes and amphotheric≡SOH sites and was calibrated on the basis of data by Bradbury & Baeyens (2002). In other reactive transport codes based on the Law of Mass Action (LMA) for solving geochemical equilibria, cation exchange processes are usually calculated assuming

  19. The Expanded Capabilities Of The Cementitious Barriers Partnership Software Toolbox Version 2.0 - 14331

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Heather; Flach, Greg; Smith, Frank; Langton, Christine; Brown, Kevin; Kosson, David; Samson, Eric; Mallick, Pramod

    2014-01-10

    The Cementitious Barriers Partnership (CBP) Project is a multi-disciplinary, multi-institutional collaboration supported by the U.S. Department of Energy (US DOE) Office of Tank Waste Management. The CBP program has developed a set of integrated tools (based on state-of-the-art models and leaching test methods) that help improve understanding and predictions of the long-term structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The CBP Software Toolbox – “Version 1.0” was released early in FY2013 and was used to support DOE-EM performance assessments in evaluating various degradation mechanisms that included sulfate attack, carbonation and constituent leaching. The sulfate attack analysis predicted the extent and damage that sulfate ingress will have on concrete vaults over extended time (i.e., > 1000 years) and the carbonation analysis provided concrete degradation predictions from rebar corrosion. The new release “Version 2.0” includes upgraded carbonation software and a new software module to evaluate degradation due to chloride attack. Also included in the newer version are a dual regime module allowing evaluation of contaminant release in two regimes – both fractured and un-fractured. The integrated software package has also been upgraded with new plotting capabilities and many other features that increase the “user-friendliness” of the package. Experimental work has been generated to provide data to calibrate the models to improve the credibility of the analysis and reduce the uncertainty. Tools selected for and developed under this program have been used to evaluate and predict the behavior of cementitious barriers used in near-surface engineered waste disposal systems for periods of performance up to or longer than 100 years for operating facilities and longer than 1000 years for waste disposal. The CBP Software Toolbox is and will continue to produce tangible benefits to the working DOE

  20. Evaluation of test methods used to characterize fiber reinforced cementitious composites

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2013-01-01

    This paper describes an investigation of fiber reinforced cementitious composites in terms of their behavior under tensile and flexural loading. Flexural testing and subsequent derivation of the tensile stress-deformation response from the flexural test data are preferred in the assessment...... of the tensile properties of Fiber Reinforced Cement Composites (FRCC) over the direct measurement of the tensile behavior because of the more convenient test setup and ease of specimen preparation. Three and four-point bending tests and round determinate panel test were carried out to evaluate the flexural...

  1. Experimental Study on Fibre-reinforced Cementitious Matrix Confined Concrete Columns under Axial Compression

    Directory of Open Access Journals (Sweden)

    Lan Zeng

    2017-03-01

    Full Text Available Poor fire resistance of fibre-reinforced polymer (FRP restricts its further application in construction structures. In this paper, a novel fibre-reinforced cementitious matrix confined concrete column (FRCMCC using fireproof grout as the fibre matrix was developed, and experiments were conducted to establish its performance and analyse the mechanical properties under axial compression. The test results show that its failure mode was more moderate compared to the traditional fibre-reinforced resinous matrix confined concrete column (FRRMCC, and the concrete columns confined with multi-layer fibres and end reinforcement could provide both good strength and ductility.

  2. Secondary alkaline batteries

    Science.gov (United States)

    McBreen, J.

    1984-03-01

    The overall reactions (charge/discharge characteristics); electrode structures and materials; and cell construction are studied for nickel oxide-cadmium, nickel oxide-iron, nickel oxide-hydrogen, nickel oxide-zinc, silver oxide-zinc, and silver oxide-cadmium, silver oxide-iron, and manganese dioxide-zinc batteries.

  3. Alkaline galvanic cells

    Energy Technology Data Exchange (ETDEWEB)

    Eisenberg, M.

    1993-06-01

    A battery is described having an anode, a cathode and an electrolyte with the anode having zinc or a zinc alloy as an active anodic material, the cathode having a metal oxide or hydroxide as an active cathodic material, and the electrolyte comprising a solution of a first salt formed by the reaction of one or more acids selected from the group consisting of boric acid, phosphoric acid and arsenic acid with an alkali or earth alkali hydroxide present in an amount to produce a stoichiometric, excess of said hydroxide to said acid in the range of 2.5 to 11.0 equivalents per liter, and a solution of a second salt which is a soluble alkali or earth alkali fluoride in an amount corresponding to a concentration range of 0.01 to 1.0 equivalents per liter of total solution.

  4. Application of Engineered Cementitious Composites (ECC) in modular floor panels

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor; Jönsson, Jeppe

    2008-01-01

    with adaptability to various loading requirements, and the efficient utilization of material resources and industrial byproducts. The work described in this paper is a continuation of previous activities on composite floor panels in which light gage steel joists were integrally cast with the ECC slab. The modular......This paper describes the design, manufacturing, and structural behavior of a prefabricated floor panel consisting of a modular assembly of a thin-walled ECC slab and steel truss girders. The features of this composite structure include light weight, the modular manufacturing process...

  5. Significance of steel electrical resistance method in the evaluation of reinforcement corrosion in cementitious systems

    Directory of Open Access Journals (Sweden)

    Krajci, L.

    2004-06-01

    Full Text Available The suitable detection system of steel reinforcement corrosion in concrete structures contributes to the reduction of their maintenance costs. Method of steel electrical resistance represents non-destructive monitoring of steel in cementitious systems. Specially prepared and arranged test specimen of steel as a corrosion sensor is embedded in mortar specimen. Verification tests of this method based on chloride corrosion of steel in mortars as well as its visual inspection are introduced. Significance of steel electrical resistance method lies in the expression of steel corrosion by these quantitative parameters: reduction of cross-section of steel, thickness of corroded layer and loss of weight of steel material. This method is an integral method that allows the indirect determination of mentioned corrosion characteristics. The comparison of verified method with gravimetric evaluation of steel corrosion gives a good correspondence. Test results on mortars with calcium chloride dosages between 0.5% and 4.0% by weight of cement prove high sensitiveness and reliability of steel electrical resistance method.

    La utilización de un sistema de detección de la corrosión de las armaduras en estructuras de hormigón puede contribuir a la reducción de sus costes de mantenimiento. El método de la resistencia eléctrica del acero consiste en la monitorización no-destructiva realizada sobre el acero en sistemas cementantes. Dentro de la muestra de mortero se coloca el sistema de detección, especialmente preparado y fijado, actuando como un sensor de la corrosión. En este trabajo se presentan ensayos de verificación de este método, junto con inspecciones visuales, en morteros sometidos a corrosión de armaduras por efecto de los cloruros. La efectividad de este método de la resistencia eléctrica del acero se expresa, en la corrosión de armaduras, de acuerdo a los siguientes parámetros cuantitativos: reducción de la sección transversal del

  6. Genome Sequence of the Alkaline-Tolerant Cellulomonas sp. Strain FA1

    Science.gov (United States)

    Hu, Ping; Nguyen, My Vu; Kamennaya, Nina; Brown, Natasha; Woyke, Tanja; Kyrpides, Nikos; Holman, Hoi-Ying; Torok, Tamas

    2015-01-01

    We present the genome of the cellulose-degrading Cellulomonas sp. strain FA1 isolated from an actively serpentinizing highly alkaline spring. Knowledge of this genome will enable studies into the molecular basis of plant material degradation in alkaline environments and inform the development of lignocellulose bioprocessing procedures for biofuel production. PMID:26089422

  7. Invited: A Stability Study of Alkali Doped PBI Membranes for Alkaline Electrolyzer Cells

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Aili, David; Hansen, Martin Kalmar

    2014-01-01

    Alkaline fuel cells and electrolyzers are attracting increasing interest. This is to a large extent due to the broad selection of catalyst materials not based on resource limited and expensive noble metals. The first fuel cells in practical use were Francis Thomas Bacon’s based on an alkaline...

  8. Self-sealing cementitious materials by using water-swelling rubber particles

    NARCIS (Netherlands)

    Lv, Leyang; Schlangen, H.E.J.G.; Xing, Feng

    2017-01-01

    Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing

  9. Evaluating and optimizing recycled concrete fines in PCC mixtures containing supplementary cementitious materials.

    Science.gov (United States)

    2010-08-01

    Portland cement concrete (PCC) is used throughout transportation infrastructure, for roads as well as bridges : and other structures. One of the most effective ways of making PCC more green is to replace a portion of the : portland cement (the ...

  10. Effect of carbon nanofiber addition in the mechanical properties and durability of cementitious materials

    Directory of Open Access Journals (Sweden)

    Galao, O.

    2012-09-01

    Full Text Available This paper reports on recent work that is directed at studying the changes in the mechanical properties of Portland cement based mortars due to the addition of carbon nanofiber (CNF. Both flexural and compression strength has been determined and related to the CNF addition to the mix, to the curing time and to the porosity and density of the matrix. Also, corrosion of embedded steel rebars in CNF cement pastes exposed to carbonation and chloride attacks has been investigated. The increase in CNF addition implies higher corrosion intensity and higher levels of mechanical properties.En este artículo se han estudiado los cambios en las propiedades mecánicas de los morteros de cemento Portland debido a la adición de nanofibras de carbono (NFC. Se han determinado las resistencias a flexotracción y a compresión de los morteros en relación a la cantidad de NFC añadidas a la mezcla, al tiempo de curado y a la porosidad y densidad de los mismos. Además se han investigado los niveles de corrosión de barras de acero embebidas en pastas de cemento con NFC expuestos al ataque por carbonatación y por ingreso de cloruros. El aumento en el porcentaje de NFC añadido se traduce en un aumento la intensidad de corrosión registrada y una mejora de las propiedades mecánicas.

  11. Application of encapsulated superabsorbent polymers in cementitious materials for stimulated autogenous healing

    Science.gov (United States)

    Pelto, Jani; Leivo, Markku; Gruyaert, Elke; Debbaut, Brenda; Snoeck, Didier; De Belie, Nele

    2017-10-01

    Superabsorbent polymers have shown potential for use in mortar and concrete as self-healing agents. The main drawback is, however, that these superabsorbent polymers also absorb mixing water during the preparation and casting of mortar or concrete, leading to a loss in workability. To avoid the absorption of mixing water, superabsorbent polymers were coated using a fluid bed spraying process. The barrier coating consisted of three successive coating layers: polyvinylbutyral as primer/wetting layer, cyclo-olefin copolymer as a barrier layer and a sol-gel derived zirconium-silicon oxide as an adhesion-promoting topcoat layer. The coated SAPs were characterized, and their swelling determined to quantify the delay in uptake of water and Ca(OH)2 solution. The last was considered as the most important, as the SAPs will finally be applied in mortar or concrete having a pore solution with high pH. The results showed that swelling could be delayed to a large extent, but for a short time. Results showed that the self-sealing efficiency of mortars was not affected by coating the SAPs. Moreover, due to the reduced uptake of mixing water, the strength reduction, noticed when uncoated SAPs were added to the mortar, could partly be compensated.

  12. Solidification of spent ion exchange resin using new cementitious material, (1)

    International Nuclear Information System (INIS)

    Matsuda, Masami; Nishi, Takashi; Chino, Koichi; Kikuchi, Makoto

    1992-01-01

    Cement solidification is a conventional technique to solidify spent ion exchange resin. Swelling property of the ion exchange resin was investigated theoretically and experimentally, as the first step to improve resin content in a cement package. Swelling pressure of the resin was first formulated based on Gregor's swelling model. It was shown that the pressure depended on such factors as ion exchange capacity, type of functional group, crosslinkage and water content. Subsequently, swelling pressures for over forty properties of cation exchange resin (DIAION SK-series) with different exchange capacities, water contents and others were experimentally evaluated using an originally developed method. The pressure changed over a range of 0 ∼ 60 MPa, depending on properties of the ion exchange resin. These results were in close agreement with values calculated by Gregor's model, indicating that the swelling pressure could be evaluated without resorting to experiments. (author)

  13. Carbonation and pH in mortars manufactured with supplementary cementitious materials

    Energy Technology Data Exchange (ETDEWEB)

    McPolin, D.O.; Basheer, P.A.M.; Long, A.E. [Queens University Belfast, Belfast (United Kingdom)

    2009-05-15

    An investigation of carbonation in mortars and methods of measuring the degree of carbonation and pH change is presented. The mortars were manufactured using ordinary portland cement, pulverized fuel ash, ground granulated blast-furnace slag, metakaolin, and microsilica. The mortars were exposed to a carbon dioxide-rich environment (5% CO{sub 2}) to accelerate carbonation. The resulting carbonation was measured using phenolphthalein indicator and thermogravimetric analysis. The pH of the pore fluid and a powdered sample, extracted from the mortar, was measured to give an accurate indication of the actual pH of the concrete. The pH of the extracted powder mortar sample was found to be similar to the pH of the pore fluid expressed from the mortars. The thermogravimetric analysis suggested two distinct regions of transport of CO{sub 2} within mortar, a surface region where convection was prevalent and a deeper region where diffusion was dominant. The use of microsilica has been shown to decrease the rate of carbonation, while pulverized fuel ash and ground granulated blast-furnace slag have a detrimental effect on carbonation. Metakaolin has little effect on carbonation.

  14. Effects of Supplemetary Cementitious Materials on the Air Permeability of Concrete

    Directory of Open Access Journals (Sweden)

    Samuel Olufemi Folagbade

    2017-03-01

    Full Text Available In order to support the use of cement combination concrete in construction, this paper investigated the resistance of Portland cement and some binary and ternary cement concretes containing fly ash, silica fume and metakaolin to air permeability at equal water/cement ratios and strengths. At equal water/cement ratios, while fly ash binary cement concretes have higher coefficients of air permeability than Portland cement concrete due to delayed pozzolanic reactivity, silica fume and metakaolin binary cement concretes have comparable coefficients with Portland cement concrete due to their higher fineness, improved particle packing and higher pozzolanic reactivity. Consequently, the ternary cement concretes have coefficients comparable with that of Portland cement concrete. At equal strengths, while silica fume and metakaolin binary cement concretes have higher coefficients than Portland cement concrete, fly ash binary cement concretes have lower coefficients which reduced with increasing content of fly ash. Consequently, all the ternary cement concretes have lower coefficients which reduced with increasing total replacement level due to the beneficial effect of fly ash. Hence, high volume fly ash would be required to increase the resistance of concrete to air permeability at equal strength.

  15. Application of Ceramic Powder as Supplementary Cementitious Material in Lime Plasters

    Directory of Open Access Journals (Sweden)

    Monika ČÁCHOVÁ

    2016-09-01

    Full Text Available In this paper, the properties of plasters based on lime – brick powder binder of varying composition (ceramics content from 0 to 80 % are studied. The plasters are prepared with a constant water amount. The pore size distribution is thus influenced in a positive way; the total porosity increases with the ceramics content but the volume of capillary pores is reduced. It results in lower water vapor diffusion resistance factor while the apparent moisture diffusivity coefficient increases just moderately. The influence of ceramic on strength of plasters is not found very important. The thermal conductivity of plasters containing ceramics is lower than those with the pure lime what is again in agreement with the pore size distribution. It can be concluded that fine brick powder can be used as pozzolanic admixture in lime based plasters with a positive influence on its functional parameters.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.7433

  16. Research on the Bond Anchorage Properties of Alkali-Activated Slag Cementitious Material

    Science.gov (United States)

    Zhu, J.; Zheng, W. Z.; Leng, Y. F.; Qin, C. Z.; Xu, Z. Z.

    2017-12-01

    By bond-anchorage property tests at 20°C ∼500°C, the distribution of shear stress between carbon fiber sheets and concrete at all levels of loading and anchorage lengths were measured, which means the bond lengths during CFRP sheets are pulled off at the same time when the concrete is torn and stripped were gotten. The failure modes were obtained. In addition, the failure loads were measured, and the calculated formulas of anchorage lengths were identified by fitting at high temperature. It can be seen that the anchorage lengths of carbon fiber sheets increase with increasing temperature at 20°C ∼100°C, the anchorage lengths of carbon fiber sheets decrease with increasing temperature at 100°C ∼500°C. Tests prove that AASCM has favorable high-temperature resistant and bond anchorage properties.

  17. Microstructure and transport phenomena in visco-elastic modelling of hardening cementitious materials

    NARCIS (Netherlands)

    Van der Ham, H.W.M.

    2011-01-01

    Since the durability depends, among other things, on the quality of the concrete and presence of cracks, it is necessary to calculate the probability of cracking in hardening concrete as reliable as possible in case of durability predictions. In this thesis, it is investigated how the accuracy of

  18. Interactive mathematical model of self-healing in carbonated cementitious materials

    NARCIS (Netherlands)

    Zemskov, S.V.; Copuroglu, O.; Vermolen, F.J.

    2013-01-01

    A mathematical model for the post-damage recovery of carbonated cement is described. The model is based on a two-dimensional initial-boundary value problem for a system of partial differential equations. The study is embedded within the framework of investigating the effect of using lightweight

  19. Visualization of water penetration in cementitious materials with superabsorbent polymers by means of neutron radiography

    International Nuclear Information System (INIS)

    Snoeck, D.; Steuperaert, S.; Van Tittelboom, K.; Dubruel, P.; De Belie, N.

    2012-01-01

    Concrete cracks due to its low tensile strength. As both harmful gases and fluids may enter the concrete by migrating into cracks, the durability is endangered. The service life decreases, repair costs rise and buildings could structurally decline. In the current research, crack sealing is enhanced by the use of superabsorbent polymers (SAP). When cracking occurs, SAP particles are exposed to the humid environment and swell, sealing the crack. By means of neutron radiography, the moisture distribution is studied during capillary absorption and water permeability tests. Capillary absorption in a crack and water permeability through a crack are reduced in specimens containing SAP particles. SAP particles are able to seal the crack, thus allowing a recovery of the water-tightness of the structure. The total uptake of potentially harmful substances hereby lowers, leading to an enhanced long-term durability and lower maintenance costs.

  20. The origin of early age expansions induced in cementitious materials containing shrinkage reducing admixtures

    International Nuclear Information System (INIS)

    Sant, Gaurav; Lothenbach, Barbara; Juilland, Patrick; Le Saout, Gwenn; Weiss, Jason; Scrivener, Karen

    2011-01-01

    Studies on the early-age shrinkage behavior of cement pastes, mortars, and concretes containing shrinkage reducing admixtures (SRAs) have indicated these mixtures frequently exhibit an expansion shortly after setting. While the magnitude of the expansion has been noted to be a function of the chemistry of the cement and the admixture dosage; the cause of the expansion is not clearly understood. This investigation uses measurements of autogenous deformation, X-ray diffraction, pore solution analysis, thermogravimetry, and scanning electron microscopy to study the early-age properties and describe the mechanism of the expansion in OPC pastes made with and without SRA. The composition of the pore solution indicates that the presence of the SRA increases the portlandite oversaturation level in solution which can result in higher crystallization stresses which could lead to an expansion. This observation is supported by deformation calculations for the systems examined.

  1. Effect of blast furnace slag on self-healing of microcracks in cementitious materials

    International Nuclear Information System (INIS)

    Huang, Haoliang; Ye, Guang; Damidot, Denis

    2014-01-01

    The physico-chemical process of self-healing in blast furnace slag cement paste was investigated in this paper. With a high slag content i.e., 66% in cement paste and saturated Ca(OH) 2 solution as activator, it was found that the reaction products formed in cracks are composed of C-S-H, ettringite, hydrogarnet and OH–hydrotalcite. The fraction of C-S-H in the reaction products is much larger than the other minerals. Large amount of ettringite formed in cracks indicates the leaching of SO 4 2− ions from the bulk paste and consequently the recrystallization. Self-healing proceeds fast within 50 h and then slows down. According to thermodynamic modeling, when the newly formed reaction products are carbonated, the filling fraction of crack increases first and then decreases. Low soluble minerals such as silica gel, gibbsite and calcite are formed. Compared to Portland cement paste, the potential of self-healing in slag cement paste is higher when the percentage of slag is high. - Highlights: • Self-healing reaction products in slag cement paste were characterized. • Self-healing reaction products formed in time were quantified with image analysis. • Self-healing in slag cement paste was simulated with a reactive transport model. • Effect of carbonation on self-healing was investigated by thermodynamic modeling. • Effect of slag on self-healing was discussed based on experiments and simulation

  2. Shock Wave Propagation in Cementitious Materials at Micro/Meso Scales

    Science.gov (United States)

    2015-08-31

    information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering...and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other... ABAQUS ®. The heterogeneity induced shock decay phenomenon under compression in this 50-micron size cube due to an OFHC Copper flyer plate impact is

  3. The effects of supplementary cementitious materials on alkali-silica reaction : [technical summary].

    Science.gov (United States)

    2015-07-01

    The Kansas Department of Transportation (KDOT) has controlled alkali-silica : reaction (ASR) for more than 70 years through the use of selected aggregates. : Sand and gravel sources had to be tested using Kansas Test Method KTMR- : 23 (1999), Wetting...

  4. The effects of supplementary cementitious materials on alkali-silica reaction.

    Science.gov (United States)

    2015-07-01

    The Kansas Department of Transportation (KDOT) has controlled alkali-silica reaction (ASR) for more than : 70 years through the use of selected aggregates. Sand and gravel sources had to be tested using Kansas Test Method : KTMR-23 (1999), Wetting an...

  5. Cementitious stabilization of chromium, arsenic, and selenium in a cooling tower sludge

    International Nuclear Information System (INIS)

    Spence, R.D.; Gilliam, T.M.; Bleier, A.

    1995-01-01

    The Federal Facility Compliance Agreement (FFCA) establishes an aggressive schedule for conducting studies and treatment method development under the treatability exclusion of RCRA for those mixed wastes for which treatment methods and capabilities have yet to be defined. One of these wastes is a radioactive cooling tower sludge. This paper presents some results of a treatability study of the stabilization of this cooling tower sludge in cementitious waste forms. The sample of the cooling tower sludge obtained for this study was found to be not characteristically hazardous in regard to arsenic, barium, chromium, lead, and selenium, despite the waste codes associated with this waste. However, the scope of this study included spiking three RCRA metals to two orders of magnitude above the initial concentration to test the limits of cementitious stabilization. Chromium and arsenic were spiked at concentrations of 200, 2,000, and 20,000 mg/kg, and selenium was spiked at 100, 1,000, and 10,000 mg/kg (concentrations based on the metal in the sludge solids). Portland cement, Class F fly ash, and slag were selected as stabilizing agents in the present study. Perlite, a fine, porous volcanic rock commonly used as a filter aid, was used as a water-sorptive agent in this study in order to control bleed water for high water contents. The highly porous perlite dust absorbs large amounts of water by capillary action and does not present the handling and processing problems exhibited by clays used for bleed water control

  6. Effects of carbonation, irradiation and temperature onto strontium immobilization into a cementitious matrix

    International Nuclear Information System (INIS)

    Bar-Nes, G.; Arbel-Haddad, M.; Chomat, L.; Poyet, S.; Mace, N.; Hossepied, C.

    2015-01-01

    In the present study, the decoupled effects of carbonation, irradiation and temperature on strontium immobilization in a CEM-I cement matrix are described. After 6 months of treatment, mineralogical characterization (X-ray diffraction - XRD and thermogravimetric analysis - TGA), leaching tests (according to ANSI.ANS-16.1 standard method) and sorption experiments were carried out. The mineralogical evolution was shown to be similar for samples submitted to irradiation at atmospheric conditions or carbonation at a controlled temperature of 40 C. degrees. The main mineralogical change during these two treatments is the formation of calcium carbonate; calcite is detected at the sample surface and the two carbonate metastable phases (aragonite and vaterite) in the depth of the sample. Although it was not possible to identify, by the techniques used, the association of Sr with any specific cementitious phase present in the investigated samples, the leaching results showed that the fraction of Sr leached from samples exposed to carbonation during their degradation process, was approximately 6 times lower compared to the corresponding samples degraded under inert conditions. The sorption experiments onto the hydrated cement paste show a small but significant retention of Sr in these matrices without allowing a possible identification of the phase responsible for the retention. Post leaching mineralogical characterization is to be performed in order to study the effect of the leaching process on the sample mineralogy and to locate the binding sites of the Sr ions within the cementitious paste. (authors)

  7. The solubility of uranium in cementitious near-field chemical conditions

    International Nuclear Information System (INIS)

    Baston, G.M.N.; Brownsword, M.; Cross, J.E.; Hobley, J.; Moreton, A.D.; Smith-Briggs, J.L.; Thomason, H.P.

    1993-05-01

    Tetravalent and hexavalent uranium solubilities have been measured in cement-equilibriated water for pH values from 4 to 13. Tetravalent uranium solubilities at pH 12 have been measured by three experimental techniques: oversaturation, undersaturation and by the use of an electrochemical cell which controlled the redox conditions. The experimentally obtained data have been simulated using the thermodynamic equilibrium program HARPHRQ in conjunction with three different sets of thermodynamic data for uranium. In each case, differences were found between the predicted and measured uranium behaviour. For hexavalent uranium at high pH values the model suggested the formation of anionic hydrolysis products which led to the prediction of uranium solubilities significantly higher than those observed. Refinement of the thermodynamic data used in the model enabled the derivation of maximum values for the formation constants of these species under cementitious conditions. Similarly, the experimental data have been used to refine a model of tetravalent uranium solubility under cementitious near-field conditions. (author)

  8. Materials

    CSIR Research Space (South Africa)

    Van Wyk, Llewellyn V

    2009-02-01

    Full Text Available community. The construction industry is a significantly consumer of materials, using 50 per cent of all products produced globally. Building materials is any material which is used for a construction purpose. Many of these materials are sources from natural...

  9. Graphite coated PVA fibers as the reinforcement for cementitious composites

    Science.gov (United States)

    Zhang, Yunhua; Zhang, Zhipeng; Liu, Zhichao

    2018-02-01

    A new preconditioning method was developed to PVA fibers as the reinforcement in cement-based materials. Virgin PVA fibers exhibits limited adhesion to graphite powders due to the presence of oil spots on the surface. Mixing PVA fibers with a moderately concentrated KMnO4-H2SO4 solution can efficiently remove the oil spots by oxidation without creating extra precipitate (MnO2) associated with the reduction reaction. This enhances the coating of graphite powders onto fiber surface and improves the mechanical properties of PVA fiber reinforced concrete (PVA-FRC). Graphite powders yields better fiber distribution in the matrix and reduces the fiber-matrix bonding, which is beneficial in uniformly distributing the stress among embedded fibers and creating steady generation and propagation of tight microcracks. This is evidenced by the significantly enhanced strain hardening behavior and improved flexural strength and toughness.

  10. Radial diffusion of radiocaesium and radioiodide through cementitious backfill

    Science.gov (United States)

    Felipe-Sotelo, M.; Hinchliff, J.; Drury, D.; Evans, N. D. M.; Williams, S.; Read, D.

    The function of the backfill material in a geological disposal facility (GDF) is to chemically condition the environment of the near field and thereby chemically retard the transport of the radionuclides present in the waste. This function of the backfill material is usually referred to as chemical containment. Diffusion experiments are being carried out over periods up to four years to assess the diffusion of Cs, Ni, Eu, Th, U and I (as I-) through Nirex Reference Vault Backfill (NRVB). The method uses cylinders of NRVB (40 mm diameter, 40-45 mm height) which can be doped via a central well with the radionuclides of interest. Diffusion occurs radially into a surrounding solution already pre-equilibrated with the cement. This paper shows the results obtained during the first two years for experiments undertaken using 137Cs and 125I- tracers with and without carrier. Comparison is made to tritiated water under identical experimental conditions. Breakthrough of Cs and I- occurred within the first week of the experiments, reaching steady state in the surrounding solution after 20-50 days. The maximum concentrations expected from the original inventories based on a simple dilution calculation have not been reached, indicating that retention in the matrix has occurred; ranging from 10% to 40% for Cs, and up to 50% for I-. Corresponding experiments using a solution containing cellulose degradation products (CDP) showed an increased diffusion for both Cs and I. Migration profiles have been obtained and the relative retention of each radionuclide has been confirmed using digital autoradiography. The results indicate that, for both isotopes, migration occurs through the cement matrix rather than through microfissures. However, whereas Cs is homogeneously distributed within the blocks, there is evidence of zones of preferential I- accumulation even where concentrations in solution have reached steady state. Transport modelling using GoldSim has replicated experimental

  11. Computational modelling of fibre-reinforced cementitious composites : An analysis of discrete and mesh-independent techniques

    NARCIS (Netherlands)

    Radtke, F.K.F.

    2012-01-01

    Failure patterns and mechanical behaviour of high performance fibre-reinforced cementitious composites depend to a large extent on the distribution of fibres within a specimen. A discrete treatment of fibres enables us to study the influence of various fibre distributions on the mechanical

  12. Self-cementitious properties of fly ashes from CFBC boilers co-firing coal and high-sulphur petroleum coke

    International Nuclear Information System (INIS)

    Sheng Guanghong; Li Qin; Zhai Jianping; Li Feihu

    2007-01-01

    Self-cementitious properties of fly ash from circulating fluidized bed combustion boiler co-firing coal and high-sulphur petroleum coke (CPFA) were investigated. CPFA was self-cementitious which was affected by its fineness and chemical compositions, especially the contents of SO 3 and free lime (f-CaO). Higher contents of SO 3 and f-CaO were beneficial to self-cementitious strength; the self-cementitious strength increases with a decrease of its 45 μm sieve residue. The expansive ratio of CPFA hardened paste was high because of generation of ettringite (AFt), which was influenced by its water to binder ratio (W/A), curing style and grinding of the ash. The paste cured in water had the highest expansive ratio, and grinding of CPFA was beneficial to its volume stability. The hydration products of CPFA detected by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were portlandite, gypsum, AFt and hydrated calcium silicate (C-S-H)

  13. 2nd Generation Alkaline Electrolysis

    DEFF Research Database (Denmark)

    Yde, Lars; Kjartansdóttir, Cecilia Kristin; Allebrod, Frank

    This report provides the results of the 2nd Generation Alkaline Electrolysis project which was initiated in 2008. The project has been conducted from 2009-2012 by a consortium comprising Århus University Business and Social Science – Centre for Energy Technologies (CET (former HIRC)), Technical...

  14. Zinc electrode in alkaline electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    McBreen, J.

    1995-12-31

    The zinc electrode in alkaline electrolyte is unusual in that supersaturated zincate solutions can form during discharge and spongy or mossy zinc deposits can form on charge at low overvoltages. The effect of additives on regular pasted ZnO electrodes and calcium zincate electrodes is discussed. The paper also reports on in situ x-ray absorption (XAS) results on mossy zinc deposits.

  15. Experimental study on mix proportion of fiber reinforced cementitious composites

    Science.gov (United States)

    Jia, Yi; Zhao, Renda; Liao, Ping; Li, Fuhai; Yuan, Yuan; Zhou, Shuang

    2017-10-01

    To study the mechanical property of fiber reinforced cementations composites influenced by the fiber length, quartz sand diameter, matrix of water cement ratio, volume fraction of fiber and magnesium acrylate solution. Several 40×40×160 mm standard test specimens, "8" specimens and long "8" specimens and 21 groups of fiber concrete specimens were fabricated. The flexural, compressive and uniaxial tensile strength were tested by using the bending resistance, compression resistance and electronic universal testing machine. The results show that flexural and compressive strength of fiber reinforced cementations composites increases along with the increase of quartz sand diameter, with the growth of the PVA fiber length increases; When the water-binder ratio is 0.25 and powder-binder ratio is 0.3, the PVA fiber content is 1.5% of the mass of cementations materials, there is a phenomenon of strain hardening; The addition of magnesium acrylate solution reduces the tensile strength of PVA fiber reinforced cementations composites, the tensile strength of the specimens in the curing age of 7d is decreased by about 21% and the specimens in curing age of 28d is decreased by more than 50%.

  16. Evaluation of some bean lines tolerance to alkaline soil

    Directory of Open Access Journals (Sweden)

    Abeer A. Radi

    2012-01-01

    Full Text Available Introduction: In less arid climates, salts are less concentrated and sodium dominates in carbonate and bicarbonate forms, which enhance the formation of alkaline soils. The development and identification of salt-tolerant crop cultivars or lines would complement salt management programs to improve the productivity and yields of salt stressed plants.Materials and methods: This work was to study the evaluation of alkalinity tolerance of some bean lines grown under different levels of sodium carbonate (Na2CO3 to select the most alkalinity tolerant lines versus the most-sensitive ones out of 6 lines of the test plants.Results: The symptoms induced by alkalinity included reduction in root, shoot growth, and leaf area which were more severe in some bean lines. Potassium leakage was severely affected by alkalinity in some lines at all tested levels, while in some others a moderate damage was manifested only at the higher levels. The increase in Na2CO3 level was associated with a gradual fall in chlorophyll a and b biosynthesis of all the test bean lines. However, alkalinity at low and moderate levels had a favorable effect on the biosynthesis of carotenoids in all the test bean lines. The increase in Na2CO3 supply had a considerable stimulatory effect on sodium accumulation, while potassium accumulation fluctuated in organs of bean lines.Conclusion: Assiut 1104 out of all the different lines investigated was found to display the lowest sensitivity to alkalinity stress, while Assiut 12/104 was the most sensitive one.

  17. Electrochemical behaviour of alkaline copper complexes

    Indian Academy of Sciences (India)

    cyanide- plating bath for copper has been developed using alkaline trisodium citrate and triethanolamine solutions5. The present investigation presents cyclic voltammetric studies on the electrochemical behaviour of alkaline copper complexes, ...

  18. Effect of alkaline earth oxides on the physical and spectroscopic properties of Dy3+- doped Li2O-B2O3 glasses for white emitting material application

    Science.gov (United States)

    Shamshad, L.; Rooh, G.; Kirdsiri, K.; Srisittipokakun, N.; Damdee, B.; Kim, H. J.; Kaewkhao, J.

    2017-02-01

    Li2O-MO-B2O3:0.5Dy2O3 glasses mixed with four different alkaline earth modifier oxides MgO, CaO, SrO and BaO were synthesized by melt quench technique. Their physical properties like density, molar volume and refractive index were measured at room temperature and the effect of alkaline earth modifier oxides were studied. Also, optical absorption and photoluminescence spectra of these glasses have been acquired at room temperature. The Judd-Ofelt theory was effectively used to characterize these spectra and spectral intensities (ƒcal), Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) and certain radiative properties have been determined. Radiative life-times (τR), branching ratios (βcal), and emission cross-sections (σp) and optical gain parameters (σp × τR) were calculated from the Judd-Ofelt intensity parameters and the variation in these parameters with the variation of glass matrix are discussed. Yellow/Blue (Y/B) ratio and chromacity color coordinates (x,y) are calculated from the emission spectra which indicates the white light generation from all the investigated samples. The correlated color temperature (CCT) for the studied glasses is found to be 4418 K. The fluorescence decay time (τexp) of the 4F9/2 level of Dy3+ has been measured from the decay profiles and compared with calculated lifetimes (τcal). Among all the studied glass matrices, the glass containing BaO exhibits high value of branching ratio, large emission cross-section and high optical gain parameter for 6F9/2 → 6H13 at 575 nm. The results indicates the suitability of all the studied glasses for laser action and white light generation.

  19. Alkaline and non-aqueous proton-conducting pouch-cell batteries

    Energy Technology Data Exchange (ETDEWEB)

    Young, Kwo-hsiung; Nei, Jean; Meng, Tiejun

    2018-01-02

    Provided are sealed pouch-cell batteries that are alkaline batteries or non-aqueous proton-conducing batteries. A pouch cell includes a flexible housing such as is used for pouch cell construction where the housing is in the form of a pouch, a cathode comprising a cathode active material suitable for use in an alkaline battery, an anode comprising an anode active material suitable for use in an alkaline battery, an electrolyte that is optionally an alkaline or proton-conducting electrolyte, and wherein the pouch does not include or require a safety vent or other gas absorbing or releasing system as the anode active material and the cathode active material do not increase the internal atmospheric pressure any more than 2 psig during cycling. The batteries provided function contrary to the art recognized belief that such battery systems were impossible due to unacceptable gas production during cycling.

  20. Anionic-exchange membrane development for application in alcohol alkaline fuel cells

    CSIR Research Space (South Africa)

    Nonjola, S

    2010-09-01

    Full Text Available Ammonium quaternized polymers such as poly (arylene ether sulfones) are being developed and studied as candidates of ionomeric materials for application in alkaline fuel cells, due to their low cost and promising electrochemical properties...

  1. Influence of cementitious additions on rheological and mechanical properties of reactive powder concretes

    Science.gov (United States)

    Zenati, A.; Arroudj, K.; Lanez, M.; Oudjit, M. N.

    2009-11-01

    Following needs of concrete market and the economic and ecological needs, several researchers, all over the world, studied the beneficial effect which the incorporation of the mineral additions in Portland cement industry can bring. It was shown that the incorporation of local mineral additions can decrease the consumption of crushing energy of cements, and reduce the CO2 emission. Siliceous additions, moreover their physical role of filling, play a chemical role pozzolanic. They contribute to improving concrete performances and thus their durability. The abundance of dunes sand and blast furnace slag in Algeria led us to study their effect like cementitious additions. The objective of this paper is to study the effect of the incorporation of dunes sand and slag, finely ground on rheological and mechanical properties of reactive powder concretes containing ternary binders.

  2. ASSESSMENT OF MIX PROPORTIONS FOR DEVELOPING LIGHTWEIGHT CEMENTITIOUS COMPOSITES WITH WOOD WASTES

    Directory of Open Access Journals (Sweden)

    Monica Garcez

    Full Text Available ABSTRACT The main objective of this work was to assess mix proportions for developing lightweight cementitious composites, manufactured with Eucalyptus grandis sawdust. Different wood:cement, water:cement and admixture:cement ratios were used to evaluate physical (water absorption, void ratio and density and mechanical (compressive strength, static and dynamic modulus of elasticity properties of the cement-wood composites. Results shows that, bulk density is directly proportional to the compressive strength and elastic modulus, and inversely proportional to the percentage of timber, considering composites with same water:cement ratio, without superplasticizer. The performance of the cement-wood composites, regarding mechanical properties, can be improved if superplasticizer is used to increase paste fluidity. Higher values of bulk density are related to lower void ratio and water absorption and higher compressive strength and modulus of elasticity.

  3. Prediction of Flexural Capacity of RC Beams Strengthened in Flexure with FRP Fabric and Cementitious Matrix

    Directory of Open Access Journals (Sweden)

    Kyusan Jung

    2015-01-01

    Full Text Available This paper presents both experimental and analytical research results for predicting the flexural capacity of reinforced concrete (RC beams strengthened in flexure with fabric reinforced cementitious matrix (FRCM. In order to assess the efficiency of the FRCM-strengthening method, six beams were strengthened in flexure with FRCM composite having different amounts and layers of FRP fabric and were tested under four-point loading. From test results, it was confirmed that the slippage between the FRP fabric and matrix occurs at a high strain level, and all of the FRCM-strengthened beams failed by the debonding of the FRCM. Additionally, a new bond strength model for FRCM considering the slippage between fabric and matrix was proposed, using a test database to predict the strengthening performance of the FRCM composite. The prediction of the proposed bond strength model agreed well with the debonding loads of the test database.

  4. Mechanical behavior of cementitious composites with processed sugar cane bagasse ashes

    International Nuclear Information System (INIS)

    Bezerra, Augusto C.S.; Saraiva, Sergio L.C.; Sena, Natalia O.; Pereira, Gabriela M.; Rodrigues, Conrado S.; Ferreira, Maria C.N.F.; Castro, Laurenn W.A.; Silva, Marcos V.M.S.; Gomes, Romero C.; Aguilar, Maria T.P.

    2014-01-01

    Sugar cane bagasse is waste from the sugar and ethanol industry and is primarily intended for burning in boilers to generate energy. As waste from the cogeneration of energy, sugar cane bagasse ashes (SCBA) are produced with no honorable destination. This paper studies the use of SCBA to partially replace Portland cement in producing cementitious composites. The ashes were processed by reburning and grinding, and after processing were characterized by a scanning electron microscope, x-ray diffraction, laser granulometry, and x-ray fluorescence spectrometry. After characterization, cement compounds were fashioned, replacing 0, 10, 20 and 30% of the cement with SCBA. The composites were mechanically evaluated by means of compression strength tests, tensile strength tests by bending. The results proved significant, indicating the possible use of SCBA when added to the cement on manufacture. (author)

  5. Phenomenological interpretation of the shear behavior of reinforced Engineered Cementitious Composite beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2016-01-01

    loaded in shear. The experimental program consists of R/ECC beams with short (8 mm) randomly distributed Polyvinyl Alcohol (PVA) fiber and conventional Reinforced Concrete (R/C) counterparts for comparison with varying shear reinforcement arrangements. Beams were loaded until failure while a Digital......This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams...... Image Correlation (DIC) measurement technique was used to measure surface displacements and crack formation. The shear crack mechanisms of R/ECC are described in detail based on findings of DIC measurements and can be characterized by an opening and sliding of the cracks. Multiple micro-cracks developed...

  6. Strength Correlation and Prediction of Engineered Cementitious Composites with Microwave Properties

    Directory of Open Access Journals (Sweden)

    Kwok L. Chung

    2016-12-01

    Full Text Available This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing ages under the influence of different initial water contents. Parallel measurements and regression analysis on compressive strength and microwave conductance were undertaken. It is shown that the strength evolution of ECCs can be accurately modeled and predicted by using microwave conductance at the early ages using bi-exponential functions. Compressive strength grows as a function of decreasing effective conductance, whereas the regression coefficients of the correlation models have a linear variation with water-to-binder ratios. These findings have highlighted the effectiveness of the microwave technique in detecting the variation of liquid phase morphology and pore structure.

  7. Materialism.

    Science.gov (United States)

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website. Copyright © 2012 John Wiley & Sons, Ltd.

  8. Les silicates alcalins, matière de base des mousses minérales isolantes. Etude bibliographique Alkaline Silicates, As a Basic Material for Insulating Mineral Foams. Bibliographie Study

    Directory of Open Access Journals (Sweden)

    Lesage J.

    2006-11-01

    Full Text Available Dans cette étude bibliographique, on décrit les méthodes d'obtention des silicates alcalins ainsi que leurs propriétés et les propriétés de leurs polymères en insistant sur l'influence du pH, de la concentration et de la température sur la polymérisation et les caractéristiques des polymères obtenus. On présente ensuite le mode d'obtention des mousses à partir de solutions aqueuses de silicates, ainsi que leurs propriétés et l'influence de divers additifs tels que les agents tensioactifs, moussants, gélifiants ou les agents de durcissement sur les propriétés des mousses. II ressort de cette bibliographie que des mousses polysilicates solubles peuvent être obtenues à partir de solutions de silicates à faible rapport molaire SiO2/Na2O. Par ailleurs, en faisant varier la composition des solutions de silicates alcalins et par l'emploi d'additifs, il est possible de produire une gamme très variée de mousses polysilicates dont les propriétés d'isolation, de solubilité et de résistance mécanique, voire de perméabilité, sont très variées, ce qui leur ouvre la voie à de nombreuses possibilités de débouchés industriels. This article gives a bibliographic description of methods for obtaining alkaline silicates as well as their properties and the properties of their polymers. Emphasis is placed on the influence of the pH, and on the influence of the concentration and temperature on the polymerization and the characteristics of the polymers obtained. Then a method is recommended for obtaining foams from aqueous silicate solutions together with the properties of such foams and the influence of different additives such as surfactants, foaming agents, gelling agents and hardening agents on the properties of foams. This bibliographic study shows that soluble polysilicate foams may be obtained from silicate solutions with a low SiO2/Na2O molar ratio. Furthermore, by varying the composition of alkaline silicate solutions and by

  9. Sorption data base for the cementitious near-field of L/ILW and ILW repositories for provisional safety analyses for SGT-E2

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E.

    2014-11-15

    The near-field of the planned Swiss repositories for low- and intermediate-level waste (L/ILW) and long-lived intermediate-level waste (ILW) consists of large quantities of cementitious materials. Hardened cement paste (HCP) is considered to be the most important sorbing material present in the near-field of L/ILW and ILW repositories. Interaction of radionuclides with HCP represents the most important mechanism retarding their migration from the near-field into the host rock. This report describes a cement sorption data base (SDB) for the safety-relevant radionuclides in the waste that will be disposed of in the L/ILW and ILW repositories. The current update on sorption values for radionuclides should be read in conjunction with the earlier SDBs CEM-94, CEM-97 and CEM-02. Sorption values have been selected based on procedures reported in these earlier SDBs. The values are revised if corresponding new information and/or data are available. The basic information results from a survey of sorption studies published between 2002 and 2013. The sorption values recommended in this report have either been selected from in-house experimental studies or from literature data, and they were further assessed with a view to the sorption values recently published in the framework of the safety analysis for the planned near surface disposal facility in Belgium. The report summarizes the sorption properties of HCP and compiles sorption values for safety-relevant radionuclides and low-molecular weight organic molecules on undisturbed and degraded HCP. A list of the safety-relevant radionuclides is provided. The radionuclide inventories are determined by the waste streams to be disposed of in the L/ILW and ILW repositories. Information on the elemental and mineral composition of HCP was obtained from hydration studies. The concentrations of the most important impurity elements in cement were obtained from dissolution studies on HCP. Particular emphasis is placed on summarizing our

  10. Characterization of cementitiously stabilized subgrades for mechanistic-empirical pavement design

    Science.gov (United States)

    Solanki, Pranshoo

    Pavements are vulnerable to subgrade layer performance because it acts as a foundation. Due to increase in the truck traffic, pavement engineers are challenged to build more strong and long-lasting pavements. To increase the load-bearing capacity of pavements, subgrade layer is often stabilized with cementitious additives. Thus, an overall characterization of stabilized subgrade layer is important for enhanced short- and long-term pavement performance. In this study, the effect of type and amount of additive on the short-term performance in terms of material properties recommended by the new Mechanistic-Empirical Pavement Design Guide (MEPDG) is examined. A total of four soils commonly encountered as subgrades in Oklahoma are utilized. Results show that the changes in the Mr, ME and UCS values stabilized specimens depend on the soil type and properties of additives. The long-term performance (or durability) of stabilized soil specimens is investigated by conducting freeze-thaw (F-T) cycling, vacuum saturation and tube suction tests on 7-day cured P-, K- and C-soil specimens stabilized with 6% lime, 10% CFA and 10% CKD. This study is motivated by the fact that during the service life of pavement stabilized layers are subjected to F-T cycles and moisture variations. It is found that that UCS value of all the stabilized specimens decreased with increase in the number of F-T cycles. A strong correlation was observed between UCS values retained after vacuum saturation and F-T cycles indicating that vacuum saturation could be used as a time-efficient and inexpensive method for evaluating durability of stabilized soils. In this study, short- and long-term observations from stabilization of sulfate bearing soil with locally available low (CFA), moderate (CKD) and high (lime) calcium-based stabilizers are determined to evaluate and compare the effect of additive type on the phenomenon of sulfate-induced heave. The impact of different factors on the development of the

  11. Histochemistry of placental alkaline phosphatase in preeclampsia

    OpenAIRE

    Shevade, Sapna Prashant; Arole, Vasanti; Paranjape, Vaishali Mohan; Bharambe, Vaishaly Kishore

    2016-01-01

    Objectives: Placental alkaline phosphatase (PALP) is synthesized in placenta and increases with gestational age. Alkaline phosphatase supports pregnancy and could play an essential role in nutrient supply and growth of the fetus. Preeclampsia is a systemic disorder which affects 5 to 7 percent of women worldwide and is a major cause for maternal and neonatal morbidity and mortality. As it has a major role in fetal growth, nutrition and defense mechanism study of alkaline phosphatase enzymatic...

  12. Alkaline Electrochemical Capacitor and Electrode Fabrication

    National Research Council Canada - National Science Library

    Finello, D

    1999-01-01

    .... The subject low cost alkaline electrochemical capacitor designs are based upon titanium nitride electrodes which exhibit 125 mF/sq cm surface capacitance density and remarkable electrochemical...

  13. Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

    International Nuclear Information System (INIS)

    Ye Weimin; Zheng Zhenji; Chen Bao; Chen Yonggui

    2011-01-01

    Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments, the effects of alkaline cation and alkaline solution on mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite are emphasized in this paper, temperature, pH values and concentration are discussed as main affecting factors. When bentonite is exposed to alkaline cation or alkaline solution, microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals, which results in the decrease of swelling pressure. The amount of the reduction of swelling pressure depends on the concentration of alkaline solution. Temperature, polyvalent cation, salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions. Therefore, future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values. (authors)

  14. Recycling of MSWI fly ash by means of cementitious double step cold bonding pelletization: Technological assessment for the production of lightweight artificial aggregates.

    Science.gov (United States)

    Colangelo, Francesco; Messina, Francesco; Cioffi, Raffaele

    2015-12-15

    In this work, an extensive study on the recycling of municipal solid waste incinerator fly ash by means of cold bonding pelletization is presented. The ash comes from an incineration plant equipped with rotary and stoker furnaces, in which municipal, hospital and industrial wastes are treated. Fly ash from waste incineration is classified as hazardous and cannot be utilized or even landfilled without prior treatment. The pelletization process uses cement, lime and coal fly ash as components of the binding systems. This process has been applied to several mixes in which the ash content has been varied from 50% (wt.%) up to a maximum of 70%. An innovative additional pelletization step with only cementitious binder has been performed in order to achieve satisfactory immobilization levels. The obtained lightweight porous aggregates are mostly suitable for recovery in the field of building materials with enhanced sustainability properties. Density, water absorption and crushing strength ranged from 1000 to 1600 kg/m(3), 7 to 16% and 1.3 to 6.2 MPa, respectively, and the second pelletization step increased stabilization efficiency. The feasibility of the process has been analyzed by testing also concrete specimens containing the artificial aggregates, resulting in lightweight concrete of average performance. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Alkaline phosphatase immobilization onto Bio-Gide(R) and Bio-Oss(R) for periodontal and bone regeneration.

    NARCIS (Netherlands)

    Oortgiesen, D.A.W.; Plachokova, A.S.; Geenen, C.; Meijer, G.J.; Walboomers, X.F.; Beucken, J.J.J.P van den; Jansen, J.B.M.J.

    2012-01-01

    AIM: To evaluate the effect of alkaline phosphatase (ALP) immobilization onto Bio-Gide((R)) in vitro, and to study the in vivo performance of ALP-enriched Bio-Gide((R)) and/or Bio-Oss((R)) with the purpose to enhance periodontal regeneration. MATERIALS AND METHODS: Alkaline phosphatase ALP was

  16. Column leaching test to evaluate the use of alkaline industrial wastes to neutralize acid mine tailings

    Energy Technology Data Exchange (ETDEWEB)

    Doye, I.; Duchesne, J. [University of Laval, Quebec City, PQ (Canada)

    2005-08-01

    Acid mine drainage is a serious environmental problem caused by the oxidation of sulfide minerals that releases highly acidic, sulfate, and metals-rich drainage. In this study, alkaline industrial wastes were mixed with acid mine tailings in order to obtain neutral conditions. A series of column leaching tests were performed to evaluate the behavior of reactive mine tailings amended with alkaline-additions under dynamic conditions. Column tests were conducted of oxidized mine tailings combined with cement kiln dust, red mud bauxite, and mixtures of cement kiln dust with red mud bauxite. The pH results show the addition of 10% of alkaline materials permits the maintenance of near neutral conditions. In the presence of 10% alkaline material, the concentration of toxic metals such as Al, Cu, Fe, Zn are significantly reduced as well as the number of viable cells (Thiobacillus ferrooxidans) compared to control samples.

  17. Alkaline azide mutagenicity in cowpea

    International Nuclear Information System (INIS)

    Mahna, S.K.; Bhargava, Anubha; Mohan, Lalit

    1990-01-01

    Sodium azide is known as a potent mutagen in cereals and legumes. It is very effective in acidic medium in barley. Here an attempt is made to measure the effectiveness of sodium azide in alkaline medium (pH 7.4) on cowpea (Vigna unguiculata (L.) Walp., variety FS-68). Seeds pre-soaked in distilled water for 5 hours were treated with different concentrations (10 -6 , 10 -5 , 10 -4 and 10 -3 M) of sodium azide (NaN 3 ) for 4 hours at 28± 2 deg. C. Bottles were intermittently shaken, then the seeds were thoroughly washed in running tap water and subsequently planted in pots. The treatment caused significant biological damage such as reduction in seed germination, length of root and shoot, number of nodules and pods per plant and morphological leaf variations. Morphological, as well as chlorophyll mutants, were detected in M 2

  18. Screening of Alkaline Protease-Producing Streptomyces diastaticus and Optimization of Enzyme Production

    OpenAIRE

    Elham Dawoodi; Keivan Beheshtimaal; Hashem Nayeri

    2014-01-01

    Background and Aim: Alkaline proteases are used in pharmaceutical, film and photography, silk production and food, leather and detergent industries. Actinomycetes are gram positive bacteria that produce different enzymes such as proteases. The aims of this research were isolation of native alkaline protease-producing Actinomycete spp. from different soil samples as well as optimizing the conditions for enzyme production. Materials and Methods: The different soil samples were collected fro...

  19. Avaliação da resistência a fadiga dos Engineered Cementitious Composites (ecc, reforçados com fibra de polipropileno e produzidos com adição de cinza de casca de arroz

    Directory of Open Access Journals (Sweden)

    Alceu Lopes de Freitas Júnior

    2017-07-01

    Full Text Available O Engineered Cementitious Composites - ECC – é um tipo especial de compósito cimentício de alto desempenho reforçado com fibra, cuja principal característica é a alta ductilidade. O traço de ECC é composto por cimento, material pozolânico, agregado miúdo e fibras. Este estudo avaliou a resistência à fadiga de traços de Engineered Cementitious Composites reforçados com fibras de polipropileno - PPECC – e cuja composição da matriz cimentícia tenha a incorporação de cinza de casca de arroz como material suplementar. Para isto, foram produzidos corpos de prova com substrato de concreto para pavimento e overlay com o traço de PPECC desenvolvido. Os corpos de prova foram submetidos aos ensaios de flexão a quatro pontos (estático e cíclico. Compararam-se os resultados obtidos no ensaio estático dos traços de PPECC com os resultados obtidos neste mesmo ensaio com corpos de prova produzidos somente por concreto para pavimento. Foram analisados os resultados dos ensaios cíclicos em diferentes intervalos de tensões. Com os resultados variação da tensão x números de ciclos, obtidos no ensaio cíclico, foi avaliado o comportamento à fadiga do compósito.

  20. catalysed oxidation of atenolol by alkaline permanganate

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Kinetics of ruthenium (III) catalyzed oxidation of atenolol by permanganate in alkaline medium at constant ionic strength of 0⋅30 mol dm3 has been studied spectrophotometrically using a rapid kinetic accessory. Reaction between permanganate and atenolol in alkaline medium exhibits 1 : 8 stoichiometry.

  1. Increased liver alkaline phosphatase and aminotransferase ...

    African Journals Online (AJOL)

    The effect of daily, oral administration of ethanolic extract of Khaya senegalensis stem bark (2mg/kg body weight) for 18days on the alkaline phosphatase, aspartate and alanine aminotransferase activities of rat liver and serum were investigated. Compared with the control, the activities of liver alkaline phosphatase (ALP), ...

  2. Alkaline Phosphatases From Camel Small Intestine | Fahmy ...

    African Journals Online (AJOL)

    Camel intestinal alkaline phosphatase have been purified and characterized. The purification was carried out by chromatography on DEAE-cellulose. Five intestinal alkaline phosphatase isoenzymes (IAP1 to IAP5) were obtained. IAP2 and IAP5 with the highest activity levels were purified to homogeneity by Sephacryl ...

  3. Handbook of Indigenous Foods Involving Alkaline Fermentation

    NARCIS (Netherlands)

    Sarkar, P.K.; Nout, M.J.R.

    2014-01-01

    This book details the basic approaches of alkaline fermentation, provides a brief history, and offers an overview of the subject. The book discusses the diversity of indigenous fermented foods involving an alkaline reaction, as well as the taxonomy, ecology, physiology, and genetics of predominant

  4. Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998

    Energy Technology Data Exchange (ETDEWEB)

    Allan, M.L.; Philippacopoulos, A.J.

    1998-11-01

    Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.

  5. The contribution of class-F fly ash to the strength of cementitious mixtures

    International Nuclear Information System (INIS)

    Malek, R.I.; Khalil, Z.H.; Imbaby, S.S.; Roy, D.M.

    2005-01-01

    The contribution of fly ash to the physical properties of cementitious mixtures has received considerable attention since its inclusion as an essential ingredient of High Performance Concrete (HPC). However, the chemical contribution to the overall structure development has not been fully understood because of the masking of its hydration products by those of cement. In a mixture of class-F fly ash and lime (Ca/Si=2), portlandite diminishes and C 4 AH 13 forms due to addition of Al to solution. The latter converts to hydrogarnet and C 3 ASH 4 . CSH is detected at 3 days and continues to increase in intensity. The 29 Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the Al/Si ratio is 0.24 and the average chain length is 10 units. The presence of Al as approximately one-fifth of the Si in a chain length of 10 units suggests that Al tetrahedra may be present in bridging positions

  6. Effect of aluminate ions on the heat of hydration of cementitious waste forms

    International Nuclear Information System (INIS)

    Lokken, R.O.

    1993-11-01

    During the hydration and setting of high-salt content liquid waste grouts, considerable heat is generated by exothermic reactions within the grout. These reactions include hydration reactions of cementitious solids and reactions between waste constituents and the solids. Adiabatic temperature rises exceeding 80 degrees C have been estimated for grouts prepared with a dry blend of 47 wt % fly ash, 47 wt % blast furnace slag, and 6 wt % type I/II Portland cement (1) Performance criteria for grout disposal specify that the temperature of the grout waste form must not exceed 90 degrees C (2) To counter the increase in temperature, inert solids were added to the ''47/47/6'' dry blend to reduce the amount of heat-generating solids, thereby decreasing the temperature rise. Based on preliminary results from adiabatic calorimetry, a dry blend consisting of 40 wt % limestone flour, 28 wt % class F fly ash, 28 wt % ground blast furnace slag, and 4 wt % type I/II Portland cement was selected for further testing

  7. Effect of cementitious permanent formwork on moisture field of internal-cured concrete under drying

    Science.gov (United States)

    Wang, Jiahe; Zhang, Jun; Ding, Xiaoping; Zhang, Jiajia

    2018-02-01

    Drying shrinkage of concrete may still be the main source of cracking in concrete structures, even though the autogenous shrinkage of concrete can be effectively reduced by using internal curing. In the present paper, the effect of internal curing with pre-soaked lightweight aggregate and engineered cementitious composite permanent formwork (ECC-PF) on a moisture distribution in three kinds of concrete in a drying environment are investigated from both aspects of experiments and theoretical modeling. The test results show that the combination use of ECC-PF and internal curing can well maintain the humidity at a relatively high level not only at a place far from drying surface, but also at a place close to the drying surfaces. The developed model can well catch the characteristics of the moisture distribution in concrete under drying and the impacts of internal curing and ECC-PF can well be reflected as well. The model can be used for the design of concrete structures with combination use of internal curing and permanent formwork.

  8. A non-destructive test method to monitor corrosion products and corrosion-induced cracking in reinforced cement based materials

    DEFF Research Database (Denmark)

    Michel, Alexander; Pease, Bradley Justin; Peterova, Adela

    2011-01-01

    This paper introduces a non-destructive test method to monitor the development of corrosion products as well as the corrosion-induced formation and propagation of cracks in cementitious materials. A parametric experimental investigation (utilizing x-ray attenuation measurement technique...

  9. Alkaline Phosphatase: MedlinePlus Lab Test Information

    Science.gov (United States)

    ... this page: https://medlineplus.gov/labtests/alkalinephosphatase.html Alkaline Phosphatase To use the sharing features on this page, please enable JavaScript. What is an Alkaline Phosphatase Test? An alkaline phosphatase (ALP) test measures ...

  10. Process for impregnating a concrete or cement body with a polymeric material

    Science.gov (United States)

    Mattus, Alfred J.; Spence, Roger D.

    1989-01-01

    A process for impregnating cementitious solids with polymeric materials by blending polymeric materials in a grout, allowing the grout to cure, and contacting the resulting solidified grout containing the polymeric materials with an organic mixture containing a monomer, a cross-linking agent and a catalyst. The mixture dissolves the polymerized particles and forms a channel for distributing the monomer throughout the network formed by the polymeric particles. The organic components are then cured to form a substantially water-impermeable mass.

  11. Multisystemic functions of alkaline phosphatases.

    Science.gov (United States)

    Buchet, René; Millán, José Luis; Magne, David

    2013-01-01

    Human and mouse alkaline phosphatases (AP) are encoded by a multigene family expressed ubiquitously in multiple tissues. Gene knockout (KO) findings have helped define some of the precise exocytic functions of individual isozymes in bone, teeth, the central nervous system, and in the gut. For instance, deficiency in tissue-nonspecific alkaline phosphatase (TNAP) in mice (Alpl (-/-) mice) and humans leads to hypophosphatasia (HPP), an inborn error of metabolism characterized by epileptic seizures in the most severe cases, caused by abnormal metabolism of pyridoxal-5'-phosphate (the predominant form of vitamin B6) and by hypomineralization of the skeleton and teeth featuring rickets and early loss of teeth in children or osteomalacia and dental problems in adults caused by accumulation of inorganic pyrophosphate (PPi). Enzyme replacement therapy with mineral-targeting TNAP prevented all the manifestations of HPP in mice, and clinical trials with this protein therapeutic are showing promising results in rescuing life-threatening HPP in infants. Conversely, TNAP induction in the vasculature during generalized arterial calcification of infancy (GACI), type II diabetes, obesity, and aging can cause medial vascular calcification. TNAP inhibitors, discussed extensively in this book, are in development to prevent pathological arterial calcification. The brush border enzyme intestinal alkaline phosphatase (IAP) plays an important role in fatty acid (FA) absorption, in protecting gut barrier function, and in determining the composition of the gut microbiota via its ability to dephosphorylate lipopolysaccharide (LPS). Knockout mice (Akp3 (-/-)) deficient in duodenal-specific IAP (dIAP) become obese, and develop hyperlipidemia and hepatic steatosis when fed a high-fat diet (HFD). These changes are accompanied by upregulation in the jejunal-ileal expression of the Akp6 IAP isozyme (global IAP, or gIAP) and concomitant upregulation of FAT/CD36, a phosphorylated fatty acid

  12. Hybrid Fiber Reinforced Concrete Incorporated With Phase Change Material

    OpenAIRE

    Chuang, Chia-So

    2015-01-01

    To further efforts toward improvement, an innovative and durable High Performance Fiber Reinforced Cementitious Composites (HPFRCC) was developed, using hybrid steel macro-fibers with designed hook-ends, and polyvinyl alcohol micro-fibers for optimal fiber synergistic effects, crack width control, durability, and reduced maintenance and life-cycle costs for bridges. For functional performance improvements, an off-the-shelf phase change material (PCM) was utilized, optimized and incorporated i...

  13. Assessing the Contribution of the CFRP Strip of Bearing the Applied Load Using Near-Surface Mounted Strengthening Technique with Innovative High-Strength Self-Compacting Cementitious Adhesive (IHSSC-CA

    Directory of Open Access Journals (Sweden)

    Alyaa Mohammed

    2018-01-01

    Full Text Available Efficient transfer of load between concrete substrate and fibre reinforced polymer (FRP by the bonding agent is the key factor in any FRP strengthening system. An innovative high-strength self-compacting non-polymer cementitious adhesive (IHSSC-CA was recently developed by the authors and has been used in a number of studies. Graphene oxide and cementitious materials are used to synthesise the new adhesive. The successful implementation of IHSSC-CA significantly increases carbon FRP (CFRP strip utilization and the load-bearing capacity of the near-surface mounted (NSM CFRP strengthening system. A number of tests were used to inspect the interfacial zone in the bonding area of NSM CFRP strips, including physical examination, pore structure analysis, and three-dimensional laser profilometery analysis. It was deduced from the physical inspection of NSM CFRP specimens made with IHSSC-CA that a smooth surface for load transfer was found in the CFRP strip without stress concentrations in some local regions. A smooth surface of the adhesive layer is very important for preventing localized brittle failure in the concrete. The pore structure analysis also confirmed that IHSSC-CA has better composite action between NSM CFRP strips and concrete substrate than other adhesives, resulting in the NSM CFRP specimens made with IHSSC-CA sustaining a greater load. Finally, the results of three-dimensional laser profilometery revealed a greater degree of roughness and less deformation on the surface of the CFRP strip when IHSSC-CA was used compared to other adhesives.

  14. Incorporation mode effect of Nano-silica on the rheological and mechanical properties of cementitious pastes and cement mortars

    Science.gov (United States)

    Safi, B.; Aknouche, H.; Mechakra, H.; Aboutaleb, D.; Bouali, K.

    2018-04-01

    Previous research indicates that the inclusion of nanosilica (NS) modifies the properties of the fresh and hardened state, compared to the traditional mineral additions. NS decreases the setting times of the cement mortar compared to silica fume (SF) and reduce of required water while improving the cohesion of the mixtures in the fresh state. Some authors estimate that the appropriate percentage of Nano-silica should be small (1 to 5% by weight) because of difficulties caused by agglomeration to particles during mixing, while others indicate that 10% by weight, if adjustments are made to the formulation to avoid an excess of self-drying and micro cracks that could impede strength. For this purpose, the present work aim to see the effect of the introduction mode of the nanosilica on the rheological and physic mechanical properties of cement mortars. In this study, NS was used either powdered with cement or in solution with the superplasticizer (Superplasticizer doped in nanosilica). Results show that the use of nanosilica powder (replacing cement on the one hand) has a negative influence on the rheological parameters and the rheological behavior of cementitious pastes. However, the introduction of nanosilica in solution in the superplasticizer (SP) was significantly improved the rheological parameters and the rheological behavior of cementitious pastes. Indeed, more the dosage of NS-doped SP increases more the shear stress and viscosities of the cementitious pastes become more fluid and manageable. A significant reduction of shear stress and plastic viscosity were observed that due to the increase in superplasticizer. A dosage of 1.5% NS-doped SP gave adequate fluidity and the shear rate was lower.

  15. Alkaline sorbent injection for mercury control

    Science.gov (United States)

    Madden, Deborah A.; Holmes, Michael J.

    2002-01-01

    A mercury removal system for removing mercury from combustion flue gases is provided in which alkaline sorbents at generally extremely low stoichiometric molar ratios of alkaline earth or an alkali metal to sulfur of less than 1.0 are injected into a power plant system at one or more locations to remove at least between about 40% and 60% of the mercury content from combustion flue gases. Small amounts of alkaline sorbents are injected into the flue gas stream at a relatively low rate. A particulate filter is used to remove mercury-containing particles downstream of each injection point used in the power plant system.

  16. Alkaline rocks and the occurrence of uranium

    International Nuclear Information System (INIS)

    Hambleton-Jones, B.B.; Toens, P.D.

    1980-10-01

    Many alkaline complexes contain uranium and other minerals in low concentrations and are regarded as constituting valuable potential reserves. Certain complex metallurgical problems, however, remain to be solved. Alkaline rocks occur in a number of forms and environments and it is noted that they are generated during periods of geological quiescence emplaced mainly in stable aseismic areas. Many occur along the extensions of oceanic transform faults beneath the continental crust and the application of this concept to areas not currently known to host alkaline complexes may prove useful in identifying potential target areas for prospecting operations [af

  17. Influence of salivary enzymes and alkaline pH environment on fatigue behavior of resin composites

    NARCIS (Netherlands)

    Mirmohammadi, H.; Kleverlaan, C.J.; Aboushelib, M.N.; Feilzer, A.J.

    2011-01-01

    Purpose: To evaluate the effect of enzymatic activity and alkaline medium on flexural strength and rotary fatigue resistance of direct and indirect resin composite restorative materials. Methods: Three direct resin composite materials Filtek Z100, Filtek Z250 and Filtek Silorane (3M ESPE), and two

  18. Defect structure of cubic solid solutions of alkaline earth and rare earth fluorides

    NARCIS (Netherlands)

    DenHartog, HW

    1996-01-01

    In this paper we will consider the disorder in some cubic solid solutions consisting of one of the alkaline earth fluorides and one of the rare earth fluorides. This is an attractive group of model materials, because these materials have a rather simple overall cubic structure. We will discuss the

  19. Subcellular localization of alkaline phosphatase in Bacillus licheniformis 749/C by immunoelectron microscopy with colloidal gold

    International Nuclear Information System (INIS)

    Tinglu, G.; Ghosh, A.; Ghosh, B.K.

    1984-01-01

    Subcellular distribution of the alkaline phosphatase of Bacillus licheniformis 749/C was determined by an immunoelectron microscopy method. Anti-alkaline phosphatase antibody labeled with 15- to 18-nm colloidal gold particles (gold-immunoglobulin G [IgG] complex) were used for the study. Both the plasma membrane and cytoplasmic material were labeled with the gold-IgG particles. These particles formed clusters in association with the plasma membrane; in contrast, in the cytoplasm the particles were largely dispersed, and only a few clusters were found. The gold-IgG binding was quantitatively estimated by stereological analysis of labeled, frozen thin sections. This estimation of a variety of control samples showed that the labeling was specific for the alkaline phosphatase. Cluster formation of the gold -IgG particles in association with the plasma membrane suggests that existence of specific alkaline phosphatase binding sites (receptors) in the plasma membrane of B. licheniformis 749/C. 27 references, 6 figures, 1 table

  20. The application of extraction chromatography for analysis of alkali and alkaline earth uranates

    International Nuclear Information System (INIS)

    Tomazic, B.; Cukovic, M.

    1978-01-01

    A method for rapid analysis of alkali and alkaline earth uranates is proposed. The method is based on the use of an HDEHP extraction chromatographic column, which makes possible quantitative separations of alkaline earth ions from macroamounts of uranium(VI). Composition of alkaline earth uranates, based on regression analysis, are presented. The results, which show that under the given experimental conditions alkaline earth triuranates precipitate, are in good agreement with previous data from same laboratory. In addition the HDEHP extraction chromatographic column can be suggested as a tool for separation of representative fission products from irradiated uranium for the purpose of determination of the burn-up factor of nuclear reactor materials. (T.G.)