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Sample records for fresh cement based

  1. Effect of Nanosilica on the Fresh Properties of Cement-Based Grouting Material in the Portland-Sulphoaluminate Composite System

    Directory of Open Access Journals (Sweden)

    Shengli Li

    2016-01-01

    Full Text Available The effect of NS particle size and content on the fresh properties of the grouting material based on the portland-sulphoaluminate composite system was analyzed. The experimental results indicated that air content increased and apparent density decreased, with increased NS content, but the NS particle sizes have minimal effect on the air content and apparent density. The setting time of mortar was significantly shortened, with increased NS content; however, NS particle sizes had little influence on the setting time. The effect of fluidity on the mortars adding NS with particle size of 30 nm is larger than NS with particle sizes of 15 and 50 nm and the fluidity decreased with increased NS content, but the fluidity of mortars with the particle sizes of 15 and 50 nm is almost not affected by the NS content. XRD analysis shows that the formation of ettringite was promoted and the process of hydration reaction of cement was accelerated with the addition of NS. At the microscopic level, the interfacial transition zone (ITZ of the grouting material became denser and the formation of C-S-H gel was promoted after adding NS.

  2. Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

    Energy Technology Data Exchange (ETDEWEB)

    Schroefl, Christof, E-mail: christof.schroefl@tu-dresden.de [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Mechtcherine, Viktor [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Vontobel, Peter; Hovind, Jan; Lehmann, Eberhard [Paul Scherrer Institut, Laboratory for Neutron Scattering and Imaging, CH-5232 Villigen/AG (Switzerland)

    2015-09-15

    Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1.

  3. On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires

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    Alessandra Fiore

    2014-01-01

    Full Text Available This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing.

  4. Changes in the drug release pattern of fresh and set simvastatin-loaded brushite cement.

    Science.gov (United States)

    Mestres, Gemma; Kugiejko, Karol; Pastorino, David; Unosson, Johanna; Öhman, Caroline; Karlsson Ott, Marjam; Ginebra, Maria-Pau; Persson, Cecilia

    2016-01-01

    Calcium phosphate cements are synthetic bone graft substitutes able to set at physiological conditions. They can be applied by minimally invasive surgery and can also be used as drug delivery systems. Consequently, the drug release pattern from the cement paste (fresh cement) is of high clinical interest. However, previous studies have commonly evaluated the drug release using pre-set cements only. Therefore, the aim of this work was to determine if the time elapsed from cement preparation until immersion in the solution (3 min for fresh cements, and 1h and 15 h for pre-set cements) had an influence on its physical properties, and correlating these to the drug release profile. Simvastatin was selected as a model drug, while brushite cement was used as drug carrier. This study quantified how the setting of a material reduces the accessibility of the release media to the material, thus preventing drug release. A shift in the drug release pattern was observed, from a burst-release for fresh cements to a sustained release for pre-set cements.

  5. Fresh-water cementation of a 1,000-year-old oolite

    Science.gov (United States)

    Halley, R. B.; Harris, P. M.

    1979-01-01

    Calcite cementation of aragonite ooid sand is producing oolite on Joulters Cays, Bahamas. During the last 1,000 years, calcite cement has formed at an average rate of between 27 and 55 cm3 /m3 /yr and is derived from dissolution of ooid aragonite in fresh water. The dissolution-reprecipitation of carbonate minerals in the aquifer results in ground waters of unusually high Sr content. Sea water and mixtures of fresh and sea water appear to inhibit cementation. A pronounced cement fabric change occurs across the water table and has produced an obvious petrographic record of fresh-water diagenesis. Above the water table, cement is typically near grain contact positions, where water is held by capillarity; below the water table, cement is more randomly distributed around grains. At the water table a transition zone, 1 meter thick, marks the boundary between cement textures. No porosity reduction is associated with cementation; calcite cement precipitation is apparently compensated by an equal or greater amount of aragonite dissolution in the interval undergoing cementation. Permeability is more variable above the water table than below it, reflecting early channelling of flow patterns in the vadose zone. Effective permeability below the water table is one to two orders of magnitude higher than above the water table because of entrained gas in the vadose zone. This permeability difference promotes preservation of unstable minerals above the water table and continued diagenetic alteration below the water table.

  6. Phosphate based oil well cements

    Science.gov (United States)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  7. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample.

    Science.gov (United States)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-30

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  8. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    Science.gov (United States)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  9. Base isolation: Fresh insight

    Energy Technology Data Exchange (ETDEWEB)

    Shustov, V.

    1993-07-15

    The objective of the research is a further development of the engineering concept of seismic isolation. Neglecting the transient stage of seismic loading results in a widespread misjudgement: The force of resistance associated with velocity is mostly conceived as a source of damping vibrations, though it is an active force at the same time, during an earthquake type excitation. For very pliant systems such as base isolated structures with relatively low bearing stiffness and with artificially added heavy damping mechanism, the so called `damping`` force may occur even the main pushing force at an earthquake. Thus, one of the two basic pillars of the common seismic isolation philosophy, namely, the doctrine of usefulness and necessity of a strong damping mechanism, is turning out to be a self-deception, sometimes even jeopardizing the safety of structures and discrediting the very idea of seismic isolation. There is a way out: breaking with damping dependancy.

  10. Cast in place temperature 5 influence on fresh concrete made with limestone filler and blended cement

    Directory of Open Access Journals (Sweden)

    Soria, E. A.

    2003-12-01

    Full Text Available Properties of fresh concrete play a relevant role on placing and consolidation; and its design strength and durability depends on them. It is well known too that the concrete temperature during placing affects all its properties in different ways and extent. This paper presents the influence of placing temperature of concretes made with portland cement, limestone filer cement and blended cement, commercially available, on slump, slump loss, setting time and bleeding. The results show that generally when concrete temperature rises, the bleeding and slump fall down and the slump loss and setting time are accelerated. However, regardless of the strength class the type of cement affects the value of these variations

    Las propiedades de los hormigones en estado fresco desempeñan un papel fundamental durante las operaciones de colocación y compactación de los mismos y de ellas depende, en gran medida, que se alcance en el estado endurecido la resistencia y la durabilidad de diseño. Es sabido, además, que la temperatura que alcanza un hormigón durante dichas operaciones, afecta en mayor o menor grado a todas sus propiedades, de manera diferente. En el presente trabajo se analizó la influencia de la temperatura de colocación sobre el asentamiento, la pérdida del asentamiento en el tiempo, los tiempos de fraguado y la exudación, en hormigones elaborados con cemento portland normal, fillerizado y compuesto, de procedencia comercial. Los resultados han mostrado, en general, que con el aumento de la temperatura de colocación disminuyen la exudación y el asentamiento; mientras que la pérdida de asentamiento y los tiempos de fraguado se aceleran. Sin embargo, las magnitudes de dichas variaciones resultan a su vez muy influenciadas por el tipo de cemento utilizado, aun siendo de la misma clase resistente.

  11. [Burns caused by cement mortar (based on expert opinion)].

    Science.gov (United States)

    Kleinhans, D

    1984-01-01

    A 35-year-old farmer with scars on his right arm, following erosion obviously due to wet cement (case of an expert opinion), was examined. Cement water had continuously soaked his shirt while he was planing a freshly applied wet cement ceiling with his right arm upwards. The cement did not contain special additives, so the normal alkalinity of wet cement and occlusion effects caused the erosion. The farmer sued the manufacturer of the cement for damages because of missing warning notices. The court decided in his favor.

  12. Investigation of cement based composites made with recycled rubber aggregate

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    Jevtić Dragica Lj.

    2012-01-01

    Full Text Available The results of experimental investigations performed on cement based composites made with addition of recycled rubber as a partial replacement of natural river aggregate are presented in this paper. Different properties of cement based mortar were analyzed, both in fresh and in hardened state. Tested properties in the fresh state included: density, consistency and volume of entrained air. In the hardened state, the following properties were tested: density, mechanical properties (compressive and flexural strength, modulus of elasticity, adhesion to concrete substrate, water absorption, freeze-thaw resistance and ultrasonic pulse velocity. The obtained results indicate that recycled rubber can be successfully applied as a partial replacement of natural river aggregate in cement based composites, in accordance with the sustainable development concept. The investigation showed that physical-mechanical properties of cementituous composites depend to a great extent on the percentage of replacement of natural river aggregate with recycled rubber, especially when the density, strength, adhesion and freeze-thaw resistance are concerned. The best results were obtained in the freeze-thaw resistance of such composites.

  13. CONCRETE BASED ON MODIFIED DISPERSE CEMENT SYSTEM

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    D. V. Rudenko

    2016-08-01

    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  14. Development of Advanced Cement-Based Building Products

    Institute of Scientific and Technical Information of China (English)

    Zongjin LI; Bin MU; Stanley N.C.CHIU

    2000-01-01

    @@ In this study, short fiber-reinforced cement-based building products of sheets, pipes and honeycomb panels incorporating various mineral admixtures such as slag, silica fume, and metakaolin have been developed by the extrusion technique. The experimental works have shown that these products do have very good mechanical properties. Since the key point for a successful extrusion is the properly designed rheology which controls both internal and external flow properties of ext rudate, a nonlinear viscoelastic model was applied to investigate the rheology behavior of a movable fresh cementitious composite in a single screw extruder channel. The theoretical analysis is used to guide the practical manufacturing.

  15. Carbonation Resistance of Sulphoaluminate Cement-based High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen

    2009-01-01

    The influences of water/cement ratio and admixtures on carbonation resistance of sulphoaluminate cement-based high performance concrete(HPC)were investigated.The experimental results show that with the decreasing water/cement ratio,the carbonation depth of sulphoaluminate cement-based HPC is decreased remarkably,and the carbonation resistance capability is also improved with the adding admixtures.The morphologies and structure characteristics of sulphoaluminate cement hydration products before and after carbonation were analyzed using SEM and XRD.The analysis results reveal that the main hydration product of sulphoaluminate cement,that is ettringite(AFt),de-composes after carbonation.

  16. Cementation of Loose Sand Particles based on Bio-cement

    Institute of Scientific and Technical Information of China (English)

    RONG Hui; QIAN Chunxiang

    2014-01-01

    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  17. Rheologic properties of fresh cement mixes for repository sealing applications: effects of superplasticizers, mixing procedures, and time

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D.M.; Asaga, K.

    1982-09-01

    As part of the design of optimally durable, hardened cementitious plugging materials for repository borheole plugging, shaft and tunnel sealing, detailed studies of rheological properties have been made. The effects of mixing procedures upon measured rheological properties of fresh cement mixes with and without superplasticizing admixtures condensates of sulfonated naphthalene- and melamine-formaldehyde have been investigated. Coaxial cylindrical viscometer measurements were made, recording shear stress-shear rate relationships and defining yield stress and plastic viscosity. In the absence of admixture, yield stress and plastic viscosity decreased substantially with increasing intensity of mixing, which caused a breakdown of particulate aggregates. However, with admixture present, the rheological properties of already well-dispersed mixes did not change significantly with increasingly intense mixing. The changes of the viscometric functions with time were investigated, and were related to admixture type and concentration, cement type, and volume concentration of cement. The mechanisms of action of the superplasticizers and their use in generating reliable workable low water/cement ratio mixes are discussed. 36 figures, 3 tables.

  18. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    DEFF Research Database (Denmark)

    Pietro, Lura; Ye, Guang; van Breugel, Klaas

    2004-01-01

    (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  19. Properties of cement based composites modified using diatomaceous earth

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Záleská, Martina; Pavlík, Zbyšek

    2017-07-01

    Diatomite belongs among natural materials rich on amorphous silica (a-SiO2). When finely milled, it can potentially substitute part of cement binder and positively support formation of more dense composite structure. In this connection, two types of diatomaceous earth applied as a partial substitution of 5, 10, 15, and 20 mass% of Portland cement in the composition of cement paste were studied. In the tested mixtures with cement blends, the amount of batch water remained same, with water/binder ratio 0.5. For fresh paste mixtures, initial and final setting times were measured. First, hardened pastes cured 28 days in water were characterized by their physical properties such as bulk density, matrix density and open porosity. Then, their mechanical and thermophysical parameters were assessed. Obtained results gave clear evidence of setting time shortening for pastes with diatomite what brought negative effect with respect to the impaired workability of fresh mixtures. On the other hand, there was observed strength improvement for mixtures containing diatomite with higher amount of SiO2. Here, the increase in mechanical resistivity was distinct up to 15 mass% of cement replacement. Higher cement substitution by diatomite resulted in an increase in porosity and thus improvement of thermal insulation properties.

  20. Densified ultra-light cement-based materials

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro

    2015-01-01

    be used as a “clean technology” in the production of cement-based materials for structural applications with a low carbon footprint. This paper describes the principles of this concept coupled with experimental results on the basic properties of this enhanced type of cement-based materials with combined...

  1. Spalling Resistant Bauxite Based Bricks for Cement Kiln

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiaohui; Peng Xigao

    2011-01-01

    @@ 1.Scope This standard specifies the term,definition,classification,labeling,technical requirements,test methods,inspection rules,packing,marking,transportation,storage,and quality certificate of spalling resistant bauxite based bricks for cement kiln.This standard is applicable to the spalling resistant bauxite based bricks for cement kiln.

  2. Bond Mechanisms in Fiber Reinforced Cement-Based Composites

    Science.gov (United States)

    1989-08-01

    Symposium on "Cement Based Composites: Bonding in Cementitious Composites," S. Mindess and S. Shah, Editors. 44. Nilson, A. H., "Bond Stress-Slip...Society Symposium on "Cement Based Composites: Bonding in Cementitious Composites," held in Boston, December 2 to 4, 1987, S. Mindess and S. Shah, 0

  3. Cement-Based Materials for Nuclear Waste Storage

    CERN Document Server

    Cau-di-Coumes, Céline; Frizon, Fabien; Lorente, Sylvie

    2013-01-01

    As the re-emergence of nuclear power as an acceptable energy source on an international basis continues, the need for safe and reliable ways to dispose of radioactive waste becomes ever more critical. The ultimate goal for designing a predisposal waste-management system depends on producing waste containers suitable for storage, transportation and permanent disposal. Cement-Based Materials for Nuclear-Waste Storage provides a roadmap for the use of cementation as an applied technique for the treatment of low- and intermediate-level radioactive wastes.Coverage includes, but is not limited to, a comparison of cementation with other solidification techniques, advantages of calcium-silicate cements over other materials and a discussion of the long-term suitability and safety of waste packages as well as cement barriers. This book also: Discusses the formulation and production of cement waste forms for storing radioactive material Assesses the potential of emerging binders to improve the conditioning of problemati...

  4. Microindentation of Polymethyl Methacrylate (PMMA Based Bone Cement

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    F. Zivic

    2011-12-01

    Full Text Available Characterization of polymethyl methacrylate (PMMA based bone cement subjected to cyclical loading using microindentation technique is presented in this paper. Indentation technique represents flexible mechanical testing due to its simplicity, minimal specimen preparation and short time needed for tests. The mechanical response of bone cement samples was studied. Realised microindentation enabled determination of the indentation testing hardness HIT and indentation modulus EIT of the observed bone cement. Analysis of optical photographs of the imprints showed that this technique can be effectively used for characterization of bone cements.

  5. Cement-based materials' characterization using ultrasonic attenuation

    Science.gov (United States)

    Punurai, Wonsiri

    The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct

  6. Porosity prediction of calcium phosphate cements based on chemical composition.

    Science.gov (United States)

    Öhman, Caroline; Unosson, Johanna; Carlsson, Elin; Ginebra, Maria Pau; Persson, Cecilia; Engqvist, Håkan

    2015-07-01

    The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% β-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37°C and 100% relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 °C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

  7. Long-term effect on the solidified degraded cellulose-based waste slurry in cement matrix

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    Hosam El-Din Mostafa Saleh

    2009-03-01

    Full Text Available The long-term effects on solidification/stabilization (s/s of the secondary wastes, resulting from the oxidative degradation of some solid cellulosic-based wastes, in Portland Cement (CEM I have been investigated by X-ray diffraction (X-RD and Fourier transform infrared spectroscopy (FT-IR techniques. The effect of seven years leaching of the cemented waste forms obtained was carried out to assess the long-term immobilization behavior of the radionuclide in the solidified/stabilized waste that maybe exposed to fresh, ground or sea water.The results of this study confirm our previously published work that the oxidative degradation treatment of some cellulosic-based wastes is essential before incorporating into the cementitious inert matrix. In addition, the release of radionuclides from the cemented waste form is a diffusion controlling process, after the first washing out period lasting for nearly thirty days.Based on the results so far obtained it is concluded that Portland Cement could be considered as a potential inert matrix to immobilize the degraded cellulosic-based wastes for a short or long time of storage or a final disposal.

  8. Pullout behavior of steel fibers from cement-based composites

    DEFF Research Database (Denmark)

    Shannag, M. Jamal; Brincker, Rune; Hansen, Will

    1997-01-01

    A comprehensive experimental program on pullout tests of steel fibers from cement based matrices is described. A specially designed single fiber pullout apparatus was used to provide a quantitative determination of interfacial properties that are relevant to toughening brittle materials through...... fiber reinforcement. The parameters investigated included a specially designed high strength cement based matrix called Densified Small Particles system (DSP), a conventional mortar matrix, fiber embeddment length, and the fiber volume fraction. The mediums from which the fiber was pulled included...

  9. Chromium speciation in hazardous, cement-based waste forms

    Science.gov (United States)

    Lee, J. F.; Bajt, S.; Clark, S. B.; Lamble, G. M.; Langton, C. A.; Oji, L.

    1995-02-01

    XANES and EXAFS techniques were used to determine the oxidation states and local structural environment of Cr in cement-based waste forms. Results show that Cr in untreated Portland cement formulations remains as toxic Cr 6+, while slag additives to the cement reduce Cr 6+ to the less toxic, less mobile Cr 3+ species. EXAFS analysis suggests that the Cr 6+ species is surrounded by four nearest oxygen atoms, while the reduced Cr 3+ sp ecies is surrounded by six oxygen atoms. The fitted CrO bond lengths for Cr 6+ and Cr 3+ species are around 1.66 and 1.98 Å, respectively.

  10. Using bio-based polymers for curing cement-based materials

    NARCIS (Netherlands)

    Zlopasa, J.; Koenders, E.A.B.; Picken, S.J.

    2014-01-01

    Curing is the process of controlling the rate and extent of moisture loss from the surface of cement based materials. It is the final stage in the production of cement-based materials and it is the essential part for achieving continuous hydration of cement, while avoiding cracking due to drying

  11. Using bio-based polymers for curing cement-based materials

    NARCIS (Netherlands)

    Zlopasa, J.; Koenders, E.A.B.; Picken, S.J.

    2014-01-01

    Curing is the process of controlling the rate and extent of moisture loss from the surface of cement based materials. It is the final stage in the production of cement-based materials and it is the essential part for achieving continuous hydration of cement, while avoiding cracking due to drying shr

  12. Strain sensitivity of carbon nanotube cement-based composites for structural health monitoring

    Science.gov (United States)

    D'Alessandro, Antonella; Ubertini, Filippo; Laflamme, Simon; Rallini, Marco; Materazzi, Annibale L.; Kenny, Josè M.

    2016-04-01

    Cement-based smart sensors appear particularly suitable for monitoring applications, due to their self-sensing abilities, their ease of use, and their numerous possible field applications. The addition of conductive carbon nanofillers into a cementitious matrix provides the material with piezoresistive characteristics and enhanced sensitivity to mechanical alterations. The strain-sensing ability is achieved by correlating the variation of external loads or deformations with the variation of specific electrical parameters, such as the electrical resistance. Among conductive nanofillers, carbon nanotubes (CNTs) have shown promise for the fabrication of self-monitoring composites. However, some issues related to the filler dispersion and the mix design of cementitious nanoadded materials need to be further investigated. For instance, a small difference in the added quantity of a specific nanofiller in a cement-matrix composite can substantially change the quality of the dispersion and the strain sensitivity of the resulting material. The present research focuses on the strain sensitivity of concrete, mortar and cement paste sensors fabricated with different amounts of carbon nanotube inclusions. The aim of the work is to investigate the quality of dispersion of the CNTs in the aqueous solutions, the physical properties of the fresh mixtures, the electromechanical properties of the hardened materials, and the sensing properties of the obtained transducers. Results show that cement-based sensors with CNT inclusions, if properly implemented, can be favorably applied to structural health monitoring.

  13. Cement industry control system based on multi agent

    Institute of Scientific and Technical Information of China (English)

    王海东; 邱冠周; 黄圣生

    2004-01-01

    Cement production is characterized by its great capacity, long-time delay, multi variables, difficult measurement and muhi disturbances. According to the distributed intelligent control strategy based on the multi agent, the multi agent control system of cement production is built, which includes integrated optimal control and diagnosis control. The distributed and multiple level structure of multi agent system for the cement control is studied. The optimal agent is in the distributed state, which aims at the partial process of the cement production, and forms the optimal layer. The diagnosis agent located on the diagnosis layer is the diagnosis unit which aims at the whole process of the cement production, and the central management unit of the system. The system cooperation is realized by the communication among optimal agents and diagnosis agent. The architecture of the optimal agent and the diagnosis agent are designed. The detailed functions of the optimal agent and the diagnosis agent are analyzed.At last the realization methods of the agents are given, and the application of the multi agent control system is presented. The multi agent system has been successfully applied to the off-line control of one cement plant with capacity of 5 000 t/d. The results show that the average yield of the clinker increases 9.3% and the coal consumption decreases 7.5 kg/t.

  14. Minimally invasive maxillofacial vertical bone augmentation using brushite based cements.

    Science.gov (United States)

    Tamimi, Faleh; Torres, Jesus; Lopez-Cabarcos, Enrique; Bassett, David C; Habibovic, Pamela; Luceron, Elena; Barralet, Jake E

    2009-01-01

    An ideal material for maxillofacial vertical bone augmentation procedures should not only be osteoconductive, biocompatible and mechanically strong, but should also be applied using minimally invasive procedures and remain stable with respect to the original bone surfaces. This way, implant exposure and infection might be reduced and good mechanical stability may be achieved. Calcium phosphate cements are proven biocompatible and osteoconductive materials that can be injected using minimally invasive procedures. Among these cements, brushite based cements have the added advantage of being biodegradable in vivo. Therefore, this material has the potential for use in the aforementioned procedures. An in vivo study was performed in rabbits to evaluate the potential use of brushite cements in minimally invasive maxillofacial vertical bone augmentation procedures. In this study, we injected self-setting brushite cements on the subperiosteal bone surface using a minimally invasive tunnelling technique. The cement pastes were stable on the bone surface and hardened soon after they were injected thereby negating the need for additional supports such as membranes or meshes. The animals were sacrificed 8 weeks after the intervention and histological observations revealed signs of successful vertical bone augmentation. Therefore, we have demonstrated a minimally invasive vertical bone augmentation procedure that is an attractive alternative to current surgical procedures in terms of increased simplicity, reduced trauma, and lower cost of surgery.

  15. In vivo characterization of polymer based dental cements

    Directory of Open Access Journals (Sweden)

    Widiyanti P

    2011-12-01

    Full Text Available Background: In vivo studies investigating the characterization of dental cements have been demonstrated. As few in vitro studies on this cement system have been performed. Previous researches in dental material has been standardized dental cement which fulfilled the physical and mechanical characteristic such as shear strength but were on in vitro condition, the animal model and clinical study of dental cement from laboratory has not been done yet. This research examined physical and mechanical characteristic in vivo using rabbit by making the caries (class III in anterior teeth especially in mesial or distal incisive, fulfilled the cavity by dental cement and analyzed the compressive strength, tensile strength, and microstructure using scanning electron microscope (SEM. Purpose: This study is aimed to describe the in vivo characterization of dental cements based on polymer (zinc phosphate cement, polycarboxylate, glass ionomer cement and zinc oxide eugenol. Methods: First, preparation was done on animal model’s teeth (6 rabbits, male, 5 months old. The cavity was made which involved the dentin. Then the cavity was filled with dental cement. After the filling procedure, the animal model should be kept until 21 days and than the compressive test, tensile test and microstructure was characterized. Compressive test and tensile test was analyzed using samples from extracted tooth and was measured with autograph. The microstructure test was measured using SEM. Results: The best compressive strength value was belongs to zinc phosphate cement which was 101.888 Mpa and the best tensile strength value was belongs to glass ionomer cement which was 6.555 Mpa. Conclusion: In conclusion, comparing with 3 others type of dental cements which are zinc phosphate, polycarboxylate and glass ionomer cement, zinc oxide eugenol cement has the worst for both physical and mechanical properties.Latar belakang: Studi in vivo meneliti karakterisasi secara in vivo dari

  16. Reinforcement of cement-based matrices with graphite nanomaterials

    Science.gov (United States)

    Sadiq, Muhammad Maqbool

    Cement-based materials offer a desirable balance of compressive strength, moisture resistance, durability, economy and energy-efficiency; their tensile strength, fracture energy and durability in aggressive environments, however, could benefit from further improvements. An option for realizing some of these improvements involves introduction of discrete fibers into concrete. When compared with today's micro-scale (steel, polypropylene, glass, etc.) fibers, graphite nanomaterials (carbon nanotube, nanofiber and graphite nanoplatelet) offer superior geometric, mechanical and physical characteristics. Graphite nanomaterials would realize their reinforcement potential as far as they are thoroughly dispersed within cement-based matrices, and effectively bond to cement hydrates. The research reported herein developed non-covalent and covalent surface modification techniques to improve the dispersion and interfacial interactions of graphite nanomaterials in cement-based matrices with a dense and well graded micro-structure. The most successful approach involved polymer wrapping of nanomaterials for increasing the density of hydrophilic groups on the nanomaterial surface without causing any damage to the their structure. The nanomaterials were characterized using various spectrometry techniques, and SEM (Scanning Electron Microscopy). The graphite nanomaterials were dispersed via selected sonication procedures in the mixing water of the cement-based matrix; conventional mixing and sample preparation techniques were then employed to prepare the cement-based nanocomposite samples, which were subjected to steam curing. Comprehensive engineering and durability characteristics of cement-based nanocomposites were determined and their chemical composition, microstructure and failure mechanisms were also assessed through various spectrometry, thermogravimetry, electron microscopy and elemental analyses. Both functionalized and non-functionalized nanomaterials as well as different

  17. Strengthening of Concrete Structures with cement based bonded composites

    DEFF Research Database (Denmark)

    Täljsten, Björn; Blanksvärd, Thomas

    2008-01-01

    Polymers). The method is very efficient and has achieved world wide attention. However, there are some drawbacks with the use of epoxy, e.g. working environment, compatibility and permeability. Substituting the epoxy adherent with a cement based bonding agent will render a strengthening system...... with improved working environment and better compatibility to the base concrete structure. This study gives an overview of different cement based systems, all with very promising results for structural upgrading. Studied parameters are structural retrofit for bending, shear and confinement. It is concluded...

  18. Effects of Two Redispersible Polymer Powders on Efflorescence of Portland Cement-based Decorative Mortar

    Directory of Open Access Journals (Sweden)

    Huimei ZHU

    2014-09-01

    Full Text Available The effects of redispersible polymer powders of ethylene/Vinyl acetate copolymer (EVA and ethylene/vinyl laurate/vinyl chloride terpolymer (E/VL/VC on the efflorescence of Portland cement-based decorative mortar (PCBDM were studied. The results showed that EVA slightly prolongs the efflorescence duration of fresh PCBDM; and exacerbates efflorescence of hardened PCBDM, because it increases the content of soluble salts such as Ca2+, K+, Na+ ions in hardened PCBDM and promotes their migration. E/VL/VC exacerbates efflorescence of fresh PCBDM due to it easily dissolves in the surface water; but reduces efflorescence of hardened PCBDM, which is attributed to that it decreases the soluble salts content in hardened PCBDM and prohibits salts migration. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4053

  19. Some aspects of cellulose ethers influence on water transport and porous structure of cement-based materials

    OpenAIRE

    Pourchez, Jérémie; Ruot, Bertrand; Debayle, Johan; Rouèche-Pourchez, Emilie; Grosseau, Philippe

    2010-01-01

    International audience; This paper evaluates and compares the impact of cellulose ethers (CE) on water transport and porous structure of cement-based materials in both fresh and hardened state. Investigations of the porous network (mercury intrusion porosimetry, apparent density, 2D and 3D observations) emphasize an air-entrained stabilisation depending on CE chemistry. We also highlight that CE chemistry leads to a gradual effect on characteristics of the water transport. The global tendenci...

  20. 掺增稠剂新拌胶凝材料浆体的结构%Research on Structure of Fresh Composite Cement Pastes with Thickener Added

    Institute of Scientific and Technical Information of China (English)

    林鲜; 阎培渝

    2000-01-01

    应用光学显微镜等分析手段,研究目前应用较多的掺聚丙烯酰胺增稠剂复合胶凝材料浆体的显微结构和流动性能.研究表明,掺增稠剂的矿渣复合胶凝材料或粉煤灰复合胶凝材料浆体内部能形成较紧密的絮凝基团,而絮凝基团间的联系较松散,从而具有较好的流动性.%In this paper, the microstructures and flowability of fresh composite cement pastes with thickener added have been investigated by light microscopy. The results show that the flocculation groups of compoite cement pastes mixed with flocculation additive are formed. In pastes of fly ash ce-ment and ground blast furnace slag cement compacted inner structure of flocculation groups is formed and loose interaction exists between flocculation groups, therefore the friction between flocculation groups is reduced and their flowability is improved.

  1. Elastoplastic cup model for cement-based materials

    Directory of Open Access Journals (Sweden)

    Yan ZHANG

    2010-03-01

    Full Text Available Based on experimental data obtained from triaxial tests and a hydrostatic test, a cup model was formulated. Two plastic mechanisms, respectively a deviatoric shearing and a pore collapse, are taken into account. This model also considers the influence of confining pressure. In this paper, the calibration of the model is detailed and numerical simulations of the main mechanical behavior of cement paste over a large range of stress are described, showing good agreement with experimental results. The case study shows that this cup model has extensive applicability for cement-based materials and other quasi-brittle and high-porosity materials in a complex stress state.

  2. Smart Behavior of Carbon Fiber Reinforced Cement-based Composite

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The electrical characteristics of cement-based material can be remarkably improved by the addition of short carbon fibers.Carbon fiber reinforced cement composite (CFRC) is an intrinsically smart material that can sense not only the stress andstrain, but also the temperature. In this paper, variations of electrical resistivity with external applied load, and relationof thermoelectric force and temperature were investigated. Test results indicated that the electrical signal is related to theincrease in the material volume resistivity during crack generation or propagation and the decrease in the resistivity duringcrack closure. Moreover, it was found that the fiber addition increased the linearity and reversibility of the Seebeck effect inthe cement-based materials. The change of electrical characteristics reflects large amount of information of inner damage andtemperature differential of composite, which can be used for stress-strain or thermal self-monitoring by embedding it in theconcrete structures.

  3. Three-dimensional Microstructure Simulation Model of Cement Based Materials,

    NARCIS (Netherlands)

    Ye, G.; Van Breugel, K.

    2003-01-01

    This paper describes a computer-based numerical model for the simulation of the development of microstructure during cement hydration. Special emphasis is on the algorithm for characterizing the pores. This includes the porosity and the pore size distribution and the topological properties of the po

  4. Multiscale Lattice Boltzmann-Finite Element Modelling of Transport Properties in Cement-based Materials

    NARCIS (Netherlands)

    Zhang, M.

    2013-01-01

    Cement-based materials are the most widely used man-made materials in the world. The durability of cement-based materials has been a major concern due to the premature failure and serviceability issues of many reinforced concrete structures. Durability of cement-based materials is to a large content

  5. Multiscale Lattice Boltzmann-Finite Element Modelling of Transport Properties in Cement-based Materials

    NARCIS (Netherlands)

    Zhang, M.

    2013-01-01

    Cement-based materials are the most widely used man-made materials in the world. The durability of cement-based materials has been a major concern due to the premature failure and serviceability issues of many reinforced concrete structures. Durability of cement-based materials is to a large content

  6. The most suitable techiniques and methods to identify high alumina cement and based portland cement in concretes

    OpenAIRE

    Blanco, M. T.; Puertas, F; Vázquez, T.; de la Fuente, A

    1992-01-01

    Instrumental techniques are indicated and the most adequated methodologies for determining the nature of the binder in concretes are explained. These methods are: a) Determination of the Silicic Moduli through chemical analysis of the sample. This test reveáis very different valúes between cement portland based concrete and high alumina cement based concretes. b) X-ray diffraction. It is considered as the best method. In the present paper the main diffraction Unes corresponding to...

  7. Effect of Nano-particles on Performance of Fresh Cement Paste%纳米颗粒对新拌水泥浆体性能的影响

    Institute of Scientific and Technical Information of China (English)

    刘小艳; 王婷; 陈雷

    2014-01-01

    In this paper, the activity of nano-SiO2, nano-clay, nano-Al2O3and nano-CaCO3is introduced.Effect of these nano-particles on water requirement of normal consistency, the fluidity and setting time of fresh cement paste are studied.The results show that, except nano-Ca-CO3, the content of the other three nano-particles is larger, the water requirement of normal consistency of cement is greater.All nano-particles enlarge the cohesiveness of fresh cement paste and decrease the fluidity of cement paste.Nano-SiO2, nano-Al2O3 and nano-CaCO3 promote the early hydration of cement and shorten the setting time, and nano-clay plays the role of delaying coagulation.%研究了单掺纳米SiO2、纳米粘土、纳米Al2 O3、纳米CaCO3颗粒对新拌水泥浆体标准稠度用水量、凝结时间、流动性的影响。研究发现:纳米SiO2、纳米粘土、纳米Al2 O3导致水泥浆体标准稠度用水量不同程度的增加,且纳米颗粒掺量越大标准稠度用水量越大;纳米颗粒使水泥浆体粘聚性增大,相同水胶比时掺入纳米颗粒使浆体流动性降低;纳米SiO2、纳米CaCO3、纳米Al2 O3促进了水泥水化,使初凝和终凝时间提前,但纳米粘土表现出一定的缓凝作用。

  8. Characterization of dicalcium phosphate dihydrate cements prepared using a novel hydroxyapatite-based formulation

    Energy Technology Data Exchange (ETDEWEB)

    Alge, Daniel L [Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47908 (United States); Cruz, Grace Santa; Chu, Tien-Min Gabriel [Department of Biomedical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202 (United States); Goebel, W Scott, E-mail: tgchu@iupui.ed [Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202 (United States)

    2009-04-15

    Dicalcium phosphate dihydrate (DCPD) cements are typically prepared using beta-tricalcium phosphate (beta-TCP) as the base component. However, hydroxyapatite (HA) is an interesting alternative because of its potential for reducing cement acidity, as well as modulating cement properties via ionic substitutions. In the present study, we have characterized DCPD cements prepared with a novel formulation based on monocalcium phosphate monohydrate (MCPM) and HA. Cements were prepared using a 4:1 MCPM:HA molar ratio. The reactivity of HA in this system was verified by showing DCPD formation using poorly crystalline HA, as well as highly crystalline HA. Evaluation of cements prepared with poorly crystalline HA revealed that setting occurs rapidly in the MCPM/HA system, and that the use of a setting regulator is necessary to maintain workability of the cement paste. Compressive testing showed that MCPM/HA cements have strengths comparable to what has previously been published for DCPD cements. However, preliminary in vitro analysis of cement degradation revealed that conversion of DCPD to HA may occur much more rapidly in the MCPM/HA system compared to cements prepared with beta-TCP. Future studies should investigate this property further, as it could have important implications for the use of HA-based DCPD cement formulations.

  9. Elastoplastic cup model for cement-based materials

    OpenAIRE

    Zhang, Yan; Shao, Jian-Fu

    2010-01-01

    Based on experimental data obtained from triaxial tests and a hydrostatic test, a cup model was formulated. Two plastic mechanisms, respectively a deviatoric shearing and a pore collapse, are taken into account. This model also considers the influence of confining pressure. In this paper, the calibration of the model is detailed and numerical simulations of the main mechanical behavior of cement paste over a large range of stress are described, showing good agreement with experimental results...

  10. Additives for cement compositions based on modified peat

    Science.gov (United States)

    Kopanitsa, Natalya; Sarkisov, Yurij; Gorshkova, Aleksandra; Demyanenko, Olga

    2016-01-01

    High quality competitive dry building mixes require modifying additives for various purposes to be included in their composition. There is insufficient amount of quality additives having stable properties for controlling the properties of cement compositions produced in Russia. Using of foreign modifying additives leads to significant increasing of the final cost of the product. The cost of imported modifiers in the composition of the dry building mixes can be up to 90% of the material cost, depending on the composition complexity. Thus, the problem of import substitution becomes relevant, especially in recent years, due to difficult economic situation. The article discusses the possibility of using local raw materials as a basis for obtaining dry building mixtures components. The properties of organo-mineral additives for cement compositions based on thermally modified peat raw materials are studied. Studies of the structure and composition of the additives are carried out by physicochemical research methods: electron microscopy and X-ray analysis. Results of experimental research showed that the peat additives contribute to improving of cement-sand mortar strength and hydrophysical properties.

  11. Additives for cement compositions based on modified peat

    Energy Technology Data Exchange (ETDEWEB)

    Kopanitsa, Natalya, E-mail: kopanitsa@mail.ru; Sarkisov, Yurij, E-mail: sarkisov@tsuab.ru; Gorshkova, Aleksandra, E-mail: kasatkina.alexandra@gmail.com; Demyanenko, Olga, E-mail: angel-n@sibmail.com [Tomsk State University of Architecture and Building, 2, Solyanaya sq., Tomsk, 634003 (Russian Federation)

    2016-01-15

    High quality competitive dry building mixes require modifying additives for various purposes to be included in their composition. There is insufficient amount of quality additives having stable properties for controlling the properties of cement compositions produced in Russia. Using of foreign modifying additives leads to significant increasing of the final cost of the product. The cost of imported modifiers in the composition of the dry building mixes can be up to 90% of the material cost, depending on the composition complexity. Thus, the problem of import substitution becomes relevant, especially in recent years, due to difficult economic situation. The article discusses the possibility of using local raw materials as a basis for obtaining dry building mixtures components. The properties of organo-mineral additives for cement compositions based on thermally modified peat raw materials are studied. Studies of the structure and composition of the additives are carried out by physicochemical research methods: electron microscopy and X-ray analysis. Results of experimental research showed that the peat additives contribute to improving of cement-sand mortar strength and hydrophysical properties.

  12. Recycling red mud from the production of aluminium as a red cement-based mortar.

    Science.gov (United States)

    Yang, Xiaojie; Zhao, Jianfeng; Li, Haoxin; Zhao, Piqi; Chen, Qin

    2017-05-01

    Current management for red mud is insufficient and a new method is needed. A series of experiments have been carried out to develop a new approach for effective management of red mud. Mortars without or with 3%, 6% and 9% red mud were prepared and their fresh and hardened properties were measured to access the possibility of recycling the red mud in the production of red cement-based mortar. The mechanisms corresponding to their mechanical performance variations were explored by X-ray powder diffraction and scanning electron microscopy. The results show that the fresh mortars with red mud present an increase of viscosity as compared with the control. However, little difference is found when the content of red mud is altered. It also can be seen that red mud increases flow time and reduces the slump flow of the mortar. Meanwhile, it is found that mortar with red mud is provided with higher air content. Red mud is eligible to adjust the decorative mortar colour. Compressive strength of mortar is improved when less than 6% red mud is added. However, overall it has a slightly negative effect on tensile bond strength. It decreases the Ca(OH)2 content and densifies the microstructure of hardened paste. The heavy metal concentrations in leachates of mortars with red mud are much lower than the values required in the standard, and it will not do harm to people's health and the environment. These results are important to recycle and effectively manage red mud via the production of red cement-based mortar.

  13. Environmental CRIteria for CEMent based products, ECRICEM. Phase I. Ordinary Portland Cements. Phase II. Blended Cements. Executive Summary

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sloot, H.A.; Van Zomeren, A. [ECN Biomass, Coal and Environmetal Research, Petten (Netherlands); Stenger, R. [Holcim Group Support Ltd, Holderbank (Switzerland); Schneider, M.; Spanka, G. [VDZ, Duesseldorf (Germany); Stoltenberg-Hansson, A. [NORCEM, HeidelbergCement Group, Brevik (Norway); Dath, P. [Holcim Belgium, Obourg (Belgium)

    2008-01-15

    The protection of the immediate environment of structural works is one of the essential requirements of the European Construction Products Directive (CPD). According to the CPD, construction products can only be put on the market, if the structural works built with them fulfil the relevant requirements for hygiene, and the protection of health and the environment. These essential requirements in the respective standards are specified at the national level by the individual member states. Cement and cementitious materials are considered to fulfil the fundamental requirements of the European Construction Products Directive and the corresponding national regulations. Therefore a technical regulation like the cement standard EN 197 in general does not cover separate requirements for determining compliance of cementitious materials with criteria on hygiene, health and environmental protection. Further regulations are laid down in cases where it appears necessary for constructive applications requiring a particular protection of water, soil and air.

  14. Glass fibre reinforced cement based composite: fatigue and fracture parameters

    Directory of Open Access Journals (Sweden)

    Seitl S.

    2009-12-01

    Full Text Available This paper introduces the basic fracture mechanics parameters of advanced building material – glass fibres reinforced cement based composite and its fracture and fatigue behaviour is investigated. To this aim three-point bend (3PB specimens with starting notch were prepared and tested under static (l–d diagram and cyclic loading (Paris law and Ẅöhler curve. To evaluate the results, the finite element method was used for estimation of the corresponding values of stress intensity factor for the 3PB specimen used. The results obtained are compared with literature data.

  15. Base Course Modification through Stabilization using Cement and Bitumen

    Directory of Open Access Journals (Sweden)

    S. M. Marandi

    2009-01-01

    Full Text Available The main objectives of this research was to analyze the use of combined cement and bitumen emulsion in base course stabilization in details and examine its replacement with conventional pavement in regions with low quality materials and limited construction period. To conduct the objectives, the research divided into three phases. Phase I involved the optimization of cement and bitumen emulsion. In this case, a series of Indirect Tensile Strength (ITS, Unconfined Compressive Strength (UCS and Marshal Tests carried out. In the second phase, various alternative roadway sections examined for minimizing the pavement thickness and increasing the bearing capacity and finally in third phase, a Falling Weight Deflectometer (FWD machine used to examine the pavement bearing capacity for three sections of the roadway. It was found that, the optimum values to eliminate the creation of shrinkage cracks in the whole project and minimize the execution period and construction costs were 3% for both binders in stabilization and its replacement with conventional pavement method (i.e., stabilized layer with conventional sub-base and base layers. Also, FWD results showed that, the bearing capacity of the constructed pavement using stabilization method is far beyond the predicted values in pavement design. Furthermore, it was found that, with high inflation rate and political situation in the region, base stabilized method decreased the final roadway construction costs in compare with conventional pavement method.

  16. Response of a PGNAA setup for pozzolan-based cement concrete specimens

    Energy Technology Data Exchange (ETDEWEB)

    Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Garwan, M.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Raashid, M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2010-04-15

    Pozzolanic materials are added to Portland cement concrete to increase its durability, particularly corrosion-resistance. In this study the elemental composition of a pozzolanic cement concrete was measured non-destructively utilizing an accelerator-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup. The optimum size of the pozzolanic cement concrete specimen was obtained through Monte Carlo simulations. The simulation results were experimentally verified through the {gamma}-ray yield measurement from the pozzolanic cement concrete specimens as a function of their radii. The concentration of the pozzolanic material in the cement concrete specimens was evaluated by measuring {gamma}-ray yield for calcium and iron from pozzolanic cement concrete specimens containing 5-80 wt% pozzolan. A good agreement was noted between the experimental values and the Monte Carlo simulation results, indicating an excellent response of the KFUPM accelerator-based PGNAA setup for pozzolan based concrete.

  17. Response of a PGNAA setup for pozzolan-based cement concrete specimens.

    Science.gov (United States)

    Naqvi, A A; Garwan, M A; Maslehuddin, M; Nagadi, M M; Al-Amoudi, O S B; Raashid, M

    2010-01-01

    Pozzolanic materials are added to Portland cement concrete to increase its durability, particularly corrosion-resistance. In this study the elemental composition of a pozzolanic cement concrete was measured non-destructively utilizing an accelerator-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup. The optimum size of the pozzolanic cement concrete specimen was obtained through Monte Carlo simulations. The simulation results were experimentally verified through the gamma-ray yield measurement from the pozzolanic cement concrete specimens as a function of their radii. The concentration of the pozzolanic material in the cement concrete specimens was evaluated by measuring gamma-ray yield for calcium and iron from pozzolanic cement concrete specimens containing 5-80 wt% pozzolan. A good agreement was noted between the experimental values and the Monte Carlo simulation results, indicating an excellent response of the KFUPM accelerator-based PGNAA setup for pozzolan based concrete.

  18. Cement-based grouts in geological disposal of radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Onofrei, M. [AECL Research, Pinnawa, Manitoba (Canada)

    1996-04-01

    The behavior and performance of a specially developed high-performance cement-based grout has been studied through a combined laboratory and in situ research program conducted under the auspices of the Canadian Nuclear Fuel Waste Management Program (CNFWMP). A new class of cement-based grouts - high-performance grouts-with the ability to penetrate and seal fine fractures was developed and investigated. These high-performance grouts, which were injected into fractures in the granitic rock at the Underground Research Laboratory (URL) in Canada, are shown to successfully reduce the hydraulic conductivity of the rock mass from <10{sup -7} m s{sup -1} to 10{sup -9} m s{sup -1} and to penetrate fissures in the rock with apertures as small as 10 {mu}m. Furthermore, the laboratory studies have shown that this high - performance grout has very low hydraulic conductivity and is highly leach resistant under repository conditions. Microcracks generated in this materials from shrinkage, overstressing or thermal loads are likely to self-seal. The results of these studies suggest that the high-performance grouts can be considered as viable materials in disposal-vault sealing applications. Further work is needed to fully justify extrapolation of the results of the laboratory studies to time scales relevant to performance assessment.

  19. Piezoresistivity in Carbon Fiber Reinforced Cement Based Composites

    Institute of Scientific and Technical Information of China (English)

    Bing CHEN; Keru WU; Wu YAO

    2004-01-01

    The resu lts of some i nteresti ng investigation on the piezoresistivity of ca rbon fi ber reinforced cement based com posites (CFRC) are presented with the prospect of developing a new nondestructive testing method to assess the integrity of the composite. The addition of short carbon fibers to cement-based mortar or concrete improves the structural performance and at the same time significantly decreases the bulk electrical resistivity. This makes CFRC responsive to the smart behavior by measuring the resistance change with uniaxial pressure. The piezoresistivity of CFRC under different stress was studied, at the same time the damage occurring inner specimens was detected by acoustic emission as well. Test results show that there exists a marking pressure dependence of the conductivity in CFRC, in which the so-called negative pressure coefficient of resistive (NPCR) and positive pressure coefficient of resistive (PPCR) are observed under low and high pressure. Under constant pressures, time-dependent resistivity is an outstanding characteristic for the composites, which is defined as resistance creep. The breakdown and rebuild-up process of conductive network under pressure may be responsible for the pressure dependence of resistivity.

  20. Calcium aluminate cement concrete: durablllty and conversión. A fresh look at an old subject

    Directory of Open Access Journals (Sweden)

    George, C. M.

    1992-12-01

    Full Text Available This paper re-examines the relationship between durability and conversion of calcium aluminate cement concretes, CACC. Conversion is a natural and inevitable process whereby these materials reach a stable mature condition. Numerous structures built more than half a century ago remain serviceable and in service today. Some of these are illustrated. They are the best testament to the durability of converted concrete having survived far longer in the converted than the unconverted condition. The unique rapid hardening characteristics of CACC offer a valuable selfheating capability. Conversión is immediate and this leads to better long term strengths because more cement is hydrated. Moreover, recent work has shown that the thermodynamically stable hydrates of converted CAC are intrinsically more resistant to attack from such aggressive agents as sulphuric acid. This provides an explanation of the excellent long term performance of Fondu concretes, for example in many saewer applications. Our knowledge and understanding today of the durability of calcium alumínate bonded materials has been built on close to 100 years of accumulated experience and laboratory studies. We know how to use these materials and we know what to expect from them. We can be confident that they will serve us well in the century ahead.

    Este trabajo examina de nuevo la relación entre durabilidad y conversión de hormigones de cemento aluminoso, HAC (High Alumina Cement. La conversión es un proceso natural e inevitable a través del cual este material consigue una condición definitiva y estable. Numerosas estructuras que se edificaron hace más de medio siglo siguen utilizables y utilizadas hoy en día. Algunas de estas estructuras vienen ilustradas en este trabajo. Ellas sirven como mejor ejemplo de la durabilidad del hormigón convertido, ya que han sobrevivido mucho más tiempo en el estado convertido que en el no convertido. Las singulares caracter

  1. Strength gain and cementation of flexible pavement bases (revised)

    Science.gov (United States)

    Zimpfer, W. H.

    1991-02-01

    The strength gain of selected carbonate Florida Department of Transportation (FDOT) flexible pavement base materials is addressed. The gain in strength after aging of base sections constructed in an inside environment and outside environment was measured. Scanning electron microscope (SEM) photographs were also taken and examined to determine changes in structure. The materials investigated were: (1) bank run shell; (2) limerock; and (3) cemented coquina. Strength tests were the Clegg Impact Value (CIV) performed on inside and outside sections and a rigid plate test performed on the inside section. There was a small gain in strength for all three carbonate bases after 22 months. Changes in the matrix particles were observed in the SEM study. The three complementary phases (CIV, plate modulus, and SEM) tend to reinforce each other, indicating a small gain in strength.

  2. Conduction calorimetric studies of ternary binders based on Portland cement, calcium aluminate cement and calcium sulphate

    OpenAIRE

    Torrens Martín, David; Fernández Carrasco, Lucía; Blanco Varela, M.Teresa

    2013-01-01

    Different binders of Portland cement, calcium aluminate cement and calcium sulphate (PC/CAC/CS) have been investigated to determinate the in¿uence the CAC and CS amount in the reactions mechanism. Several mixtures were studied, ratios of 100, 85/15 and 75/25 of PC/CAC with 0, 3 and 5 % of CS. Conduction calorimetric technique was used to follow the hydration during 100 h. The XRD and FTIR techniques were used as support in the analysis of the hydration products. The results have shown tha...

  3. Hybrid Polyvinyl Alcohol and Cellulose Fiber Pulp Instead of Asbestos Fibers in Cement-Based Composites

    Science.gov (United States)

    Shokrieh, M. M.; Mahmoudi, A.; Shadkam, H. R.

    2015-05-01

    The Taguchi method was used to determine the optimum content of a four-parameters cellulose fiber pulp, polyvinyl alcohol (PVA) fibers, a silica fume, and bentonite for cement-based composite sheets. Then cement composite sheets from the hybrid of PVA and the cellulose fiber pulp were manufactured, and their moduli of rapture were determined experimentally. The result obtained showed that cement composites with a hybrid of PVA and cellulose fiber pulp had a higher flexural strength than cellulose-fiber- reinforced cement ones, but this strength was rather similar to that of asbestos-fiber-reinforced cement composites. Also, using the results of flexural tests and an analytical method, the tensile and compressive moduli of the hybrid of PVA and cement sheet were calculated. The hybrid of PVA and cellulose fiber pulp is proposed as an appropriate alternative for substituting asbestos in the Hatschek process.

  4. Thermal Properties of Cement-Based Composites for Geothermal Energy Applications.

    Science.gov (United States)

    Bao, Xiaohua; Memon, Shazim Ali; Yang, Haibin; Dong, Zhijun; Cui, Hongzhi

    2017-04-27

    Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural-functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles.

  5. Photons and electrons: advances in using cold plasma, irradiation, UV and other energy-based treatments for fresh and fresh-cut produce

    Science.gov (United States)

    Conventional antimicrobial treatments for fresh produce rely on chemical compounds and physical contact to inactivate and remove bacterial contamination. Recent research has identified a number of energy-based alternative technologies to improve the safety of fresh and fresh-cut fruits and vegetable...

  6. Development of Mechanistic-Empirical Pavement Design for Tropical Climate Using Cement-Treated Base Layer

    Directory of Open Access Journals (Sweden)

    O. S. Aderinola

    2016-08-01

    Full Text Available A mechanistic-empirical pavement design method is developed characterising cement-treated base layers for pavement design in Nigeria or other similar tropical and subtropical countries. Asphalt Concrete surface, Subbase and Aggregate base were characterised based on back calculation data from Claros et al (1986 while cement-treated base layer was based on modulus tests that had been conducted by past researchers. Failure criteria for the Asphalt Concrete fatigue failure and the subgrade rutting failure were based on those by Claros and Ijeh (1987 for Nigerian pavements. Cracking criterion used for the cement-treated layer was that developed by Otee et al. (1982. The comparison between the Soil-Cement and Aggregate base showed that at a low Equivalent Single Axle Load (ESAL (0.5 million repetitions was considered, the use of Aggregate base was better than Soil-Cement base. That for Aggregate base and Cement-Treated Gravel Base showed that the Cement-Treated Gravel Base was better than the Aggregate base at high ESAL (2.5 million repetitions was considered

  7. Properties of lightweight cement-based composites containing waste polypropylene

    Science.gov (United States)

    Záleská, Martina; Pavlíková, Milena; Pavlík, Zbyšek

    2016-07-01

    Improvement of buildings thermal stability represents an increasingly important trend of the construction industry. This work aims to study the possible use of two types of waste polypropylene (PP) for the development of lightweight cement-based composites with enhanced thermal insulation function. Crushed PP waste originating from the PP tubes production is used for the partial replacement of silica sand by 10, 20, 30, 40 and 50 mass%, whereas a reference mixture without plastic waste is studied as well. First, basic physical and thermal properties of granular PP random copolymer (PPR) and glass fiber reinforced PP (PPGF) aggregate are studied. For the developed composite mixtures, basic physical, mechanical, heat transport and storage properties are accessed. The obtained results show that the composites with incorporated PP aggregate exhibit an improved thermal insulation properties and acceptable mechanical resistivity. This new composite materials with enhanced thermal insulation function are found to be promising materials for buildings subsoil or floor structures.

  8. ASHES AS AN AGENT FOR CEMENT-LIME BASED SOLIDIFICATION/STABILIZATION OF THE HAZARDOUS WASTE

    Directory of Open Access Journals (Sweden)

    Barbora Lyčkova

    2008-12-01

    Full Text Available One of the common treatment methods for the hazardous waste is the cement and cement-lime based solidification/stabilization (S/S. This article deals with the possibility of currently used recipe modification using fluidized bed heating plant ashes as an agent.

  9. Glycerol Salicylate-based Pulp-Capping Material Containing Portland Cement.

    Science.gov (United States)

    Portella, Fernando Freitas; Collares, Fabrício Mezzomo; Santos, Paula Dapper; Sartori, Cláudia; Wegner, Everton; Leitune, Vicente Castelo Branco; Samuel, Susana Maria Werner

    2015-01-01

    The purpose of this study was to evaluate the water sorption, solubility, pH and ability to diffuse into dentin of a glycerol salicylate-based, pulp-capping cement in comparison to a conventional calcium hydroxide-based pulp capping material (Hydcal). An experimental cement was developed containing 60% glycerol salicylate resin, 10% methyl salicylate, 25% calcium hydroxide and 5% Portland cement. Water sorption and solubility were determined based on mass changes in the samples before and after the immersion in distilled water for 7 days. Material discs were stored in distilled water for 24 h, 7 days and 28 days, and a digital pHmeter was used to measure the pH of water. The cement's ability to diffuse into bovine dentin was assessed by Raman spectroscopy. The glycerol salicylate-based cement presented higher water sorption and lower solubility than Hydcal. The pH of water used to store the samples increased for both cements, reaching 12.59 ± 0.06 and 12.54 ± 0.05 after 7 days, for Hydcal and glycerol salicylate-based cements, respectively. Both cements were able to turn alkaline the medium at 24 h and sustain its alkalinity after 28 days. Hydcal exhibited an intense diffusion into dentin up to 40 µm deep, and the glycerol salicylate-based cement penetrated 20 µm. The experimental glycerol salicylate-based cement presents good sorption, solubility, ability to alkalize the surrounding tissues and diffusion into dentin to be used as pulp capping material.

  10. Long-term modeling of glass waste in portland cement- and clay-based matrices

    Energy Technology Data Exchange (ETDEWEB)

    Stockman, H.W.; Nagy, K.L. [Sandia National Labs., Albuquerque, NM (United States); Morris, C.E. [Wollongong Univ., NSW (Australia). Dept. of Civil and Mining Engineering

    1995-12-01

    A set of ``templates`` was developed for modeling waste glass interactions with cement-based and clay-based matrices. The templates consist of a modified thermodynamic database, and input files for the EQ3/6 reaction path code, containing embedded rate models and compositions for waste glass, cement, and several pozzolanic materials. Significant modifications were made in the thermodynamic data for Th, Pb, Ra, Ba, cement phases, and aqueous silica species. It was found that the cement-containing matrices could increase glass corrosion rates by several orders of magnitude (over matrixless or clay matrix systems), but they also offered the lowest overall solubility for Pb, Ra, Th and U. Addition of pozzolans to cement decreased calculated glass corrosion rates by up to a factor of 30. It is shown that with current modeling capabilities, the ``affinity effect`` cannot be trusted to passivate glass if nuclei are available for precipitation of secondary phases that reduce silica activity.

  11. Development of Mechanistic-Empirical Pavement Design for Tropical Climate Using Cement-Treated Base Layer

    OpenAIRE

    Aderinola, O.S

    2016-01-01

    A mechanistic-empirical pavement design method is developed characterising cement-treated base layers for pavement design in Nigeria or other similar tropical and subtropical countries. Asphalt Concrete surface, Subbase and Aggregate base were characterised based on back calculation data from Claros et al (1986) while cement-treated base layer was based on modulus tests that had been conducted by past researchers. Failure criteria for the Asphalt Concrete fatigue failure and the s...

  12. Comparison of the fixation effects of heavy metals by cement rotary kiln co-processing and cement based solidification/stabilization.

    Science.gov (United States)

    Zhang, Junli; Liu, Jianguo; Li, Cheng; Jin, Yiying; Nie, Yongfeng; Li, Jinhui

    2009-06-15

    Cement rotary kiln co-processing of hazardous wastes and cement based solidification/stabilization could both immobilize heavy metals. The different retention mechanisms of the two technologies lead to different fixation effects of heavy metals. The same amount of heavy metal compounds were treated by the two types of fixation technologies. Long-term leaching test (160 days), the maximum availability leaching test (NEN 7341) and a modified three-step sequential extraction procedure, proposed by the Commission of the European Communities Bureau of Reference (BCR) were employed to compare the fixation effects of the two fixation technologies. The leaching concentrations in NEN 7341 and long-term leaching tests were compared with identification standard for hazardous wastes (GB5085.3-1996) and drinking water standard (GB5749-2005). The results indicate that the leaching concentrations of the long-term leaching test and NEN 7341 test were lower than the regulatory limits and the leached ratios were small. Both cement based solidification/stabilization and cement rotary kiln co-processing could effectively fix heavy metals. Calcination in a cement rotary kiln and the following hydration that follows during cement application could fix As, Cd, Pb and Zn more effectively and decrease the release to the environment. Cement solidification/stabilization technology has better effect in immobilizing Cr and Ni. Cr wastes are more fitful to be treated by cement solidification/stabilization.

  13. Microstructure and mechanical properties of WC-Ni-Al based cemented carbides developed for engineering applications

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Edmilson O.; Santos, Julio N. [Universidade Federal de Itajuba, Minas Gerais (Brazil). Inst. de Engenharia Mecanica; Klein, Aloisio N. [Universidade Federal de Santa Catarina, Florianopolis (Brazil). Dept. de Engenharia de Materiais

    2011-11-15

    In this paper the influence of the Ni binder metal and Al as an additional alloying element on the microstructure and mechanical properties of WC-based cemented carbides processed by conventional powder metallurgy was studied. Microstructural examinations of the cemented carbides with 3 and 5 wt.% of Al in the binder metal indicated the presence of a very low and evenly distributed porosity as well as the presence of islands of metal binder in the microstructure. With the cemented carbide with 7 wt.% of Al in the metal binder, the presence of brittle needle-like regions was observed. The WC particles inside these regions were rounded and had a larger mean free path. Vickers hardness and flexural strength tests indicated that the cemented carbide WC-Ni - Al with addition of 5 wt.% of Al in the binder metal presented bulk hardness similar to the conventional WC-Co cemented carbides as well as superior flexure strength and fracture toughness. (orig.)

  14. Novel phosphate-based cements for clinical applications

    OpenAIRE

    2012-01-01

    This Thesis aims at the development of two novel families of inorganic phosphate cements with suitable characteristics for clinical applications in hard tissue regeneration or replacement. It is organized in two distinct parts. The first part focuses at the development of silicon-doped a-tricalcium phosphate and the subsequent preparation of a silicon-doped calcium phosphate cement for bone regeneration applications. For this purpose, silicon-doped a-tricalcium phosphate was synthesized b...

  15. Cellulose Associated with Pet Bottle Waste in Cement Based Composites

    OpenAIRE

    Farrapo,Camila Laís; Fonseca,Camila Soares; Pereira,Tamires Galvão Tavares; Tonoli,Gustavo Henrique Denzin; Savastano Junior,Holmer; Mendes, Rafael Farinassi

    2017-01-01

    The present study was to evaluate the effect of polyethylene terephthalate (PET) particle sizes on the mechanical and physical properties of extruded fiber-cement composites with different particle sizes combined to cellulose pulp in the production of fiber cement by the extrusion process. The design consisted of four formulations, one composed of 5% cellulose and the other three with 2.5% cellulosic pulp and 2.5% of PET particles with different particle sizes. Physical, mechanical and micros...

  16. An ongoing investigation on modeling the strength properties of water-entrained cement-based materials

    DEFF Research Database (Denmark)

    Esteves, L.P.

    2012-01-01

    Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...

  17. Summary report on the development of a cement-based formula to immobilize Hanford facility waste

    Energy Technology Data Exchange (ETDEWEB)

    Gilliam, T.M.; McDaniel, E.W.; Dole, L.R.; Friedman, H.A.; Loflin, J.A.; Mattus, A.J.; Morgan, I.L.; Tallent, O.K.; West, G.A.

    1987-09-01

    This report recommends a cement-based grout formula to immobilize Hanford Facility Waste in the Transportable Grout Facility (TGF). Supporting data confirming compliance with all TGF performance criteria are presented. 9 refs., 24 figs., 50 tabs.

  18. Properties and interfacial microstructure of cement-based materials with composite micro-grains

    Institute of Scientific and Technical Information of China (English)

    FENG Qi; BA Heng-jing; LIU Jun-zhe

    2005-01-01

    Silica fume, fly ash and nano-fiber mineral materials (NR powder) are employed to incorporate into cement-based materials. According to the grain grading mathematical model of cement-based materials, two packing systems, namely, spherical grading system and nano-fiber reinforced system were designed. Properties and interfacial microstructure of the two systems were studied according to secondary interface theory. It was shown that nano-fiber mineral materials can improve the grain grading of the admixture, increase the density of the system, improve the microstructure of the interface and the hardened paste, and enhance the uniformity of cement-based materials mixed with composite micro-grains and greatly increase their wearable rigidity and flexure strength. In this paper, two kinds of interface models, including spherical grain model and nano-fiber reinforced interface model of the cement-based materials mixed with composite micro-grains, were brought forward.

  19. Fish freshness rapid detection based on fish-eye image

    Science.gov (United States)

    Wang, Feng; Zang, Yue; Wo, Qiqi; Zou, Chen; Wang, Nan; Wang, Xiaobo; Li, Dadong

    Study a new method for detecting fish freshness. During the experiment, we choose freshest fish-eyes images via digital camera to add computing the synthesis of the latest fish-eye image .Next figure out every image's signal strength. Finally, we analysis relation between the change of the image's energy and the value (pH, electrical conductivity, TVBN) by Modeling of Partial Least Squares Regression. The result shows that we can detect freshness of fish quickly, conveniently, simply and accurately through the fish-eye image energy change.

  20. Properties and Mechanism of CFBC Fly Ash-cement based Stabilizers for Lake Sludge

    Institute of Scientific and Technical Information of China (English)

    TANG Hua; LIXiangguo; LI Menglei; SONG Liuqing; WU Zhenjun; XU Haixing

    2012-01-01

    Circulating fluidized bed combustion (CFBC) fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge.In order to understand the influences of stabilizers on the lake sludge properties,tests unconfined compressive strength,water stability and SEM observation were performed.The experimental results show that with the increase of the curing time,the strength of all the stabilized specimens increase,especially the samples containing cement.The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio,the optimum ratio between CFBC fly ash and cement is 2:3.The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime.Moreover,the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products,i e,C-S-H gel and the AFt crystal,which act as benders to solidify those particles together and fill in the packing void of the aggregates.

  1. Sorption of radionuclides by cement-based barrier materials

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kefei, E-mail: likefei@tsinghua.edu.cn; Pang, Xiaoyun

    2014-11-15

    This paper investigates the sorption of radionuclide ions, {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+}, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+} sorptions must be weak; (2) the sorption kinetics is rapid and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C–A–S–H hydrates and the measured K{sub d} values can be predicted from C–S–H sorption data with Ca/Si ratio equal to Ca/(Si + Al) ratio.

  2. MACHINING OF NICKEL BASED ALLOYS USING DIFFERENT CEMENTED CARBIDE TOOLS

    Directory of Open Access Journals (Sweden)

    BASIM A. KHIDHIR

    2010-09-01

    Full Text Available This paper presents the results of experimental work in dry turning of nickel based alloys (Haynes – 276 using Deferent tool geometer of cemented carbide tools. The turning tests were conducted at three different cutting speeds (112, 152, 201and 269 m/min while feed rate and depth of cut were kept constant at 0.2 mm/rev and 1.5 mm, respectively. The tool holders used were SCLCR with insert CCMT-12 and CCLNR – M12-4 with insert CNGN-12. The influence of cutting speed, tool inserts type and workpiece material was investigated on the machined surface roughness. The worn parts of the cutting tools were also examined under scanning electron microscope (SEM. The results showed that cutting speed significantly affected the machined surface finish values in related with the tool insert geometry. Insert type CCMT-12 showed better surface finish for cutting speed to 201 m/min, while insert type CNGN-12 surface roughness increased dramatically with increasing of speed to a limit completely damage of insert geometer beyond 152 m/min.

  3. Dry mixtures based on aluminate cements for self-leveling floors

    Directory of Open Access Journals (Sweden)

    Kaddo Maria

    2017-01-01

    Full Text Available In this study the results of the structure, shrinkage and physical and mechanical properties of concrete obtained from dry mixes on the base of aluminate cements for self-leveling floors are presented. Principle possibility of obtaining unshrinkable concretes with the formation of ettringite using aluminate cement, gypsum and modern superplasticizers. Studies of free shrinkage of mixed binder showed that binder can be attribute to binders with compensated shrinkage. Cracking resistance of the composition is provided by the fact that the vast expansion in the initial stage of curing and shrinkage of the final stage is in 5…10 times lower than these values for gypsum and portland cement.

  4. Damping Property of a Cement-Based Material Containing Carbon Nanotube

    Directory of Open Access Journals (Sweden)

    Wei-Wen Li

    2015-01-01

    Full Text Available This study aimed to explore the damping property of a cement-based material with carbon nanotube (CNT. In the study, the cement composites with different contents of CNT (0 wt%, 0.033 wt%, 0.066 wt%, and 0.1 wt% were investigated. Logarithmic Decrement method and Dynamic Mechanical Analysis (DMA method were utilized to study the damping property of CNT/cement composite. The influences of CNT on pore size distribution and microstructure of composite were analyzed by Mercury Intrusion Porosimetry (MIP and Scanning Electron Microscopy (SEM, respectively. The experimental results showed that CNT/cement composite presented higher flexural strength index than that of a pure cement paste. Additional CNT could improve the vibration-reduction capacity of cement paste. Furthermore, the experiments proved that CNT could bridge adjacent hydration products and support load transfer within cement matrix, which contributed to the energy dissipation during the loading process.

  5. Lignin-based cement fluid loss control additive

    Energy Technology Data Exchange (ETDEWEB)

    Schilling, P.

    1990-05-22

    This patent describes a hydraulic cement slurry composition. It comprises: a hydraulic cement, and the following expressed as parts by weight per 100 parts of the hydraulic cement, water from about 25 to 105 parts, and from abut 0.5 to 2.5 parts of a compound selected from the group consisting of a sulfonated lignin and a sulfomethylated lignin, wherein the lignin has been sequentially crosslinked by reacting the lignin with a member of the group consisting of formaldehyde and epichlorohydrin and alkoxylated with between about 2 to about 6 moles of a compound selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide and a combination thereof per 1000 g of the lignin.

  6. THE USE OF SISAL FIBRE AS REINFORCEMENT IN CEMENT BASED COMPOSITES

    Directory of Open Access Journals (Sweden)

    Romildo Dias Tolêdo Filho

    1999-08-01

    Full Text Available ABSTRACT The inclusion of fibre reinforcement in concrete, mortar and cement paste can enhance many of the engineering properties of the basic materials, such as fracture toughness, flexural strength and resistance to fatigue, impact, thermal shock and spalling. In recent years, a great deal of interest has been created worldwide on the potential applications of natural fibre reinforced, cement based composites. Investigations have been carried out in many countries on various mechanical properties, physical performance and durability of cement based matrices reinforced with naturally occurring fibres including sisal, coconut, jute, bamboo and wood fibres. These fibres have always been considered promising as reinforcement of cement based matrices because of their availability, low cost and low consumption of energy. In this review, the general properties of the composites are described in relation to fibre content, length, strength and stiffness. A chronological development of sisal fibre reinforced, cement based matrices is reported and experimental data are provided to illustrate the performance of sisal fibre reinforced cement composites. A brief description on the use of these composite materials as building products has been included. The influence of sisal fibres on the development of plastic shrinkage in the pre-hardened state, on tensile, compressive and bending strength in the hardened state of mortar mixes is discussed. Creep and drying shrinkage of the composites and the durability of natural fibres in cement based matrices are of particular interest and are also highlighted. The results show that the composites reinforced with sisal fibres are reliable materials to be used in practice for the production of structural elements to be used in rural and civil construction. This material could be a substitute asbestos-cement composite, which is a serious hazard to human and animal health and is prohibited in industrialized countries. The

  7. Spectroscopic and microscopic characterization of portland cement based unleached and leached solidified waste

    Science.gov (United States)

    Salaita, Ghaleb N.; Tate, Philip H.

    1998-05-01

    In this study, portland cement based solidified/stabilized (S/S) waste and a cement-only control were studied before and after leaching. The solidified waste samples were prepared from a mix of organic-containing industrial waste sludge and portland cement. Toxicity characterization leaching procedure (TCLP) was the leaching test employed. The samples were studied using multi-surface analytical techniques including XPS, SIMS, XRD, FE-SEM and EDS. The data obtained from the various techniques show that leaching does not measurably affect the morphology or composition of the solidified waste sample. However, subtle changes in the composition of the cement control sample were observed. While the concentration of the elements observed on the surface of leached and unleached waste samples by XPS are very similar (except for Mg, Na and N), study of the corresponding cement samples exhibit differences in the level of C, Si, S, and Ca. The unleached cement sample shows lower levels of C and Si, but higher levels of O, S, Ca and Mg, indicating that leaching alters the cement sample. EDS analyses of the elemental composition of the bulk of the leached and unleached waste samples are similar, and also are similar for the leached and unleached cement samples, indicating that under the conditions of the TCLP test, leaching has no effect on the bulk. The high level of Ca present on the surface of the solidified waste indicates entrapment of the waste by the cement. The information and results obtained show that the surface analytical techniques used in this work, when combined with environmental wet methods, can provide a more complete picture of the concentration, chemical state and immobility of solidified waste.

  8. Piezoresistive Response Extraction for Smart Cement-based Composites/Sensors

    Institute of Scientific and Technical Information of China (English)

    HAN Baoguo; QIAO Guofu; JIANG Haifeng

    2012-01-01

    A kind of piezoresistive response extraction method for smart cement-based composites/sensors was proposed.Two kinds of typical piezoresistive cement-based composites/sensors were fabricated by respectively adding carbon nanotubes and nickel powders as conductive fillers into cement paste or cement mortar.The variation in measured electrical resistance of such cement-based composites/sensors was explored without loading and under repeated compressive loading and impulsive loading.The experimental results indicate that the measured electrical resistance of piezoresistive cement-based composites/sensors exhibits a two-stage variation trend of fast increase and steady increase with measurement time without loading,and an irreversible increase after loading.This results from polarization caused by ionic conduction in these composites/sensors.After reaching a plateau,the measured electrical resistance can be divided into an electrical resistance part and an electrical capacity part.The piezoresistive responses of electrical resistance part in measured electrical resistance to loading can be extracted by eliminating the linear electrical capacity part in measured electrical resistance.

  9. Comparative Analysis of Selected Physicochemical Properties of Pozzolan Portland and MTA-Based Cements.

    Science.gov (United States)

    Dorileo, Maura Cristiane Gonçales Orçati; Villa, Ricardo Dalla; Guedes, Orlando Aguirre; Aranha, Andreza Maria Fábio; Semenoff-Segundo, Alex; Bandeca, Matheus Coelho; Borges, Alvaro Henrique

    2014-01-01

    Physicochemical properties of pozzolan Portland cement were compared to ProRoot MTA and MTA BIO. To test the pH, the samples were immersed in distilled water for different periods of time. After the pH analysis, the sample was retained in the plastic recipient, and the electrical conductivity of the solution was measured. The solubility and radiopacity properties were evaluated according to specification 57 of the American National Standard Institute/American Dental Association (ANSI/ADA). The statistical analyses were performed using ANOVA and Tukey's test at a 5% level of significance. Pozzolan Portland cement exhibited pH and electrical conductivity mean values similar to those of the MTA-based cements. The solubilities of all tested materials were in accordance with the ANSI/ADA standards. Only the MTA-based cements met the ANSI/ADA recommendations for radiopacity. It might be concluded that the pH and electrical conductivity of pozzolan Portland cement are similar to and comparable to those of MTA-based cements.

  10. Modeling fracture behavior of cement paste based on its microstructure

    NARCIS (Netherlands)

    Qian, Z.; Ye, G.; Schlangen, E.; Van Breugel, K.

    2012-01-01

    Concrete is a composite construction material, which is composed primarily of coarse aggregates, sands and cement paste. The fracture processes in concrete are complicated, because of the multiscale and multiphase nature of the material. In the past decades, comprehensive effort has been put to stud

  11. Early Carbonation Behavior of High-volume Dolomite Powder-cement Based Materials

    Institute of Scientific and Technical Information of China (English)

    YANG Huamei; HE zhen; SHAO Yixin

    2015-01-01

    Combined with DTG analysis, X-Ray diffraction analysis (XRD) andfi eld emission scanning electron microscopy analysis (FSEM) affi liated with energy dispersive spectrometer analysis (EDS), the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio (0.15) was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refi nement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation of nanometer CaCO3 skeleton network at early age.

  12. Temperature prediction and analysis based on BP and Elman neural network for cement rotary kiln

    Science.gov (United States)

    Yang, Baosheng; Ma, Xiushui

    2011-05-01

    In order to reduce energy consumption and improve the stability of cement burning system production, it is necessary to conduct in-depth analysis of the cement burning system, control the operation state and law of the system. In view of the rotary kiln consumes most of the fuel, we establish the simulation model of the cement kiln used to find effective control methods. It is difficult to construct mathematical model for the rotary cement kiln as the complex parameters, so we expressed directly using neural network method to establish the simulation model for the kiln. Choosing reasonable state and control variables and collecting actual operation data to train neural network weights. We first in-depth analyze mechanism and working parameters correlation to determine factors of the yield and quality as the model input variables; then constructed cement kiln model based on BP and Elman network, both achieved good fitting results. Elman network model has a faster convergence speed, high precision and good generalization ability. So the Elman network based model can be used as simulation model of the cement rotary kiln for exploring new control method.

  13. Dimensional stability of materials based on Portland cement at the early stages

    Science.gov (United States)

    Mesa Yandy, Angélica; Zerbino, Raúl L.; Giaccio, Graciela M.; Russo, Nélida A.; Duchowicz, Ricardo

    2014-09-01

    In this work two fiber optic sensing techniques are used to study the dimensional stability in fresh state of different cementitious materials. A conventional Portland cement mortar and two commercial grouts were selected. The measurements were performed by using a Bragg grating embedded in the material and a non-contact Fizeau interferometer. The first technique was applied in a horizontal sample scheme, and the second one, by using a vertical configuration. In addition, a mechanical length comparator was used in the first case in order to compare the results. The evolution with time of the dimensional changes of the samples and the analysis of the observed behavior are included.

  14. Durability Index Performance of High Strength Concretes Made Based on Different Standard Portland Cements

    Directory of Open Access Journals (Sweden)

    Stephen O. Ekolu

    2012-01-01

    Full Text Available A consortium of three durability index test methods consisting of oxygen permeability, sorptivity and chloride conductivity were used to evaluate the potential influence of four (4 common SANS 10197 cements on strength and durability of concrete. Twenty four (24 concrete mixtures of water-cement ratios (w/c's = 0.4, 0.5, 0.65 were cast using the cement types CEM I 42.5N, CEM II/A-M (V-L 42.5N, CEM IV/B 32.5R and CEM II/A-V 52.5N. The concretes investigated fall in the range of normal strength, medium strength and high strength concretes. It was found that the marked differences in oxygen permeability and sorptivity results observed at normal and medium strengths tended to vanish at high concrete strengths. Also, the durability effects attributed to use of different cement types appear to diminish at high strengths. Cements of low strength and/or that contained no extenders (CEM 32.5R, CEM I 42.5N showed greater sensitivity to sorptivity, relative to other cement types. Results also show that while concrete resistance to chlorides generally improves with increase in strength, adequately high chloride resistance may not be achieved based on high strength alone, and appropriate incorporation of extenders may be necessary.

  15. Pulp response to a novel adhesive calcium hydroxide based cement.

    Science.gov (United States)

    Watts, A; Paterson, R C; Cohen, B D; Combe, E C

    1994-09-01

    This study compares pulp responses to 3 formulations of calcium hydroxide, namely: a) An experimental adhesive calcium hydroxide cement containing polyacrylic acid, b) Dycal (L.D> Caulk Co, Milford, Delaware) Batch Nos 176970/176990, c) "Analar" calcium hydroxide mixed with sterile distilled water. After 28 days dentine bridges were present in 77% of teeth capped with the test material, 64% of teeth treated with Dycal and in 62% of teeth capped with calcium hydroxide and water. Inflammatory infiltrates were observed in a number of teeth remote from the bridges. Bacteria were detected in these specimens. Exposed rat molar pulp responses to an experimental adhesive calcium hydroxide cement were similar to to those observed with 2 other calcium hydroxide formulations.

  16. Thermal Properties of Cement-Based Composites for Geothermal Energy Applications

    Directory of Open Access Journals (Sweden)

    Xiaohua Bao

    2017-04-01

    Full Text Available Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural–functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs. Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles.

  17. Influence of silica-based hybrid material on the gas permeability of hardened cement paste

    Science.gov (United States)

    Li, R.; Hou, P.; Xie, N.; Zhou, Z.; Cheng, X.

    2017-03-01

    Surface treatment is one of the most effective ways to elongate the service life of concrete. The surface treatment agents, including organic and inorganic types, have been intensively studied. In this paper, the silica-based hybrid nanocomposite, which take advantages of both organic and inorganic treatment agents, was synthesized and used for surface treatment of hardened cement-based material. The effectiveness of organic and inorganic hybrid nanocomposite was evaluated through investigations on the gas permeability of cement-based materials. The results showed that SiO2/PMHS hybrid nanocomposite can greatly decrease the gas transport properties of hardened cement-based materials and has a great potential for surface treatment of cementitious materials.

  18. Online Monitoring Volume Deformation of Cement-based Materials in Multiple Enviroments

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Comparing and analyzing some volume deformation measuring means for cement-based materials at home and abroad, a continuous online monitor of cement-based material volume deformation in multiple environments is developed. The device is designed based on the environmental simulation technology, micro-distance measuring technology of laser and eddy current, and transmission agent online monitoring the deformation of multi-group samples. This device can be used widely, such as glass, ceramics, walling material, and so on, with high precision, low testing cost, and intellectualization.

  19. Attack of Limestone Cement-based Material Exposed to Magnesium Sulfate Solution at Low Temperature

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fengchen; WU Shengxing; FANG Yonghao; ZHOU Jikai; LI Zhonghua

    2014-01-01

    Limestone in cement could be a source of CO32-needed for thaumasite formation which will result in thaumasite form of sulfate attack (TSA) probably. TSA has more deterioration than ettringite or gypsum form of sulfate attack because it targets the calcium silicate hydrates (C-S-H) which is the main binder phase in all Portland cement-based materials. By means of physical and mechanical property testing as well as erosion phases analysis, magnesium sulfate attack of cement-based material containing 35% limestone powder by mass at 5 ± 2℃is investigated. The compressive strength and flexural strength of mortar specimen immersed in MgSO4 solution increase firstly, then decrease rapidly with the immersing age. Relative dynamic elastic modulus of mortar specimen changes in a phased process. After immersing in MgSO4 solution for 15 weeks, the main erosion phases in paste specimen change from four phases compounds, three phases compounds to two phases compounds from surface to inside. Deterioration course of limestone cement-based material exposed to magnesium sulfate aggressive environment appears progressive damage layer by layer, and every layer probably suffers four stages, which are property strengthening stage, initial degradation stage, thaumasite formation stage and cementation loss stage, respectively.

  20. RECYCLED WASTE-BASED CEMENT COMPOSITE PATCH MATERIALS FOR RAPID/PERMANENT ROAD RESTORATION.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2001-07-31

    Over the past year, KeySpan Energy sponsored a research program at Brookhaven National Laboratory (BNL) aimed at recycling boiler ash (BA) and waste water treatment sludge (WWTS) byproducts generated from Keyspan's power stations into potentially useful materials, and at reducing concurrent costs for their disposal. Also, KeySpan has an interest in developing strategies to explicitly integrate industrial ecology and green chemistry. From our collaborative efforts with Keyspan (Diane Blankenhom Project Manager, and Kenneth Yager), we succeeded in recycling them into two viable products; Pb-exchange adsorbents (PEAs), and high-performance cements (HpCs). These products were made from chemically bonded cement and ceramic (CBC) materials that were synthesized through two-step chemical reaction pathways, acid-base and hydration. Using this synthesis technology, both the WWTS and BA served in acting as solid base reactants, and sodium polyphosphate, [-(-NaPO{sub 3}-)-{sub n}], known as an intermediator of fertilizer, was employed as the acid solution reactant. In addition, two commercial cement additives, Secar No. 51 calcium aluminate cement (CAC) and Type I calcium silicate cement (CSC), were used to improve mechanical behavior and to promote the rate of acid-base reaction of the CBC materials.

  1. Novel bioactive composite bone cements based on the beta-tricalcium phosphate-monocalcium phosphate monohydrate composite cement system.

    Science.gov (United States)

    Huan, Zhiguang; Chang, Jiang

    2009-05-01

    Bioactive composite bone cements were obtained by incorporation of tricalcium silicate (Ca3SiO5, C3S) into a brushite bone cement composed of beta-tricalcium phosphate [beta-Ca3(PO4)2, beta-TCP] and monocalcium phosphate monohydrate [Ca(H2PO4)2.H2O, MCPM], and the properties of the new cements were studied and compared with pure brushite cement. The results indicated that the injectability, setting time and short- and long-term mechanical strength of the material are higher than those of pure brushite cement, and the compressive strength of the TCP/MCPM/C3S composite paste increased with increasing aging time. Moreover, the TCP/MCPM/C3S specimens showed significantly improved in vitro bioactivity in simulated body fluid and similar degradability in phosphate-buffered saline as compared with brushite cement. Additionally, the reacted TCP/MCPM/C3S paste possesses the ability to stimulate osteoblast proliferation and promote osteoblastic differentiation of the bone marrow stromal cells. The results indicated that the TCP/MCPM/C3S cements may be used as a bioactive material for bone regeneration, and might have significant clinical advantage over the traditional beta-TCP/MCPM brushite cement.

  2. Observation and quantification of water penetration into Strain Hardening Cement-based Composites (SHCC) with multiple cracks by means of neutron radiography

    Science.gov (United States)

    Zhang, P.; Wittmann, F. H.; Zhao, T. J.; Lehmann, E. H.; Tian, L.; Vontobel, P.

    2010-08-01

    Durability of reinforced concrete structures has become a crucial issue with respect to economy, ecology and sustainability. One major reason for durability problems of concrete structures is the limited strain capacity of cement-based materials under imposed tensile stress. By adding PVA fibers, a new material named Strain Hardening Cement-based Composites (SHCC) with high strain capacity can be produced. Due to the formation of multiple micro-cracks, wide cracks can be avoided in SHCC under an imposed strain. The high strain capacity, however, is beneficial with respect to durability only if the multi-crack formation in SHCC does not lead to significantly increased water penetration. If water and aggressive chemical compounds such as chlorides and sulfates dissolved in water penetrate into the cement-based matrix and reach the steel reinforcement service-life of reinforced concrete structures will be reduced significantly. In this project, neutron radiography was applied to observe and quantify the process of water penetration into uncracked SHCC and after the multi-crack formation. In addition, water penetration into integral water repellent cracked and uncracked SHCC, which has been produced by adding a silane-based water repellent agent to the fresh SHCC mortar has been investigated. Results will be discussed with respect to durability.

  3. Observation and quantification of water penetration into Strain Hardening Cement-based Composites (SHCC) with multiple cracks by means of neutron radiography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, P. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Wittmann, F.H., E-mail: wittmann@aedificat.d [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Aedificat Institute Freiburg, D-79100 Freiburg (Germany); Zhao, T.J. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Lehmann, E.H. [Department of Spallation Neutron Source (ASQ), Paul Scherrer Institute (PSI), CH-5232 Villigen (Switzerland); Tian, L. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Vontobel, P. [Department of Spallation Neutron Source (ASQ), Paul Scherrer Institute (PSI), CH-5232 Villigen (Switzerland)

    2010-08-21

    Durability of reinforced concrete structures has become a crucial issue with respect to economy, ecology and sustainability. One major reason for durability problems of concrete structures is the limited strain capacity of cement-based materials under imposed tensile stress. By adding PVA fibers, a new material named Strain Hardening Cement-based Composites (SHCC) with high strain capacity can be produced. Due to the formation of multiple micro-cracks, wide cracks can be avoided in SHCC under an imposed strain. The high strain capacity, however, is beneficial with respect to durability only if the multi-crack formation in SHCC does not lead to significantly increased water penetration. If water and aggressive chemical compounds such as chlorides and sulfates dissolved in water penetrate into the cement-based matrix and reach the steel reinforcement service-life of reinforced concrete structures will be reduced significantly. In this project, neutron radiography was applied to observe and quantify the process of water penetration into uncracked SHCC and after the multi-crack formation. In addition, water penetration into integral water repellent cracked and uncracked SHCC, which has been produced by adding a silane-based water repellent agent to the fresh SHCC mortar has been investigated. Results will be discussed with respect to durability.

  4. Long-term Durability of Cement-based Materials with Very Low w/b

    Institute of Scientific and Technical Information of China (English)

    XIE Youjun; LIU Yunhua; LONG Guangeheng

    2008-01-01

    To investigate the durability, especially the long-term stability of cement-based materials with very low w/b, the air permeability test, carbonation test, capillary absorption rate test and dilation Dotential test were adopted under long-term heat treatment condition. Microstructure of these materials is also analyzed by scannmg electronic microscopy (SEM) and mercury intrusion porosimeter (MIP) in order to further unveil its mechanism and interrelation between microstructure and its properties. The results indicate that in the area investigated, cement-based material with w/b 0.17, like RPC, possesses low porosity and excellent durability. Moreover, its porosity will further decrease under long-term heat treatment compared with normal heat treatment. Its long-term durability is much superior to that of other cement-based materials with w/b 0.25 or 0.35 as high strength concrete (HSC).

  5. An ongoing investigation on modeling the strength properties of water-entrained cement-based materials

    DEFF Research Database (Denmark)

    Esteves, L.P.

    2012-01-01

    -based materials. Beyond the discussion of whether or not the introduction of superabsorbent polymers leads to a strength reduction, this paper uses both experimental and theoretical background to separate the effect of SAP in both pore structure and internal relative humidity and the effect from the active......Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...

  6. Evolution of cement based materials in a repository for radioactive waste and their chemical barrier function

    Energy Technology Data Exchange (ETDEWEB)

    Kienzler, Bernhard; Metz, Volker; Schlieker, Martina; Bohnert, Elke [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. fuer Nukleare Entsorgung (INE)

    2015-07-01

    The use of cementitious materials in nuclear waste management is quite widespread. It covers the solidification of low/intermediate-level liquid as well as solid wastes (e.g. laboratory wastes) and serves as shielding. For both high-level and intermediate-low level activity repositories, cement/concrete likewise plays an important role. It is used as construction material for underground and surface disposals, but more importantly it serves as barrier or sealing material. For the requirements of waste conditioning, special cement mixtures have been developed. These include special mixtures for the solidification of evaporator concentrates, borate binding additives and for spilling solid wastes. In recent years, low-pH cements were strongly discussed especially for repository applications, e.g. (Celine CAU DIT COUMES 2008; Garcia-Sineriz, et al. 2008). Examples for relevant systems are Calcium Silicate Cements (ordinary Portland cement (OPC) based) or Calcium Aluminates Cements (CAC). Low-pH pore solutions are achieved by reduction of the portlandite content by partial substitution of OPC by mineral admixtures with high silica content. The blends follow the pozzolanic reaction consuming Ca(OH){sub 2}. Potential admixtures are silica fume (SF) and fly ashes (FA). In these mixtures, super plasticizers are required, consisting of polycarboxilate or naphthalene formaldehyde as well as various accelerating admixtures (Garcia-Sineriz, et al. 2008). The pH regime of concrete/cement materials may stabilize radionuclides in solution. Newly formed alteration products retain or release radionuclides. An important degradation product of celluloses in cement is iso-saccharin acid. According to Glaus 2004 (Glaus and van Loon 2004), it reacts with radionuclides forming dissolved complexes. Apart from potentially impacting radionuclide solubility limitations, concrete additives, radionuclides or other strong complexants compete for surface sites for sorbing onto cement phases. In

  7. Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede; Hansen, Kurt Kielsgaard

    2001-01-01

    The influence of cement particle-size distribution on autogenous strains and stresses in cement pastes of identical water-to-cement ratios is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage, to quantify degree of hydration; internal...... relative humidity development; autogenous deformation; and eigenstress development, using a novel embedded spherical stress sensor. Because the latter three measurements are conducted under sealed conditions, whereas chemical-shrinkage measurements are made under "saturated" conditions, the National...... controls the initial pore-size distribution of the cement paste, which, in turn, regulates the magnitude of the induced autogenous shrinkage stresses produced by the water/air menisci in the air-filled pores formed throughout the hydration process. The experimental results indicate that a small autogenous...

  8. Influence of frost damage and sample preconditioning on the porosity characterization of cement based materials using low temperature calorimetry

    DEFF Research Database (Denmark)

    Wu, Min; Fridh, Katja; Johannesson, Björn

    2015-01-01

    Low temperature calorimetry (LTC) can be used to study the meso-porosity of cement based materials. The influence of frost damage on the meso-porosity determination by LTC was explored on a model material MCM-41 and two cement pastes by conducting repeated cycles of freezing and melting measureme......Low temperature calorimetry (LTC) can be used to study the meso-porosity of cement based materials. The influence of frost damage on the meso-porosity determination by LTC was explored on a model material MCM-41 and two cement pastes by conducting repeated cycles of freezing and melting...

  9. Characterization of composite materials based on cement-ceramic powder blended binder

    Science.gov (United States)

    Kulovaná, Tereza; Pavlík, Zbyšek

    2016-06-01

    Characterization of newly developed composite mortars with incorporated ceramic powder coming from precise brick cutting as partial Portland cement replacement up to 40 mass% is presented in the paper. Fine ceramic powder belongs to the pozzolanic materials. Utilization of pozzolanic materials is accompanied by lower request on energy needed for Portland clinker production which generally results in lower production costs of blended binder and lower CO2 emission. In this paper, the ceramic powder is used in cement based mortar composition in amount of 8, 16, 24, 32, and 40 mass% of cement. Chemical composition of ceramic powder is analyzed by X-Ray Fluorescence and X-Ray Diffraction. The particle size distribution of ceramics is accessed on laser diffraction principle. For 28 days cured mortar samples, basic physical and mechanical properties are experimentally determined. The obtained results demonstrate that ceramic powder has potential to replace a part of Portland cement in composition of cement based composites and to reduce negative environmental impact of their production.

  10. Investigation of the physical properties of tricalcium silicate cement-based root-end filling materials.

    Science.gov (United States)

    Grech, L; Mallia, B; Camilleri, J

    2013-02-01

    Tricalcium silicate-based cements have been displayed as suitable root-end filling materials. The physical properties of prototype radiopacified tricalcium silicate cement, Bioaggregate and Biodentine were investigated. Intermediate restorative material was used as a control. The physical properties of a prototype zirconium oxide replaced tricalcium silicate cement and two proprietary cements composed of tricalcium silicate namely Bioaggregate and Biodentine were investigated. Intermediate restorative material (IRM) was used as a control. Radiopacity assessment was undertaken and expressed in thickness of aluminum. In addition the anti-washout resistance was investigated using a novel basket-drop method and the fluid uptake, sorption and solubility were investigated using a gravimetric method. The setting time was assessed using an indentation technique and compressive strength and micro-hardness of the test materials were investigated. All the testing was performed with the test materials immersed in Hank's balanced salt solution. All the materials tested had a radiopacity value higher than 3mm thickness of aluminum. IRM exhibited the highest radiopacity. Biodentine demonstrated a high washout, low fluid uptake and sorption values, low setting time and superior mechanical properties. The fluid uptake and setting time was the highest for Bioaggregate. The addition of admixtures to tricalcium silicate-based cements affects the physical properties of the materials. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes

    Science.gov (United States)

    Yang, Mei; Guo, Zhixing; Qi, Kaifeng; Huang, Kun; Deng, Jianxiong; Liu, Jia

    2016-12-01

    TiC-based coating is prepared by depositing TiO2 sol on cemented carbide compact and liquid phase sintering. TiC forms due to carbothermal reduction reaction of TiO2 and then reacts with WC and transforms to TiC-based solid solution. Ti content changes the WC growth mechanism and results in the multi-stepped morphology. When sintered cemented carbide is used as substrate, WC keeps the equilibrium truncated triangle prism morphology due to the relatively weak diffusion among Ti, WC, and Co.

  12. Electrical Response of Cement-Based Piezoelectric Ceramic Composites under Mechanical Loadings

    Directory of Open Access Journals (Sweden)

    Biqin Dong

    2011-01-01

    Full Text Available Electrical responses of cement-based piezoelectric ceramic composites under mechanical loadings are studied. A simple high order model is presented to explain the nonlinear phenomena, which is found in the electrical response of the composites under large mechanical loadings. For general situation, this nonlinear piezoelectric effect is quite small, and the composite is suitable for dynamic mechanical sensor as holding high static stability. The experimental results are consistent with the relationship quite well. The study shows that cement-based piezoelectric composite is suitable for potential application as dynamic mechanical sensor with excellent dynamic response and high static stability.

  13. Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes

    Science.gov (United States)

    Yang, Mei; Guo, Zhixing; Qi, Kaifeng; Huang, Kun; Deng, Jianxiong; Liu, Jia

    2017-02-01

    TiC-based coating is prepared by depositing TiO2 sol on cemented carbide compact and liquid phase sintering. TiC forms due to carbothermal reduction reaction of TiO2 and then reacts with WC and transforms to TiC-based solid solution. Ti content changes the WC growth mechanism and results in the multi-stepped morphology. When sintered cemented carbide is used as substrate, WC keeps the equilibrium truncated triangle prism morphology due to the relatively weak diffusion among Ti, WC, and Co.

  14. Properties of Cement-based Composite Materials under Different Storing Environment Temperature

    Science.gov (United States)

    Weng, T. L.; Weng, S. H.; Cho, S. W.

    2017-02-01

    This study reports on the properties of cement-based composite materials (mortars) under different storing environment temperature, as determined using the accelerated chloride migration test (ACMT). Mortars with a water/cement ratio of 0.45 and five fine aggregate volume fractions (0%, 15%, 30%, 50% and 60%) under various environment temperatures (25, 40, 60 and 80°C) were evaluated according to the passage of chloride ions through the specimens using ACMT. Calculate chloride migration coefficients on the steady-state. Cement-based composite materials with 60 % fine aggregate presented a migration coefficient higher than that of other specimens, whereas mortar with 30 % fine aggregate was lower, due to the effects of dilution and tortuosity.

  15. Microcrack Identification in Cement-Based Materials Using Nonlinear Acoustic Waves

    Science.gov (United States)

    Chen, X. J.; Kim, J.-Y.; Qu, J.; Kurtis, K. E.; Wu, S. C.; Jacobs, L. J.

    2007-03-01

    This paper presents results from tests that use nonlinear acoustic waves to distinguish microcracks in cement-based materials. Portland cement mortar samples prepared with alkali-reactive aggregate were exposed to an aggressive environment to induce cracking were compared to control samples, of the same composition, but which were not exposed to aggressive conditions. Two nonlinear ultrasonic methods were used to characterize the samples, with the aim of identifying the time and extent of microcracking; these techniques were a nonlinear acoustical modulation (NAM) method and a harmonic amplitude relation (HAR) method. These nonlinear acoustic results show that both methods can distinguish damaged samples from undamaged ones, demonstrating the potential of nonlinear acoustic waves to provide a quantitative evaluation of the deterioration of cement-based materials.

  16. Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements.

    Science.gov (United States)

    Sener, Isil; Turker, Begum; Valandro, Luiz Felipe; Ozcan, Mutlu

    2014-01-01

    This in vitro study evaluated the marginal gap, cement thickness, and microleakage of glass-ionomer cement (GIC) and phosphate monomer-containing resin cement (MDP-RC) under 2 zirconia crown systems (Cercon and DC-Zirkon). Forty human premolars were prepared for all-ceramic zirconia crowns with a 1 mm circumferential finish line and a 1.5 mm occlusal reduction. The crowns (n = 10 per group) from each zirconia system were randomly divided into 2 groups and cemented either with GIC (Vivaglass CEM) or MDP-RC (Panavia F 2.0) cement. The cemented crowns were thermocycled 5000 times (5°-55°C). The crowns were immersed in 0.5% basic fuchsine dye solution for 24 hours and sectioned buccolingually and mesiodistally. Specimens were examined under optical microscope (100X). Data were analyzed using Student t-test and chi-square tests (α = 0.05). Mean marginal gap values for Cercon (85 ± 11.4 μm) were significantly higher than for DC-Zircon (75.3 ± 13.2 μm) (P = 0.018). The mean cement thickness values of GIC (81.7 ± 13.9 μm) and MDP-RC (78.5 ± 12.5 μm) were not significantly different (P = 0.447). Microleakage scores did not demonstrate significant difference between GIC (P = 0.385) and MDP-RC (P = 0.631) under Cercon or DC-Zircon. Considering the cement thickness values and microleakage scores obtained, both zirconia crown systems could be cemented in combination with either GIC or MDP-RC.

  17. Experimental Calcium Silicate-Based Cement with and without Zirconium Oxide Modulates Fibroblasts Viability.

    Science.gov (United States)

    Slompo, Camila; Peres-Buzalaf, Camila; Gasque, Kellen Cristina da Silva; Damante, Carla Andreotti; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro; de Oliveira, Rodrigo Cardoso

    2015-01-01

    The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (pzirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

  18. CALIBRATIONS BASED ON NEAR INFRARED SPECTROSCOPIC DATA TO ESTIMATE WOOD-CEMENT PANEL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Paulo Ricardo Gherardi Hein

    2009-11-01

    Full Text Available Some scientific contributions have used near infrared (NIR spectroscopy as a rapid and reliable tool for characterizing engineered wood products. However, to our knowledge, there are no published papers that used this technique in order to evaluate wood-cement panels. The main objective of this paper was to evaluate the ability of NIR spectroscopy to estimate physical and mechanical properties in wood-cement panels. The wood-cement panels were produced using Eucalyptus grandis x E. urophylla, Pinus taeda, and Toona ciliata woods with Portland cement under different manufacturing conditions. Wood-cement panels were characterized by traditional methods, and Partial Least Squares regressions were used to build calibrations. Our cross-validated models for MOR, IB, and TS24h of the panels yielded good coefficients of determination (0.80, 0.82, and 0.91, respectively. Based on the significant absorption bands and regression coefficients of the PLS models, our results indicate that cellulose and aromatic groups in lignin are components that play an important role in the calibrations.

  19. A Hybrid Fresh Apple Export Volume Forecasting Model Based on Time Series and Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Lihua Yang

    2015-04-01

    Full Text Available Export volume forecasting of fresh fruits is a complex task due to the large number of factors affecting the demand. In order to guide the fruit growers’ sales, decreasing the cultivating cost and increasing their incomes, a hybrid fresh apple export volume forecasting model is proposed. Using the actual data of fresh apple export volume, the Seasonal Decomposition (SD model of time series and Radial Basis Function (RBF model of artificial neural network are built. The predictive results are compared among the three forecasting model based on the criterion of Mean Absolute Percentage Error (MAPE. The result indicates that the proposed combined forecasting model is effective because it can improve the prediction accuracy of fresh apple export volumes.

  20. Improvement of Water Sensitivity of Macro-defect-free Cement Based Composites with Cross Coupling Agent

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The enhancement of interface bonding between cement and polymer and the structural reticulation of the water-soluble polymer are proposed to minimize the shortening of the mechanical properties of macro-defect-free (MDF) cement based composites at high relative humidity. The MDF composites incorporated with various cross-coupling agents were studied experimentally. The results show that the MDF composites modified with small amounts of cross-coupling agent had raised mechanical properties, but it is more important that the modified MDF composites had a significant increase in water resistance compared to the original one. In the meantime if the water resistant material such as fine powder of α-alumina was used to substitute for the unreacted cement grains in the MDF composites, a more efficient improvement of water resistance would be obtained. The loss in flexural strength of the MDF composites after 90 days of water immersion decreased from 62% before unmodified to 15% after modified.

  1. Modelling Inter-Particle Forces and Resulting Agglomerate Sizes in Cement-Based Materials

    DEFF Research Database (Denmark)

    Kjeldsen, Ane Mette; Geiker, Mette Rica

    2005-01-01

    The theory of inter-particle forces versus external shear in cement-based materials is reviewed. On this basis, calculations on maximum agglomerate size present after the combined action of superplasticizers and shear are carried out. Qualitative experimental results indicate that external shear...... affects the particle size distribution of Mg(OH)2 (used as model material) as well as silica, whereas the addition of superplasticizers affects only the smallest particles in cement and thus primarily acts as water reducers and not dispersers....

  2. Eugenol-based temporary luting cement possesses antioxidative properties

    Directory of Open Access Journals (Sweden)

    Ilić Dragan

    2014-01-01

    Full Text Available Introduction. Antioxidants protect against reactive oxygen species and expose beneficial anti-inflammatory activity when in contact with biological tissues. Dental materials that are used as temporary luting on fixed dental restorations are often in contact with injured gingival tissue, hence they should contain anti-inflammatory characteristics that are essential after prosthetic procedures preceding cementation of final restauration. Objective. The aim of this study was to investigate the antioxidant effect through the oxidation inhibition (OI of mixed dental cement for temporary luting or their liquid component. Methods. Eight study groups were prepared each by ten samples: 1 ex tempore preparation of zinc-oxide eugenol paste (Kariofil Z Galenika, Serbia, 2 Viko Temp paste (Galenika, Serbia, 3 Temp Bond NE paste (Kerr, Germany, 4 ScutaBond (ESPE, Germany, 5 Cp-CAP paste (Germany, Lege Artis and oil component of 6 Kariofil Z, 7 Viko Temp and 8 Cp-CAP. The samples were subjected to spectrophotometer to measure OI 2,2’-azino-di-(3-ethyl-benzthiazoline-6-sulphonic acid (ABTS using Randox kit, United Kingdom. The control samples were pure ascorbic acid (1% w/v. Results. High values of OI exposed materials (groups 1, 5, 6, 7, 8 with content of eugenol (or its derivates in the range of 100-88.8% were statistically more significant than the values of non-eugenol substances (groups 2, 3, 4 with the range of 8.2-43.5%. Conclusion. Eugenol containing temporary fixation materials show significant antioxidative properties and therefore they may be used in those clinical situations where surrounding gingival tissue is injured during restorative procedure. [Projekat Ministarstva nauke Republike Srbije, br. III 45005

  3. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    Science.gov (United States)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-06-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used.

  4. Electrical modelling of carbon nanotube cement-based sensors for structural dynamic monitoring

    Science.gov (United States)

    D'Alessandro, Antonella; Ubertini, Filippo; Materazzi, Annibale Luigi; Porfiri, Maurizio

    2014-06-01

    Some of the authors have recently developed a new nanocomposite cement-based sensor, termed "carbon nanotube cement-based sensor", for applications in vibration-based structural health monitoring of civil structures. The sensor is made of a self-sensing cement paste doped with multi walled carbon nanotubes. The mechanical deformation of this composite material results into a measurable change of its electrical resistance. Previous work was devoted to fabrication, dynamic characterization and to implementation in full-scale structural components. This work addresses electrical modelling of the sensor, and specifically seeks to validate a lumped circuit model for use in dynamic sensing. After a brief overview of carbon nanotube cement-based sensors, the electrical model is presented. Salient parameters of the circuit are identified on sensors with varying electrodes' morphologies. The results indicate that the proposed equivalent circuit model is capable of closely replicating the step response of the sensor to an imposed potential difference. Notably, such linear model is likely to anticipate superharmonic components in the electrical current in the response to sinusoidal mechanical deformations.

  5. Modelling the effect of electrical current flow on the hydration process of cement-based materials

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.; Koenders, E.A.B.

    2014-01-01

    Stray current is essentially an electrical current “leakage” from metal conductors and electrical installations. When it flows through cement-based systems, electrical energy is converted to thermal energy that causes increasing temperature due to Joule heating phenomena. The aim of this paper is to

  6. Improved microstructure of cement-based composites through the addition of rock wool particles

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wei-Ting [Dept. of Civil Engineering, National Ilan University, Ilan 26047, Taiwan (China); Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan 32546, Taiwan (China); Cheng, An, E-mail: ancheng@niu.edu.tw [Dept. of Civil Engineering, National Ilan University, Ilan 26047, Taiwan (China); Huang, Ran; Zou, Si-Yu [Dept. of Harbor and River Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China)

    2013-10-15

    Rock wool is an inorganic fibrous substance produced by steam blasting and cooling molten glass. As with other industrial by-products, rock wool particles can be used as cementitious materials or ultra fine fillers in cement-based composites. This study investigated the microstructure of mortar specimens produced with cement-based composites that include various forms of rock wool particles. It conducted compressive strength testing, rapid chloride penetration tests, X-ray diffraction analysis, thermo-gravimetric analysis, and scanning electronic microscopy to evaluate the macro- and micro-properties of the cement-based composites. Test results indicate that inclusion of rock wool particles in composites improved compressive strength and reduced chloride ion penetration at the age of 91 days due to the reduction of calcium hydroxide content. Microscopic analysis confirms that the use of rock wool particles contributed to the formation of a denser, more compact microstructure within the hardened paste. In addition, X-ray diffraction analysis shows few changes in formation of pozzolanic reaction products and no new hydrations are formed with incorporating rock wool particles. - Highlights: • We report the microstructural characterization of cement-based composites. • Different mixes produced with various rock wool particles have been tested. • The influence of different mixes on macro and micro properties has been discussed. • The macro properties are included compressive strength and permeability. • XRD and SEM observations confirm the pozzolanic reaction in the resulting pastes.

  7. The Integration of EIS parameters and bulk matrix characterization in studying reinforced cement-based materials

    NARCIS (Netherlands)

    Koleva, D.A.; Van Breugel, K.

    2012-01-01

    Corrosion in reinforced concrete is a major and costly concern, arising from the higher complexity of involved phenomena on different levels of material science (e.g. electrochemistry, concrete material science) and material properties (macro/micro/ nano). Reinforced cement-based systems (e.g. reinf

  8. The integration of eis parameters and bulk matrix characteristics in studying reinforced cement-based materials

    NARCIS (Netherlands)

    Koleva, D.A.; Van Breugel, K.

    2011-01-01

    Corrosion in reinforced concrete is a major and costly concern, arising from the higher complexity of involved phenomena on different levels of material science (e.g. electrochemistry, concrete material science) and material properties (macro/micro/ nano). Reinforced cement-based systems (e.g. reinf

  9. Thermophysical properties of cement based composites and their changes after artificial ageing

    Science.gov (United States)

    Šín, Peter; Pavlendová, Gabriela; Lukovičová, Jozefa; Kopčok, Michal

    2017-07-01

    The usage of recycled plastic materials in concrete mix gained increased attention. The behaviour of such environmental friendly material is studied. In this paper an investigation of the thermophysical properties of cement based composites containing plastic waste particles with different percentage is presented. Measurements were carried out using pulse transient method before and after artificial ageing in climatic chamber BINDER MKF (E3).

  10. The integration of eis parameters and bulk matrix characteristics in studying reinforced cement-based materials

    NARCIS (Netherlands)

    Koleva, D.A.; Van Breugel, K.

    2011-01-01

    Corrosion in reinforced concrete is a major and costly concern, arising from the higher complexity of involved phenomena on different levels of material science (e.g. electrochemistry, concrete material science) and material properties (macro/micro/ nano). Reinforced cement-based systems (e.g.

  11. The Integration of EIS parameters and bulk matrix characterization in studying reinforced cement-based materials

    NARCIS (Netherlands)

    Koleva, D.A.; Van Breugel, K.

    2012-01-01

    Corrosion in reinforced concrete is a major and costly concern, arising from the higher complexity of involved phenomena on different levels of material science (e.g. electrochemistry, concrete material science) and material properties (macro/micro/ nano). Reinforced cement-based systems (e.g.

  12. Modelling the effect of electrical current flow on the hydration process of cement-based materials

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.; Koenders, E.A.B.

    2014-01-01

    Stray current is essentially an electrical current “leakage” from metal conductors and electrical installations. When it flows through cement-based systems, electrical energy is converted to thermal energy that causes increasing temperature due to Joule heating phenomena. The aim of this paper is to

  13. Incinerated sewage sludge ash as alternative binder in cement-based materials

    DEFF Research Database (Denmark)

    Krejcirikova, Barbora; Goltermann, Per; Hodicky, Kamil

    2013-01-01

    it can minimize the need of ash landfill disposal. The objective of this study is to show potential use of incinerated sewage sludge ash (ISSA), an industrial byproduct, as possible binder in cement-based materials. Chemical and mechanical characteristics are presented and compared with results obtained...

  14. Tridimensional quantitative porosity characterization of three set calcium silicate-based repair cements for endodontic use.

    Science.gov (United States)

    De Souza, Erika Thuanne Gonçalves; Nunes Tameirão, Michele Dias; Roter, Juliana Marins; De Assis, Joaquim Teixeira; De Almeida Neves, Aline; De-Deus, Gustavo André

    2013-10-01

    The aim of the this study was to quantitatively evaluate in three-dimensional (3D), the porosity degree of three improved silicate-based endodontic repair cements (iRoot BP Plus®, Biodentine®, and Ceramicrete) compared to a gold-standard calcium silicate bioactive cement (Pro Root® MTA). From each tested cement, four samples were prepared by a single operator following the manufacturer's instructions in terms of proportion, time, and mixing method, using cylindrical plastic split-ring moulds. The moulds were lubricated and the mixed cements were inserted with the aid of a cement spatula. The samples were scanned using a compact micro-CT device (Skyscan 1174, Bruker micro-CT, Kontich, Belgium) and the projection images were reconstructed into cross-sectional slices (NRecon v.1.6.9, Bruker micro-CT). From the stack of images, 3D models were rendered and the porosity parameters of each tested material were obtained after threshold definition by comparison with standard porosity values of Biodentine®. No statistically significant differences in the porosity parameters among the different materials were seen. Regarding total porosity, iRoot BP Plus® showed a higher percentage of total porosity (9.58%), followed by Biodentine® (7.09%), Pro Root® MTA (6.63%), and Ceramicrete (5.91%). Regarding closed porosity, Biodentine® presented a slight increase in these numbers compared to the other sealers. No significant difference in porosity between iRoot BP Plus®, Biodentine®, and Ceramicrete were seen. In addition, no significant difference in porosity between the new calcium silicate-containing repair cements and the gold-standard MTA were found.

  15. Investigation on Flowability and Microstructure of Fresh Cement Asphalt Binder%新拌水泥沥青浆体的流动性及显微结构研究

    Institute of Scientific and Technical Information of China (English)

    孔祥明; 张艳荣; 张敬义; 马晓伟; 曹恩祥; 刘永亮; 黄婉利

    2011-01-01

    研究了乳化沥青对新拌水泥沥青浆体流动性和显微结构的影响;分析测试了添加不同类型及不同掺量的乳化沥青后新拌浆体的流动性(扩展度)及水化热;采用光学显微镜原位观察了分散体系显微结构的形成及演化过程.结果表明:乳化沥青的加入可大大提高浆体的流动性和流动保持性,同时可延缓水泥水化进程;随乳化沥青掺量的增大,浆体流动性先增大后降低,流动保持性逐渐增强,诱导期逐渐延长;阴离子乳化沥青对浆体流动性和流动保持性的改善及其对水泥水化的延缓效果较阳离子乳化沥青更为显著;浆体显微结构的形成及演化包括乳化沥青颗粒对水泥颗粒的吸附、乳化沥青破乳同时伴随水泥水化等几个过程,最终形成水泥、水化产物和沥青膜互穿的有机-无机复合结构.%Influence of asphalt emulsion on the flowability and microstructure of fresh cement asphalt binder was investigated. The spread diameter of fresh cement asphalt paste with different asphalt content and type was measured. Optical microscope was used to observe the formation and evolution of the microstructure. Results show that the flowability and flow retention of the paste were significantly improved, and the time to reach peak temperature of hydration curve was delayed obviously. As the asphalt content increased, the flowability became better at first but got poorer then. The flow retention was enhanced and dormant period increased. The effect of anionic asphalt emulsion on the flowability, flow retention and microstructure was more obvious than cationic asphalt emulsion. It was proved from direct observation on fresh cement asphalt paste by optical microscope that the evolution process of microstructure included three stages:the adsorption of asphalt particles on the cement grains, the demulsification and film-forming of asphalt particles as well as the hydration of cement. The final

  16. Damage model of fresh concrete in sulphate environment

    Institute of Scientific and Technical Information of China (English)

    张敬书; 张银华; 冯立平; 金德保; 汪朝成; 董庆友

    2015-01-01

    A model of damage to fresh concrete in a corrosive sulphate environment was formulated to investigate how and why the strength of corroded concrete changes over time. First, a corroded concrete block was divided into three regions:an expanded and dense region;a crack-development region;and a noncorroded region. Second, based on the thickness of the surface corrosion layer and the rate of loss of compressive strength of the corroding region, a computational model of the concrete blocks’ corrosion-resistance coefficient of compressive strength in a sulphate environment was generated. Third, experimental tests of the corrosion of concrete were conducted by immersing specimens in a corrosive medium for 270 d. A comparison of the experimental results with the computational formulae shows that the calculation results and test results are in good agreement. A parameter analysis reveals that the corrosion reaction plays a major role in the corrosion of fresh concrete containing ordinary Portland cement, but the diffusion of the corrosion medium plays a major role in the corrosion of concrete mixtures containing fly ash and sulphate-resistant cement. Fresh concrete with a high water-to-cement ratio shows high performance during the whole experiment process whereas fresh concrete with a low water-to-cement ratio shows poor performance during the late experiment period.

  17. Cytotoxicity and genotoxicity of calcium silicate-based cements on an osteoblast lineage

    Directory of Open Access Journals (Sweden)

    Ana Lívia GOMES-CORNÉLIO

    2016-01-01

    Full Text Available Abstract Several calcium silicate-based biomaterials have been developed in recent years, in addition to Mineral Trioxide Aggregate (MTA. The aim of this study was to evaluate the cytotoxicity, genotoxicity and apoptosis/necrosis in human osteoblast cells (SAOS-2 of pure calcium silicate-based cements (CSC and modified formulations: modified calcium silicate-based cements (CSCM and three resin-based calcium silicate cements (CSCR1 (CSCR 2 (CSCR3. The following tests were performed after 24 hours of cement extract exposure: methyl-thiazolyl tetrazolium (MTT, apoptosis/necrosis assay and comet assay. The negative control (CT- was performed with untreated cells, and the positive control (CT+ used hydrogen peroxide. The data for MTT and apoptosis were submitted to analysis of variance and Bonferroni’s posttest (p < 0.05, and the data for the comet assay analysis, to the Kruskal-Wallis and Dunn tests (p < 0.05. The MTT test showed no significant difference among the materials in 2 mg/mL and 10 mg/mL concentrations. CSCR3 showed lower cell viability at 10 mg/mL. Only CSC showed lower cell viability at 50 mg/mL. CSCR1, CSCR2 and CSCR3 showed a higher percentage of initial apoptosis than the control in the apoptosis test, after 24 hours exposure. The same cements showed no genotoxicity in the concentration of 2 mg/mL, with the comet assay. CSC and CSCR2 were also not genotoxic at 10 mg/mL. All experimental materials showed viability with MTT. CSC and CSCR2 presented a better response to apoptosis and genotoxicity evaluation in the 10 mg/mL concentration, and demonstrated a considerable potential for use as reparative materials.

  18. Correlation between the degree of conversion and the elution of leachable components from dental resin-based cements

    Directory of Open Access Journals (Sweden)

    KOSOVKA OBRADOVIĆ-DJURIČIĆ

    2011-09-01

    Full Text Available This study examined the possible correlation between the degree of conversion (DC and the amount of substances eluted from three commercial cured resin-based cements. The DC of the various resin-based cements was measured by Raman spectroscopy, while the quantity of unreacted monomers released from the cement matrix (triethylene glycol dimethacrylate, TEGDMA, urethane dimethacrylate, UDMA, 2-hydroxyethyl methacrylate, HEMA and bisphenol A was determined by high pressure liquid chromatography (HPLC. The obtained results, after multiple statistical evaluation (one way ANOVA, LSD post hoc test, showed no significant differences in the DC values between the resin cements. On the contrary, the results of the HPLC analysis depicted statistically significant differences between the three materials with respect to the amount of leached monomers. In addition, no correlation between the DC and the amount of eluted substances from the tested cured composite cements was found.

  19. Improved Encapsulation Method of Sensing Element for Cement-Based Piezoelectric Sensor

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaoming; LI Zongjin; LI Zhongxian

    2006-01-01

    An improved encapsulation method of a sensing element for a cement-based piezoelectric sensor used in civil engineering structure was developed and some tests were carried out for validating this method. The cement-based piezoelectric sensor of this kind is mainly used in concrete structure due to its compatibility with concrete, and the encapsulation method of its sensing element is important to the effectiveness and accuracy of the transfer of the stress from concrete to the sensing element. The sensor's measurement error of the previous encapsulation method, which was induced by the area of the encapsulation material and the inherent difference of Young's modulus between cement and encapsulation material, was analyzed theoretically using parallel model. In the improved method, the error is minimized by decreasing the area of the encapsulation material and changing the configuration of the cement and piezoelectric material in the sensor. Two sensors made by the previous and improved methods were embedded in two prisms respectively and the prisms were compressed on Material Test System. Through the comparison of the measurement errors of the two sensors, the improved method was evaluated. The test results show that the improved encapsulation method is effective and feasible.

  20. Effects of TEA·HCl hardening accelerator on the workability of cement-based materials

    Science.gov (United States)

    Pan, Wenhao; Ding, Zhaoyang; Chen, Yanwen

    2017-03-01

    The aim of the test is to research the influence rules of TEA·HCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what’s more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEA·HCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

  1. Alginate- and gellan-based edible films for probiotic coatings on fresh-cut fruits.

    Science.gov (United States)

    Tapia, M S; Rojas-Graü, M A; Rodríguez, F J; Ramírez, J; Carmona, A; Martin-Belloso, O

    2007-05-01

    Alginate- (2% w/v) or gellan-based (0.5%) edible films, containing glycerol (0.6% to 2.0%), N-acetylcysteine (1%), and/or ascorbic acid (1%) and citric acid (1%), were formulated and used to coat fresh-cut apple and papaya cylinders. Water vapor permeability (WVP) was significantly higher (P fresh-cut fruits. Fresh-cut apple and papaya cylinders were successfully coated with 2% (w/v) alginate or gellan film-forming solutions containing viable bifidobacteria. WVP in alginate (6.31 and 5.52 x 10(-9) g m/Pa s m2) or gellan (3.65 and 4.89 x 10(-9) g m/Pa s m2) probiotic coatings of papaya and apple, respectively, were higher than in the corresponding cast films. The gellan coatings and films exhibited better water vapor properties in comparison with the alginate coatings. Values > 10(6) CFU/g B. lactis Bb-12 were maintained for 10 d during refrigerated storage of fresh-cut fruits, demonstrating the feasibility of alginate- and gellan-based edible coatings to carry and support viable probiotics on fresh-cut fruit.

  2. Biomonitoring Study of Heavy Metals in Blood from a Cement Factory Based Community

    Directory of Open Access Journals (Sweden)

    Bank M.S.

    2014-07-01

    Full Text Available Little is known about the effects of cement factory pollution, emissions, and kiln dust on contaminant exposure in human populations, including school environments, in close proximity to these point sources. In Ravena, New York, USA and vicinity, environmental pollution from a local cement plant is considered significant and substantial according to the United States Environmental Protection Agency’s Toxic Release Inventory, published in 2006, 2007, and 2010. We hypothesized that cement factory based communities, such as the one in Ravena, NY, may be differentially exposed to heavy metals, including mercury, via dust, soil, and air in addition to any contributions from fish consumption, dental amalgams, smoking habits, and occupational exposures, etc. Here we report measurements of several heavy metals in blood (Pb, Cd, As, Hg, Se and Al and, for comparative purposes, total mercury in hair from a local (six-mile radius population of Caucasian adults and children. We also report and synthesize local atmospheric emissions inventory information and new indoor air data (NYSERDA, 2011 from the local school which is situated directly across the street (within 750 feet from the cement factory and quarry. In addition, to our human and environmental heavy metal results we also discuss scientific outreach coordination, and public health action opportunities that will likely have wide applicability for other community and environmental health studies confronting similar pollution issues.

  3. Modeling Framework for Fracture in Multiscale Cement-Based Material Structures

    Science.gov (United States)

    Qian, Zhiwei; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

    2017-01-01

    Multiscale modeling for cement-based materials, such as concrete, is a relatively young subject, but there are already a number of different approaches to study different aspects of these classical materials. In this paper, the parameter-passing multiscale modeling scheme is established and applied to address the multiscale modeling problem for the integrated system of cement paste, mortar, and concrete. The block-by-block technique is employed to solve the length scale overlap challenge between the mortar level (0.1–10 mm) and the concrete level (1–40 mm). The microstructures of cement paste are simulated by the HYMOSTRUC3D model, and the material structures of mortar and concrete are simulated by the Anm material model. Afterwards the 3D lattice fracture model is used to evaluate their mechanical performance by simulating a uniaxial tensile test. The simulated output properties at a lower scale are passed to the next higher scale to serve as input local properties. A three-level multiscale lattice fracture analysis is demonstrated, including cement paste at the micrometer scale, mortar at the millimeter scale, and concrete at centimeter scale. PMID:28772948

  4. Analysis of Metal Contents in Portland Type V and MTA-Based Cements

    Directory of Open Access Journals (Sweden)

    Maura Cristiane Gonçales Orçati Dorileo

    2014-01-01

    Full Text Available The aim of this study was to determine, by Atomic Absorption Spectrometry (AAS, the concentration levels of 11 metals in Type V gray and structural white PC, ProRoot MTA, and MTA Bio. Samples, containing one gram of each tested cement, were prepared and transferred to a 100 mL Teflon tube with a mixture of 7.0 mL of nitric acid and 21 mL of hydrochloric acid. After the reaction, the mixture was filtered and then volumed to 50 mL of distilled water. For each metal, specific patterns were determined from universal standards. Arsenic quantification was performed by hydride generator. The analysis was performed five times and the data were statistically analyzed at 5% level of significance. Only the cadmium presented concentration levels of values lower than the quantification limit of the device. The AAS analysis showed increased levels of calcium, nickel, and zinc in structural white PC. Type V PC presented the greatest concentration levels of arsenic, chromium, copper, iron, lead, and manganese (P<0.05. Bismuth was found in all cements, and the lowest concentration levels were observed in Portland cements, while the highest were observed in ProRoot MTA. Both PC and MTA-based cements showed evidence of metals inclusion.

  5. Simulation of expansion in cement based materials subjected to external sulfate attack

    Directory of Open Access Journals (Sweden)

    O.A. Hodhod

    2014-03-01

    Full Text Available The standard test for length change in hydraulic-cement mortars exposed to sulfate solution, ASTM C1012-95, has been widely used by researchers to study the sulfate resistance of cement based materials. However, there are deficiencies in this test method including lengthy measuring period, insensitivity of the measurement tool to sulfate attack, effect of curing and pH change. So, in this study, a model will be built by artificial neural networks (ANNs to simulate this test and overcome these defects. This model will deal with different types of cement in the presence of blast-furnace slag (GGBFS or fly ash (PFA. From the results of simulations, it is possible to understand the impact of cement chemistry and these two types of additions on resistance of sulfate attack more readily, faster, and accurately. Such an understanding improves the decision making process in every stage of construction and maintenance and will help in better administration of resources.

  6. Development and comparison of neural network based soft sensors for online estimation of cement clinker quality.

    Science.gov (United States)

    Pani, Ajaya Kumar; Vadlamudi, Vamsi Krishna; Mohanta, Hare Krishna

    2013-01-01

    The online estimation of process outputs mostly related to quality, as opposed to their belated measurement by means of hardware measuring devices and laboratory analysis, represents the most valuable feature of soft sensors. As of now there have been very few attempts for soft sensing of cement clinker quality which is mostly done by offline laboratory analysis resulting at times in low quality clinker. In the present work three different neural network based soft sensors have been developed for online estimation of cement clinker properties. Different input and output data for a rotary cement kiln were collected from a cement plant producing 10,000 tons of clinker per day. The raw data were pre-processed to remove the outliers and the resulting missing data were imputed. The processed data were then used to develop a back propagation neural network model, a radial basis network model and a regression network model to estimate the clinker quality online. A comparison of the estimation capabilities of the three models has been done by simulation of the developed models. It was observed that radial basis network model produced better estimation capabilities than the back propagation and regression network models.

  7. GIS Based Multi-Criteria Decision Analysis For Cement Plant Site Selection For Cuddalore District

    Science.gov (United States)

    Chhabra, A.

    2015-12-01

    India's cement industry is a vital part of its economy, providing employment to more than a million people. On the back of growing demands, due to increased construction and infrastructural activities cement market in India is expected to grow at a compound annual growth rate (CAGR) of 8.96 percent during the period 2014-2019. In this study, GIS-based spatial Multi Criteria Decision Analysis (MCDA) is used to determine the optimum and alternative sites to setup a cement plant. This technique contains a set of evaluation criteria which are quantifiable indicators of the extent to which decision objectives are realized. In intersection with available GIS (Geographical Information System) and local ancillary data, the outputs of image analysis serves as input for the multi-criteria decision making system. Moreover, the following steps were performed so as to represent the criteria in GIS layers, which underwent the GIS analysis in order to get several potential sites. Satellite imagery from LANDSAT 8 and ASTER DEM were used for the analysis. Cuddalore District in Tamil Nadu was selected as the study site as limestone mining is already being carried out in that region which meets the criteria of raw material for cement production. Several other criteria considered were land use land cover (LULC) classification (built-up area, river, forest cover, wet land, barren land, harvest land and agriculture land), slope, proximity to road, railway and drainage networks.

  8. The influence of iron on water radiolysis in cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bouniol, P., E-mail: pascal.bouniol@cea.f [CEA, DEN, DPC, SCCME, Laboratoire d' Etude du Comportement des Betons et des Argiles, F-91991 Gif-Sur-Yvette (France)

    2010-08-15

    For the time being, assessing the H{sub 2} source term generated by {gamma} irradiated cement-based materials consists of simulating the radiolysis of the pore liquid on the only elementary reactions relating to the decomposition of alkaline water. Such incomplete description does not take into account the impurities contained in the cement and leads to underestimate the production of H{sub 2}. Systematically present in cement materials, iron is likely to influence radiolysis by the disturbance induced on radical chemistry throughout the irradiation period. The faster reactivity of e{sub aq}{sup -} and OH{sup {center_dot}} radicals on Fe(III) and Fe(II), respectively, than on H{sub 2}O{sub 2} and H{sub 2} is responsible for the lower recycling capability of the 'Allen's chain reaction', allowing for H{sub 2} to be preserved in a closed system. A critical review of reaction data about iron complexes (hydroxo-, peroxo-) is presented in order to build up an 'iron' database. Radiolysis simulations in cement porewater in the presence of Fe(OH){sub 3} (considered as a model phase) show, as expected, an increase in the effective production of radiolytic H{sub 2} and the co-existence of exotic valence Fe(IV) with Fe(II) and (III) during the irradiation period ({gamma}).

  9. Sulfate deterioration of cement-based materials examined by x-ray microtomography

    Science.gov (United States)

    Naik, Nikhila N.; Kurtis, Kimberly E.; Wilkinson, Angus P.; Jupe, Andrew C.; Stock, Stuart R.

    2004-10-01

    Sulfate ions present in soil, groundwater, seawater, decaying organic matter, acid rain, and industrial effluent adversely affect the long-term durability of portland cement concrete, but lack of complete understanding of the nature and consequences of sulfate attack hamper our ability to accurately predict performance of concrete in sulfate-rich environments. One impediment to improved understanding of sulfate deterioration of cement-based materials has been the lack of appropriate non-destructive characterization techniques. Laboratory x-ray microtomography affords an opportunity to study in situ the evolution of physical manifestations of damage due to sulfate exposure. The influence of materials selection and mixture parameters - including water-to-cement ratio, cement type, and presence or absence of aggregate, as well as the influence of sulfate exposure conditions, including sulfate and cation type (i.e., Na2SO4 and MgSO4) and concentration - have been examined by microtomography to determine their influence on the rate and character of the sulfate-induced deterioration.

  10. Characterisation and use of biomass fly ash in cement-based materials.

    Science.gov (United States)

    Rajamma, Rejini; Ball, Richard J; Tarelho, Luís A C; Allen, Geoff C; Labrincha, João A; Ferreira, Victor M

    2009-12-30

    This paper presents results about the characterisation of the biomass fly ashes sourced from a thermal power plant and from a co-generation power plant located in Portugal, and the study of new cement formulations incorporated with the biomass fly ashes. The study includes a comparative analysis of the phase formation, setting and mechanical behaviour of the new cement-fly ash formulations based on these biomass fly ashes. Techniques such as X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermal gravimetric and differential thermal analysis (TG/DTA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and environmental scanning electron spectroscopy (ESEM) were used to determine the structure and composition of the formulations. Fly ash F1 from the thermal power plant contained levels of SiO(2), Al(2)O(3) and Fe(2)O(3) indicating the possibility of exhibiting pozzolanic properties. Fly ash F2 from the co-generation plant contained a higher quantity of CaO ( approximately 25%). The fly ashes are similar to class C fly ashes according to EN 450 on the basis of chemical composition. The hydration rate and phase formation are greatly dependant on the samples' alkali content and water to binder (w/b) ratio. In cement based mortar with 10% fly ash the basic strength was maintained, however, when 20% fly ash was added the mechanical strength was around 75% of the reference cement mortar. The fly ashes contained significant levels of chloride and sulphate and it is suggested that the performance of fly ash-cement binders could be improved by the removal or control of these chemical species.

  11. Research on Supply Chain Performance Evaluation of Fresh Agriculture Products Based on BP Neural Network

    Directory of Open Access Journals (Sweden)

    Hankun Ye

    2014-05-01

    Full Text Available Evaluating supply chain performance of fresh agricultural products is one of the key techniques and a research hotspot in supply chain management and in fields related. The paper designs a new evaluation indicator system and presents a new model for evaluating supply chain performance of fresh agriculture product companies. First, based on analyzing the specific characteristics of the supply chain performance evaluation of fresh agriculture products, the paper designs a new evaluation indicator system including external and internal performance. Second, some improvements, such as adjusting dynamic strategy and the value of momentum factor, are taken to speed up calculation convergence and simplify the structure and to improve evaluating accuracy of the original BP evaluation model. Finally the model is realized with the data from certain supply chains of three fresh agriculture product companies and the experimental results show that the algorithm can improve calculation efficiency and evaluation accuracy when used for supply chain performance evaluation of fresh agriculture product companies practically.

  12. Physico-mechanical and physico-chemical properties of synthesized cement based on plasma- and wet technologies

    Science.gov (United States)

    Sazonova, Natalya; Skripnikova, Nelli

    2016-01-01

    In this work we studied the influence of plasma-chemical technology of cement clinker synthesis under conditions of high-concentrated heat streams on the properties of cement on fixing such factors as raw-material type (chemical and mineralogical composition), fraction composition, homogenization and module characters of the raw-material mixture. In this connection the sludge of the cement plant in town Angarsk, based on which the cement clinker synthesis using the wet- and plasma-chemical technologies was performed, was used in the studies. The results of chemical X-ray-phase analysis, petrography of cement clinkers, differential scanning colorimetry of hardened cement paste are represented in this work. The analysis of building-technical properties of inorganic viscous substances was performed. It was found that in using the identical raw-material mixture the cement produced with temperature higher by 1650 °C than the traditional one may indicate the higher activity. The hardened cement paste compressive strength at the age of 28 days was higher than the strength of the reference samples by 40.8-41.4 %.

  13. Link-up between Farmers and Supermarket based on China’s Fresh Agricultural Products

    Institute of Scientific and Technical Information of China (English)

    YANG Jian-ying; TANG Bu-long

    2012-01-01

    Link-up between farmers and supermarket is a new move adopted actively by the current government, conducive to consumers, farmers and circulation enterprises. At present, link-up between farmers and supermarket is launched in China’s 15 provinces and cities, which will set off the revolution in the field of agricultural circulation. Based on the current situation of link-up between farmers and supermarket and the existing problems, we put forth the following recommendations: promoting the quality of farmers’ cooperative organizations; establishing the logistics center of fresh agricultural products; using economies of scale to reduce the fresh logistics costs; improving the operation and management level of fresh agricultural products in supermarket.

  14. 18-year survival of posterior composite resin restorations with and without glass ionomer cement as base.

    Science.gov (United States)

    van de Sande, Françoise H; Rodolpho, Paulo A Da Rosa; Basso, Gabriela R; Patias, Rômulo; da Rosa, Quéren F; Demarco, Flávio F; Opdam, Niek J; Cenci, Maximiliano S

    2015-06-01

    Advantages and disadvantages of using intermediate layers underneath resin-composite restorations have been presented under different perspectives. Yet, few long-term clinical studies evaluated the effect of glass-ionomer bases on restoration survival. The present study investigated the influence of glass-ionomer-cement base in survival of posterior composite restorations, compared to restorations without base. Original datasets of one dental practice were used to retrieve data retrospectively. The presence or absence of an intermediate layer of glass-ionomer-cement was the main factor under analysis, considering survival, annual failure rate and types of failure as outcomes. Other investigated factors were: patient gender, jaw, tooth, number of restored surfaces and composite. Statistical analysis was performed using Fisher's exact test, Kaplan-Meier method and multivariate Cox-regression. In total 632 restorations in 97 patients were investigated. Annual failure rates percentages up to 18-years were 1.9% and 2.1% for restorations with and without base, respectively. In restorations with glass-ionomer-cement base, fracture was the predominant reason for failure, corresponding to 57.8% of total failures. Failure type distribution was different (p=0.007) comparing restorations with and without base, but no effect in the overall survival of restorations was found (p=0.313). The presence of a glass-ionomer-cement base did not affect the survival of resin-composite restorations in the investigated sample. Acceptable annual failure rates after 18-years can be achieved with both techniques, leading to the perspective that an intermediate layer, placed during an interim treatment, may be maintained without clinical detriment, but no improvement in survival should be expected based on such measure. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. Strengthening of concrete structures using carbon fibre reinforced polymers and cement-based adhesives

    OpenAIRE

    Hashemi, Siavash

    2017-01-01

    The research project conducted in this study concerns the investigation of the application of cement-based adhesives in CFRP strengthening of reinforced concrete members. The results demonstrate that mineral-based adhesives can provide the desired matrices for CFRP reinforcement. The literature review covers the background of CFRP application with conventional techniques. The bond characteristics of CFRP to concrete substrate, the flexural performance of retrofitted RC beams, and the fa...

  16. Analysis of an Orthotropic Deck Stiffened with a Cement-Based Overlay

    DEFF Research Database (Denmark)

    Walter, Rasmus; Olesen, John Forbes; Stang, Henrik

    2007-01-01

    Over the past years, with increasing traffic volumes and higher wheel loads, fatigue damage in steel parts of typical orthotropic steel bridge decks has been experienced on heavily trafficked routes. A demand exists to find a durable system to increase the fatigue safety of orthotropic steel bridge...... decks. A solution might be to enhance the stiffness of the traditional orthotropic bridge deck by using a cement-based overlay. In this paper, an orthotropic steel bridge deck stiffened with a cement-based overlay is analyzed. The analysis is based on nonlinear fracture mechanics, and utilizes...... of crack widths. Furthermore, the analysis shows that debonding is initiated for a certain crack width in the overlay. The load level where cracking and debonding is initiated depends on the stress-crack opening relationship of the material....

  17. The effect of temperature rise on microstructural properties of cement-based materials: correlation of experimental data and a simulation approach

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.

    2015-01-01

    This work reports on the influence of stray current flow on temperature rise in hardening cement-based materials and consequently altered cement hydration. To simulate stray current, different levels of electrical current were applied to cement paste and mortar specimens immediately after casting. I

  18. The effect of temperature rise on microstructural properties of cement-based materials: correlation of experimental data and a simulation approach

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.

    2015-01-01

    This work reports on the influence of stray current flow on temperature rise in hardening cement-based materials and consequently altered cement hydration. To simulate stray current, different levels of electrical current were applied to cement paste and mortar specimens immediately after casting.

  19. Hardness of resin cement cured under different thickness of lithium disilicate-based ceramic

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xuan; WANG Fu

    2011-01-01

    Background The lithium disilicate-based ceramic is a newly developed all-ceramic material,which is lithium disilicate-based and could be used for fabricating almost all kinds of restorations.The extent of light attenuation by ceramic material was material-dependent.Ceramic materials with different crystal composition or crystalline content would exhibit distinct light-absorbing characteristics.The aim of this study was to analyze the influence of ceramic thickness and light-curing time on the polymerization of a dual-curing resin luting material with a lithium disilicate-based ceramic.Methods A lithium disilicate-based ceramic was used in this study.The light attenuation caused by ceramic with different thickness was determined using a spectral radiometer.The commercial dual-cured resin cement was light-cured directly or through ceramic discs with different thickness (1,2 and 3 mm,respectively) for different times (10,20,30,40,50 and 60 seconds,respectively).The polymerization efficiency of resin cement was expressed in terms as Vickers hardness (VHN) measured after 24 hours storage.Two-way analysis of variance (ANOVA) and Tukey's HSD tests were used to determine differences.Results Intensity of polymerizing light transmitted through ceramic discs was reduced from 584 mW/cm2 to about 216 mW/cm2,80 mW/cm2 and 52 mW/cm2 at thicknesses of 1 mm,2 mm and 3 mm,respectively.Resin cement specimens self-cured alone showed significantly lower hardness values.When resin cement was light-cured through ceramic discs with a thickness of 1 mm,2 mm and 3 mm,no further increasing in hardness values was observed when light-curing time was more than 30 seconds,40 seconds and 60 seconds,respectively.Conclusions Within the limitation of the present study,ceramic thickness and light-curing time had remarkable influence on the polymerization of dual-cured resin cement.When resin cement is light-cured beneath a lithium disilicate ceramic with different thickness,prolonging light

  20. Statistical Analyses of Optimum Partial Replacement of Cement by Fly Ash Based on Complete Consumption of Calcium Hydroxide

    Directory of Open Access Journals (Sweden)

    Ouypornprasert Winai

    2016-01-01

    Full Text Available The objectives of this technical paper were to propose the optimum partial replacement of cement by fly ash based on the complete consumption of calcium hydroxide from hydration reactions of cement and the long-term strength activity index based on equivalent calcium silicate hydrate as well as the propagation of uncertainty due to randomness inherent in main chemical compositions in cement and fly ash. Firstly the hydration- and pozzolanic reactions as well as stoichiometry were reviewed. Then the optimum partial replacement of cement by fly ash was formulated. After that the propagation of uncertainty due to main chemical compositions in cement and fly ash was discussed and the reliability analyses for applying the suitable replacement were reviewed. Finally an applicability of the concepts mentioned above based on statistical data of materials available was demonstrated. The results from analyses were consistent with the testing results by other researchers. The results of this study provided guidelines of suitable utilization of fly ash for partial replacement of cement. It was interesting to note that these concepts could be extended to optimize partial replacement of cement by other types of pozzolan which were described in the other papers of the authors.

  1. Effect of thermally induced strain on optical fiber sensors embedded in cement-based composites

    Science.gov (United States)

    Yuan, Li-bo; Zhou, Li-min; Jin, Wei; Lau, K. T.; Poon, Chi-kin

    2003-04-01

    A critical issue in developing a fiber-optic strain gauge is its codependency on temperature and strain. Any changes in the output of the optical fiber sensor due to its own thermal sensitivity and the thermal expansion of the most material will be misinterpreted as a change in shape-induced strain in the structure. This codependence is often referred to as thermally induced apparent strain or simply apparent strain. In this paper, an analytical model was developed to evaluate the thermally induced strain in fiber optic sensors embedded in cement-based composites. The effects of thermal induced strain on embedded optical fiber were measured with a white-light fiber-optic Michelson sensing interferometer for a number of cement-based host materials.

  2. A multi-scale micromechanical investigation on thermal conductivity of cement-based composites

    Science.gov (United States)

    Liu, Jiahan; Xu, Shilang; Zeng, Qiang

    2017-01-01

    Cement-based composites (CBCs) are one of the most widely used materials in construction. An appealing characterization of thermal conductivity of CBCs plays an essential role to evaluate the energy consumption in buildings and to facilitate the development of novel thermal insulation materials. Based on Eshelby equivalent inclusion principle and multi-scale methodology, this paper attempted to present a generalized multi-scale micromechanical model in terms of thermal performance of the CBCs, which covers some classic models for thermal conductivity estimation. A Mori-Tanaka homogenization method was applied to investigate the thermal conductivity of the CBCs of different compounds, water-to-cement ratios and curing ages. In addition, saturation degree factor was considered. The results of this model are in good agreement with the experimental value, showing that the multi-scale model developed in this paper is able to evaluate the thermal conductivity of the CBCs in different conditions.

  3. Utilization of cement treated recycled concrete aggregates as base or subbase layer in Egypt

    Directory of Open Access Journals (Sweden)

    Ahmed Ebrahim Abu El-Maaty Behiry

    2013-12-01

    Full Text Available Recently, environmental protection has a great concern in Egypt where recycling of increased demolition debris has become a viable option to be incorporated into roads applications. An extensive laboratory program is conducted to study the feasibility of using recycled concrete aggregate (RCA mixed with traditional limestone aggregate (LSA which is currently being used in base or subbase applications in Egypt. Moreover, the influence of mixture variables on the mechanical properties of cement treated recycled aggregate (CTRA is investigated. Models to predict the compressive and tensile strengths based on mixture parameters are established. The results show that the adding of RCA improves the mechanical properties of the mixture where the unconfined compressive strength (UCS is taken as an important quality indicator. Variables influencing the UCS such as cement content, curing time, dry density play important roles to determine the performance of CTRA.

  4. Evaluation of leaching behavior and immobilization of zinc in cement-based solidified products

    Directory of Open Access Journals (Sweden)

    Krolo Petar

    2012-01-01

    Full Text Available This study has examined leaching behavior of monolithic stabilized/solidified products contaminated with zinc by performing modified dynamic leaching test. The effectiveness of cement-based stabilization/solidification treatment was evaluated by determining the cumulative release of Zn and diffusion coefficients, De. The experimental results indicated that the cumulative release of Zn decreases as the addition of binder increases. The values of the Zn diffusion coefficients for all samples ranged from 1.210-8 to 1.1610-12 cm2 s-1. The samples with higher amounts of binder had lower De values. The test results showed that cement-based stabilization/solidification treatment was effective in immobilization of electroplating sludge and waste zeolite. A model developed by de Groot and van der Sloot was used to clarify the controlling mechanisms. The controlling leaching mechanism was found to be diffusion for samples with small amounts of waste material, and dissolution for higher waste contents.

  5. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  6. Influence of adjuvants on the properties of underwater cast concrete on base of cement (HRS 32.5 N

    Directory of Open Access Journals (Sweden)

    Rouis Mohamed Jamel

    2014-04-01

    *The characterization tests of concrete in the hardened state including destructive and non destructive tests performed on specimens made in concrete (based on portland cement, with varying dosages and adjuvants at different times (28d and 90d.

  7. Vacuum extraction based response equipment for recovery of fresh fuel spills from soil.

    Science.gov (United States)

    Halmemies, Sakari; Gröndahl, Siri; Arffman, Mika; Nenonen, Keijo; Tuhkanen, Tuula

    2003-02-28

    Accidental overturns of fuel tankers can have, depending on soil types, severe consequences. This applies, particularly in areas of shallow soils where the groundwater is located 2-4m below the ground surface. By rapid, vacuum extraction based recovery emergency services, which would normally be the first to arrive on the scene, could minimize consequences of fresh fuel spills and even prevent groundwater contamination, the primary purpose of emergency response. Powerful vacuum extraction-based response (PER), equipment has been developed to recover freshly spilt volatile fuels from the soil, primary by emergency services, but also by other trained responders. The main components of mobile PER-equipment are perforated extraction pipes, a recovery vacuum tank, a vacuum pump and an incinerator. The PER-equipment has been tested in summer and sub-zero winter conditions, and in both cases 50-80% of fresh gasoline spilled into sandy soil was recovered during the first 2h of operation. Gasoline was recovered in both liquid and vapor form, and hydrocarbon vapors were destroyed by controlled incineration at a safe distance from the spill. Recovery of less volatile diesel oil is not so effective from the sandy soil, but about 30% of it could be pumped from a fresh pool directly after a seepage time of 15 min.

  8. Petrographic Analysis of Portland Cement Concrete Cores from Pease Air National Guard Base, New Hampshire

    Science.gov (United States)

    2016-11-01

    Petrographic Analysis of Portland Cement Concrete Cores from Pease Air National Guard Base, New Hampshire E n g in e e r R e s e a rc h a n d...id, age of the concrete being evaluated and tests performed...4 3 Preface This study was conducted in support of the Air Force Civil Engineer Center (AFCEC) to assess concrete obtained from Pease

  9. Sequestration of phosphorus from wastewater by cement-based or alternative cementitious materials.

    Science.gov (United States)

    Wang, Xinjun; Chen, Jiding; Kong, Yaping; Shi, Xianming

    2014-10-01

    Cement-based and alternative cementitious materials were tested in the laboratory for their capability of removing phosphate from wastewater. The results demonstrated that both Langmuir and Freundlich adsorption isotherms were suitable for describing the adsorption characteristics of these materials. Among the four types of filter media tested, the cement-based mortar A has the highest value of maximum adsorption (30.96 mg g(-1)). The P-bonding energy (KL) and adsorption capacity (K) exhibited a positive correlation with the total content of Al2O3 and Fe2O3 in each mortar. The maximum amount of P adsorbed (Qm) and adsorption intensity (1/n) exhibited a positive correlation with the CaO content in each mortar. For three of them, the P-removal rates were in excess of 94 percent for phosphorus concentrations ranging from 20 to 1000 mg L(-1). The underlying mechanisms were examined using field emission scanning microscopy (FESEM), coupled with energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). The results reveal that the removal of phosphate predominantly followed a precipitation mechanism in addition to weak physical interactions between the surface of adsorbent filter media and the metallic salts of phosphate. The use of cement-based or alternative cementitious materials in the form of ground powder shows great promise for developing a cost-effective and environmentally sustainable technology for P-sequestration and for wastewater treatment.

  10. The grain grading model and prediction of deleterious porosity of cement-based materials

    Institute of Scientific and Technical Information of China (English)

    FENG Qi; LIU Jun-zhe

    2008-01-01

    The calculating model for the packing degree of spherical particles system was modified. The grain grading model of cement-based materials was established and could be applied in the global grading system as well as in the nano-fiber reinforced system. According to the grain grading model, two kinds of mortar were de-signed by using the global grain materials and nano-fiber materials such as fly ash, silica fume and NR powder.In this paper, the densities of two above systems cured for 90d were tested and the relationship of deleterious porosity and the total porosity of hardened mortar was discussed. Research results show that nano-fiber materialsuch as NR powder can increase the density of cement-based materials. The relationship of deleterious porosity and the total porosity of hardened mortar accords with logarithmic curve. The deleterious porosity and the ration-ality of the grading can be roughly predicted through calculating the packing degree by the grain grading model of cement-based materials.

  11. On the effect of mixing on property development of cement pastes

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Bøhm, Anja; Kjeldsen, Ane Mette

    2006-01-01

    The method of mixing may affect the degree of agglomeration of particles in cement-based materials and thus the properties of the materials in their fresh, hardening, and hardened state. Paste (w/c=0.35) of white Portland cement with and without 10% silica fume and 0.65% superplasticizer were mixed...... was observed. The effect of mixing on development of hydration was not reflected in the resistance to migration of chloride ions in 28 days old samples....

  12. Effects of Leaching Behavior of Calcium Ions on Compression and Durability of Cement-based Materials with Mineral Admixtures

    Directory of Open Access Journals (Sweden)

    Wei-Ting Lin

    2013-05-01

    Full Text Available Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials.

  13. Effect of carbon nanotubes on properties of cement-sand-based piezoelectric composites

    Science.gov (United States)

    Kim, Sunjung; Zhao, Ping; Enemuoh, Emmanuel

    2015-04-01

    Carbon Nanotubes (CNTs) were dispersed in a cement-sand-based piezoelectric smart composite as conductive fillers to improve its poling efficiency, leading to a desirable piezoelectric effect. By introducing a small amount of CNTs, continuous electric networks between Lead Zirconate Titanate (PZT) particles were created, thus making the composite poling easier. Specimens were prepared by mixing PZT powders, Portland cement and sand with CNTs, followed by pressing it with a load frame system. The effect of quantity of CNTs ranging from 0 to 1.0 volume percent on properties of the composite, including its piezoelectric coefficient, dielectric constant and loss, and sensing effects, were characterized. It was found that the addition of CNTs facilitated effective poling at room temperature and improved the piezoelectric and dielectric properties of the composite. The composite modified by CNTs achieved optimal properties when the CNTs content was 0.7 vol.%.

  14. Multi-scale Modeling of the Effective Chloride lon Diffusion Coefficient in Cement-based Composite Materials

    Institute of Scientific and Technical Information of China (English)

    SUN Guowen; SUN Wei; ZHANG Yunsheng; LIU Zhiyong

    2012-01-01

    N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone (ITZ) between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself.For the convenience of applications,the mortar and concrete were considered as a four-phase spherical model,consisting of cement continuous phase,dispersed aggregates phase,interface transition zone and their homogenized effective medium phase.A general effective medium equation was estabhshed to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure.During calculation,the tortuosity (n) and eonstrictivity factors (Ds/D0) of pore in the hardened pastes are n≈3.2,Ds/D0=1.0× 10-4 respectively from the test data.The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results; The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.

  15. Model of Coherent Interface Formation in Cement-Based Composites Containing Polyblend of Polyvinyl Alcohol and Methylcellulose

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA),methylcellulose (MC) and their polyblend in an amount of 10 wt % with respect to cement,as well as the texture of dehydrated bodies of PVA,MC,and the polyblend solutions,were investigated with SEM.The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehydrated bodies of PVA and MC.The network texture has restrained the movement of polyblend molecules in the cement mortar but is helpful to forming a coherent interface between cement paste and quartz.The key factor of forming the coherent interface is not the neutralization reaction between H+ from hydrolysis of quartz and OH- from hydration of cement,but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and anions from hydrolysis of quartz and hydration of cement,respectively.The model of the coherent interface formation is that excessive [HSiO3]- and [SiO3]2- anions are bonded with the hydrated cations such as Ca2+ and Al3+,which is confirmed by the gel containing Ca and Si on the quartz surface.

  16. In vitro degradation and in vivo resorption of dicalcium phosphate cement based grafts.

    Science.gov (United States)

    Sheikh, Zeeshan; Zhang, Yu Ling; Grover, Liam; Merle, Géraldine E; Tamimi, Faleh; Barralet, Jake

    2015-10-01

    There are two types of DCP: dihydrated (brushite) and anhydrous (monetite). After implantation, brushite converts to hydroxyapatite (HA) which resorbs very slowly. This conversion is not observed after implantation of monetite cements and result in a greater of resorption. The precise mechanisms of resorption and degradation however of these ceramics remain uncertain. This study was designed to investigate the effect of: porosity, surface area and hydration on in vitro degradation and in vivo resorption of DCP. Brushite and two types of monetite cement based grafts (produced by wet and dry thermal conversion) were aged in phosphate buffered saline (PBS) and bovine serum solutions in vitro and were implanted subcutaneously in rats. Here we show that for high relative porosity grafts (50-65%), solubility and surface area does not play a significant role towards in vitro mass loss with disintegration and fragmentation being the main factors dictating mass loss. For grafts having lower relative porosity (35-45%), solubility plays a more crucial role in mass loss during in vitro ageing and in vivo resorption. Also, serum inhibited dissolution and the formation of HA in brushite cements. However, when aged in PBS, brushite undergoes phase conversion to a mixture of octacalcium phosphate (OCP) and HA. This phase conversion was not observed for monetite upon ageing (in both serum and PBS) or in subcutaneous implantation. This study provides greater understanding of the degradation and resorption process of DCP based grafts, allowing us to prepare bone replacement materials with more predictable resorption profiles.

  17. Non destructive determination of the free chloride content in cement based materials

    Energy Technology Data Exchange (ETDEWEB)

    Elsener, B. [Department of Inorganic and Analytical Chemistry, University of Cagliari, I-09128 Cagliari (Italy); Institute of Materials Chemistry and Corrosion, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zuerich (Switzerland); Zimmermann, L.; Boehni, H. [Institute of Materials Chemistry and Corrosion, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zuerich (Switzerland)

    2003-06-01

    A non-destructive chloride sensitive sensor element for use in cement based porous materials is presented. The sensor element determines the activity of the free chloride ions in solutions and in porous cement based materials such as cement paste, mortar or concrete. The calibration in synthetic pore solution showed a response according to Nernst law over three decades of chloride concentration. The sensor element has shown excellent reproducibility and long term stability. The sensor element has been used to monitor the chloride uptake into mortar specimens. The results show a good agreement between the free chloride content determined by the sensor and by pore water expression. Applications in monitoring of reinforced concrete structures and their limitations are discussed. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] In der vorliegenden Arbeit wird ein Chloridsensor zur zerstoerungsfreien Erfassung des Chloridgehalts in zementoesen Materialien beschrieben. Der Sensor bestimmt die Aktivitaet der freien Chloridionen in Loesungen und in Zementstein, Moertel oder Beton. Die Kalibrierungskurve in synthetischer Betonporenloesung zeigt das erwartete Nernst'sche Verhalten ueber mehr als drei Konzentrationsdekaden. Der Sensor weist eine sehr hohe Reproduzierbarkeit und Langzeitstabilitaet auf. Der Chloridsensor wurde eingesetzt, um das Eindringen der Chloridionen in Moertelpruefkoerpern zu untersuchen. Ein Vergleich der Chloridkonzentration bestimmt durch Auspressen der Porenloesung am Ende der Versuche mit den von Sensoren bestimmten Chloridkonzentration zeigt eine sehr gute Uebereinstimmung. Praktische Anwendungen und die Einsatzgrenzen des Sensors werden diskutiert. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  18. Evaluation of frost damage in cement-based materials by a nonlinear elastic wave technique

    Science.gov (United States)

    Eiras, J. N.; Kundu, T.; Popovics, J. S.; Monzó, J.; Soriano, L.; Payá, J.

    2014-03-01

    Frost resistance of concrete is a major concern in cold regions. RILEM (International union of laboratories and experts in construction materials, systems and structures) recommendations provide two alternatives for evaluating frost damage by nondestructive evaluation methods for concrete like materials. The first method is based on the ultrasonic pulse velocity measurement, while the second alternative technique is based on the resonant vibration test. In this study, we monitor the frost damage in Portland cement mortar samples with water to cement ratio of 0.5 and aggregate to cement ratio of 3. The samples are completely saturated by water and are frozen for 24 hours at -25°C. The frost damage is monitored after 0, 5, 10, 15 and 20 freezing-thawing cycles by nonlinear impact resonance acoustic spectroscopy (NIRAS). The results obtained are compared with those obtained by resonant vibration tests, the second alternative technique recommended by RILEM. The obtained results show that NIRAS is more sensitive to early stages of damage than the standard resonant vibration tests.

  19. A literature review of mixed waste components: Sensitivities and effects upon solidification/stabilization in cement-based matrices

    Energy Technology Data Exchange (ETDEWEB)

    Mattus, C.H.; Gilliam, T.M.

    1994-03-01

    The US DOE Oak Ridge Field Office has signed a Federal Facility Compliance Agreement (FFCA) regarding Oak Ridge Reservation (ORR) mixed wastes subject to the land disposal restriction (LDR) provisions of the Resource conservation and Recovery Act. The LDR FFCA establishes an aggressive schedule for conducting treatability studies and developing treatment methods for those ORR mixed (radioactive and hazardous) wastes listed in Appendix B to the Agreement. A development, demonstration, testing, and evaluation program has been initiated to provide those efforts necessary to identify treatment methods for all of the wastes that meet Appendix B criteria. The program has assembled project teams to address treatment development needs in a variety of areas, including that of final waste forms (i.e., stabilization/solidification processes). A literature research has been performed, with the objective of determining waste characterization needs to support cement-based waste-form development. The goal was to determine which waste species are problematic in terms of consistent production of an acceptable cement-based waste form and at what concentrations these species become intolerable. The report discusses the following: hydration mechanisms of Portland cement; mechanisms of retardation and acceleration of cement set-factors affecting the durability of waste forms; regulatory limits as they apply to mixed wastes; review of inorganic species that interfere with the development of cement-based waste forms; review of radioactive species that can be immobilized in cement-based waste forms; and review of organic species that may interfere with various waste-form properties.

  20. Assessment of Pozzolanic Activity Using Methods Based on the Measurement of Electrical Conductivity of Suspensions of Portland Cement and Pozzolan

    OpenAIRE

    Sergio Velázquez; JOSÉ M. MONZÓ; María V. Borrachero; Jordi Payá

    2014-01-01

    The use of methods based on measuring electrical conductivity to assess pozzolanic activity has recently been used primarily in aqueous suspensions of pozzolan: calcium hydroxide. However, the use of similar methods in suspensions of cement with pozzolans has not been widely studied. This paper proposes a new method for rapid assessment of the pozzolanic activity of mineral admixtures in aqueous cement suspensions. In this study, the conditions for the application of the method were optimized...

  1. Dynamic intratubular biomineralization following root canal obturation with pozzolan‐based mineral trioxide aggregate sealer cement

    Science.gov (United States)

    Yoo, Yeon‐Jee; Baek, Seung‐Ho; Kum, Kee‐Yeon; Shon, Won‐Jun; Woo, Kyung‐Mi

    2015-01-01

    Summary The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan‐based (Pz‐) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta‐percha (GP) and Pz‐MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz‐MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin‐material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz‐MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment. SCANNING 38:50–56, 2016. © 2015 The Authors. Scanning Published by Wiley Periodicals, Inc. PMID:26179659

  2. Dynamic intratubular biomineralization following root canal obturation with pozzolan-based mineral trioxide aggregate sealer cement.

    Science.gov (United States)

    Yoo, Yeon-Jee; Baek, Seung-Ho; Kum, Kee-Yeon; Shon, Won-Jun; Woo, Kyung-Mi; Lee, WooCheol

    2016-01-01

    The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan-based (Pz-) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta-percha (GP) and Pz-MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz-MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin-material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz-MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment.

  3. Influence of fluoride- or triclosan-based desensitizing agents on adhesion of resin cements to dentin.

    Science.gov (United States)

    Dündar, Mine; Cal, Ebru; Gökçe, Bülent; Türkün, Murat; Ozcan, Mutlu

    2010-10-01

    Effect of desensitizers on the bond strength of resin cements to dentin was evaluated. Intact premolars (N = 90) were embedded in polymethyl methacrylate; dentin surfaces were exposed, and they were randomly divided into two main groups of cements (Duolink (D), Variolink II (V); n = 45 per group) and then into three desensitizer subgroups (n = 15 per subgroup). Teeth in controls (C) were treated according to cements' adhesion protocols; the other two groups received either fluoride- [Aqua-Prep F (F)] or triclosan-based [Seal&Protect (T)] desensitizers. Ceramic disks (Empress 2) were adhered; specimens were thermocycled (×5,000 cycles, 5-55 ± 1°C, dwell time 30 s) and subjected to shear bond strength test (MPa ± SD) in a universal testing machine (crosshead speed 1 mm/min). Failure types were classified using scanning electron microscope. For V, application of both desensitizers (29.6 ± 7.8 and 22.8 ± 2.8 for F and T, respectively) did not present significantly different results than that of the VC (21.2 ± 2.3; p > 0.05, one-way ANOVA). In D, F (20.6 ± 2.4) showed significantly higher results (p types.

  4. Cement Based Batteries and their Potential for Use in Low Power Operations

    Science.gov (United States)

    Byrne, A.; Holmes, N.; Norton, B.

    2015-11-01

    This paper presents the development of an innovative cement-electrolyte battery for low power operations such as cathodic protection of reinforced concrete. A battery design was refined by altering different constituents and examining the open circuit voltage, resistor loaded current and lifespan. The final design consisted of a copper plate cathode, aluminium plate anode, and a cement electrolyte which included additives of carbon black, plasticiser, Alum salt and Epsom salt. A relationship between age, temperature and hydration of the cell and the current it produced was determined. It was found that sealing the battery using varnish increased the moisture retention and current output. Current was also found to increase with internal temperature of the electrolyte and connecting two cells in parallel further doubled or even tripled the current. Parallel-connected cells could sustain an average current of 0.35mA through a 10Ω resistor over two weeks of recording. The preliminary findings demonstrate that cement-based batteries can produce sufficient sustainable electrical outputs with the correct materials and arrangement of components. Work is ongoing to determine how these batteries can be recharged using photovoltaics which will further enhance their sustainability properties.

  5. Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®).

    Science.gov (United States)

    Cantekin, Kenan; Avci, Serap

    2014-01-01

    Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA). It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB) composites, silorane-based (SB) composites, and glass ionomer cement (GIC) to Biodentine® and mineral trioxide aggregate (MTA). Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole) were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS) test, each block was secured in a universal testing machine. The highest (17.7 ± 6.2 MPa) and the lowest (5.8 ± 3.2 MPa) bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7 ± 6.2) than it did to MTA (8.9 ± 5.7) (p Biodentine® = 8.0 ± 3,6) and GIC (GIC and MTA = 5.8 ± 3.2; GIC and Biodentine = 6.7 ± 2.6) showed similar bond strength performance with MTA compared with Biodentine (p = 0.73 and p = 0.38, respectively). The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.

  6. Evaluation of shear bond strength of two resin-based composites and glass ionomer cement to pure tricalcium silicate-based cement (Biodentine®

    Directory of Open Access Journals (Sweden)

    Kenan CANTEK?N

    2014-07-01

    Full Text Available Objectives: Tricalcium silicate is the major constituent phase in mineral trioxide aggregate (MTA. It is thus postulated that pure tricalcium silicate can replace the Portland cement component of MTA. The aim of this study was to evaluate bond strength of methacrylate-based (MB composites, silorane-based (SB composites, and glass ionomer cement (GIC to Biodentine® and mineral trioxide aggregate (MTA. Material and Methods: Acrylic blocks (n=90, 2 mm high, 5 mm diameter central hole were prepared. In 45 of the samples, the holes were fully filled with Biodentine® and in the other 45 samples, the holes were fully filled with MTA. The Biodentine® and the MTA samples were randomly divided into 3 subgroups of 15 specimens each: Group-1: MB composite; Group-2: SB composite; and Group-3: GIC. For the shear bond strength (SBS test, each block was secured in a universal testing machine. Results: The highest (17.7±6.2 MPa and the lowest (5.8±3.2 MPa bond strength values were recorded for the MB composite-Biodentine® and the GIC-MTA, respectively. Although the MB composite showed significantly higher bond strength to Biodentine (17.7±6.2 than it did to MTA (8.9±5.7 (p<0.001, the SB composite (SB and MTA=7.4±3.3; SB and Biodentine®=8.0±3,6 and GIC (GIC and MTA=5.8±3.2; GIC and Biodentine=6.7±2.6 showed similar bond strength performance with MTA compared with Biodentine (p=0.73 and p=0.38, respectively. Conclusions: The new pure tricalcium-based pulp capping, repair, and endodontic material showed higher shear bond scores compared to MTA when used with the MB composite.

  7. Polycarboxylate Based Superplasticizers as Dispersant Agents for Exfoliated Graphene Nanoplatelets Reinforcing Cement Based Materials

    Directory of Open Access Journals (Sweden)

    Z. S. Metaxa

    2015-12-01

    Full Text Available Graphene nanoplatelets (GNPs are considered one of the most advanced nanomaterials that hold the promise of providing multifunctional characteristics to the cementitious matrix. To effectively employ the GNPs as a nanoreinforcement, their uniform dispersion within the matrix must be achieved. The present study investigates the efficiency of four different polycarboxylate based superplasticizers, which are fully compatible with cement-based materials, to be exploited as GNPs dispersant agents. Exfoliated GNPs were selected that had a quite small diameter/lateral size of ~5 µm. The dispersing efficiency of the superplasticizers was investigated experimentally by measuring the electrical resistivity of the resulting nanocomposites. A discussion explaining the dispersing mechanism of these types of surfactants is provided. The use of a superplasticizer in conjunction with ultrasonic energy application was found to be necessary to properly disperse the GNPs. The results prove that the polycarboxylate based superplasticizers can be employed to promote the GNPs uniform distribution in cementitious materials. The polycarboxylate ester superplasticizer showed poor results, while the polycarboxylate polymer superplasticizers were found to be more effective to uniformly disperse the GNPs.

  8. Effect of artificial saliva and pH on shear bond strength of resin cements to zirconia-based ceramic.

    Science.gov (United States)

    Geramipanah, F; Majidpour, M; Sadighpour, L; Fard, M J Kharazi

    2013-03-01

    The aim of the present study was to evaluate the effect of media with different pH on shear and strength of resin cements to zirconia-based ceramics. Sixty rectangularly shaped specimens made of a zirconia based ceramic (Cercon, Dentsply) were prepared, air-blasted with 110 microm aluminum oxide particles (Al203) and randomly assigned into three groups (n = 30). A universal resin composite (Filtek Z250, 3M/ESPE) was bonded to each specimen using one of the following three cements: Calibra (Dentsply), Panavia F2 (kurary) and Unicem (3M/ESPE). Specimens were thermal cycled and stored in one of the following three media for two weeks: water at pH = 7, saliva at pH = 7 and saliva at pH = 3.5. The mean shear bond strength of each group was analyzed using the Kruskal-Wallis test (alpha = 0.05). The modes of failure were recorded using a streomicroscope. All specimens in the Calibra groups showed premature debonding. No significant difference was found between the two other cements or different media. The failure modes in the two latter cements were predominantly adhesive. Despite the adverse effect of acidic media on the properties of restorative materials, the media did not significantly influence the bond strength of MDP-containing resin cement and a self-adhesive cement to a zirconia- based ceramic.

  9. Evaluation of Compatibility between Beetle-Killed Lodgepole Pine (Pinus Contorta var. Latifolia Wood with Portland Cement

    Directory of Open Access Journals (Sweden)

    Ian D. Hartley

    2010-12-01

    Full Text Available The compatibility of wood from mountain pine beetle (Dendroctonus ponderosa killed lodgepole pine (Pinus contorta var. latifolia with Portland cement was investigated based on time-since-death as a quantitative estimator, and the presence of blue-stained sapwood, brown rot, or white rot as qualitative indicators. The exothermic behavior of cement hydration, maximum heat rate, time to reach this maximum, and total heat released within a 3.5–24 h interval were used for defining a new wood-cement compatibility index (CX. CX was developed and accounted for large discrepancies in assessing wood-cement compatibility compared to the previous methods. Using CX, no significant differences were found between fresh or beetle-killed wood with respect to the suitability for cement; except for the white rot samples which reached or exceeded the levels of incompatibility. An outstanding physicochemical behavior was also found for blue-stained sapwood and cement, producing significantly higher compatibility indices.

  10. Production of Algal-based Biofuel from Non-fresh Water Sources

    Science.gov (United States)

    Sun, A. C.; Reno, M. D.

    2008-12-01

    A system dynamics model is developed to assess the availability and feasibility of non-traditional water sources from dairy wastewater, produced water from crude oil production and from coal-bed methane gas extraction for the production of algal-based biofuel. The conceptual framework is based on two locales within New Mexico, the San Juan basin in the northwest and the Permian basin in the southeast, where oil and gas drilling have increased considerably in the last ten years. The simulation framework contains an algal growth module, a dairy module, an oil production module, and a gas production module. Our preliminary investigation indicates a cyclical demand for non-fresh water due to the cyclical nature of algal biomass production and crop evapotranspiration. The wastewater from the dairy industry is not a feasible non-fresh water source because the agricultural water demand for cow's dry feed far exceeds the amount generated at the dairy. The uncertainty associated with the water demand for cow's dry matter intake is the greatest in this model. The oil and gas produced water, ignoring the quality, provides ample supply for water demand in algal biomass production. There remains work to address technical challenges associated with coupling the appropriate non-fresh water source to the local demand.

  11. Prediction of SEM–X-ray images’ data of cement-based materials using artificial neural network algorithm

    Directory of Open Access Journals (Sweden)

    Ashraf Ragab Mohamed

    2014-09-01

    Full Text Available Recent advances of computational capabilities have motivated the development of more sophisticated models to simulate cement-based hydration. However, the input parameters for such models, obtained from SEM–X-ray image analyses, are quite complicated and hinder their versatile application. This paper addresses the utilization of the artificial neural networks (ANNs to predict the SEM–X-ray images’ data of cement-based materials (surface area fraction and the cement phases’ correlation functions. ANNs have been used to correlate these data, already obtained for 21 types of cement, to basic cement data (cement compounds and fineness. Two approaches have been proposed; the ANN, and the ANN-regression method. Comparisons have shown that the ANN proves effectiveness in predicting the surface area fraction, while the ANN-regression is more computationally suitable for the correlation functions. Results have shown good agreement between the proposed techniques and the actual data with respect to hydration products, degree of hydration, and simulated images.

  12. Near-field microwave inspection and characterization of cement based materials

    Science.gov (United States)

    Bois, Karl Joseph

    The objective of this research project has been to investigate the potential of correlating the near-field microwave reflection coefficient properties of hardened cement paste (water and cement powder), mortar (water, cement powder and sand) and concrete (water, cement powder, sand and coarse aggregate) specimens to their various constituent make-up and compressive strengths. The measurements were conducted using open-ended rectangular waveguide probes operating at various microwave frequencies and in-contact with cubic specimens. For each material, various properties of the measured microwave reflection coefficient, such as the mean of the measured magnitude of reflection coefficient, and the standard deviation of the measured magnitude of reflection coefficient at various frequencies were monitored. Subsequently, the measurements were correlated to important parameters such as w/c ratio, s/c ratio, ca/c ratio, cure-state, constituent volume content and compressive strength. Other issues such as the detection of aggregate segregation in concrete as well as the detection chloride in cement paste and mortar were also addressed. Other related issues such as the detection of grout in masonry blocks were also investigated. In achieving these objectives, several theoretical modeling efforts were required, constituting significant contributions to the available literature. A complete analytical full wave expression (i.e. inclusion of higher-order modes) for the fields at the aperture of an open-ended waveguide probe radiating into a dielectric infinite half-space was derived. Also a novel two-port transmission line dielectric property measurement technique for granular and liquid materials was developed. A decision making process, based on the maximum likelihood scheme, was also implemented to determine w/c, s/c and ca/c ratios from the measured mean and standard deviation of reflection coefficient at two frequency bands. Finally, the issue of non-contact measurement was

  13. Gas permeability of cement based materials; Etude de la permeabilite au gaz des materiaux cimentaires

    Energy Technology Data Exchange (ETDEWEB)

    Galle, Ch.; Pin, M. [CEA Saclay, Dept. d' Entreposage et de Stockage des Dechets (DCC/DESD/SESD), 91 - Gif-sur-Yvette (France); Daian, J.F. [Universite Joseph-Fourier, Grenoble I, (INPG/CNRS/IRD), 38 (France)

    2000-07-01

    The study of the permeability of cement based materials is an important issue for their transport properties, which are good indicators of their durability. Studies were undertaken to acquire experimental data and to model the gas permeability of cement based materials. Among many parameters like cement type, water-cement ratio (w/c), curing, etc, the degree of water saturation and microstructural properties are the two main parameters controlling the ability of such type of materials to transport gas. It is well known that the higher the water saturation, the lower the gas permeability. Under pressure, gas will be also transported through the biggest pore accesses. It must be emphasized that the w/c ratio is the fundamental parameter for cement based materials. This ratio controls the hydration process and hence the material porosity. Gas permeability was calculated with Darcy law as modified by the Hagen-Poiseuille formula (1). Various materials were investigated: pure cement pastes prepared with different types of cement (CEM I-OPC, CEM V-BFS-PFA) and various w/c ratios, and industrial concretes. After curing, the samples were stored under controlled relative humidity conditions using saline solutions to reach a stable hydric state. N{sup 2} gas permeability tests were then performed with a Hassler apparatus. The microstructural properties of CEM I and CEM V materials are given in Figure 2. Examples of experimental results obtained with pure pastes are shown in Figure 3. A comparative example of paste and concrete data is provided in Figure 4. It was experimentally observed that gas permeability is extremely sensitive to material water saturation: up to five orders of magnitude of variation (between 10{sup -16} and 10{sup -21} m{sup 2} on average) for water saturations from a few % to 100%. The higher the w/c ratio, the higher the gas permeability. CEM I pastes are also less permeable than CEM V pastes. The higher total porosity effect of CEM V materials is not

  14. Development of a novel aluminum-free glass ionomer cement based on magnesium/strontium-silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Ae [Department of Biomaterials Science, College of Dentistry, Dankook University, Cheonan 330-714 (Korea, Republic of); Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University Graduate School, Cheonan 330-714 (Korea, Republic of); Abo-Mosallam, Hany A. [Glass Research Department, National Research Centre, Dokki, Cairo (Egypt); Lee, Hye-Young [Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University Graduate School, Cheonan 330-714 (Korea, Republic of); Institute of Tissue Regeneration Engineering (ITREN), Dankook University, Cheonan 330-714 (Korea, Republic of); Kim, Gyu-Ri [Department of Biomaterials Science, College of Dentistry, Dankook University, Cheonan 330-714 (Korea, Republic of); Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University Graduate School, Cheonan 330-714 (Korea, Republic of); Kim, Hae-Won [Department of Biomaterials Science, College of Dentistry, Dankook University, Cheonan 330-714 (Korea, Republic of); Department of Nanobiomedical Science and BK21 Plus NBM Global Research Center for Regenerative Medicine, Dankook University Graduate School, Cheonan 330-714 (Korea, Republic of); Institute of Tissue Regeneration Engineering (ITREN), Dankook University, Cheonan 330-714 (Korea, Republic of); Lee, Hae-Hyoung, E-mail: haelee@dku.edu [Department of Biomaterials Science, College of Dentistry, Dankook University, Cheonan 330-714 (Korea, Republic of); Institute of Tissue Regeneration Engineering (ITREN), Dankook University, Cheonan 330-714 (Korea, Republic of)

    2014-09-01

    The effects of strontium substitution for magnesium in a novel aluminum-free multicomponent glass composition for glass ionomer cements (GICs) were investigated. A series of glass compositions were prepared based on SiO{sub 2}-P{sub 2}O{sub 5}-CaO-ZnO-MgO{sub (1-X)}-SrO{sub X}-CaF{sub 2} (X = 0, 0.25, 0.5 and 0.75). The mechanical properties of GICs prepared were characterized by compressive strength, flexural strength, flexural modules, and microhardness. Cell proliferation was evaluated indirectly by CCK-8 assay using various dilutions of the cement and rat mesenchyme stem cells. Incorporation of strontium instead of magnesium in the glasses has a significant influence on setting time of the cements and the properties. All mechanical properties of the GICs with SrO substitution at X = 0.25 were significantly increased, then gradually decreased with further increase of the amount of strontium substitution in the glass. The GIC at X = 0.25, also, showed an improved cell viability at low doses of the cement extracts in comparison with other groups or control without extracts. The results of this study demonstrate that the glass compositions with strontium substitution at low levels can be successfully used to prepare aluminum-free glass ionomer cements for repair and regeneration of hard tissues. - Highlights: • We developed multicomponent glass compositions for a novel aluminum-free glass ionomer cement (GIC). • The effects of MgO replacement with SrO in the glasses on the mechanical properties and cell proliferation were evaluated. • Substitution of MgO with SrO at low levels led to improvement of mechanical properties and cell viability of the cements. • Microstructural degradations in the cement matrix of the GICs with strontium at high levels were observed after aging.

  15. EFFECT OF FLUORIDE-CONTAINING DESENSITIZING AGENTS ON THE BOND STRENGTH OF RESIN-BASED CEMENTS TO DENTIN

    Science.gov (United States)

    Saraç, Duygu; Külünk, Safak; Saraç, Y. Sinasi; Karakas, Özlem

    2009-01-01

    Objective: The objective of this study was to evaluate the effect of desensitizing agents containing different amounts of fluoride on the shear bond strength of a dual polymerized resin cement and a resin-modified glass ionomer cement (RMGIC) to dentin. Material and Methods: One hundred human molars were mounted in acrylic resin blocks and prepared until the dentin surface was exposed. The specimens were treated with one of four desensitizing agents: Bifluorid 12, Fluoridin, Thermoline and PrepEze. The remaining 20 specimens served as untreated controls. All groups were further divided into 2 subgroups in which a dual polymerized resin cement (Bifix QM) or a resin-modified glass ionomer cement (AVANTO) was used. The shear bond strength (MPa) was measured using a universal testing machine at a 0.5 mm/min crosshead speed. The data were analyzed statistically with a 2-way ANOVA, Tukey HSD test and regression analysis (α=0.05). The effect of the desensitizing agents on the dentin surface was examined by scanning electron microscopy. Results: The fluoride-containing desensitizing agents affected the bond strength of the resin-based cements to dentin (p<0.001). PrepEze showed the highest bond strength values in all groups (p<0.001). Conclusion: Regression analysis showed a reverse relation between bond strength values of resin cements to dentin and the amount of fluoride in the desensitizing agent (p<0.05). PMID:19936532

  16. PMMA-based composite materials with reactive ceramic fillers: IV. Radiopacifying particles embedded in PMMA beads for acrylic bone cements.

    Science.gov (United States)

    Abboud, M; Casaubieilh, L; Morvan, F; Fontanille, M; Duguet, E

    2000-01-01

    New acrylic bone cements were prepared from alumina particles previously treated by 3-(trimethoxysilyl)propylmethacrylate (gamma-MPS) and embedded in poly(methylmethacrylate-co-ethylacrylate) beads with about 7 mol% of ethyl acrylate repeating units. The encapsulation was performed through a conventional suspension polymerization process. The influence of (i) the concentration of the dispersion stabilizer and (ii) the alumina content upon the shape, size, and size distribution of the acrylic beads was studied. Cements were prepared from each batch by hand-mixing alumina-filled acrylic beads with a liquid monomer mixture containing methyl methacrylate, n-butyl methacrylate, and N,N-dimethyl-p-toluidine. Benzoyl peroxide was previously added to the solid part. The powder-to-liquid ratio was equal to 2 for each formulation. Compressive strength of cured cement decreases with alumina content, whereas compressive modulus remains roughly constant. These results are in contradiction to those obtained for cements based on a mixture of gamma-MPS-treated alumina and unfilled acrylic beads. Nevertheless, they are interpreted in terms of alumina arrangement in the cement. In the first case, alumina particles contribute to the reinforcement of the dispersed acrylic phase, with poor benefits for the whole materials. In the second case, they allow the reinforcement of the continuous acrylic phase and, therefore, the cement's one.

  17. Fresh Frozen Plasma Administration in the Neonatal Intensive Care Unit: Evidence-Based Guidelines.

    Science.gov (United States)

    Motta, Mario; Del Vecchio, Antonio; Chirico, Gaetano

    2015-09-01

    Neonates receiving fresh frozen plasma (FFP) should do so according to evidence-based guidelines so as to reduce inappropriate use of this life-saving and costly blood product and to minimize associated adverse effects. The consensus-based uses of FFP in neonatology involve neonates with active bleeding and associated coagulopathy. However, because of limited and poor-quality evidence, considerable FFP utilization occurs outside these recommendations. In this review, we describe what we conclude are currently the best practices for the use of FFP in neonates, including interpreting neonatal coagulation tests and strategies for reducing unnecessary FFP transfusions.

  18. Finite element-based preclinical testing of cemented total hip implants

    NARCIS (Netherlands)

    Stolk, J.; Janssen, D.; Huiskes, R.; Verdonschot, N.J.J.

    2007-01-01

    We developed a finite element model to preclinically test cemented hip implants for damage accumulation, including cement crack formation, creep, and stem migration. Using this model, we simulated the mechanical failure processes of four cemented total hip arthroplasty implants (Lubinus SPII,

  19. Investigation of Phosphate Cement-based Binder with Super High Early Strength for Repair of Concrete

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Magnesium phosphate cement-based binder (MPB) for repair of concrete was prepared by proportionally mixing over burned MgO powder (M) with NHH2PO4 powder (P) and set modifying admixtures. It is characteristic by excellent properties such as rapid setting,high strength and high bond strength to old concrete.. The study is focused on the key factors influencing the setting time and strength of MPB, the bond property of MPB to old concrete and the kinetic feature of the hydration of MPB.

  20. Abnormal gradient microstructure in Cr3C2 based cemented carbide

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With OLYMPUS PMG3 metallograph, an abnormal throe-layer gradient structure , i. e. coarsegrain zone, binder enrichment zone and normal structure zone from surface to inner, was observed in Cr3C2based cemented carbide. In the binder enrichment zone, three different shapes of anomalous coarse carbideswere observed. It is shown that the transverse rapture strength can be raised remarkably, up 20.7% from thealloy with abnormal gradient structure by removing the abnormal gradient structure. The results suggested thatthe abnormal gradient structure in the surface, especially the anomalous coarse carbides in the binder enrichment zone is the mair reason for the lower strength.

  1. ALKALI-ACTIVATED CEMENT MORTARS CONTAINING RECYCLED CLAY-BASED CONSTRUCTION AND DEMOLITION WASTE

    OpenAIRE

    Puertas, F.; Santos, R.; Alonso M. M.; Del Rio M.

    2015-01-01

    The use of clay-based waste as an aggregate for concrete production is an amply studied procedure. Nonetheless, research on the use of this recycled aggregate to prepare alkaline cement mortars and concretes has yet to be forthcoming. The present study aimed to determine: the behaviour of this waste as a pozzolan in OPC systems, the mechanical strength in OPC, alkali-activated slag (AAS) and fly ash (AAFA) mortars and the effect of partial replacement of the slag and ash themselves with groun...

  2. Preparation of lunar regolith based geopolymer cement under heat and vacuum

    Science.gov (United States)

    Davis, Gabrielle; Montes, Carlos; Eklund, Sven

    2017-04-01

    Ever since the beginning of the space program, lunar habitation has always been on peoples' minds. Prior researchers have explored habitat building materials - some based on earth-based construction materials, some based on in-situ lunar resources. Geopolymer cement is a cementitious binder made of aluminosilicate materials such as lunar regolith. A cementitious binder made of lunar regolith as the main geopolymer precursor, instead of as an added aggregate, is a solution that has not been deeply explored in prior works. This research explores the curing process of lunar regolith based geopolymer cement in an environment that loosely approximates the lunar environment, using the lunar average daytime temperature and a vacuum. The results did not show much promise for the samples cured under both heat and vacuum as the longest-cured data point did not meet compressive strength standards, but another pathway to lunar habitation may be found in a separate set of samples that cured under heat and ambient atmospheric pressure.

  3. Nanohydroxyapatite Silicate-Based Cement Improves the Primary Stability of Dental Implants: An In Vitro Study

    Directory of Open Access Journals (Sweden)

    Hooman Khorshidi

    2017-01-01

    Full Text Available Objectives. Insufficient cortical bone volume when placing implants can lead to lack of primary stability. The use of cement as a bone fill material in bone defects around dental implant could result in better clinical outcome. HA has shown excellent biological properties in implant dentistry. The purpose of this study was to evaluate the effect of nanohydroxyapatite powder (Nano-HA in combination with accelerated Portland cement (APC on implant primary stability in surgically created circumferential bone defects in a bovine rib in vitro model. Materials and Methods. Sixteen bovine rib bones and thirty-six implants of same type and size (4 mm × 10 mm were used. Implants were divided into six groups: no circumferential bone defect, defect and no grafting, bone chips grafting, Nano-HA grafting, APC grafting, and Nano-HA mixed to APC grafting (Nano-HA-APC. Circumferential defects around the implants were prepared. The implant stability quotient (ISQ values were measured before and after the grafting. Results. APC exhibited the highest ISQ values. A significant increase of ISQ values following the grafting of Nano-HA-APC (18.08±5.82 and APC alone (9.50±4.12 was achieved. Increase of ISQ values after 72 hours was 24.16±5.01 and 17.58±4.89, respectively. Nano-HA grafting alone exhibited the least rise in ISQ values. Conclusions. Nanohydroxyapatite silicate-based cement could improve the primary stability of dental implants in circumferential bone defect around implants.

  4. Effect of Fly Ash on TSA Resistance of Cement-based Material

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fengchen; MA Baoguo; WU Shengxing; ZHOU Jikai

    2011-01-01

    Thaumasite form of sulfate attack (TSA) is a major concern in evaluating durability of concrete structures subjected to sulfate and carbonate ions. By means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM),and energy dispersive spectrum (EDS)as well as Raman spectra of erosion substances, effect of fly ash on TSA resistance of Portland cement-based material were investigated. Immersed in magnesium sulfate solution with 33 800 ppm mass concentration of SO42- at 5±2 ℃ for 15 weeks, ratio of compressive strength loss decreased as binder replacement ratio of fly ash increased. Furthermore, when binder replacement of fly ash was 60%, compressive strength increased. When thaumasite came into being in samples with 0, 15% binder replacement ratio of fly ash, ettringite and gypsum appeared in those with 30%, 45%, 60% binder replacement ratio of fly ash. Results mentioned above showed that fly ash can restrain formation of thaumasite and improve TSA resistance of Portland cement-based material sufficiently.

  5. Radiopacity evaluation of Portland and MTA-based cements by digital radiographic system

    Directory of Open Access Journals (Sweden)

    Alvaro Henrique Borges

    2011-06-01

    Full Text Available OBJECTIVE: The aim of the present study was to evaluate the radiopacity of Portland and MTA-based cements using the Digora TM digital radiographic system. MATERIAL AND METHODS: The performed tests followed specification number 57 from the American National Standard Institute/American Dental Association (2000 for endodontic sealing materials. The materials were placed in 5 acrylic plates, especially designed for this experiment, along with a graduated aluminum stepwedge varying from 1 to 10 mm in thickness. The set was radiographed at a 30 cm focus-object distance and with 0.2 s exposure time. After the radiographs were taken, the optical laser readings of radiographs were performed by Digora TM system. Five radiographic density readings were performed for each studied material and for each step of the aluminum scale. RESULTS: White ProRoot MTA (155.99±8.04, gray ProRoot MTA (155.96±16.30 and MTA BIO (143.13±16.94 presented higher radiopacity values (p<0.05, while white non-structural Portland (119.76±22.34, gray Portland (109.71±4.90 and white structural Portland (99.59±12.88 presented lower radiopacity values (p<0.05. CONCLUSIONS: It was concluded that MTA-based cements were the only materials presenting radiopacity within the ANSI/ADA specifications.

  6. Quantification of uncertainty of experimental measurement in leaching test on cement-based materials.

    Science.gov (United States)

    Coutand, M; Cyr, M; Clastres, P

    2011-10-01

    When mineral wastes are reused in construction materials, a current practice is to evaluate their environmental impact using standard leaching test. However, due to the uncertainty of the measurement, it is usually quite difficult to estimate the pollutant potential compared to other materials or threshold limits. The aim of this paper is to give a quantitative evaluation of the uncertainty of leachate concentrations of cement-based materials, as a function of the number of test performed. The relative standard deviations and relative confidence intervals are determined using experimental data in order to give a global evaluation of the uncertainty of leachate concentrations (determination of total relative standard deviation). Various combinations were realized in order to point out the origin of large dispersion of the results (determination of relative standard deviation linked to analytical measured and to leaching procedure), generalisation was suggested and the results were compared to literature. An actual example was given about the introduction of residue (meat and bone meal bottom ash--MBM-BA) in mortar, leaching tests were carried out on various samples with and without residue MBM-BA. In conclusion large dispersion were observed and mainly due to heterogeneity of materials. So heightened attention needed to analyse leaching result on cement-based materials and further more other tests (e.g. ecotoxicology) should be performed to evaluate the environmental effect of these materials.

  7. Evaluation of sealing ability of two temporary resin-based cements used in Endodontics

    Directory of Open Access Journals (Sweden)

    Paloma Mariana Ramos Bitencourt

    2010-07-01

    Full Text Available Introduction: The outcome of endodontic treatment is related to the sealing ability of temporary dental restoration, which aims to prevent bacterial infiltration and recontamination of the root canal system.Objective: The purpose of this study was to evaluate the sealing ability of two temporary resin-based cements: Fill Magic Tempo and Bioplic.Material and methods: Twenty-four third molars were used, and twenty-two of them were opened to the pulp chamber (resulting in a class I cavity and randomly divided: group 1 was restored using Fill Magic Tempo (n = 10 and group 2 was restored using Bioplic (n = 10.The negative control group was not opened (n = 2, and the positive control group was opened but not restored (n = 2. Then the root and apex of the teeth were varnished to become impermeable. All samples were immersed in 2% methylene blue and kept at 37°C for 72h.After longitudinal sectioning, the linear leakage was measured in mm.In sequence, the statistical analysis was performed using Mann-Whitney test with a level of significance of 5%. Results: Most part of the samples showed leakage of 1 mm, and only the negative control group showed total leakage. There was no significant difference between the tested materials. Conclusion: It is possible to conclude that both resin-based cements showed satisfactory results on sealing ability during endodontic treatment.

  8. Research on a Defects Detection Method in the Ferrite Phase Shifter Cementing Process Based on a Multi-Sensor Prognostic and Health Management (PHM System

    Directory of Open Access Journals (Sweden)

    Bo Wan

    2016-08-01

    Full Text Available The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM theory. Aiming at these process defects, the reasons that lead to defects are analyzed in this paper. In the meanwhile, the key process parameters were determined and Differential Scanning Calorimetry (DSC tests during the cure process of resin cementing were carried out. At the same time, in order to get data on changing cementing strength, multiple-group cementing process tests of different key process parameters were designed and conducted. A relational model of cementing strength and cure temperature, time and pressure was established, by combining data of DSC and process tests as well as based on the Avrami formula. Through sensitivity analysis for three process parameters, the on-line detection decision criterion and the process parameters which have obvious impact on cementing strength were determined. A PHM system with multiple temperature and pressure sensors was established on this basis, and then, on-line detection, diagnosis and control for ferrite phase shifter cementing process defects were realized. It was verified by subsequent process that the on-line detection system improved the reliability of the ferrite phase shifter cementing process and reduced the incidence of insufficient cementing strength defects.

  9. Research on a Defects Detection Method in the Ferrite Phase Shifter Cementing Process Based on a Multi-Sensor Prognostic and Health Management (PHM) System

    Science.gov (United States)

    Wan, Bo; Fu, Guicui; Li, Yanruoyue; Zhao, Youhu

    2016-01-01

    The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM) theory. Aiming at these process defects, the reasons that lead to defects are analyzed in this paper. In the meanwhile, the key process parameters were determined and Differential Scanning Calorimetry (DSC) tests during the cure process of resin cementing were carried out. At the same time, in order to get data on changing cementing strength, multiple-group cementing process tests of different key process parameters were designed and conducted. A relational model of cementing strength and cure temperature, time and pressure was established, by combining data of DSC and process tests as well as based on the Avrami formula. Through sensitivity analysis for three process parameters, the on-line detection decision criterion and the process parameters which have obvious impact on cementing strength were determined. A PHM system with multiple temperature and pressure sensors was established on this basis, and then, on-line detection, diagnosis and control for ferrite phase shifter cementing process defects were realized. It was verified by subsequent process that the on-line detection system improved the reliability of the ferrite phase shifter cementing process and reduced the incidence of insufficient cementing strength defects. PMID:27517935

  10. Research on a Defects Detection Method in the Ferrite Phase Shifter Cementing Process Based on a Multi-Sensor Prognostic and Health Management (PHM) System.

    Science.gov (United States)

    Wan, Bo; Fu, Guicui; Li, Yanruoyue; Zhao, Youhu

    2016-08-10

    The cementing manufacturing process of ferrite phase shifters has the defect that cementing strength is insufficient and fractures always appear. A detection method of these defects was studied utilizing the multi-sensors Prognostic and Health Management (PHM) theory. Aiming at these process defects, the reasons that lead to defects are analyzed in this paper. In the meanwhile, the key process parameters were determined and Differential Scanning Calorimetry (DSC) tests during the cure process of resin cementing were carried out. At the same time, in order to get data on changing cementing strength, multiple-group cementing process tests of different key process parameters were designed and conducted. A relational model of cementing strength and cure temperature, time and pressure was established, by combining data of DSC and process tests as well as based on the Avrami formula. Through sensitivity analysis for three process parameters, the on-line detection decision criterion and the process parameters which have obvious impact on cementing strength were determined. A PHM system with multiple temperature and pressure sensors was established on this basis, and then, on-line detection, diagnosis and control for ferrite phase shifter cementing process defects were realized. It was verified by subsequent process that the on-line detection system improved the reliability of the ferrite phase shifter cementing process and reduced the incidence of insufficient cementing strength defects.

  11. Evaluation of Calcium Fluoroaluminosilicate Based Glass Ionomer Luting Cements Processed Both by Conventional and Microwave Assisted Methods

    Directory of Open Access Journals (Sweden)

    Nagaraja Upadhya P.

    2015-03-01

    Full Text Available Calcium fluoroaluminosilicate glasses (CAS are used in the formulation of glass ionomer cements for dental applications. However, the cements obtained from CAS glasses were found to be radiolucent. In this study, the influence of substituting Zn, Sr and Mg for Ca of CAS glasses was investigated with respect to the structure and setting characteristics, mechanical properties, and radiopacity of cements designed for luting applications. Three glass compositions based on substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio was synthesized. They were coded as the G 021 (Ca: Zn, G 022 (Ca: Sr, G 023 (Ca: Mg. G 021 and G 022 glasses were processed by conventional melt quench route, whereas G 023 was processed by microwave melt–quench route. Each glass was then mixed with Fuji Type I GIC liquid in order to evaluate the properties of novel cements at different powder/liquid ratios. X-ray diffraction and Fourier Transform-Infrared spectroscopy analysis confirmed the structure of the processed glasses. The average particle size of the processed glass powders was within specification limits for luting applications (<15 μm. The substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio increased the reactivity of the respective glasses. This has been reflected in their respective setting characteristics and mechanical properties. The optimal combination of setting time, strength and radiopacity for the cements examined here was shown by G 022 cements. The microwave melting can be utilized for processing ionomer glasses as it did not alter the structure and properties of G 023 cement.

  12. Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

    Science.gov (United States)

    Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

    Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

  13. Study on Strength and Microstructure of Cement-Based Materials Containing Combination Mineral Admixtures

    Directory of Open Access Journals (Sweden)

    Meijuan Rao

    2016-01-01

    Full Text Available The compressive strength of complex binders containing two or three blended mineral admixtures in terms of glass powder (GP, limestone powder (LP, and steel slag powder (SP was determined by a battery solution type compressive testing machine. The morphology and microstructure characteristics of complex binder hydration products were also studied by microscopic analysis methods, such as XRD, TG-DTA, and SEM. The mechanical properties of the cement-based materials were analyzed to reveal the most appropriate mineral admixture type and content. The early sample strength development with GP was very slow, but it rapidly grew at later stages. The micro aggregate effect and pozzolanic reaction mutually occurred in the mineral admixture. In the early stage, the micro aggregate effect reduced paste porosity and the small particles connected with the cement hydration products to enhance its strength. In the later stage, the pozzolanic reaction of some components in the complex powder occurred and consumed part of the calcium hydroxide to form C-S-H gel, thus improving the hydration environment. Also, the produced C-S-H gel made the structure more compact, which improved the structure’s strength.

  14. Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration.

    Science.gov (United States)

    Sarkar, Swapan Kumar; Lee, Byung Yeol; Padalhin, Andrew Reyas; Sarker, Avik; Carpena, Nathaniel; Kim, Boram; Paul, Kallyanshish; Choi, Hwan Jun; Bae, Sang-Ho; Lee, Byong Taek

    2016-01-01

    In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation.

  15. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials

    Directory of Open Access Journals (Sweden)

    Selen Küçükkaya

    2016-01-01

    Full Text Available The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P>0.05. MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P<0.05. Biodentine showed significantly less cell viability (73% after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P<0.05. Despite the significant changes in cell viability over time, materials presented similar cytotoxicity profile. Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  16. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials.

    Science.gov (United States)

    Küçükkaya, Selen; Görduysus, Mehmet Ömer; Zeybek, Naciye Dilara; Müftüoğlu, Sevda Fatma

    2016-01-01

    The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM) cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P > 0.05). MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P Biodentine showed significantly less cell viability (73%) after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  17. Development of shrinkage and fracture parameters in selected fine-grained cement-based composites

    Directory of Open Access Journals (Sweden)

    Kucharczyková Barbara

    2017-01-01

    Full Text Available The paper summarizes results of a pilot study aimed at the evaluation of an experimental investigation focused on determination of the material characteristics development of selected fine-grained cement-based composites during their ageing. The composition of composites being investigated differed only in a water to cement (w/c ratio and in amount of superplasticizer. Quite extensive experiments were performed with the aim to determine shrinkage, dynamic a static modulus of elasticity and fracture properties on test specimens exposed to free drying during the whole time of its ageing (including the early stage of setting and hardening. The article presents especially results (including their statistical evaluation of shrinkage and fracture parameters development within 90 days of composites’ ageing. Experimental results show the dependence of the investigated characteristics on the value of w/c ratio. The most visible effect was observed in the case of shrinkage development. The curing conditions were reflected especially in high variability of the test results.

  18. Cytotoxicities and genotoxicities of cements based on calcium silicate and of dental formocresol.

    Science.gov (United States)

    Ko, Hyunjung; Jeong, Youngdan; Kim, Miri

    2017-03-01

    Increasing interest is being paid to the toxicities of dental materials. The purpose of this study was to determine the cytotoxicities and genotoxicities of endodontic compounds to Chinese hamster ovary (CHO-K1) reproductive cells. Cultured CHO-K1 cells were treated with dental formocresol, two types of calcium hydroxide paste, and two types of mineral trioxide aggregate cement for 24h. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was performed on each culture, and the micronucleus frequency was determined by performing a micronucleus assay. Alkaline comet assay and γ-H2AX immunofluorescence assay were used to detect DNA damage. Out of the five materials tested, only dental formocresol significantly increased DNA damage. The mineral trioxide aggregate cements based on calcium silicate were not found to be potentially genotoxic. The data suggest that dental formocresol should not be recommended for use in vital pulp therapy on young teeth. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid...

  20. Development of a novel aluminum-free glass ionomer cement based on magnesium/strontium-silicate glasses.

    Science.gov (United States)

    Kim, Dong-Ae; Abo-Mosallam, Hany A; Lee, Hye-Young; Kim, Gyu-Ri; Kim, Hae-Won; Lee, Hae-Hyoung

    2014-09-01

    The effects of strontium substitution for magnesium in a novel aluminum-free multicomponent glass composition for glass ionomer cements (GICs) were investigated. A series of glass compositions were prepared based on SiO2-P2O5-CaO-ZnO-MgO(1-X)-SrOX-CaF2 (X=0, 0.25, 0.5 and 0.75). The mechanical properties of GICs prepared were characterized by compressive strength, flexural strength, flexural modules, and microhardness. Cell proliferation was evaluated indirectly by CCK-8 assay using various dilutions of the cement and rat mesenchyme stem cells. Incorporation of strontium instead of magnesium in the glasses has a significant influence on setting time of the cements and the properties. All mechanical properties of the GICs with SrO substitution at X=0.25 were significantly increased, then gradually decreased with further increase of the amount of strontium substitution in the glass. The GIC at X=0.25, also, showed an improved cell viability at low doses of the cement extracts in comparison with other groups or control without extracts. The results of this study demonstrate that the glass compositions with strontium substitution at low levels can be successfully used to prepare aluminum-free glass ionomer cements for repair and regeneration of hard tissues.

  1. Characterization of a calcium phosphate cement based on alpha-tricalcium phosphate obtained by wet precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Thurmer, M.B.; Diehl, C.E.; Vieira, R.S.; Coelho, W.T.G.; Santos, L.A., E-mail: monicathurmer@yahoo.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia de Materiais

    2012-07-01

    There are several systems of calcium phosphate cements being studied. Those based on alpha-tricalcium phosphate are of particular interest. After setting they produce calcium deficient hydroxyapatite similar to bone like hydroxyapatite. This work aims to obtain alpha-tricalcium phosphate powders by the wet precipitation process, using calcium nitrate and phosphoric acid as reagents. This powder was characterized by infrared spectroscopy, X-ray diffraction and particle size distribution. In order to prepare the calcium phosphate cement, the powder was mixed with an accelerator in an aqueous solution. The mechanical properties of the cement were assessed and it was evaluated by means of apparent density, X-ray diffraction and scanning electron microscopy. The described method produced crystalline alpha-tricalcium phosphate as the major phase. The calcium phosphate cement showed high values of compression strength (50 MPa). The soaking of the cement in a simulated body fluid (SBF) formed a layer of hydroxyapatite like crystals in the surface of the samples. (author)

  2. Limitation in obtainable surface roughness of hardened cement paste: 'virtual' topographic experiment based on focussed ion beam nanotomography datasets.

    Science.gov (United States)

    Trtik, P; Dual, J; Muench, B; Holzer, L

    2008-11-01

    Surface roughness affects the results of nanomechanical tests. The surface roughness values to be measured on a surface of a porous material are dependent on the properties of the naturally occurring pore space. In order to assess the surface roughness of hardened cement paste (HCP) without the actual influence of the usual sample preparation for nanomechanical testing (i.e. grinding and polishing), focussed ion beam nanotomography datasets were utilized for reconstruction of 3D (nanoscale resolution) surface profiles of hardened cement pastes. 'Virtual topographic experiments' were performed and root mean square surface roughness was then calculated for a large number of such 3D surface profiles. The resulting root mean square (between 115 and 494 nm) is considerably higher than some roughness values (as low as 10 nm) reported in the literature. We suggest that thus-analysed root mean square values provide an estimate of a 'hard' lower limit that can be achieved by 'artefact-free' sample preparation of realistic samples of hardened cement paste. To the best of our knowledge, this 'hard' lower limit was quantified for a porous material based on hydraulic cement for the first time. We suggest that the values of RMS below such a limit may indicate sample preparation artefacts. Consequently, for reliable nanomechanical testing of disordered porous materials, such as hardened cement paste, the preparation methods may require further improvement.

  3. Biomonitoring Study of Heavy Metals in Blood from a Cement Factory Based Community

    OpenAIRE

    Bank M.S.; Spengler J.D.

    2014-01-01

    Little is known about the effects of cement factory pollution, emissions, and kiln dust on contaminant exposure in human populations, including school environments, in close proximity to these point sources. In Ravena, New York, USA and vicinity, environmental pollution from a local cement plant is considered significant and substantial according to the United States Environmental Protection Agency’s Toxic Release Inventory, published in 2006, 2007, and 2010. We hypothesized that cement facto...

  4. Surface and subsurface damage detection in cement-based materials using electrical resistance tomography

    Science.gov (United States)

    Ruan, T.; Poursaee, A.

    2016-04-01

    Cement-based materials are widely used in infrastructure facilities. However, often the degradation of structures leads to the failures earlier than designed service life. Thus, non-destructive testing techniques are urgently needed to evaluate the health information of the structures. In this paper, the implementation of Electrical Resistance Tomography (ERT) was investigated. This low cost, radiation free and easy to perform modality is based on measuring the electrical properties of the material under test and using that to evaluate the existence of defects in that material. It uses a set of boundary potentials and injected current to reconstruct the conductivity distribution. An automatic measurement system was developed and surface damages as well as subsurface damages on mortar specimens were investigated. The reconstructed images were capable to show the presence and the location of the damages.

  5. Pavement structure mechanics response of flexible on semi-flexible overlay that based on the old cement concrete pavement damage

    Directory of Open Access Journals (Sweden)

    Jiang Ruinan

    2015-01-01

    Full Text Available The old cement pavement damage status directly affect the design of the paving renovation. Based on the state of the old road investigation, combined with the research data at home and abroad, use the control index that average deflection, deflection value and CBR value to determine the reasonable time to overlay. Draw up the typical pavement structure according to the principle of combination of old cement pavement overlay structure design, and calculated that the tensile stress and shear stress in asphalt layer ,semi-flexible layer and the tensile in the old cement pavement adopting BISA3.0 statics finite element analysis model when modulus in the old road was diminishing. Use the computed result to analyses the influence of old road damage condition the influence of pavement structure.

  6. Applications of solid-state Nuclear Magnetic Resonance (NMR) in studies of Portland cements-based materials

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Andersen, Morten Daugaard; Jakobsen, Hans Jørgen

    2007-01-01

    Solid-state NMR spectroscopy represents an important research tool in the characterization of a range of structural properties for cement-based materials. Different approaches of the technique can be used to obtain information on hydration kinetics, mobile and bound water, porosity, and local...... atomic structures. After a short introduction to these NMR techniques, it is exemplified how magic-angle spinning (MAS) NMR can provide quantitative and structural information about specific phases in anhydrous and hydrated Portland cements with main emphasis on the incorporation of Al3+ ions...

  7. Polarization Second Harmonic Generation Discriminates Between Fresh and Aged Starch-Based Adhesives Used in Cultural Heritage.

    Science.gov (United States)

    Psilodimitrakopoulos, Sotiris; Gavgiotaki, Evaggelia; Melessanaki, Kristallia; Tsafas, Vassilis; Filippidis, George

    2016-10-01

    In this work, we report that polarization second harmonic generation (PSHG) microscopy, commonly used in biomedical imaging, can quantitatively discriminate naturally aged from fresh starch-based glues used for conservation or restoration of paintings, works of art on paper, and books. Several samples of fresh and aged (7 years) flour and starch pastes were investigated by use of PSHG. In these types of adhesives, widely used in cultural heritage conservation, second harmonic generation (SHG) contrast originates primarily from the starch granules. It was found that in aged glues, the starch SHG effective orientation (SHG angle, θ) shifts to significantly higher values in comparison to the fresh granules. This shift is attributed to the different degree of granule hydration between fresh and aged adhesives. Thus noninvasive high-resolution nonlinear scattering can be employed to detect and quantify the degree of deterioration of restoration adhesives and to provide guidance toward future conservation treatments.

  8. Effect of physicochemical properties of a cement based on silicocarnotite/calcium silicate on in vitro cell adhesion and in vivo cement degradation.

    Science.gov (United States)

    Aparicio, Julia Lucas; Rueda, Carmen; Manchón, Ángel; Ewald, Andrea; Gbureck, Uwe; Alkhraisat, Mohammad Hamdan; Jerez, Luis Blanco; Cabarcos, Enrique López

    2016-08-02

    A silicon calcium phosphate cement (Si-CPC) was developed to produce a composite of calcium phosphate and calcium silicate. The silicon cements prepared with low silicon (Si) content were composed of crystalline phases of brushite and silicocarnotite. However, the cements prepared with high Si content were mainly composed of amorphous phases of silicocarnotite, hydroxyapatite and calcium silicate. The cement porosity was about 40% with a shift of the average pore diameter to the nanometric range with increasing Si content. Interestingly, this new cement system provides a matrix with a high specific surface area of up to 29 m(2) g(-1). The cytocompatibility of the new Si-doped cements was tested with a human osteoblast-like cell line (MG-63) showing an enhancement of cell proliferation (up to threefold) when compared with unsubstituted material. Cements with a high silica content also improved the cell attachment. The in vivo results indicated that Si-CPCs induce the formation of new bone tissue, and modify cement resorption. We conclude that this cement provides an optimal environment to enhance osteoblast growth and proliferation that could be of interest in bone engineering.

  9. Development programs in the United States of America for the application of cement-based grouts in radioactive waste management

    Energy Technology Data Exchange (ETDEWEB)

    Dole, L.R.; Row, T.H.

    1984-01-01

    This paper briefly reviews seven cement-based waste form development programs at six of the US Department of Energy (DOE) sites. These sites have developed a variety of processes that range from producing 25 mm (1 in.) diameter pellets in a glove box to producing 240 m (800 ft.) diameter grout sheets within the bedding planes of a deep shale formation. These successful applications of cement-based waste forms to the many radioactive waste streams from nuclear facilities bear witness to the flexibility and reliability of this class of materials. This paper also discusses the major issues regarding the application of cement-based waste forms to radioactive waste management problems. These issues are (1) leachability, (2) radiation stability, (3) thermal stability, (4) phase complexity of the matrix, and (5) effects of the waste stream composition. A cursory review of current research in each of these areas is given This paper also discusses future trends in cement-based waste form development and applications. 31 references, 11 figures.

  10. High Water Content Material Based on Ba-Bearing Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    CHANG Jun; CHENG Xin; LU Lingchao; HUANG Shifeng; YE Zhengmao

    2005-01-01

    A new type of high water content material which is made up of two pastes is prepared, one is made from lime and gypsum, and another is based on Ba-bearing stdphoaluminate cement. It has excellent properties such as slow single paste solidifing,fast double pastes solidifing,fast coagulating and hardening, high early strength, good suspension property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD , DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.

  11. Measurement with corrugated tubes of early-age autogenous shrinkage of cement-based material

    DEFF Research Database (Denmark)

    Tian, Qian; Jensen, Ole Mejlhede

    2009-01-01

    The use of a special corrugated mould enables transformation of volume strain into horizontal, linear strain measurement in the fluid stage. This allows continuous measurement of the autogenous shrinkage of cement-based materials since casting, and also effectively eliminates unwanted influence...... on the measuring results from gravity, temperature variation and mould restraint. In this paper the principle of the corrugated tube measurement is described. A systematic study was carried out on the influence on the measuring results of the material properties, size effects and encapsulated air in the corrugated...... tube. The experimental results show that there is a minor influence on the measuring results of the stiffness and size of the plastic tube as well as of the encapsulated air. However, the influence decreases with the hardening process and becomes negligible a few hours after final set....

  12. Si-based thin film coating on Y-TZP: Influence of deposition parameters on adhesion of resin cement

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz, José Renato Cavalcanti, E-mail: joserenatocq@hotmail.com [Potiguar University, Department of Biotechnology, Natal (Brazil); Nogueira Junior, Lafayette [São Paulo State University, Department of Prosthodontics and Dental Materials, São José dos Campos (Brazil); Massi, Marcos [Federal University of São Paulo, Institute of Science and Technology, São José dos Campos (Brazil); Silva, Alecssandro de Moura; Bottino, Marco Antonio [São Paulo State University, Department of Prosthodontics and Dental Materials, São José dos Campos (Brazil); Sobrinho, Argemiro Soares da Silva [Technological Institute of Aeronautics, Department of Physics, São José dos Campos (Brazil); Özcan, Mutlu [University of Zurich, Dental Materials Unit, Center for Dental and Oral Medicine, Clinic for Fixed and Removable Prosthodontics and Dental Materials Science, Zurich (Switzerland)

    2013-10-01

    This study evaluated the influence of deposition parameters for Si-based thin films using magnetron sputtering for coating zirconia and subsequent adhesion of resin cement. Zirconia ceramic blocks were randomly divided into 8 groups and specimens were either ground finished and polished or conditioned using air-abrasion with alumina particles coated with silica. In the remaining groups, the polished specimens were coated with Si-based film coating with argon/oxygen magnetron discharge at 8:1 or 20:1 flux. In one group, Si-based film coating was performed on air-abraded surfaces. After application of bonding agent, resin cement was bonded. Profilometry, goniometry, Energy Dispersive X-ray Spectroscopy and Rutherford Backscattering Spectroscopy analysis were performed on the conditioned zirconia surfaces. Adhesion of resin cement to zirconia was tested using shear bond test and debonded surfaces were examined using Scanning Electron Microscopy. Si-based film coating applied on air-abraded rough zirconia surfaces increased the adhesion of the resin cement (22.78 ± 5.2 MPa) compared to those of other methods (0–14.62 MPa) (p = 0.05). Mixed type of failures were more frequent in Si film coated groups on either polished or air-abraded groups. Si-based thin films increased wettability compared to the control group but did not change the roughness, considering the parameters evaluated. Deposition parameters of Si-based thin film and after application of air-abrasion influenced the initial adhesion of resin cement to zirconia.

  13. Underwater Depth and Temperature Sensing Based on Fiber Optic Technology for Marine and Fresh Water Applications

    Directory of Open Access Journals (Sweden)

    Dinesh Babu Duraibabu

    2017-05-01

    Full Text Available Oceanic conditions play an important role in determining the effects of climate change and these effects can be monitored through the changes in the physical properties of sea water. In fact, Oceanographers use various probes for measuring the properties within the water column. CTDs (Conductivity, Temperature and Depth provide profiles of physical and chemical parameters of the water column. A CTD device consists of Conductivity (C, Temperature (T and Depth (D probes to monitor the water column changes with respect to relative depth. An optical fibre-based point sensor used as a combined pressure (depth and temperature sensor and the sensor system are described. Measurements accruing from underwater trials of a miniature sensor for pressure (depth and temperature in the ocean and in fresh water are reported. The sensor exhibits excellent stability and its performance is shown to be comparable with the Sea-Bird Scientific commercial sensor: SBE9Plus.

  14. Underwater Depth and Temperature Sensing Based on Fiber Optic Technology for Marine and Fresh Water Applications.

    Science.gov (United States)

    Duraibabu, Dinesh Babu; Leen, Gabriel; Toal, Daniel; Newe, Thomas; Lewis, Elfed; Dooly, Gerard

    2017-05-27

    Oceanic conditions play an important role in determining the effects of climate change and these effects can be monitored through the changes in the physical properties of sea water. In fact, Oceanographers use various probes for measuring the properties within the water column. CTDs (Conductivity, Temperature and Depth) provide profiles of physical and chemical parameters of the water column. A CTD device consists of Conductivity (C), Temperature (T) and Depth (D) probes to monitor the water column changes with respect to relative depth. An optical fibre-based point sensor used as a combined pressure (depth) and temperature sensor and the sensor system are described. Measurements accruing from underwater trials of a miniature sensor for pressure (depth) and temperature in the ocean and in fresh water are reported. The sensor exhibits excellent stability and its performance is shown to be comparable with the Sea-Bird Scientific commercial sensor: SBE9Plus.

  15. Effect of carbonation on the linear and nonlinear dynamic properties of cement-based materials

    Science.gov (United States)

    Eiras, Jesus N.; Kundu, Tribikram; Popovics, John S.; Monzó, José; Borrachero, María V.; Payá, Jordi

    2016-01-01

    Carbonation causes a physicochemical alteration of cement-based materials, leading to a decrease of porosity and an increase of material hardness and strength. However, carbonation will decrease the pH of the internal pore water solution, which may depassivate the internal reinforcing steel, giving rise to structural durability concerns. Therefore, the proper selection of materials informed by parameters sensitive to the carbonation process is crucial to ensure the durability of concrete structures. The authors investigate the feasibility of using linear and nonlinear dynamic vibration response data to monitor the progression of the carbonation process in cement-based materials. Mortar samples with dimensions of 40×40×160 mm were subjected to an accelerated carbonation process through a carbonation chamber with 55% relative humidity and >95% of CO2 atmosphere. The progress of carbonation in the material was monitored using data obtained with the test setup of the standard resonant frequency test (ASTM C215-14), from a pristine state until an almost fully carbonated state. Linear dynamic modulus, quality factor, and a material nonlinear response, evaluated through the upward resonant frequency shift during the signal ring-down, were investigated. The compressive strength and the depth of carbonation were also measured. Carbonation resulted in a modest increase in the dynamic modulus, but a substantive increase in the quality factor (inverse attenuation) and a decrease in the material nonlinearity parameter. The combined measurement of the vibration quality factor and nonlinear parameter shows potential as a sensitive measure of material changes brought about by carbonation.

  16. Analysis of Cement-Based Pastes Mixed with Waste Tire Rubber

    Science.gov (United States)

    Sola, O. C.; Ozyazgan, C.; Sayin, B.

    2017-03-01

    Using the methods of thermal gravimetry, differential thermal analysis, Furier transform infrared analysis, and capillary absorption, the properties of a cement composite produced by introducing waste tyre rubber into a cement mixture were investigated. It was found that the composite filled with the rubber had a much lower water absorption ability than the unfilled one.

  17. Environmental Assessment of Different Cement Manufacturing Processes Based on Emergy and Ecological Footprint Analysis

    Science.gov (United States)

    Due to its high environmental impact and energy intensive production, the cement industry needs to adopt more energy efficient technologies to reduce its demand for fossil fuels and impact on the environment. Bearing in mind that cement is the most widely used material for housin...

  18. Numerical modelling of porous cement-based materials by superabsorbent polymers

    DEFF Research Database (Denmark)

    Viejo, Ismael; Esteves, Luis Pedro; Laspalas, Manuel;

    2016-01-01

    The development of new cementitious materials raises new challenges with regard to structural design. One of the potential applications of superabsorbent polymers (SAP) is to deliver well-defined porosity to cement systems. This is particularly interesting for the development of porous cement...

  19. Environmental Assessment of Different Cement Manufacturing Processes Based on Emergy and Ecological Footprint Analysis

    Science.gov (United States)

    Due to its high environmental impact and energy intensive production, the cement industry needs to adopt more energy efficient technologies to reduce its demand for fossil fuels and impact on the environment. Bearing in mind that cement is the most widely used material for housin...

  20. Cytotoxic effects of new MTA-based cement formulations on fibroblast-like MDPL-20 cells.

    Science.gov (United States)

    Garcia, Lucas da Fonseca Roberti; Santos, Alailson Domingos dos; Moraes, João Carlos Silos; Costa, Carlos Alberto de Souza

    2016-01-01

    The present study aimed at evaluating the cytotoxic effects of a novel cement called CER on periodontal fibroblast-like cells of mice (MDPL-20), in comparison with different formulations of Mineral Trioxide Aggregate (MTA), by means of the cell viability test (MTT) and cell morphology analysis. Thirty-two round-shaped samples were fabricated with the following cements: white MTA, white and gray CER and experimental white MTA. The samples were immersed in serum-free culture medium for 24 hours or 7 days (n = 16). The extracts (culture medium + components released from the cements) were applied for 24 hours to previously cultured cells (40.000 cells/cm2) in the wells of 24-well plates. Cells seeded in complete culture medium were used as a negative control. Cell viability was assessed using the MTT assay. Two samples of each cement were used for cell morphology analysis by Scanning Electron Microscopy (SEM). The extracts obtained at the 7-day period presented higher cytotoxicity compared with the 24-hour period (p MTA presented the lowest, similar to the control (p > 0.05). However, at the 7-day period, the experimental white MTA presented no significant difference in comparison with the other cements (p > 0.05). At the 7-day period, CER cement presented cytotoxic effects on fibroblast-like cells, similar to different MTA formulations. However, the immersion period in the culture medium influenced the cytotoxicity of the cements, which was greater for CER cement at 24 hours.

  1. Effect of Lime on Mechanical and Durability Properties of Blended Cement Based Concrete

    Science.gov (United States)

    Acharya, Prasanna Kumar; Patro, Sanjaya Kumar; Moharana, Narayana C.

    2016-06-01

    This work presents the results of experimental investigations performed to evaluate the effect of lime on mechanical and durability properties of concrete mixtures made with blended cement like Portland Slag Cement (PSC) and Portland Pozzolana Cement (PPC) with lime content of 0, 5, 7 and 10 %. Test result indicated that inclusion of hydraulic lime on replacement of cement up to 7 % increases compressive strength of concrete made with both PSC and PPC. Flexural strength increased with lime content. Highest flexural strength is reported at 7 % lime content for both PSC and PPC. Workability is observed to decrease with lime addition which could be compensated with introduction of super plasticizer. Acid and sulphate resistance increase slightly up to 7 % of lime addition and is found to decrease with further addition of lime. Lime addition up to 10 % does not affect the soundness of blended cements like PSC and PPC.

  2. Effect of metakaolin on strength and efflorescence quantity of cement-based composites.

    Science.gov (United States)

    Weng, Tsai-Lung; Lin, Wei-Ting; Cheng, An

    2013-01-01

    This study investigated the basic mechanical and microscopic properties of cement produced with metakaolin and quantified the production of residual white efflorescence. Cement mortar was produced at various replacement ratios of metakaolin (0, 5, 10, 15, 20, and 25% by weight of cement) and exposed to various environments. Compressive strength and efflorescence quantify (using Matrix Laboratory image analysis and the curettage method), scanning electron microscopy, and X-ray diffraction analysis were reported in this study. Specimens with metakaolin as a replacement for Portland cement present higher compressive strength and greater resistance to efflorescence; however, the addition of more than 20% metakaolin has a detrimental effect on strength and efflorescence. This may be explained by the microstructure and hydration products. The quantity of efflorescence determined using MATLAB image analysis is close to the result obtained using the curettage method. The results demonstrate the best effectiveness of replacing Portland cement with metakaolin at a 15% replacement ratio by weight.

  3. Vibrational study on the bioactivity of Portland cement-based materials for endodontic use

    Science.gov (United States)

    Taddei, P.; Tinti, A.; Gandolfi, M. G.; Rossi, P. L.; Prati, C.

    2009-04-01

    The bioactivity of a modified Portland cement (wTC) and a phosphate-doped wTC cement (wTC-P) was studied at 37 °C in Dulbecco's Phosphate Buffered Saline (DPBS). The cements, prepared as disks, were analysed at different ageing times (from 1 day to 2 months) by micro-Raman and ATR/FT-IR spectroscopies. The presence of deposits on the surface of the cements and the composition changes as a function of the storage time were investigated. The presence of an apatite deposit on the surface of both cements was already revealed after one day of ageing in DPBS. The trend of the I 965/I 991 Raman intensity ratio indicated the formation of a meanly thicker apatite deposit on the wTC-P cement at all the investigated times. This result was confirmed by the trend of the I 1030/I 945 IR intensity ratio calculated until 14 days of ageing. At 2 months, the thickness of the apatite deposit on wTC and wTC-P was about 200 and 500 μm, respectively, as estimated by micro-Raman spectroscopy, confirming the higher bioactivity of the phosphate-doped cement. Vibrational techniques allowed to gain more insights into the cement transformation and the different hydration rates of the various cement component. The setting of the cement and the formation of the hydrated silicate gel (C-S-H phase) was spectroscopically monitored through the I 830/I 945 IR intensity ratio.

  4. Modelling quality of fresh-cut tomato based on stage of maturity and storage conditions

    NARCIS (Netherlands)

    Moreira Lana, M.

    2005-01-01

    Fresh-cut or minimally processed vegetables are those which have been trimmed and/or peeled and/or cut into 100% usable product and still maintain freshness. Contrary to other processing methods (freezing, canning and drying for example) the minimal processing operations reduce the shelf life in rel

  5. Modelling quality of fresh-cut tomato based on stage of maturity and storage conditions

    NARCIS (Netherlands)

    Moreira Lana, M.

    2005-01-01

    Fresh-cut or minimally processed vegetables are those which have been trimmed and/or peeled and/or cut into 100% usable product and still maintain freshness. Contrary to other processing methods (freezing, canning and drying for example) the minimal processing operations reduce the shelf life in rel

  6. Modelling quality of fresh-cut tomato based on stage of maturity and storage conditions

    NARCIS (Netherlands)

    Moreira Lana, M.

    2005-01-01

    Fresh-cut or minimally processed vegetables are those which have been trimmed and/or peeled and/or cut into 100% usable product and still maintain freshness. Contrary to other processing methods (freezing, canning and drying for example) the minimal processing operations reduce the shelf life in

  7. Utilization of sewage sludge-biomass gasification residue in cement-based materials: effect of pozzolant type.

    Science.gov (United States)

    Kalpokaitė-Dičkuvienė, Regina; Lukošiūtė, Irena; Brinkienė, Kristina; Striūgas, Nerijus; Baltušnikas, Arūnas; Lukauskaitė, Raimonda; Čėsnienė, Jūratė

    2017-09-03

    In this study, the viability to utilize the residue, obtained from a sewage sludge (SS) and biomass combustion/gasification plant (GR), in cement-based materials was analysed. Two pozzolanic materials were selected to make GR more recyclable: metakaolin (MK) and spent catalyst waste (Z), received from fluidized-bed catalytic cracking process. Functional and environmental properties of standard cement pastes and mortars as well as binary and ternary combinations of GR with MK and Z were assessed. Results showed that enhanced mechanical strength, reduced water absorption and heavy metals release were obtained for compositions when GR was combined with one of the pozzolanic material MK or Z. Microstructural analysis revealed that due to addition of pozzolan the surface of GR particles was covered by a layer of hydration products. In particular, the use of MK led to the formation of more porous layer whereas application of Z tends to the formation of a dense-layered structure on the surface of GR. N2 sorption results showed that contrary to MK the incorporation of Z into cement composition with GR reduced volume of small capillary pores, and therefore, resulted in lower water absorption and heavy metals release. The obtained results suggest that the application of Z appears to be advantageous pozzolan for the stabilization of SS-biomass gasification residue in cement-based materials.

  8. BLENDED CALCIUM ALUMINATE-CALCIUM SULFATE CEMENT-BASED GROUT FOR P-REACTOR VESSEL IN-SITU DECOMMISSIONING

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Stefanko, D.

    2011-03-10

    The objective of this report is to document laboratory testing of blended calcium aluminate - calcium hemihydrate grouts for P-Reactor vessel in-situ decommissioning. Blended calcium aluminate - calcium hemihydrate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout which has a pH greater than 12.4. In addition, blended calcium aluminate - calcium hemihydrate cement compositions can be formulated such that the primary cementitious phase is a stable crystalline material. A less alkaline material (pH {<=} 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts [Wiersma, 2009a and b, Wiersma, 2010, and Serrato and Langton, 2010]. Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere [Griffin, 2010, Stefanko, 2009 and Wiersma, 2009 and 2010, Bobbitt, 2010, respectively]. Radiolysis calculations are also provided in a separate document [Reyes-Jimenez, 2010].

  9. Use of Different Barium Salts to Inhibit the Thaumasite Form of Sulfate Attack in Cement-based Materials

    Institute of Scientific and Technical Information of China (English)

    SU Ying; WEI Xiaochao; HUANG Jian; WANG Yingbin; HE Xingyang; WANG Xiongjue; MA Baoguo

    2016-01-01

    We investigated the effects of different barium compounds on the thaumasite form of sulphate attack (TSA) resistance of cement-based materials when they were used as admixtures in mortars. Moreover, we analyzed the inhibition mechanisms within different types of barium salts, namely BaCO3 and Ba(OH)2, on the thaumasite formation. The control cement mortar and mortars with barium salts to cement and limestone weight ratios of 0.5%, 1.0%, and 1.5% were immersed in 5% (by weight) MgSO4 solution at 5℃ to mimic TSA. Appearance, mass, and compressive strength of the mortar samples were monitored and measured to assess the general degradation extent of these samples. The products of sulphate attack were further analyzed by XRD, FTIR, and SEM, respectively. Experimental results show that different degradation extent is evident in all mortars cured in MgSO4 solution. However, barium salts can greatly inhibit such degradation. Barium in hydroxide form has better effectiveness in protection against TSA than carbonate form, which may be due to their solubility difference in alkaline cement pore solution, and the presence of these barium compounds can reduce the degree of TSA by comparison with the almost completely decomposed control samples.

  10. Optimizing the control system of cement milling: process modeling and controller tuning based on loop shaping procedures and process simulations

    Directory of Open Access Journals (Sweden)

    D. C. Tsamatsoulis

    2014-03-01

    Full Text Available Based on a dynamical model of the grinding process in closed circuit mills, efficient efforts have been made to optimize PID controllers of cement milling. The process simulation is combined with an autoregressive model of the errors between the actual process values and the computed ones. Long term industrial data have been used to determine the model parameters. The data include grinding of various cement types. The M - Constrained Integral Gain Optimization (MIGO loop shaping method is utilized to determine PID sets satisfying a certain robustness constraint. The maximum sensitivity is considered as such a criterion. Both dynamical parameters and PID sets constitute the inputs of a detailed simulator which involves all the main process characteristics. The simulation is applied over all the PID sets aiming to find the parameter region that provides the minimum integral of absolute error, which functions as a performance criterion. For each cement type a PID set is selected and put in operation in a closed circuit cement mill. The performance of the regulation is evaluated after a sufficient time period, concluding that the developed design combining criteria of both robustness and performance leads to PID controllers of high efficiency.

  11. Microstructure, characterizations, functionality and compressive strength of cement-based materials using zinc oxide nanoparticles as an additive

    Energy Technology Data Exchange (ETDEWEB)

    Nochaiya, Thanongsak [Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Sekine, Yoshika [Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Choopun, Supab [Applied Physics Research Laboratory, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Chaipanich, Arnon, E-mail: arnon.chaipanich@cmu.ac.th [Advanced Cement-Based Materials Research Unit, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-05-05

    Highlights: • Nano zinc oxide was used as an additive material. • Microstructure and phase characterization of pastes were characterized using SEM and XRD. • TGA and FTIR were also used to determine the hydration reaction. • Compressive strength of ZnO mixes was found to increase at 28 days. - Abstract: Zinc oxide nanoparticles as a nanophotocatalyst has great potential for self-cleaning applications in concrete structures, its effects on the cement hydration, setting time and compressive strength are also important when using it in practice. This paper reports the effects of zinc oxide nanoparticles, as an additive material, on properties of cement-based materials. Setting time, compressive strength and porosity of mortars were investigated. Microstructure and morphology of pastes were characterized using scanning electron microscope and X-ray diffraction (XRD), respectively. Moreover, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectrometer (FTIR) were also used to determine the hydration reaction. The results show that Portland cement paste with additional ZnO was found to slightly increase the water requirement while the setting time presented prolongation period than the control mix. However, compressive strength of ZnO mixes was found to be higher than that of PC mix up to 15% (at 28 days) via filler effect. Microstructure, XRD and TGA results of ZnO pastes show less hydration products before 28 days but similar at 28 days. In addition, FTIR results confirmed the retardation when ZnO was partially added in Portland cement pastes.

  12. Magnetic Nanoparticle Based Nonviral MicroRNA Delivery into Freshly Isolated CD105+ hMSCs

    Directory of Open Access Journals (Sweden)

    Anna Schade

    2014-01-01

    Full Text Available Genetic modifications of bone marrow derived human mesenchymal stem cells (hMSCs using microRNAs (miRs may be used to improve their therapeutic potential and enable innovative strategies in tissue regeneration. However, most of the studies use cultured hMSCs, although these can lose their stem cell characteristics during expansion. Therefore, we aimed to develop a nonviral miR carrier based on polyethylenimine (PEI bound to magnetic nanoparticles (MNPs for efficient miR delivery in freshly isolated hMSCs. MNP based transfection is preferable for genetic modifications in vivo due to improved selectivity, safety of delivery, and reduced side effects. Thus, in this study different miR/PEI and miR/PEI/MNP complex formulations were tested in vitro for uptake efficiency and cytotoxicity with respect to the influence of an external magnetic field. Afterwards, optimized magnetic complexes were selected and compared to commercially available magnetic vectors (Magnetofectamine, CombiMag. We found that all tested transfection reagents had high miR uptake rates (yielded over 60% and no significant cytotoxic effects. Our work may become crucial for virus-free introduction of therapeutic miRs as well as other nucleic acids in vivo. Moreover, in the field of targeted stem cell therapy nucleic acid delivery prior to transplantation may allowfor initial cell modulation in vitro.

  13. Effect of saliva and blood contamination on the bi-axial flexural strength and setting time of two calcium-silicate based cements: Portland cement and biodentine.

    Science.gov (United States)

    Alhodiry, W; Lyons, M F; Chadwick, R G

    2014-03-01

    This study evaluated the effect of contamination with saliva and blood on the bi-axial flexural strength and setting time of pure gray Portland cement and Biodentine (Septodont, Allington, UK). A one-way ANOVA showed that contamination caused no significant difference between the cements in bi-axial flexural strength (P> 0.05). However there was a significant difference in setting time (Pcement taking longer than Biodentine, regardless of the contaminant, and contamination with blood increased the setting time of both materials. Biodentine was similar in strength to Portland cement, but had a shorter setting time for both contaminated and non-contaminated samples.

  14. Electrical behavior of structural cement-based materials: Science and applications

    Science.gov (United States)

    Cao, Jingyao

    The electrical behavior of cement-based structural materials was studied for damage/microstructural evolution investigation, electromagnetic interference (EMI) shielding, fiber dispersion characterization, and for understanding of polarization, depolarization, the role of moisture, and the effects of aggregates and silica fume. Monitoring was performed in real time during static loading, dynamic loading creep, freeze-thaw cycling and drying shrinkage. It involved the use of the cement-based material itself as the sensor and was based on the dependence of the DC electrical resistivity on the damage/microstructural condition. The volume resistivity was the attribute used for monitoring interfaces in the material. The interfaces included that between steel rebar and concrete and that between old concrete and new concrete. The resistivity increased upon damage infliction or damage aggravation, but decreased upon damage diminution. In addition, it increased during microstructural change, which occurred even in the early stage of compressive elastic deformation. An increase in compressive strain rate was found to cause the fractional increase in resistivity to be less at the same strain, because micro structural change took time. The fractional increase in resistivity per unit strain was the parameter used to describe the extent of strain-induced micro structural change. Its value was much higher during creep or drying shrinkage than during static loading up to failure, due to the long time associated with creep and the hydration that accompanied drying shrinkage. Freeze-thaw cycling caused damage, which progressed cycle by cycle and occurred in each cycle more significantly upon cooling than upon heating. The presence of sand increased the fractional change in resistivity at the same drying shrinkage strain, whereas the presence of silica fume decreased the fractional change in resistivity at the same shrinkage strain. The presence of sand or silica fume also enhanced

  15. Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement

    Science.gov (United States)

    Akhlaghi, Omid; Menceloglu, Yusuf Ziya; Akbulut, Ozge

    2017-01-01

    Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems. Utilization of a monomer that, instead, facilitates gradual adsorption of a superplasticizer provides workability retention. For the first time in literature, we report a superplasticizer that caters to the properties of CAC such as high rate of surface development and surface charge. While neat CAC was almost unworkable after 1 hour, with the addition of only 0.4% of the optimized superplasticizer, 90% fluidity retention was achieved.

  16. Research on Demand Prediction of Fresh Food Supply Chain Based on Improved Particle Swarm Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    He Wang

    2015-04-01

    Full Text Available Demand prediction of supply chain is an important content and the first premise in supply management of different enterprises and has become one of the difficulties and hot research fields for the researchers related. The paper takes fresh food demand prediction for example and presents a new algorithm for predicting demand of fresh food supply chain. First, the working principle and the root causes of the defects of particle swarm optimization algorithm are analyzed in the study; Second, the study designs a new cloud particle swarm optimization algorithm to guarantee the effectiveness of particles in later searching phase and redesigns its cloud global optimization searching method and crossover operation; Finally, a certain fresh food supply chain is taken for example to illustrate the validity and feasibility of the improved algorithm and the experimental results show that the improved algorithm can improve prediction accuracy and calculation efficiency when used for demand prediction of fresh food supply chain.

  17. POF based smart sensor for studying the setting dynamics of cement paste

    Energy Technology Data Exchange (ETDEWEB)

    Rajesh, M [City University, Northampton square, London, ECV1 0HB (United Kingdom); Sheeba, M [Cochin University of Science and Technology, Cochin, 680022 (India); Nampoori, V P N [Cochin University of Science and Technology, Cochin, 680022 (India)

    2007-10-15

    Fiber optic smart sensors are used to monitor the civil structures. One of the important parameters in civil engineering is the setting characteristics of concrete made of cement. The paper discusses how a simple polymer optical fiber can be used to characterise the setting dynamics of various grades of cement. The results explain the comparative performance of polymer fiber over silica fiber. The basic principle underlying the sensor is that as the cement sets, it exerts a stress on the sensing fiber, which is laid within the cement paste. This stress induces strain on the optical fiber, which can be thought of as a series of aperiodic microbends on the surface of the fiber. This in turn changes the characteristics of the light signal transmitted through the fiber and can be viewed as stress induced modulation of light in the fiber. By monitoring the intensity variation of transmitted light signal with time we can determine the cement setting rate. This can be used as an effective tool for quality testing of commercially available cements of different grades.

  18. Strength of Limestone-based Non-calcined Cement and its Properties

    Institute of Scientific and Technical Information of China (English)

    LIN Zongshou; ZHAO Qian

    2009-01-01

    A new type of cement was prepared with ground limestone powder,blastfurnace slag,steel slag and gypsum without calcination.The fraction of ground limestone powder in the cement was as high as 40 wt%-60 wt%without Portland clinker.All of its physical properties can meet the requirements of masonry cement standards.The impact of limestone content on physical properties of the cement and determined its impact on law was investigated.The steel slag can excit the aquation activity of this cement effectively,and the influence of its quantity on the strength of the materials was studied,which shows that the optimum quantity of mixing is 10%.By way of changing the different content of the lime stone by quartzy sample,the law of the compression strength and the PH value was determined,confirming that the lime stone can promote the early aquation of the slag and improve the early strength.The main hydration product of this cement is calcium aluminate hydrate, ettringite and calcium silicate hydrate,as indicated by XRD and SEM analysis.

  19. DSC and TG Analysis of a Blended Binder Based on Waste Ceramic Powder and Portland Cement

    Science.gov (United States)

    Pavlík, Zbyšek; Trník, Anton; Kulovaná, Tereza; Scheinherrová, Lenka; Rahhal, Viviana; Irassar, Edgardo; Černý, Robert

    2016-03-01

    Cement industry belongs to the business sectors characteristic by high energy consumption and high {CO}2 generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of 25°C to 1000°C in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.

  20. β-Dicalcium silicate-based cement: synthesis, characterization and in vitro bioactivity and biocompatibility studies.

    Science.gov (United States)

    Correa, Daniel; Almirall, Amisel; García-Carrodeguas, Raúl; dos Santos, Luis Alberto; De Aza, Antonio H; Parra, Juan; Delgado, José Ángel

    2014-10-01

    β-dicalcium silicate (β-Ca₂ SiO₄, β-C₂ S) is one of the main constituents in Portland cement clinker and many refractory materials, itself is a hydraulic cement that reacts with water or aqueous solution at room/body temperature to form a hydrated phase (C-S-H), which provides mechanical strength to the end product. In the present investigation, β-C₂ S was synthesized by sol-gel process and it was used as powder to cement preparation, named CSiC. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid solutions and human osteoblast cell cultures for various time periods, respectively. The results showed that the sol-gel process is an available synthesis method in order to obtain a pure powder of β-C₂ S at relatively low temperatures without chemical stabilizers. A bone-like apatite layer covered the material surface after soaking in SBF and its compressive strength (CSiC cement) was comparable with that of the human trabecular bone. The extracts of this cement were not cytotoxic and the cell growth and relative cell viability were comparable to negative control.

  1. Relaxation study of cement based grouting material using nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Li Xianzhong; Lin Baiquan; Zhai Cheng; Ni Guanhua; Li Ziwen

    2012-01-01

    Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage,by adding a water reducing agent,cement paste for hole sealing was produced.The changes of initial distribution,weighted average values and total relaxation signal intensity of transverse relaxation time (T2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance (NMR).The results show that there are four peaks in T2 distribution curves of cement paste:the first peak is related to the bound water in flocculation,the second and the third peaks are related to the water in flocculation,water reducing agent makes it extending towards the long relaxation time,increasing its liquidity,and the fourth peak is related to the free water.By using weighted average values of T2 and total relaxation signal intensity,hydration process of cement pastes could be roughly divided into four stages:the initial period,reaction period,accelerated period and steady period.By analyzing the periods,it makes sure that the grouting process should be completed in the reaction period in the site,and the drainage process should be started in the steady period.The results have great guiding significance to the hole sealing and methane drainage.

  2. Relaxation study of cement based grouting material using nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Li; Xianzhong; Lin; Baiquan; Zhai; Cheng; Ni; Guanhua; Li; Ziwen

    2012-01-01

    Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage,by adding a water reducing agent,cement paste for hole sealing was produced.The changes of initial distribution,weighted average values and total relaxation signal intensity of transverse relaxation time(T 2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance(NMR).The results show that there are four peaks in T2 distribution curves of cement paste:the first peak is related to the bound water in flocculation,the second and the third peaks are related to the water in flocculation,water reducing agent makes it extending towards the long relaxation time,increasing its liquidity,and the fourth peak is related to the free water.By using weighted average values of T2 and total relaxation signal intensity,hydration process of cement pastes could be roughly divided into four stages:the initial period,reaction period,accelerated period and steady period.By analyzing the periods,it makes sure that the grouting process should be completed in the reaction period in the site,and the drainage process should be started in the steady period.The results have great guiding significance to the hole sealing and methane drainage.

  3. Coagulated silica - a-SiO2 admixture in cement paste

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Záleská, Martina; Rovnaníková, Pavla; Pavlík, Zbyšek

    2016-07-01

    Amorphous silica (a-SiO2) in fine-grained form possesses a high pozzolanic activity which makes it a valuable component of blended binders in concrete production. The origin of a-SiO2 applied in cement-based composites is very diverse. SiO2 in amorphous form is present in various amounts in quite a few supplementary cementing materials (SCMs) being used as partial replacement of Portland cement. In this work, the applicability of a commercially produced coagulated silica powder as a partial replacement of Portland cement in cement paste mix design is investigated. Portland cement CEM I 42.5R produced according to the EU standard EN 197-1 is used as a reference binder. Coagulated silica is applied in dosages of 5 and 10 % by mass of cement. The water/binder ratio is kept constant in all the studied pastes. For the applied silica, specific surface area, density, loss on ignition, pozzolanic activity, chemical composition, and SiO2 amorphous phase content are determined. For the developed pastes on the basis of cement-silica blended binder, basic physical properties as bulk density, matrix density, and total open porosity are accessed. Pore size distribution is determined using MIP analysis. Initial and final setting times of fresh mixtures are measured by automatic Vicat apparatus. Effect of silica admixture on mechanical resistivity is evaluated using compressive strength, bending strength, and dynamic Young's modulus measurement. The obtained data gives evidence of a decreased workability of paste mixtures with silica, whereas the setting process is accelerated. On the other hand, reaction activity of silica with Portland cement minerals results in a slight decrease of porosity and improvement of mechanical resistivity of cement pastes containing a-SiO2.

  4. Advanced Nanoscale Characterization of Cement Based Materials Using X-Ray Synchrotron Radiation: A Review

    KAUST Repository

    Chae, Sejung R.

    2013-05-22

    We report various synchrotron radiation laboratory based techniques used to characterize cement based materials in nanometer scale. High resolution X-ray transmission imaging combined with a rotational axis allows for rendering of samples in three dimensions revealing volumetric details. Scanning transmission X-ray microscope combines high spatial resolution imaging with high spectral resolution of the incident beam to reveal X-ray absorption near edge structure variations in the material nanostructure. Microdiffraction scans the surface of a sample to map its high order reflection or crystallographic variations with a micron-sized incident beam. High pressure X-ray diffraction measures compressibility of pure phase materials. Unique results of studies using the above tools are discussed-a study of pores, connectivity, and morphology of a 2,000 year old concrete using nanotomography; detection of localized and varying silicate chain depolymerization in Al-substituted tobermorite, and quantification of monosulfate distribution in tricalcium aluminate hydration using scanning transmission X-ray microscopy; detection and mapping of hydration products in high volume fly ash paste using microdiffraction; and determination of mechanical properties of various AFm phases using high pressure X-ray diffraction. © 2013 The Author(s).

  5. ALKALI-ACTIVATED CEMENT MORTARS CONTAINING RECYCLED CLAY-BASED CONSTRUCTION AND DEMOLITION WASTE

    Directory of Open Access Journals (Sweden)

    F. Puertas

    2015-09-01

    Full Text Available The use of clay-based waste as an aggregate for concrete production is an amply studied procedure. Nonetheless, research on the use of this recycled aggregate to prepare alkaline cement mortars and concretes has yet to be forthcoming. The present study aimed to determine: the behaviour of this waste as a pozzolan in OPC systems, the mechanical strength in OPC, alkali-activated slag (AAS and fly ash (AAFA mortars and the effect of partial replacement of the slag and ash themselves with ground fractions of the waste. The pozzolanic behaviour of clay-based waste was confirmed. Replacing up to 20 % of siliceous aggregate with waste aggregate in OPC mortars induced a decline in 7 day strength (around 23 wt. %. The behaviour of waste aggregate in AAMs mortars, in turn, was observed to depend on the nature of the aluminosilicate and the replacement ratio used. When 20 % of siliceous aggregate was replaced by waste aggregate in AAS mortars, the 7 day strength values remained the same (40 MPa. In AAFA mortars, waste was found to effectively replace both the fly ash and the aggregate. The highest strength for AAFA mortars was observed when they were prepared with both a 50 % replacement ratio for the ash and a 20 % ratio for the aggregate.

  6. Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1998-03-10

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

  7. X-ray microtomography for fracture studies in cement-based materials

    Science.gov (United States)

    Landis, Eric N.; Keane, Denis T.

    1999-09-01

    In this study we are interested in microstructure-property relationships in portland cement-based materials. Specifically, we are interested in relating microfracture and damage to bulk mechanical properties. To do this a high resolution three-dimensional scanning technique called x-ray microtomography was applied to measure internal damage and crack growth in small mortar cylinders loaded in uniaxial compression. Synchrotron-based microtomography allows us to resolve internal features that are only a few microns in size. Multiple tomographic scans were made of the same specimen at different levels of deformation, the deformation being applied through a custom built loading frame. Three-dimensional image analysis was used to measure internal crack growth during each deformation increment. Measured load-deformation curves were used to calculate the non-recoverable work of load on the specimen. Incremental non-recoverable work of load was related to measured incremental change in crack surface area to estimate work-of-fracture in three dimensions. Initial results indicate a nearly constant work-of-fracture for the early stages of crack growth. These results show that basic fracture mechanics principles may be applied to concrete in compression, however we must think in terms of 3D multiple crack systems rather than traditional 2D single crack systems.

  8. The use of glass powder as a partial Portland cement replacement

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Tydlitát, Vratislav; Scheinherrová, Lenka; Rovnaníková, Pavla; Pavlík, Zbyšek

    2017-07-01

    Finely grinded waste glass powder can become material having suitable properties from the point of view of particle size and pozzolanic activity. Glass powder incorporation into cement paste and cement-based composites can bring improvement in porous structure resulting in increased mechanical strength and durability characteristics. On this account, two types of recycled glass powder are investigated in the presented paper as a possible partial Portland cement substitutes in cement blends. For raw glass powders, basic physical parameters and chemical composition are measured. The studied glass powders are applied as 5, 10 and 20 mass% of Portland cement replacement in cement paste mix composition, whereas water/binder ratio of 0.3 is used for all studied pastes. Fresh paste mixtures are characterized using initial and final setting time measurement. For hardened pastes cured 28 days in water, bulk density, matrix density, total open porosity and mechanical properties represented by flexural and compressive strength are accessed. Portlandite consumption by the pozzolanic reaction is monitored with TGA. The obtained results show effectiveness of a borosilicate glass powder that acts as a pozzolanic active admixture. This resulted in improvement of mechanical characteristics for cement substitution up to 10 mass%.

  9. Monitoring the Freshness of Moroccan Sardines with a Neural-Network Based Electronic Nose

    Directory of Open Access Journals (Sweden)

    Benachir Bouchikhi

    2006-10-01

    Full Text Available An electronic nose was developed and used as a rapid technique to classify thefreshness of sardine samples according to the number of days spent under cold storage (4 ±1°C, in air. The volatile compounds present in the headspace of weighted sardine sampleswere introduced into a sensor chamber and the response signals of the sensors wererecorded as a function of time. Commercially available gas sensors based on metal oxidesemiconductors were used and both static and dynamic features from the sensorconductance response were input to the pattern recognition engine. Data analysis wasperformed by three different pattern recognition methods such as probabilistic neuralnetworks (PNN, fuzzy ARTMAP neural networks (FANN and support vector machines(SVM. The objective of this study was to find, among these three pattern recognitionmethods, the most suitable one for accurately identifying the days of cold storage undergoneby sardine samples. The results show that the electronic nose can monitor the freshness ofsardine samples stored at 4°C, and that the best classification and prediction are obtainedwith SVM neural network. The SVM approach shows improved classificationperformances, reducing the amount of misclassified samples down to 3.75 %.

  10. Improvement of Cracking-resistance and Flexural Behavior of Cement-based Materials by Addition of Rubber,Particles

    Institute of Scientific and Technical Information of China (English)

    KANG Jingfu; JIANG Yongqi

    2008-01-01

    By ring test and bend test,the improvement of waste tire rubber particles on the crack-resistance and flexural behaviors of cement-based materials were investigated.Test results show that the cracking time of the ring specimens can be retarded by the incorporation of rubber particles in the cement paste and mortar.The improvement in the crack-resistance depended on the rubber fraction.When the rubber fraction was 20%in volume,the cracking time was retarded about 15 h for the paste and 24 d for the mortar respectively.Flexural properties were evaluated based on the bend test results for both mortar and concrete containing different amount of rubber particles.Test results show that rubberized mortar and concrete specimens exhibit ductile failure and significant deformation before fracture.The ultimate deformations of both mortar and concrete specimen increase more than 2-4 times than control specimens.

  11. Self-healing Action of Permeable Crystalline Coating on Pores and Cracks in Cement-based Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Guiming; YU Jianying

    2005-01-01

    The self-healing action of a permeable crystalline coating on the porous mortar was investigated by two times impermeability test. Moreover, the self-healing mechanism of cement-based materials with the permeable crystalline coating was studied by SEM. The results indicate that the permeable crystalline coating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or cracks produced by freeze-thaw cycles. Therefore, cement-based materials can be improved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great quantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.

  12. Composition-structure-property relationships for non-classical ionomer cements formulated with zinc-boron germanium-based glasses.

    Science.gov (United States)

    Zhang, Xiaofang; Werner-Zwanziger, Ulrike; Boyd, Daniel

    2015-04-01

    Non-classical ionomer glasses like those based on zinc-boron-germanium glasses are of special interest in a variety of medical applications owning to their unique combination of properties and potential therapeutic efficacy. These features may be of particular benefit with respect to the utilization of glass ionomer cements for minimally invasive dental applications such as the atruamatic restorative treatment, but also for expanded clinical applications in orthopedics and oral-maxillofacial surgery. A unique system of zinc-boron-germanium-based glasses (10 compositions in total) has been designed using a Design of Mixtures methodology. In the first instance, ionomer glasses were examined via differential thermal analysis, X-ray diffraction, and (11)B MAS NMR spectroscopy to establish fundamental composition - structure-property relationships for the unique system. Secondly, cements were synthesized based on each glass and handling characteristics (working time, Wt, and setting time, St) and compression strength were quantified to facilitate the development of both experimental and mathematical composition-structure-property relationships for the new ionomer cements. The novel glass ionomer cements were found to provide Wt, St, and compression strength in the range of 48-132 s, 206-602 s, and 16-36 MPa, respectively, depending on the ZnO/GeO2 mol fraction of the glass phase. A lower ZnO mol fraction in the glass phase provides higher glass transition temperature, higher N4 rate, and in combination with careful modulation of GeO2 mol fraction in the glass phase provides a unique approach to extending the Wt and St of glass ionomer cement without compromising (in fact enhancing) compression strength. The data presented in this work provide valuable information for the formulation of alternative glass ionomer cements for applications within and beyond the dental clinic, especially where conventional approaches to modulating working time and strength exhibit co

  13. Static and Dynamic Strain Monitoring of Reinforced Concrete Components through Embedded Carbon Nanotube Cement-Based Sensors

    Directory of Open Access Journals (Sweden)

    Antonella D’Alessandro

    2017-01-01

    Full Text Available The paper presents a study on the use of cement-based sensors doped with carbon nanotubes as embedded smart sensors for static and dynamic strain monitoring of reinforced concrete (RC elements. Such novel sensors can be used for the monitoring of civil infrastructures. Because they are fabricated from a structural material and are easy to utilize, these sensors can be integrated into structural elements for monitoring of different types of constructions during their service life. Despite the scientific attention that such sensors have received in recent years, further research is needed to understand (i the repeatability and accuracy of sensors’ behavior over a meaningful number of sensors, (ii testing configurations and calibration methods, and (iii the sensors’ ability to provide static and dynamic strain measurements when actually embedded in RC elements. To address these research needs, this paper presents a preliminary characterization of the self-sensing capabilities and the dynamic properties of a meaningful number of cement-based sensors and studies their application as embedded sensors in a full-scale RC beam. Results from electrical and electromechanical tests conducted on small and full-scale specimens using different electrical measurement methods confirm that smart cement-based sensors show promise for both static and vibration-based structural health monitoring applications of concrete elements but that calibration of each sensor seems to be necessary.

  14. The antimicrobial effect of spice-based marinades against Campylobacter jejuni on contaminated fresh broiler wings.

    Science.gov (United States)

    Zakarienė, Gintarė; Rokaitytė, Anita; Ramonaitė, Sigita; Novoslavskij, Aleksandr; Mulkytė, Kristina; Zaborskienė, Gintarė; Malakauskas, Mindaugas

    2015-03-01

    The antimicrobial effect of spice-based marinades against Campylobacter jejuni on inoculated fresh broiler wings was investigated. Experiments were carried out with 1 strain of C. jejuni and 6 marinades. Four experimental marinades were composed for the study and contained spices (thyme, rosemary, basil, marjoram, and so on) and different combination of bioactive compounds. Two marinades were commercial and contained spices (black pepper, sweet red pepper, and so on) and chemical additives (monosodium glutamate, sodium diacetate, calcium lactate), 1 commercial marinade was also enriched with bioactive compounds (linalool, cinnamaldehyde, lactic acid). Total aerobic bacterial count was examined to estimate the possible effect of tested marinades on the shelf-life of marinated broiler wings. Study revealed that thyme-based marinade was the most effective against C. jejuni on broiler wings and reduced the numbers of campylobacters by 1.04 log colony forming unit (CFU)/g (P ≤ 0.05) during storage for 168 h at 4 °C temperature. Moreover, it was more effective against C. jejuni than commercial marinade with 0.47 log CFU/g (P ≤ 0.05) reduction effect. Both experimental and commercial marinades had very similar effect on the total aerobic bacterial count. Although experimental and commercial marinades had different effect on pH of broiler wings, this parameter did not show a major impact on the antimicrobial effect of tested marinades (P ≥ 0.05). Our study shows that experimental natural thyme-based marinade can reduce numbers of C. jejuni more effectively than tested commercial marinades.

  15. A Numerical Comparison of Ionic Multi-Species Diffusion with and without Sorption Hysteresis for Cement-Based Materials

    DEFF Research Database (Denmark)

    Jensen, Mads Mønster; Johannesson, Björn; Geiker, Mette Rica

    2015-01-01

    the sorption hysteresis model. The examples illustrate the impact of changing relative humidity at the mass transport boundary on the adsorption and desorption stages of a cement-based material. Changes in the pore solution ion concentrations are a result of the changing moisture content, which are shown...... by the example. Comparing the two approaches showed significant deviations in the liquid content and ion concentrations, in parts of the domain considered....

  16. Multi-Scale Studies of Transport and Adsorption Phenomena of Cement-based Materials in Aqueous and Saline Environment

    OpenAIRE

    Yoon, Se Yoon

    2012-01-01

    The transport and adsorption phenomena in cement-based materials are the most important processes in the durability of concrete structures or nuclear waste containers, as they are precursors to a number of deterioration processes such as chloride-induced corrosion, sulfate attack, carbonation, etc. Despite this importance, our understanding of these processes remains limited because the pore structure and composition of concrete are complex. In addition, the range of the pore sizes, from nano...

  17. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    Directory of Open Access Journals (Sweden)

    Ortega, J. M.

    2014-03-01

    Full Text Available Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepared with blast furnace slag cement at different w/c ratios are characterised and compared to the findings for a reference portland cement grout. The results show that slag grout exhibits greater durability than the portland cement material and complies with the compressive strength requirements laid down in the respective codes.Actualmente es muy frecuente el empleo de cimentaciones especiales, entre las que destacan los micropilotes y los anclajes. En España, las lechadas de cemento para estos trabajos geotécnicos especiales se preparan habitualmente con cemento Portland, aunque las diferentes normativas al respecto no restringen el tipo de cemento a emplear, siempre que se alcance una determinada resistencia a compresión. Respecto a la dosificación de las lechadas, la normativa permite emplear diferentes relaciones agua/cemento dentro de un determinado rango. En vista de ello, en este trabajo se han caracterizado las propiedades de durabilidad y resistencia a compresión de lechadas de cemento preparadas con un cemento con escoria de alto horno y con diferentes relaciones a/c, tomando como referencia de comportamiento lechadas de cemento Portland. El uso de un cemento con escoria conlleva una mejora en la durabilidad de las lechadas, cumpliendo los requisitos de resistencia a compresión establecidos por la normativa.

  18. Self-healing phenomena in cement-based materials state-of-the-art report of RILEM Technical Committee 221-SHC Self-Healing Phenomena in Cement-Based Materials

    CERN Document Server

    Tittelboom, Kim; Belie, Nele; Schlangen, Erik

    2013-01-01

    Self-healing materials are man-made materials which have the built-in capability to repair damage. Failure in materials is often caused by the occurrence of small microcracks throughout the material. In self-healing materials phenomena are triggered to counteract these microcracks. These processes are ideally triggered by the occurrence of damage itself. Thus far, the self-healing capacity of cement-based materials has been considered as something "extra". This could be called passive self-healing, since it was not a designed feature of the material, but an inherent property of it. Centuries-old buildings have been said to have survived these centuries because of the inherent self-healing capacity of the binders used for cementing building blocks together. In this State-of-the-Art Report a closer look is taken at self-healing phenomena in cement-based materials. It is shown what options are available to design for this effect rather than have it occur as a "coincidental extra".

  19. Drying Shrinkage of Cement-Based Materials Under Conditions of Constant Temperature and Varying Humidity

    Institute of Scientific and Technical Information of China (English)

    MA Bao-guo; WEN Xiao-dong; WANG Ming-yuan; YAN Jia-jia; Gao Xiao-jian

    2007-01-01

    Currently,deformations along the central axis of specimens were usually measured under fixed environmental conditions. Seldom were the effects of environmental factors on the drying-shrinkage deformation of cement-based material considered. For this paper, the drying-shrinkage deformation at different w/b ratios and different additions to mortars was investigated under different environments at a temperature of 20 ℃ and humidity ranging from 100% to 50%. The specimens were cured in water for 28 days before measurement. The results illustrate that mortar shows much less shrinkage under various drying conditions when a lower w/b ratio is adopted. With a decrease in relative humidity the speed of drying-shrinkage becomes gradually lower. The addition of silica fume reduces the drying-shrinkage of mortar under higher relative humidity, because the pore structure of mortar with silica fume becomes more refined. The addition of fly ash increases the total porosity and the volume of coarse pores in the mortar. The drying-shrinkage of mortar under different conditions increases with the addition of more of fly ash.

  20. STUDY OF HORIZONTAL SCREEN STRENGTH CREATED BY INJECTION TECHNOLOGY CEMENT BINDER BASED

    Directory of Open Access Journals (Sweden)

    BORISOV A. A.

    2016-09-01

    Full Text Available Annotation. Formulation of the problem. An important indicator in the planning of injection works is a particle size distribution of the soil and the very composition of injection. The ideal case is to comply with the injection optimum ratio between the size of particles in solution and injectable medium. This ratio corresponds to complete impregnation of the environment. Today in the field of building technologies known classical methods of grouting with the injection process [9]. This may be a cementation or silicification with different chemical compositions. Due to the fact that we have proposed an innovative technology of impervious curtain device, special attention should be paid to the performance and physical and mechanical properties of the resulting soil-injection. This is due to the fact that the proposed technology provides for lesser known technical solutions, the use of which should ultimately result in impervious screens with desired properties. Goal. The aim of this study is to investigate the properties of the resulting soil-concrete impervious screen. Such structures should have defined a number of physical and mechanical properties. In this paper, it was of interest to study the compressive strength of the resulting soil-concrete structure. Conclusion. As a result of experimentation and implementation of complex obtained experimentally-statistical models that describe the main soil-quality indicators. Based on these data is possible optimal selection of formulation and technological structure for sandy soils with different modules size of its particles.

  1. Acoustic emission for characterising the crack propagation in strain-hardening cement-based composites (SHCC)

    Energy Technology Data Exchange (ETDEWEB)

    Paul, S.C. [Department of Civil Engineering, Stellenbosch University (South Africa); Pirskawetz, S. [BAM Federal Institute for Materials Research and Testing (Germany); Zijl, G.P.A.G. van, E-mail: gvanzijl@sun.ac.za [Department of Civil Engineering, Stellenbosch University (South Africa); Schmidt, W. [BAM Federal Institute for Materials Research and Testing (Germany)

    2015-03-15

    This paper presents the analysis of crack propagation in strain-hardening cement-based composite (SHCC) under tensile and flexural load by using acoustic emission (AE). AE is a non-destructive technique to monitor the development of structural damage due to external forces. The main objective of this research was to characterise the cracking behaviour in SHCC in direct tensile and flexural tests by using AE. A better understanding of the development of microcracks in SHCC will lead to a better understanding of pseudo strain-hardening behaviour of SHCC and its general performance. ARAMIS optical deformation analysis was also used in direct tensile tests to observe crack propagation in SHCC materials. For the direct tensile tests, SHCC specimens were prepared with polyvinyl alcohol (PVA) fibre with three different volume percentages (1%, 1.85% and 2.5%). For the flexural test beam specimens, only a fibre dosage of 1.85% was applied. It was found that the application of AE in SHCC can be a good option to analyse the crack growth in the specimens under increasing load, the location of the cracks and most importantly the identification of matrix cracking and fibre rupture or slippage.

  2. Experimental evidence of the influence of iron on pore water radiolysis in cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bouniol, P., E-mail: pascal.bouniol@cea.fr [CEA, DEN, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des Argiles, F-91991 Gif-Sur-Yvette (France); Muzeau, B. [CEA, DEN, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des Argiles, F-91991 Gif-Sur-Yvette (France); Dauvois, V. [CEA, DEN, DPC, SECR, Laboratoire de Radiolyse et de la Matière Organique, F-91991 Gif-Sur-Yvette (France)

    2013-06-15

    Hydrated tricalcium silicate based cement pastes or mixes, with the addition or not of amorphous iron oxyhydroxide, were irradiated for 1 year in a closed system (γ radiation) with the aim of provoking radiolysis of the alkaline pore solution (pH > 13). The data collected (on-line monitoring of the total pressure and the H{sub 2} content in 500 cm{sup 3} mini-containers irradiated at 45 °C and 1.07 kGy/h with V{sub gas}/V{sub paste} ≈ 1) enable us to conclude that the addition of 1% of FeOOH{sub am} gives rise to about 26% of additional residual H{sub 2} after 1 year. This result appears to validate the hypothesis of a partial mobilisation of the e{sub aq}{sup -} and O{sup ·−} radicals in a continuous process of Fe(III) ↔ Fe(II) oxidation–reduction, at the expense of their action within the Allen type reaction chain that is responsible for the recycling of H{sub 2}. Despite the complexity of the porous material, the simulation of the experiment with the CHEMSIMUL application leads to a result that is quite close, and stresses the importance of the kinetic coupling between gas transport in the porous material and the reaction system.

  3. Modelling of chemical degradation of blended cement-based materials by leaching cycles with Callovo-Oxfordian porewater

    Science.gov (United States)

    Olmeda, Javier; Henocq, Pierre; Giffaut, Eric; Grivé, Mireia

    2017-06-01

    The present work describes a thermodynamic model based on pore water replacement cycles to simulate the chemical evolution of blended cement (BFS + FA) by interaction with external Callovo-Oxfordian (COx) pore water. In the framework of the radioactive waste management, the characterization of the radionuclide behaviour (solubility/speciation, adsorption) in cementitious materials needs to be done for several chemical degradation states (I to IV). In particular, in the context of the deep geological radioactive waste disposal project (Cigéo), cement-based materials will be chemically evolved with time in contact with the host-rock (COx formation). The objective of this study is to provide an equilibrium solution composition for each degradation state for a CEM-V cement-based material to support the adsorption and diffusion experiments reproducing any state of degradation. Calculations have been performed at 25 °C using the geochemical code PhreeqC and an up-to-date thermodynamic database (ThermoChimie v.9.0.b) coupled to SIT approach for ionic strength correction. The model replicates experimental data with accuracy. The approach followed in this study eases the analysis of the chemical evolution in both aqueous and solid phase to obtain a fast assessment of the geochemical effects associated to an external water intrusion of variable composition on concrete structures.

  4. Modelling of interfacial transition zone effect on resistance to crack propagation in fine-grained cement-based composites

    Directory of Open Access Journals (Sweden)

    H. Šimonová

    2017-07-01

    Full Text Available In this paper, the attention is paid to investigation of the importance of the interfacial transition zone (ITZ in selected fine-grained cement-based composites for the global fracture behaviour. This is a region of cement paste around the aggregate particles which specific features could have significant impact on the final behaviour of cement composites with a crack tip nearby this interface under applied tension. The aim of this work is to show the basic interface microstructure by scanning electron microscopy (SEM done by MIRA3 TESCAN and to analyse the behaviour of such composite by numerical modelling. Numerical studies assume two different ITZ thicknesses taken from SEM analysis. A simplified cracked geometry (consisting of three phases – matrix, ITZ, and aggregate is modelled by means of the finite element method with a crack terminating at the matrix–ITZ interface. ITZ’s modulus of elasticity is taken from generalized self-consistent scheme. A few conclusions are discussed based on comparison of the average values of the opening stress ahead of the crack tip with their critical values. The analyses dealing with the effect of ITZ’s properties on the stress distribution should contribute to better description of toughening mechanisms in silicate-based composites.

  5. Furfural Determination with Disposable Polymer Films and Smartphone-Based Colorimetry for Beer Freshness Assessment.

    Science.gov (United States)

    Rico-Yuste, Alberto; González-Vallejo, Victoria; Benito-Peña, Elena; de Las Casas Engel, Tomás; Orellana, Guillermo; Moreno-Bondi, María Cruz

    2016-04-05

    We have developed disposable color-changing polymeric films for quantification of furfural-a freshness indicator-in beer using a smartphone-based reader. The films are prepared by radical polymerization of 4-vinylaniline, as a furfural-sensitive indicator monomer, 2-hydroxymethyl methacrylate as a comonomer, and ethylene dimethyl methacrylate (EDMA) as a cross-linker. The sensing mechanism is based on the Stenhouse reaction in which aniline and furfural react in acidic media with the generation of a deep red cyanine derivative, absorbing at 537 nm, which is visible to the naked eye. The colorimetric response has been monitored using either a portable fiber-optic spectrophotometer or the built-in camera of a smartphone. Under the optimized conditions, a linear response to furfural in beer was obtained in the 39 to 500 μg L(-1) range, with a detection limit of 12 μg L(-1), thus improving the performance of other well-established colorimetric or chromatographic methods. The novel films are highly selective to furfural, and no cross-reactivity has been observed from other volatile compounds generated during beer aging. A smartphone application (app), developed for Android platforms, measures the RGB color coordinates of the sensing membranes after exposure to the analyte. Following data processing, the signals are converted into concentration values by preloaded calibration curves. The method has been applied to determination of furfural in pale lager beers with different storage times at room temperature. A linear correlation (r > 0.995) between the storage time and the furfural concentration in the samples has been confirmed; our results have been validated by HPLC with diode-array detection.

  6. Investigation on the Mechanical Properties of a Cement-Based Material Containing Carbon Nanotube under Drying and Freeze-Thaw Conditions

    Directory of Open Access Journals (Sweden)

    Wei-Wen Li

    2015-12-01

    Full Text Available This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT could improve to different degrees the mechanical properties (compressive and flexural strengths and physical performances (shrinkage and water loss of cement-based materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for cement-based materials, as well as the density of materials due to CNT’s filling action.

  7. Application of Neutron imaging in pore structure of hydrated wellbore cement: comparison of hydration of H20 with D2O based Portland cements

    Science.gov (United States)

    Dussenova, D.; Bilheux, H.; Radonjic, M.

    2012-12-01

    Wellbore Cement studies have been ongoing for decades. The studies vary from efforts to reduce permeability and resistance to corrosive environment to issues with gas migration also known as Sustained Casing Pressure (SCP). These practical issues often lead to health and safety problems as well as huge economic loss in oil and gas industry. Several techniques have been employed to reduce the impact of gas leakage. In this study we purely focus on expandable liners, which are introduced as part of oil well reconstruction and work-overs and as well abandonment procedures that help in prevention of SCP. Expandable liner is a tube that after application of a certain tool can increase its diameter. The increase in diameter creates extra force on hydrated cement that results in reducing width of interface fractures and cement-tube de-bonding. Moreover, this also causes cement to change its microstructure and other porous medium properties, primarily hydraulic conductivity. In order to examine changes before and after operations, cement pore structure must be well characterized and correlated to cement slurry design as well as chemical and physical environmental conditions. As modern oil well pipes and tubes contain iron, it is difficult to perform X-ray tomography of a bulk measurement of the cement in its wellbore conditions, which are tube wall-cement-tube wall. Neutron imaging is a complementary technique to x-ray imaging and is well suited for detection of light elements imbedded in metallic containers. Thus, Neutron Imaging (NI) is investigated as a tool for the detection of pore structure of hydrated wellbore cement. Recent measurements were conducted at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) neutron imaging facility. NI is is highly sensitive to light elements such as Hydrogen (H). Oil well cements that have undergone a full hydration contain on average 30%-40% of free water in its pore structure. The unreacted water is the main

  8. Cementation of sand grains based on carbonate precipitation induced by microorganism

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Microbes can produce 2 3 CO32-in an environment conductive to precipitation,so the incompact sands will be consolidated.This technology is environmentally friendly not only because it gives strength to the sand body,but also it allows water to penetrate into the sand body,which is unlike silicate cement that will destroy the ecosystem of the earth.After comparing the activity of three kinds of bacteria,the most suitable one was chosen for the study.However,the activity of this bacterium was still not high enough for the purpose,so it was purified.A suitable program for the consolidation and cementation of sands was also found in the experiment.The compressive strength and the porosity of the cemented sand body were tested to characterize the cementation effectiveness.XRD analysis showed that a new phase of calcite was produced between sand grains.The content of calcite was detected by TG.The study showed that the precipitation program was quite important to obtain a sound cemented sand body in addition to the activity of the bacteria.

  9. Assessment of Pozzolanic Activity Using Methods Based on the Measurement of Electrical Conductivity of Suspensions of Portland Cement and Pozzolan

    Science.gov (United States)

    Velázquez, Sergio; Monzó, José M.; Borrachero, María V.; Payá, Jordi

    2014-01-01

    The use of methods based on measuring electrical conductivity to assess pozzolanic activity has recently been used primarily in aqueous suspensions of pozzolan: calcium hydroxide. However, the use of similar methods in suspensions of cement with pozzolans has not been widely studied. This paper proposes a new method for rapid assessment of the pozzolanic activity of mineral admixtures in aqueous cement suspensions. In this study, the conditions for the application of the method were optimized, such as time, temperature, w/c ratio and dosage procedure. Finally, results are presented from the application of this method for characterizing the pozzolanic activity of the spent catalytic cracking catalyst. These results corroborate as previously reported, namely the high reactivity of this pozzolan obtained by other methods, such as thermogravimetry or evolution of the mechanical strength. In addition, the pozzolanic activity of the catalyst was compared with other pozzolans such as metakaolin and silica fume. PMID:28788261

  10. Using low temperature calorimetry and moisture fixation method to study the pore structure of cement based materials

    DEFF Research Database (Denmark)

    Wu, Min

    attention was devoted to investigating important factors influencing the analysis of measured LTC data and using LTC to characterize the pore structure of cement based materials. Besides, the moisture fixation method was selected as a comparison and complementary method to the LTC. Attempts have been made...... consideration of including the model material in this investigation was to validate the applicability of the chosen methods in the context of pore size determination. In addition, data from literature were used. LTC investigations conducted in this PhD study include the ice content determination from measured...... data, the impact of sample saturation on the detected porosity, the effect of frost damage on the pore size distribution determination by LTC, the effect of preconditioning the cement paste samples on the freezing and melting behavior of the pore solution, the impact of sample crushing...

  11. Assessment of Pozzolanic Activity Using Methods Based on the Measurement of Electrical Conductivity of Suspensions of Portland Cement and Pozzolan

    Directory of Open Access Journals (Sweden)

    Sergio Velázquez

    2014-11-01

    Full Text Available The use of methods based on measuring electrical conductivity to assess pozzolanic activity has recently been used primarily in aqueous suspensions of pozzolan: calcium hydroxide. However, the use of similar methods in suspensions of cement with pozzolans has not been widely studied. This paper proposes a new method for rapid assessment of the pozzolanic activity of mineral admixtures in aqueous cement suspensions. In this study, the conditions for the application of the method were optimized, such as time, temperature, w/c ratio and dosage procedure. Finally, results are presented from the application of this method for characterizing the pozzolanic activity of the spent catalytic cracking catalyst. These results corroborate as previously reported, namely the high reactivity of this pozzolan obtained by other methods, such as thermogravimetry or evolution of the mechanical strength. In addition, the pozzolanic activity of the catalyst was compared with other pozzolans such as metakaolin and silica fume.

  12. Rapid Classification of Hairtail Fish and Pork Freshness Using an Electronic Nose Based on the PCA Method

    OpenAIRE

    Yong-Ming Zhang; Qiang Cai; Xiu-Ying Tian

    2011-01-01

    We report a method for building a simple and reproducible electronic nose based on commercially available metal oxide sensors (MOS) to monitor the freshness of hairtail fish and pork stored at 15, 10, and 5 °C. After assembly in the laboratory, the proposed product was tested by a manufacturer. Sample delivery was based on the dynamic headspace method, and two features were extracted from the transient response of each sensor using an unsupervised principal component analysis (PCA) method. Th...

  13. Evaluation of the physicochemical properties and push-out bond strength of MTA-based root canal cement.

    Science.gov (United States)

    Chávez-Andrade, Gisselle Moraima; Kuga, Milton Carlos; Duarte, Marco Antonio Hungaro; Leonardo, Renato de Toledo; Keine, Katia Cristina; Sant'Anna-Junior, Arnaldo; Só, Marcus Vinicius Reis

    2013-11-01

    This study investigated the flowability, setting time, pH, calcium release and bond strength of a MTA-based cement (MTA Fillapex(®)) compared to AH Plus and Sealapex. For the flowability test, the ISO 6876:2001 specification was utilized and for the setting time test, the ASTM C266-03 specification was utilized. For the pH and calcium release measurements, 10 samples were prepared for each group and analyzed for several different periods. For the push-out test, dentin disks were distributed into three groups, according to the cement utilized and into three subgroups, according to the root third (n = 10). After obturation, the specimens underwent push-out testing. The data were compared statistically using a significance level of 5%. The flowability of all materials was found to be similar (p > 0.05). The setting times were different among the groups tested (MTA Fillapex MTA Fillapex presented the higher pH values (p MTA Fillapex was similar to that of Sealapex (p > 0.05). AH Plus presented the lowest pH and calcium release values (p MTA Fillapex and Sealapex were significantly lower than that of AH Plus (p MTA Fillapex and Sealapex presented several similar properties and both were found to be different than AH Plus. This study evaluated the physicochemical and mechanical properties of new MTA-based root canal cement, in order to use this scaler in root canal fillings. MTA Fillapex showed satisfactory properties for clinical use.

  14. Effects of Nano-TiO2 on the Toughness and Durability of Cement-Based Material

    Directory of Open Access Journals (Sweden)

    Baoguo Ma

    2015-01-01

    Full Text Available The effects of nano-TiO2 (NT on microstructures and mechanical properties of cement mortars were studied by scanning electron microscopy (SEM, X-ray diffraction (XRD, and mercury intrusion porosimetry (MIP. Results show that 3% NT can remarkably increase the tensile/flexural strengths (i.e., the toughness is improved and promote the precipitation of AFt crystal. The flexural and tensile strengths have significant positive correlation to the formation amount of AFt. The pores of mortars can be significantly refined and shift to harmless pores by controlling the growth of CH crystal and increasing the hydration reaction rate. The durability of cement-based materials is discussed by testing their water absorption and water-vapour permeability. Results show that the addition of 3% NT can decrease the water absorption ratio by 40–65%, water absorption coefficients by more than 40%, and water-vapour permeability coefficients by 43.9%, indicating that 3% NT can effectively improve the compactness and durability of cement-based materials.

  15. 磷石膏基胶结材固结磷尾矿性能及浸出特征%Properties and leaching characteristics of cemented phosphate tailings backfill with phosphogypsum-based cementation material

    Institute of Scientific and Technical Information of China (English)

    黄绪泉; 赵小蓉; 唐次来; 冯思源; 杜奕锦; 陈伯宇

    2016-01-01

    以磷石膏基材料代替水泥作为磷尾矿充填胶结材,研究了磷尾矿固结浆体和硬化体性能、浸出液污染特性和固结机理.结果表明,在同样条件下,磷石膏基材料固结磷尾矿浆体比水泥泌水量要小、浆体流动性能更优;磷石膏基材料胶结磷尾矿硬化体除3d抗压强度略低外,其他龄期的强度是水泥的1.21~1.95倍.3d之后,磷石膏基材料和水泥胶结尾矿硬化体浸出液总磷含量基本相近,但pH明显远低于水泥,总磷也低于污水综合排放标准限值,对环境危害低.硬化体SEM和XRD分析发现,磷石膏基材料水化生成的水化硅酸钙凝胶、针状钙矾石晶体和磷尾矿中白云石、含磷矿物生成的透钙磷石等,是整个磷尾矿固结硬化体具有较高强度、较低总磷含量和pH值主要原因.该研究表明,磷石膏基材料固化磷尾矿比水泥更有应用前景.%Cementation mechanism and properties,which include the cementation slurry and a hardened specimen,along with the contamination properties of liquid leaching of phosphate tailings cementation with a phosphogypsum-based material (PM),as opposed to cement,were investigated in this study.The results showed that the bleeding quantity of a phosphate tailing cementation slurry with PM was smaller,and that the slurry fluidity with PM was better than that with cement under the same conditions.The compressive strength of the phosphate tailing hardened specimen with PM with different hydration age was 1.21 to 1.95 times higher than that with cement,except for a 3 day hydration.After a 3 day hydration period,the total phosphorus in the liquid leaching of hardened specimens with PM and cement was similar,but the pH with PM was far lower than that with cement.The total phosphorus in liquid leaching with PM was below the integrated wastewater discharge standard of China,which implied that the liquid leaching of hardened specimens with PM was safe to the environment.SEM and XRD

  16. Physical and Chemical Aspects of the Nucleation of Cement-Based Materials

    Directory of Open Access Journals (Sweden)

    Pavel Demo

    2012-01-01

    Full Text Available A theoretical model of the nucleation of portlandite is proposed, and the critical size of a portlandite cluster and the energy barrier of nucleation are determined. The steady state nucleation rate and the time lag of the nucleation of portlandite are estimated for a pure solution of Ca(OH2 in water. Possible connections with the corresponding properties for cement paste are discussed. A new method is developed for experimentally determining the concentration of Ca2+ ions during the initial stage of hydration of a cement paste. The time dependence of Ca2+ ions is measured for various water-to-cement ratio values. The results are discussed from the point of view of existing models of the induction period.

  17. Simulation of fresh concrete flow state-of-the art report of the RILEM technical committee 222-SCF

    CERN Document Server

    Gram, Annika

    2014-01-01

    This work deals with numerical simulations of fresh concrete flows. After the first introductory chapter dealing with the various physical phenomena involved in flows of fresh cementitious materials, the aim of the second chapter is to give an overview of the work carried out on simulation of flow of cement-based materials using computational fluid dynamics (CFD). This includes governing equations, constitutive equations, analytical and numerical solutions, and examples showing simulations of testing, mixing and castings. The third chapter focuses on the application of Discrete Element Method (DEM) in simulating the flow of fresh concrete. The fourth chapter is an introductory text about numerical errors both in CFD and DEM whereas the fifth and last chapter give some recent examples of numerical simulations developed by various authors in order to simulate the presence of grains or fibers in a non-Newtonian cement matrix.

  18. Film Thickness and Flow Properties of Resin-Based Cements at Different Temperatures

    Directory of Open Access Journals (Sweden)

    Bagheri R.

    2013-06-01

    Full Text Available Statement of Problem: For a luting agent to allow complete seating of prosthetic restorations, it must obtain an appropriate flow rate maintaining a minimum film thickness. The performance of recently introduced luting agents in this regard has not been evaluated. Purpose: To measure and compare the film thickness and flow properties of seven resin-containing luting cements at different temperatures (37°C, 25°C and10°C. Material and Methods: Specimens were prepared from five resin luting cements; seT (SDI, Panavia F (Kuraray, Varioloink II (Ivoclar, Maxcem (Kerr, Nexus2 (Kerr and two resin-modified glass-ionomer luting cements (RM-GICs; GC Fuji Plus (GC Corporation, and RelyX Luting 2 (3 M/ESPE. The film thickness and flow rate of each cement (n=15 was determined using the test described in ISO at three different temperatures. Results: There was a linear correlation between film thickness and flow rate for most of the materials. Cooling increased fluidity of almost all materials while the effect of temperature on film thickness was material dependent. At 37°C, all products revealed a film thickness of less than 25µm except for GC Fuji Plus. At 25°C, all cements pro-duced a film thickness of less than 27 µm except for seT. At 10°C, apart from seT and Rely X Luting 2, the remaining cements showed a film thickness smaller than 20 µm.Conclusion: Cooling increased fluidity of almost all materials, however. the film thickness did not exceed 35 µm in either condition, in spite of the lowest film thickness being demonstrated at the lowest temperature.

  19. Development of a Laboratory Cement Quality Analysis Apparatus Based on Laser-Induced Breakdown Spectroscopy

    Science.gov (United States)

    Fan, Juanjuan; Zhang, Lei; Wang, Xin; Li, Yufang; Gong, Yao; Dong, Lei; Ma, Weiguang; Yin, Wangbao; Wang, Zhe; Li, Zheng; Zhang, Xiangjie; Li, Yi; Jia, Suotang

    2015-11-01

    Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a laboratory laser-induced breakdown spectroscopy (LIBS) apparatus mainly comprising a sealed optical module and an analysis chamber has been designed for possible application in cement plants for on-site quality analysis of cement. Emphasis is placed on the structure and operation of the LIBS apparatus, the sealed optical path, the temperature controlled spectrometer, the sample holder, the proper calibration model established for minimizing the matrix effects, and a correction method proposed for overcoming the ‘drift’ obstacle. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The absolute measurement errors presented here for oxides analysis are within 0.5%, while those of ratio values are in the range of 0.02 to 0.05. According to the obtained results, this laboratory LIBS apparatus is capable of performing reliable and accurate, composition and proximate analysis of cement and is suitable for application in cement plants. supported by National Natural Science Foundation of China (Nos. 61127017, 61378047, 61205216, 61178009, 61108030, 61475093, and 61275213), the National Key Technology R&D Program of China (No. 2013BAC14B01), the 973 Program of China (No. 2012CB921603), the Shanxi Natural Science Foundation, China (Nos. 2013021004-1, 2012021022-1), and the Shanxi Scholarship Council of China (Nos. 2013-011 and 2013-01)

  20. 基于水泥水化模拟的水泥石毛细孔结构分析%Cement Hydration Simulation Based Analysis of Capillary Pore Structure in Cement Paste

    Institute of Scientific and Technical Information of China (English)

    吴芬; 郑建军; 周欣竹

    2015-01-01

    通过水泥水化模拟分析了水泥石毛细孔结构。基于水化动力学原理,模拟水泥水化全过程,将模拟所得的水化度与试验结果比较,验证了模拟方法的有效性。提出了水泥石毛细孔隙率和内表面积的数值方法,数值结果表明,孔隙率随着时间不断减小,内表面积先随着时间不断增大,到达峰值后随着时间逐渐减小,水灰比越小,出现峰值的时间越短。水化28 d 时,水灰比为0.3的水泥石毛细孔隙率和内表面积分别比水灰比为0.5的水泥石毛细孔隙率和内表面积小61%和11%。%The capillary pore structure in cement paste is analyzed through cement hydration simulation.Based on the principles of hydration kinetics,the whole process of cement hydration is simulated.The validity of the simulation method is verified by comparing the simulated degree of hydration with experimental results.A numerical method is presented for the porosity and internal surface area of capillary pores in cement paste.Numerical results show the cap-illary porosity decreases with time.The internal surface area of capillary pores first increases continuously with time and then decreases gradually with time after the peak value reached.The smaller the water/cement ratio is,the shorter the time corresponding to the peak value is.At the age of 28 days,the porosity and internal surface area of capillary pores in cement paste with a water/cement ratio of 0.3 is smaller than those with a water/cement ratio of 0.5 by 61%and 1 1%,respectively.

  1. Analytical approach for predicting fresh water discharge in an estuary based on tidal water level observations

    NARCIS (Netherlands)

    Cai, H.; Savenije, H.H.G.; Jiang, C.

    2014-01-01

    As the tidal wave propagates into an estuary, the tidally averaged water level tends to rise in landward direction due to the density difference between saline and fresh water and the asymmetry of the friction. The effect of friction on the residual slope is even more remarkable when accounting for

  2. Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC) by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement.

    Science.gov (United States)

    García Calvo, José Luis; Sánchez Moreno, Mercedes; Alonso Alonso, María Cruz; Hidalgo López, Ana; García Olmo, Juan

    2013-06-18

    Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected.

  3. Use of metakaolin to stabilize sewage sludge ash and municipal solid waste incineration fly ash in cement-based materials.

    Science.gov (United States)

    Cyr, M; Idir, R; Escadeillas, G

    2012-12-01

    The landfilling of municipal incineration residues is an expensive option for municipalities. This work evaluates an alternative way to render waste inert in cement-based materials by combining the reduction of waste content with the immobilization properties of metakaolin (MK). The functional and environmental properties of ternary and quaternary binders using cement, metakaolin, and two industrial by-products from combustion processes (MSWIFA - Municipal Solid Waste Incineration Fly Ash and SSA - Sewage Sludge Ash) were evaluated. The binders were composed of 75% cement, 22.5% metakaolin and 2.5% residue. Results on the impact of residues on the functional and environmental behavior of mortars showed that the mechanical, dimensional and leaching properties were not affected by the residues. In particular, the use of metakaolin led to a significant decrease in soluble fractions and heavy metals released from the binder matrix. The results are discussed in terms of classification of the leaching behavior, efficiency and role of metakaolin in the immobilization of heavy metals in of MSWIFA and SSA, and the pertinence of the dilution process.

  4. Push-out bond strength of MTA HP, a new high-plasticity calcium silicate-based cement.

    Science.gov (United States)

    Silva, Emmanuel Jnl; Carvalho, Nancy Kudsi; Zanon, Mayara; Senna, Plínio Mendes; DE-Deus, Gustavo; Zuolo, Mário Luis; Zaia, Alexandre Augusto

    2016-06-14

    This study was designed to investigate the resistance to dislodgment provided by MTA HP, a new high-plasticity calcium silicate-based cement. Biodentine and White MTA Angelus were used as reference materials for comparison. Three discs 1 ± 0.1 mm thick were obtained from the middle third of the roots of 5 maxillary canines. Three 0.8-mm-wide holes were drilled on the axial surface of each root disc. Standardized irrigation was performed. Then the holes were dried with paper points and filled with one of the three tested cements. The filled dental slices were immersed in a phosphate-buffered saline (PBS) solution (pH 7.2) for 7 days before the push-out assessment. The Kruskal-Wallis test was applied to assess the effect of each endodontic cement on the push-out bond strength. Mann-Whitney with Bonferroni correction was used to isolate the differences. The alpha-type error was set at 0.05. All specimens had measurable push-out values and no premature failure occurred. There were significant differences among the materials (p MTA HP had significantly higher bond strength than White MTA (p MTA HP showed better push-out bond strength than its predecessor, White MTA; however, Biodentine had higher dislodgment resistance than both MTA formulations.

  5. In vitro cytotoxicity of four calcium silicate-based endodontic cements on human monocytes, a colorimetric MTT assay

    Directory of Open Access Journals (Sweden)

    Sedigheh Khedmat

    2014-08-01

    Full Text Available Objectives This study was performed to evaluate the cytotoxicity of four calcium silicate-based endodontic cements at different storage times after mixing. Materials and Methods Capillary tubes were filled with Biodentine (Septodont, Calcium Enriched Mixture (CEM cement, BioniqueDent, Tech Biosealer Endo (Tech Biosealer and ProRoot MTA (Dentsply Tulsa Dental. Empty tubes and tubes containing Dycal were used as negative and positive control groups respectively. Filled capillary tubes were kept in 0.2 mL microtubes and incubated at 37℃. Each material was divided into 3 groups for testing at intervals of 24 hr, 7 day and 28 day after mixing. Human monocytes were isolated from peripheral blood mononuclear cells and cocultered with 24 hr, 7 day and 28 day samples of different materials for 24 and 48 hr. Cell viability was evaluated using an MTT assay. Results In all groups, the viability of monocytes significantly improved with increasing storage time regardless of the incubation time (p < 0.001. After 24 hr of incubation, there was no significant difference between the materials regarding monocyte viability. However, at 48 hr of incubation, ProRoot MTA and Biodentine were less cytotoxic than CEM cement and Biosealer (p < 0.01. Conclusions Biodentine and ProRoot MTA had similar biocompatibility. Mixing ProRoot MTA with PBS in place of distilled water had no effect on its biocompatibility. Biosealer and CEM cement after 48 hr of incubation were significantly more cytotoxic to on monocyte cells compared to ProRoot MTA and Biodentine.

  6. Fuzzy logic based control system for fresh water aquaculture: A MATLAB based simulation approach

    Directory of Open Access Journals (Sweden)

    Rana Dinesh Singh

    2015-01-01

    Full Text Available Fuzzy control is regarded as the most widely used application of fuzzy logic. Fuzzy logic is an innovative technology to design solutions for multiparameter and non-linear control problems. One of the greatest advantages of fuzzy control is that it uses human experience and process information obtained from operator rather than a mathematical model for the definition of a control strategy. As a result, it often delivers solutions faster than conventional control design techniques. The proposed system is an attempt to apply fuzzy logic techniques to predict the stress factor on the fish, based on line data and rule base generated using domain expert. The proposed work includes a use of Data acquisition system, an interfacing device for on line parameter acquisition and analysis, fuzzy logic controller (FLC for inferring the stress factor. The system takes stress parameters on the fish as inputs, fuzzified by using FLC with knowledge base rules and finally provides single output. All the parameters are controlled and calibrated by the fuzzy logic toolbox and MATLAB programming.

  7. Early, Prehospital Activation of the Walking Blood Bank Based on Mechanism of Injury Improves Time to Fresh Whole Blood Transfusion.

    Science.gov (United States)

    Bassett, Aaron K; Auten, Jonathan D; Zieber, Tara J; Lunceford, Nicole L

    2016-01-01

    Balanced component therapy (BCT) remains the mainstay in trauma resuscitation of the critically battle injured. In austere medical environments, access to packed red blood cells, apheresis platelets, and fresh frozen plasma is often limited. Transfusion of warm, fresh whole blood (FWB) has been used to augment limited access to full BCT in these settings. The main limitation of FWB is that it is not readily available for transfusion on casualty arrival. This small case series evaluates the impact early, mechanism-of-injury (MOI)-based, preactivation of the walking blood bank has on time to transfusion. We report an average time of 18 minutes to FWB transfusion from patient arrival. Early activation of the walking blood bank based on prehospital MOI may further reduce the time to FWB transfusion.

  8. A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

    Science.gov (United States)

    Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

    2016-01-01

    AIM: To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. MATERIALS AND METHOD: The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. RESULTS: GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. CONCLUSION: It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation. PMID:28028417

  9. A brief on high-volume Class F fly ash as cement replacement – A guide for Civil Engineer

    Directory of Open Access Journals (Sweden)

    Alaa M. Rashad

    2015-12-01

    Full Text Available Disposal of fly ash (FA resulting from the combustion of coal-fired electric power stations is one of the major environmental challenges. This challenge continues to increase with increasing the amount of FA and decreasing the capacity of landfill space. Therefore, studies have been carried out to re-use high-volumes of fly ash (HVFA as cement replacement in building materials. This paper presents an overview of the previous studies carried out on the use of high volume Class F FA as a partial replacement of cement in traditional paste/mortar/concrete mixtures based on Portland cement (PC. Fresh properties, mechanical properties, abrasion resistance, thermal properties, drying shrinkage, porosity, water absorption, sorptivity, chemical resistance, carbonation resistance and electrical resistivity of paste/mortar/concrete mixtures containing HVFA (⩾45% as cement replacement have been reviewed. Furthermore, additives used to improve some properties of HVFA system have been reviewed.

  10. Liquid water permeability of partially saturated cement paste assessed by dem-based methodology

    NARCIS (Netherlands)

    Li, K.; Stroeven, P.; Stroeven, M.; Sluys, L.J.

    2015-01-01

    Permeability of virtual cement seems to exceed experimental data by several orders of magnitude. The differences may actually not be that dramatic, since experimental samples are in practice not always fully saturated as generally assumed. This paper demonstrates that this has enormous effects on pe

  11. Impact of zeolite-based nanomodified additive on the structure and strength of the cement stone

    Science.gov (United States)

    Egorova, A. D.; Filippova, K. E.

    2015-01-01

    Portland cement is the main binder in the building materials industry; its properties strongly influence properties of mortars and concretes. Some regions experience difficulties with delivery and storage of Portland cement, raising the need to develop an effective additive from the available raw materials. Such materials for the Republic of Sakha (Yakutia) are zeolite-containing rocks. Studies have shown that introducing of dibutylphthalate to the composition of modified additive during mechanochemical activation leads to achievement of up to 11% of total amount particles with the size of 3-30 nm. After introducing 0.5% of the obtained additives, the compressive strength of cement-sand slurry samples increases up to 28%. Positive effect of additives introduction is also observed at high flow rate of water (W / C = 0.7). Gaining strength reaches 23%, allowing the efficient use of additive for movable mixtures with enhanced strength properties. In general, the proposed supplement allows reducing the water flow in the solution without decreasing its mobility, and increasing strength properties, which makes it possible to obtain a whole class of solutions of modified cement binder. The market value of the developed additives is 18 rubles per 1 kg, making sound competition in the market of modifying additives.

  12. Ductile Cement-Based Composites with Wood Fibres - material design and experimental approach

    NARCIS (Netherlands)

    Sierra-Beltran, M.G.

    2011-01-01

    In order to turn a brittle cement matrix into a ductile composite different types of man-made fibres such as steel, glass and polyvinyl alcohol are currently used as reinforcement, as well as some natural fibres. Compared to synthetic fibres, natural fibres are more easily available worldwide and th

  13. Mechanical, electrical and microstructural properties of cement-based materials in conditions of stray current flow

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Copuroglu, O.; Van Beek, C.; Van Breugel, K.

    2013-01-01

    This investigation presents a comparative study on mechanical properties, electrical resistivity and microstructure of mortar under DC current, compared to mortar in rest (no current) conditions. Monitoring was performed from 24h after casting until 84 days of cement hydration. A current

  14. Innovation based on tradition: Blast furnace slag cement for durable concrete structures in Norway?

    NARCIS (Netherlands)

    Polder, R.B.; Nijland, T.; De Rooij, M.; Larsen, C.K.; Pedersen, B.

    2014-01-01

    Blast furnace slag cement (BFSC) has been used to build reinforced concrete structures in marine and road environment in The Netherlands for nearly a century. The experience is good and structures with long service lives can be obtained, as has been shown by several field studies. This is caused by

  15. Action-Dependent Adaptive Critic Design Based Neurocontroller for Cement Precalciner Kiln

    Directory of Open Access Journals (Sweden)

    Baosheng Yang

    2009-10-01

    Full Text Available There are many factors that can affect the calciner process of cement production, such as highly nonlinearity and time-lag, making it very difficult to establish an accurate model of the cement precalciner kiln (PCK system. In order to reduce transport energy consumption and to ensure the quality of cement clinker burning, one needs to explore different control methods from the traditional way. Adaptive Critic Design (ACD integrated neural network, reinforcement learning and dynamic programming techniques, is a new optimal method. As the PCK system parameters change frequently with high real-time property, ADACD (Action-Dependant ACD algorithm is used in PCK system to control the temperature of furnace export and oxygen content of exhaust. ADACD does not depend on the system model, it may use historical data to train a controller offline, and then adapt online. Also the BP network of artificial neural network is used to accomplish the network modeling, and action and critic modules of the algorithm. The results of simulation show that, after the fluctuations in the early control period, the controlled parameters tend to be stabilized guaranteeing the quality of cement clinker calcining.

  16. Rapid classification of hairtail fish and pork freshness using an electronic nose based on the PCA method.

    Science.gov (United States)

    Tian, Xiu-Ying; Cai, Qiang; Zhang, Yong-Ming

    2012-01-01

    We report a method for building a simple and reproducible electronic nose based on commercially available metal oxide sensors (MOS) to monitor the freshness of hairtail fish and pork stored at 15, 10, and 5 °C. After assembly in the laboratory, the proposed product was tested by a manufacturer. Sample delivery was based on the dynamic headspace method, and two features were extracted from the transient response of each sensor using an unsupervised principal component analysis (PCA) method. The compensation method and pattern recognition based on PCA are discussed in the current paper. PCA compensation can be used for all storage temperatures, however, pattern recognition differs according to storage conditions. Total volatile basic nitrogen (TVBN) and aerobic bacterial counts of the samples were measured simultaneously with the standard indicators of hairtail fish and pork freshness. The PCA models based on TVBN and aerobic bacterial counts were used to classify hairtail fish samples as "fresh" (TVBN ≤ 25 g and microbial counts ≤ 10(6) cfu/g) or "spoiled" (TVBN ≥ 25 g and microbial counts ≥ 10(6) cfu/g) and pork samples also as "fresh" (TVBN ≤ 15 g and microbial counts ≤ 10(6) cfu/g) or "spoiled" (TVBN ≥ 15 g and microbial counts ≥ 10(6) cfu/g). Good correlation coefficients between the responses of the electronic nose and the TVBN and aerobic bacterial counts of the samples were obtained. For hairtail fish, correlation coefficients were 0.97 and 0.91, and for pork, correlation coefficients were 0.81 and 0.88, respectively. Through laboratory simulation and field application, we were able to determine that the electronic nose could help ensure the shelf life of hairtail fish and pork, especially when an instrument is needed to take measurements rapidly. The results also showed that the electronic nose could analyze the process and level of spoilage for hairtail fish and pork.

  17. Predicting cement distribution in geothermal sandstone reservoirs based on estimates of precipitation temperatures

    Science.gov (United States)

    Olivarius, Mette; Weibel, Rikke; Whitehouse, Martin; Kristensen, Lars; Hjuler, Morten L.; Mathiesen, Anders; Boyce, Adrian J.; Nielsen, Lars H.

    2016-04-01

    Exploitation of geothermal sandstone reservoirs is challenged by pore-cementing minerals since they reduce the fluid flow through the sandstones. Geothermal exploration aims at finding sandstone bodies located at depths that are adequate for sufficiently warm water to be extracted, but without being too cemented for warm water production. The amount of cement is highly variable in the Danish geothermal reservoirs which mainly comprise the Bunter Sandstone, Skagerrak and Gassum formations. The present study involves bulk and in situ stable isotope analyses of calcite, dolomite, ankerite, siderite and quartz in order to estimate at what depth they were formed and enable prediction of where they can be found. The δ18O values measured in the carbonate minerals and quartz overgrowths are related to depth since they are a result of the temperatures of the pore fluid. Thus the values indicate the precipitation temperatures and they fit the relative diagenetic timing identified by petrographical observations. The sandstones deposited during arid climatic conditions contain calcite and dolomite cement that formed during early diagenesis. These carbonate minerals precipitated as a response to different processes, and precipitation of macro-quartz took over at deeper burial. Siderite was the first carbonate mineral that formed in the sandstones that were deposited in a humid climate. Calcite began precipitating at increased burial depth and ankerite formed during deep burial and replaced some of the other phases. Ankerite and quartz formed in the same temperature interval so constrains on the isotopic composition of the pore fluid can be achieved. Differences in δ13C values exist between the sandstones that were deposited in arid versus humid environments, which suggest that different kinds of processes were active. The estimated precipitation temperatures of the different cement types are used to predict which of them are present in geothermal sandstone reservoirs in

  18. 21 CFR 872.3275 - Dental cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns or...

  19. Odontoblastic Differentiation, Inflammatory Response, and Angiogenic Potential of 4 Calcium Silicate-based Cements: Micromega MTA, ProRoot MTA, RetroMTA, and Experimental Calcium Silicate Cement.

    Science.gov (United States)

    Chang, Seok-Woo; Bae, Won-Jung; Yi, Jin-Kyu; Lee, Soojung; Lee, Deok-Won; Kum, Kee-Yeon; Kim, Eun-Cheol

    2015-09-01

    The aim of this study was to analyze the effects of different calcium silicate-based cements (CSCs) for pulp capping materials including MicroMega MTA (MMTA; MicroMega, Besanchon, France), RetroMTA (RMTA; BioMTA, Seoul, Korea), ProRoot MTA (PMTA; Dentsply, Tulsa, OK), and experimental CSC (ECSC) on odontoblastic differentiation, in vitro angiogenesis, and the inflammatory response in human dental pulp cells. Differentiation was evaluated by alkaline phosphatase activity, alizarin red staining, and reverse-transcriptase polymerase chain reaction (RT-PCR) for the marker genes. The levels of inflammatory mediators and cytokines were measured by RT-PCR and an enzyme-linked immunosorbent assay. In vitro angiogenesis was assessed by RT-PCR for angiogenic genes and an endothelial tube formation assay. PMTA, MMTA, and ECSC increased the alkaline phosphatase activity and mineralization nodule formation and up-regulated messenger RNA (mRNA) expression of odontoblastic markers compared with RMTA. In addition, PMTA, MMTA, and ECSC up-regulated the mRNA of angiogenic genes in human dental pulp cells and increased the capillary tube formation of endothelial cells compared with RMTA. However, all CSCs showed similar expression levels of inducible nitric oxide synthase and cyclooxygenase-2 protein as well as proinflammatory mediators such as nitric oxide, prostaglandin E2, tumor necrosis factor alpha, interleukin (IL)-1β, IL-6, and IL-8 mRNA. Taken together, our experimental results suggest that all CSCs are favorable materials for pulp capping, but PMTA, MMTA, and ECSC may be recommended over RMTA. Copyright © 2015 American Association of Endodontists. All rights reserved.

  20. Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, K.M.; Serne, R.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-05-01

    The US Nuclear Regulatory Commission is developing a technical position document that provides guidance regarding the performance assessment of low-level radioactive waste disposal facilities. This guidance considers the effects that the chemistry of the vault disposal system may have on radionuclide release. The geochemistry of pore waters buffered by cementitious materials in the disposal system will be different from the local ground water. Therefore, the cement-buffered environment needs to be considered within the source term calculations if credit is taken for solubility limits and/or sorption of dissolved radionuclides within disposal units. A literature review was conducted on methods to model pore-water compositions resulting from reactions with cement, experimental studies of cement/water systems, natural analogue studies of cement and concrete, and radionuclide solubilities experimentally determined in cement pore waters. Based on this review, geochemical modeling was used to calculate maximum concentrations for americium, neptunium, nickel, plutonium, radium, strontium, thorium, and uranium for pore-water compositions buffered by cement and local ground-water. Another literature review was completed on radionuclide sorption behavior onto fresh cement/concrete where the pore water pH will be greater than or equal 10. Based on this review, a database was developed of preferred minimum distribution coefficient values for these radionuclides in cement/concrete environments.

  1. Human tooth germ stem cell response to calcium-silicate based endodontic cements

    Directory of Open Access Journals (Sweden)

    Esra Pamukcu Guven

    2013-07-01

    Full Text Available OBJECTIVE: The aim of this study was to compare the cytotoxic effects of endodontic cements on human tooth germ stem cells (hTGSCs. MTA Fillapex, a mineral trioxide aggregate (MTA-based, salicylate resin containing root canal sealer, was compared with iRoot SP, a bioceramic sealer, and AH Plus Jet, an epoxy resin-based root canal sealer. MATERIAL AND METHODS: To evaluate cytotoxicity, all materials were packed into Teflon rings (4 mmµ3 mm and co-cultured with hTGSCs with the aid of 24-well Transwell permeable supports, which had a pore size of 0.4 µm. Coverslips were coated with MTA Fillapex, iRoot SP and AH Plus Jet and each coverslip was placed onto the bottom of one well of a six-well plate for scanning electron microscopy (SEM analysis. Before the cytotoxicity and SEM analysis, all samples were stored at 37ºC and at 95% humidity and 5% CO2 for 24 hours to set. The cellular viability was analyzed using MTS test (3-(4,5-dimethyl-thiazol-2-yl-5-(3-carboxy-methoxy-phenyl-2-(4-sulfo-phenyl-2H-tetrazolium. The cytotoxic effects and SEM visualization of the tested materials were analyzed at 24-hour, 72-hour, one-week and two-week periods. RESULTS: On the 1st day, only MTA Fillapex caused cytotoxicity compared to negative control (NC group (p0.05. After 14 days of incubation with the test materials, MTA Fillapex exhibited significantly higher cytotoxicity compared with iRoot SP, AH Plus Jet and the NC group (P<0.008. In the SEM analysis, the highest levels of cell attachment were observed for iRoot SP and the control group. After 24 hours, MTA Fillapex reduced the number of cells attached to the surface. CONCLUSIONS: Within the limitations of this study, sealers exerted different cytotoxic effects on hTGSCs. Although all materials have exerted cellular toxicity, iRoot SP and AH Plus Jet may promote better attachment to hTGSCs.

  2. Multi-Scale Studies of Transport and Adsorption Phenomena of Cement-based Materials in Aqueous and Saline Environment

    Science.gov (United States)

    Yoon, Se Yoon

    The transport and adsorption phenomena in cement-based materials are the most important processes in the durability of concrete structures or nuclear waste containers, as they are precursors to a number of deterioration processes such as chloride-induced corrosion, sulfate attack, carbonation, etc. Despite this importance, our understanding of these processes remains limited because the pore structure and composition of concrete are complex. In addition, the range of the pore sizes, from nanometers to millimeters, requires the multi-scale modeling of the transport and adsorption processes. Among the various environments that cement-based materials are exposed to, aqueous and saline environments represent the most common types. Therefore, this dissertation investigates the adsorption and transport phenomena of cement-based materials exposed to an aqueous and saline environment from atomic to macro-scales using different arrays of novel spectroscopic techniques and simulation methods, such as scanning transmission X-ray microscopy (STXM), X-ray absorption near edge structure (XANES), molecular dynamics (MD), and finite element method (FEM). The structure and transport of water molecules through interlayer spacing of tobermorite was investigated using MD simulations because the interlayer water of calcium silicate hydrate (C-S-H) gel influences various material properties of concrete. The adsorption processes of cementitious phases interacting with sodium and chloride ions at the nano-scale were identified using STXM and XANES measurements. A mathematical model and FEM procedure were developed to identify the effect of surface treatments at macro-scale on ionic transport phenomena of surface-treated concrete. Finally, this dissertation introduced a new material, calcined layered double hydroxide (CLDH), to prevent chloride-induced deterioration.

  3. The effect of CNTs reinforcement on thermal and electrical properties of cement-based materials

    Science.gov (United States)

    Exarchos, D. A.; Dalla, P. T.; Tragazikis, I. K.; Matikas, T. E.

    2015-03-01

    This research aims to investigate the influence of the nano-reinforcement on the thermal properties of cement mortar. Nano-modified cement mortar with carbon nanotubes (CNTs) leading to the development of innovative materials possessing multi-functionality and smartness. Such multifunctional properties include enhanced mechanical behavior, electrical and thermal conductivity, and piezo-electric characteristics. The assessment of the thermal behavior was evaluated using IR Thermography. Two different thermographic techniques are used to monitor the influence of the nano-reinforcement. To eliminate any extrinsic effects (e.g. humidity) the specimens were dried in an oven before testing. The electrical resistivity was measured with a contact test method using a custom made apparatus and applying a known D.C. voltage. This study indicate that the CNTs nano-reinforcement enhance the thermal and electrical properties and demonstrate them useful as sensors in a wide variety of applications.

  4. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  5. Comparative Analysis of Selected Physicochemical Properties of Pozzolan Portland and MTA-Based Cements

    OpenAIRE

    Dorileo, Maura Cristiane Gonçales Orçati; Villa, Ricardo Dalla; Guedes, Orlando Aguirre; Aranha, Andreza Maria Fábio; Semenoff-Segundo, Alex; Bandeca, Matheus Coelho; Borges, Alvaro Henrique

    2014-01-01

    Physicochemical properties of pozzolan Portland cement were compared to ProRoot MTA and MTA BIO. To test the pH, the samples were immersed in distilled water for different periods of time. After the pH analysis, the sample was retained in the plastic recipient, and the electrical conductivity of the solution was measured. The solubility and radiopacity properties were evaluated according to specification 57 of the American National Standard Institute/American Dental Association (ANSI/ADA). Th...

  6. Mechanical Properties and Biocompatibility of a Biomaterial Based on Deproteinized Hydroxyapatite and Endodentine Cement

    Directory of Open Access Journals (Sweden)

    Rupeks Lauris

    2016-05-01

    Full Text Available Hydroxyapatite is used for bone reconstruction, in order to improve its mechanical properties different substances can be added. In our study new biomaterial is created from deproteinised hydroxyaptite and endodentic cement, its mechanical properties were tested. Material was implanted subcutaneous in rats, then histological and biocompatability tests were performed. Results indicate that stuff has good mechanical properties, short setting time and gradual resorption creating porosity and ability to integrate in bone.

  7. Leaching of metals on stabilization of metal sludge using cement based materials

    Institute of Scientific and Technical Information of China (English)

    Carmalin Sophia A; K. Swaminathan

    2005-01-01

    Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371.5mg/L, 1.95 mg/L and 1.99 mg/L respectively. Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.

  8. The Estimation of Compaction Parameter Values Based on Soil Properties Values Stabilized with Portland Cement

    Science.gov (United States)

    Lubis, A. S.; Muis, Z. A.; Pasaribu, M. I.

    2017-03-01

    The strength and durability of pavement construction is highly dependent on the properties and subgrade bearing capacity. This then led to the idea of the selection methods to estimate the density of the soil with the proper implementation of the system, fast and economical. This study aims to estimate the compaction parameter value namely the maximum dry unit weight (γd max) and optimum moisture content (wopt) of the soil properties value that stabilized with Portland Cement. Tests conducted in the laboratory of soil mechanics to determine the index properties (fines and liquid limit) and Standard Compaction Test. Soil samples that have Plasticity Index (PI) between 0-15% then mixed with Portland Cement (PC) with variations of 2%, 4%, 6%, 8% and 10%, each 10 samples. The results showed that the maximum dry unit weight (γd max) and wopt has a significant relationship with percent fines, liquid limit and the percentation of cement. Equation for the estimated maximum dry unit weight (γd max) = 1.782 - 0.011*LL + 0,000*F + 0.006*PS with R2 = 0.915 and the estimated optimum moisture content (wopt) = 3.441 + 0.594*LL + 0,025*F + 0,024*PS with R2 = 0.726.

  9. Optimization of compressive strength in admixture-reinforced cement-based grouts

    Directory of Open Access Journals (Sweden)

    Sahin Zaimoglu, A.

    2007-12-01

    Full Text Available The Taguchi method was used in this study to optimize the unconfined (7-, 14- and 28-day compressive strength of cement-based grouts with bentonite, fly ash and silica fume admixtures. The experiments were designed using an L16 orthogonal array in which the three factors considered were bentonite (0%, 0.5%, 1.0% and 3%, fly ash (10%, 20%, 30% and 40% and silica fume (0%, 5%, 10% and 20% content. The experimental results, which were analyzed by ANOVA and the Taguchi method, showed that fly ash and silica fume content play a significant role in unconfined compressive strength. The optimum conditions were found to be: 0% bentonite, 10% fly ash, 20% silica fume and 28 days of curing time. The maximum unconfined compressive strength reached under the above optimum conditions was 17.1 MPa.En el presente trabajo se ha intentado optimizar, mediante el método de Taguchi, las resistencias a compresión (a las edades de 7, 14 y 28 días de lechadas de cemento reforzadas con bentonita, cenizas volantes y humo de sílice. Se diseñaron los experimentos de acuerdo con un arreglo ortogonal tipo L16 en el que se contemplaban tres factores: la bentonita (0, 0,5, 1 y 3%, las cenizas volantes (10, 20, 30 y 40% y el humo de sílice (0, 5, 10 y 20% (porcentajes en peso del sólido. Los datos obtenidos se analizaron con mediante ANOVA y el método de Taguchi. De acuerdo con los resultados experimentales, el contenido tanto de cenizas volantes como de humo de sílice desempeña un papel significativo en la resistencia a compresión. Por otra parte, las condiciones óptimas que se han identificado son: 0% bentonita, 10% cenizas volantes, 20% humo de sílice y 28 días de tiempo de curado. La resistencia a compresión máxima conseguida en las anteriores condiciones era de 17,1 MPa.

  10. Self-healing of Early Age Cracks in Cement-based Materials by Mineralization of Carbonic Anhydrase Microorganism

    Directory of Open Access Journals (Sweden)

    Chunxiang eQian

    2015-11-01

    Full Text Available This research investigated the self-healing potential of early age cracks in cement-based materials incorporating the bacteria which can produce carbonic anhydrase. Cement-based materials specimens were pre-cracked at the age of 7, 14, 28, 60 days to study the repair ability influenced by cracking time, the width of cracks were between 0.1 and 1.0 mm to study the healing rate influenced by width of cracks. The experimental results indicated that the bacteria showed excellent repairing ability to small cracks formed at early age of 7 days, cracks below 0.4 mm was almost completely closed. The repair effect reduced with the increasing of cracking age. Cracks width influenced self-healing effectiveness significantly. The transportation of CO2 and Ca2+ controlled the self-healing process. The computer simulation analyses revealed the self-healing process and mechanism of microbiologically precipitation induced by bacteria and the depth of precipitated CaCO3 could be predicted base on valid Ca2+.

  11. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  12. Concentration Limits in the Cement Based Swiss Repository for Long-lived, Intermediate-level Radioactive Wastes (LMA)

    Energy Technology Data Exchange (ETDEWEB)

    Berner, Urs

    1999-12-01

    The Swiss repository concept for long-lived, intermediate-level radioactive wastes (LMA), in Swiss terminology) foresees cylindrical concrete silos surrounded by a ring of granulated bentonite to deposit the waste. As one of the possible options and similar to the repository for high level wastes, the silos will be located in a deep crystalline host rock. Solidified with concrete in steel drums, the waste is stacked into a silo and the silo is then backfilled with a porous mortar. To characterize the release of radionuclides from the repository, the safety assessment considers first the dissolution into the pore water of the concrete, and then diffusion through the outer bentonite ring into the deep crystalline groundwater. For 19 safety relevant radionuclides (isotopes of U, Th, Pa, Np, Pu, Am, Ni, Zr, Mo, Nb, Se, Sr, Ra, Tc, Sn, I, C, Cs, Cl) the report recommends maximum elemental concentrations to be expected in the cement pore water of the particularly considered repository. These limits will form the parameter base for subsequent release model chains. Concentration limits in a geochemical environment are usually obtained from thermodynamic equilibrium calculations performed with geochemical speciation codes. However, earlier studies revealed that this procedure does not always lead to reliable results. Main reasons for this are the complexity of the systems considered, as well as the lacking completeness of, and the uncertainty associated with the thermodynamic data. To improve the recommended maximum concentrations for a distinct repository design, this work includes additional design- and system-dependent criteria. The following processes, inventories and properties are considered in particular: a) recent experimental investigations, particularly from cement systems, b) thermodynamic model calculations when reliable data are available, c) total inventories of radionuclides, d) sorption- and co-precipitation processes, e) dilution with stable isotopes, f

  13. Effect of Adding Time of Water Reducing Agent on the Rheologic Properties of Fresh Cement Pastes%减水剂的加入时间对新拌水泥浆体流变性能的影响

    Institute of Scientific and Technical Information of China (English)

    曹强; 朱斌

    2012-01-01

    研究了三聚氰胺甲醛磺酸盐(MFS)减水剂的掺加时间对普通硅酸盐水泥浆体在初始120 min的水化时间内流变性能的影响,研究中MFS的后掺时间为0 min、5 min、10 min、15 min、20 min和25 min。检测了在不同减切速率(3~147 s-1)下水泥浆体水化30 min和120 min时的剪切应力和表观粘度。测定了水化120 min后的水泥浆体的Ca2+浓度和化学结合水。结果表明:推迟减水剂的后掺时间降低了水泥浆体在120 min内的屈服应力和表观粘度,减水剂MFS的最佳后掺时间为10~15 min。%The influence of the time addition of melamine formaldehyde sulfonate(MFS) water reducing agent on the rheological properties of ordinary portland cement pastes through the first 120 min of hydration was investigated.The admixture addition was delayed by 0,5,10,15,20,and 25 min.Shear stress and apparent viscosity of the cement pastes were determined at different shear rates(3~147 s-1) and hydration times of 30 and 120 min.The concentration of Ca2+ and the combined water content of the cement pastes were determined after 120 min.The results showed that an increase in the addition time of the admixture reduced the yield stress and the plastic viscosity of the cement pastes at the early ages(120 min).The optimum delaying time of MFS addition was found to be 10~15 min.

  14. Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

    Directory of Open Access Journals (Sweden)

    Jesús Carmona

    2015-05-01

    Full Text Available This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

  15. Performance of Cement-Based Materials in Aggressive Aqueous Environments State-of-the-Art Report, RILEM TC 211 - PAE

    CERN Document Server

    Bertron, Alexandra; Belie, Nele

    2013-01-01

    Concrete and cement-based materials must operate in increasingly aggressive aqueous environments, which may be either natural or industrial.  These materials may suffer degradation in which ion addition and/or ion exchange reactions occur, leading to a breakdown of the matrix microstructure and consequent weakening.  Sometimes this degradation can be extremely rapid and serious such as in acidic environments, while in other cases degradation occurs over long periods.  Consequences of material failure are usually severe – adversely affecting the health and well-being of human communities and disturbing ecological balances. There are also large direct costs of maintaining and replacing deteriorated infrastructure and indirect costs from loss of production during maintenance work, which place a great burden on society. The focus of this book is on addressing issues concerning performance of cement-based materials in aggressive aqueous environments , by way of this State-of-the-Art Report. The book represe...

  16. In situ stress monitoring of the concrete beam under static loading with cement-based piezoelectric sensors

    Science.gov (United States)

    Dong, Biqin; Liu, Yuqing; Qin, Lei; Wang, Yaocheng; Fang, Yuan; Xing, Feng; Chen, Xianchuan

    2015-10-01

    In this paper, the application of a novel cement-based piezoelectric ceramic sensor is stated for the in situ stress monitoring of the reinforced concrete beam under static loading. Smart beam composite structures were designed and characterised by a range of experimental methods. Finite element analysis is used to analyse the mechanical response of the concrete beam under static loading. The results show that the mechanical-electrical response of sensors embedded in reinforced concrete beams follows a linear relationship under various loading conditions. The sensors are able to record the stress history of the beam under static loads. Moreover, the measured stress data agree well with the simulated results and the smart structures are found to be capable of reliably monitoring the response of a beam during stress testing for static loading modes to real concrete structures. The study indicates that such cement-based piezoelectric composites have a high feasibility and applicability to the in situ stress monitoring of reinforced concrete structures.

  17. Numerical Analysis and Optimization on Piezoelectric Properties of 0–3 Type Piezoelectric Cement-Based Materials with Interdigitated Electrodes

    Directory of Open Access Journals (Sweden)

    Jianlin Luo

    2017-03-01

    Full Text Available The health conditions of complicated concrete structures require intrinsic cement-based sensors with a fast sensing response and high accuracy. In this paper, static, modal, harmonic, and transient dynamic analyses for the 0–3 type piezoelectric cement-based material with interdigitated electrodes (IEPCM wafer were investigated using the ANSYS finite element numerical approach. Optimal design of the IEPCM was further implemented with electrode distance (P, electrode width (W, and wafer density (H as the main parameters. Analysis results show that the maximum stress and strain in the x-polarization direction of the IEPCM are 2.6 and 3.19 times higher than that in the y-direction, respectively; there exists no repetition frequency phenomenon for the IEPCM. These indicate 0–3 type IEPCM possesses good orthotropic features, and lateral driving capacity notwithstanding, a hysteresis effect exists. Allowing for the wafer width (Wp of 1 mm, the optimal design of the IEPCM wafer arrives at the best physical values of H, W and P are 6.2, 0.73 and 1.02 mm respectively, whereas the corresponding optimal volume is 10.9 mm3.

  18. Antibacterial activity of selected glass ionomer cements

    Directory of Open Access Journals (Sweden)

    Elżbieta Łuczaj-Cepowicz

    2014-01-01

    Full Text Available Introduction: The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus.Material and methods: Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC, Fuji IX (GC, Ketac Molar (3M Espe and Ketac Silver (3M Espe. Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Results: Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Discussion: Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  19. Antibacterial activity of selected glass ionomer cements.

    Science.gov (United States)

    Luczaj-Cepowicz, Elżbieta; Marczuk-Kolada, Grażyna; Zalewska, Anna; Pawińska, Małgorzata; Leszczyńska, Katarzyna

    2014-01-22

    The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus. Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC), Fuji IX (GC), Ketac Molar (3M Espe) and Ketac Silver (3M Espe). Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep) were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  20. Cemented total hip arthroplasty with Boneloc bone cement.

    Science.gov (United States)

    Markel, D C; Hoard, D B; Porretta, C A

    2001-01-01

    Boneloc cement (WK-345, Biomet Inc, Warsaw, Ind) attempted to improve cement characteristics by reducing exotherm during polymerization, lowering residual monomer and solubility, raising molecular weight, and lowering airborne monomer and aromatic amines. To study the efficacy of this cement, a selected group of 20 patients were prospectively enrolled and followed up after hip arthroplasty. All components were cemented. During the enrollment period, approximately 70 other hip arthroplasties were performed. Clinical evaluation was based on the Harris hip score. Radiographic evaluation was based on assessment of position of the components, subsidence, and/or presence of radiolucencies. Patients had follow-up for an average of 42 months (11 to 58 months); 1 was lost to follow-up. Of these, 7 (35%) had failure at last follow-up. Despite its initial promise, Boneloc cement had an unacceptably high failure rate over a relatively short follow-up period and is not recommended for use. Despite the longevity and odor toxicity problems with conventional bone cement, new cement technologies must be approached with caution.

  1. Effects on Mechanical Properties of Recycled PET in Cement-Based Composites

    Directory of Open Access Journals (Sweden)

    Liliana Ávila Córdoba

    2013-01-01

    Full Text Available Concretes consisting of portland cement (OPC, silica sand, gravel, water, and recycled PET particles were developed. Specimens without PET particles were prepared for comparison. Curing times, PET particle sizes, and aggregate concentrations were varied. The compressive strength, compressive strain at yield point, and Young modulus were determined. Morphological and chemical compositions of recycled PET particles were seen in a scanning electron microscopy. Results show that smaller PET particle sizes in lower concentrations generate improvements on compressive strength and strain, and Young’s modulus decreases when the size of PET particles used was increased.

  2. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  3. Evaluation of the Katz-Thompson model for estimating the water permeability of cement-based materials from mercury intrusion porosimetry data

    Energy Technology Data Exchange (ETDEWEB)

    El-Dieb, A.S.; Hooton, R.D. (Univ. of Toronto, Ontario (Canada). Dept. of Civil Engineering)

    1994-01-01

    The permeability of concrete is becoming a focal characteristic with regard to the durability and performance of cement-based materials, pastes, mortars and concretes. Since it is mainly affected by the microstructure of the porous media, many models and theories have been developed relating the permeability of porous media to their microstructural parameters. One which proved to be useful in predicting the permeability of sedimentary rock, from mercury intrusion porosimetry data, is the Katz-Thompson theory. A review of this theory and its assumptions is presented, and its applicability to cementitious materials is investigated using two sets of data of various hardened cement pastes and concretes. Also, the major differences between cement-based materials and sedimentary rock from the microstructural point of view is reported.

  4. Design, Explanation, and Evaluation of Training Model Structures Based on Learning Organization--In the Cement Industry with a Nominal Production Capacity of Ten Thousand Tons

    Science.gov (United States)

    Rahimian, Hamid; Kazemi, Mojtaba; Abbspour, Abbas

    2017-01-01

    This research aims to determine the effectiveness of training based on learning organization in the staff of cement industry with production capacity over ten thousand tons. The purpose of this study is to propose a training model based on learning organization. For this purpose, the factors of organizational learning were introduced by…

  5. In situ grouting of low-level burial trenches with a cement-based grout at Oak Ridge National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Francis, C.W.; Spence, R.D.; Tamura, T.; Spalding, B.P.

    1993-01-01

    A technology being evaluated for use in the closure of one of the low-level radwaste burial grounds at ORNL is trench stabilization using a cement-based grout. To demonstrate the applicability and effectiveness of this technology, two interconnecting trenches in SWSA 6 were selected as candidates for in situ grouting with a particulate grout. The primary objective was to demonstrate the increased trench stability (characterized by trench penetration tests) and the decreased potential for leachate migration (characterized by hydraulic conductivity tests) following in situ injection of a particulate grout into the waste trenches. Stability against trench subsidence is a critical issue. For example, construction of impermeable covers to seal the trenches will be ineffectual unless subsequent trench subsidence is permanently suspended. A grout composed of 39% Type 1 Portland cement, 55.5% Class F fly ash, and 5.5% bentonite mixed at 12.5 lb/gal of water was selected. Before the trenches were grouted, the primary characteristics relating to physical stability, hydraulic conductivity, and void volume of the trenches were determined. Their physical stability was evaluated using soil-penetration tests.

  6. Design, fabrication, and properties of 2-2 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution

    Energy Technology Data Exchange (ETDEWEB)

    Dongyu, Xu [Shandong Provincial Key Laboratory of Construction Materials Preparation and Measurement, School of Materials Science and Engineering, University of Jinan, Jinan, Shandong 250022 (China); Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States); Xin, Cheng; Shifeng, Huang [Shandong Provincial Key Laboratory of Construction Materials Preparation and Measurement, School of Materials Science and Engineering, University of Jinan, Jinan, Shandong 250022 (China); Banerjee, Sourav [Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States)

    2014-12-28

    The laminated 2-2 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution were fabricated by employing Lead Zirconium Titanate ceramic as active phase, and mixture of cement powder, epoxy resin, and hardener as matrix phase with a mass proportion of 4:4:1. The dielectric, piezoelectric, and electromechanical coupling properties of the composites were studied. The composites with large total volume fraction of piezoelectric phase have large piezoelectric strain constant and relative permittivity, and the piezoelectric and dielectric properties of the composites are independent of the dimensional variations of the piezoelectric ceramic layer. The composites with small total volume fraction of piezoelectric phase have large piezoelectric voltage constant, but also large dielectric loss. The composite with gradually increased dimension of piezoelectric ceramic layer has the smallest dielectric loss, and that with the gradually increased dimension of matrix layer has the largest piezoelectric voltage constant. The novel piezoelectric composites show potential applications in fabricating ultrasonic transducers with varied surface vibration amplitude of the transducer.

  7. Modelling of the interaction between chemical and mechanical behaviour of ion exchange resins incorporated into a cement-based matrix

    Directory of Open Access Journals (Sweden)

    Le Bescop P.

    2013-07-01

    Full Text Available In this paper, we present a predictive model, based on experimental data, to determine the macroscopic mechanical behavior of a material made up of ion exchange resins solidified into a CEM III cement paste. Some observations have shown that in some cases, a significant macroscopic expansion of this composite material may be expected, due to internal pressures generated in the resin. To build the model, we made the choice to break down the problem in two scale’s studies. The first deals with the mechanical behavior of the different heterogeneities of the composite, i.e. the resin and the cement paste. The second upscales the information from the heterogeneities to the Representative Elementary Volume (REV of the composite. The heterogeneities effects are taken into account in the REV by applying a homogenization method derived from the Eshelby theory combined with an interaction coefficient drawn from the poroelasticity theory. At the first scale, from the second thermodynamic law, a formulation is developed to estimate the resin microscopic swelling. The model response is illustrated on a simple example showing the impact of the calculated internal pressure, on the macroscopic strain.

  8. Chemical characterization and bioactivity of epoxy resin and Portland cement-based sealers with niobium and zirconium oxide radiopacifiers.

    Science.gov (United States)

    Viapiana, Raqueli; Guerreiro-Tanomaru, Juliane Maria; Hungaro-Duarte, Marco Antonio; Tanomaru-Filho, Mário; Camilleri, Josette

    2014-09-01

    The purpose of this study was to characterize and to evaluate the bioactivity potential of experimental root canal sealers (ES) based on Portland cement, epoxy resin with nano- and micro-particles of niobium or zirconium oxide used as radiopacifiers in comparison to AH Plus and MTA Fillapex. Specimens of the sealers (10 mm in diameter×1 mm thick) were prepared and the radiopacity was evaluated according to ISO 6876 (2012) specifications. Characterization of the sealers was performed under the scanning electron microscope (SEM) immediately after setting and after immersion for 28 days in Hank's balanced salt solution (HBSS). In addition X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were also performed. The pH and calcium ion release were measured after 1, 7, 14, 21 and 28 days after completion of seating using a digital pH meter and an atomic absorption spectrophotometer, respectively. The experimental sealers exhibited an average radiopacity of 2.5 mm thickness of aluminum, which was similar to MTA Fillapex (P>0.05) and inferior to AH Plus (Pepoxy resin and radiopacifier exhibited a degree of bioactivity although no evidence of cement hydration was demonstrated on material characterization. The radiopacifier particle size had limited effect on the sealer microstructure and chemical properties. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Cement-base bearing pads mortar for connections in the precast concrete: study of surface roughness

    Directory of Open Access Journals (Sweden)

    M. K. El Debs

    Full Text Available Bearing pads are used in precast concrete connections to avoid concentrated stresses in the contact area between the precast elements. In the present research, the bearing pads are Portland cement mortar with styrene-butadiene latex (SB, lightweight aggregate (expanded vermiculite-term and short fibers (polypropylene, glass and PVA, in order to obtain a material with low modulus of elasticity and high tenacity, compared with normal Portland cement mortar. The objective of this paper is to analyze the influence of surface roughness on the pads and test other types of polypropylene fibers. Tests were carried out to characterize the composite and test on bearing pads. Characterization tests show compressive strength of 41MPa and modulus of elasticity of 12.8GPa. The bearing pads tests present 30% reduction of stiffness in relation to a reference mortar. The bearing pads with roughness on both sides present a reduction up to 30% in stiffness and an increase in accumulated deformation of more than 120%, regarding bearing pads with both sides smooth.

  10. Improvement, characterization and use of waste corn cob ash in cement-based materials

    Science.gov (United States)

    Suwanmaneechot, P.; Nochaiya, T.; Julphunthong, P.

    2015-12-01

    This work investigates the development of waste corn cob ash as supplementary cement replacement materials. The study focused on the effects of heat treatment on chemical composition, physical properties and engineering properties of corn cob ash. The results suggest corn cob ash that was heat treated at 600°C for 4 h shows percentage of SiO2 + Al2O3 + Fe2O3 around 72%, which can be classified as Class N calcined natural pozzolan, as prescribed by ASTM C618. The X-ray diffraction patterns indicated that the amorphous silica phase increased with increasing calcining temperatures. The water requirement, initial setting time and final setting time of specimens increased with increasing replacement percentage of raw or treated corn cob ash. The morta cubes which used 20% of treated corn cob ash replaced cement showed 103% of the 28 days compressive strength as compared to reference samples. The corn cob ash that was treated at 600°C for 4 h samples shows slightly higher effectiveness for improving the splitting tensile strength and compressive strength of concrete when compared to the untreated corn cob ash.

  11. EFFECTS OF BLAST-FURNACE SLAG ON NATURAL POZZOLAN-BASED GEOPOLYMER CEMENT

    Directory of Open Access Journals (Sweden)

    MAHSHAD YAZDANIPOUR

    2011-03-01

    Full Text Available A number of geopolymer cement mixes were designed and produced by alkali-activation of a pumice-type natural pozzolan. Effects of blast-furnace slag on basic engineering properties of the mixes were studied. Different engineering properties of the mixes such as setting times and 28-day compressive strength were studied at different amounts of blast-furnace slag, sodium oxide content, and water-to-cement ratio. The mix comprising of 5 wt.% blast-furnace slag and 8 wt.% Na2O with a water-to-dry binder ratio of 0.30 exhibits the highest 28-day compressive strength, i.e. 36 MPa. Mixes containing 5 wt.% of ground granulated blast furnace slag showed the least efflorescence or best soundness. Laboratory techniques of X-ray diffractometry (XRD, fourier transform infrared spectroscopy (FTIR, and scanning electron microscopy (SEM were utilized for characterizing a number of mixes and studying their molecular and micro-structure. Investigations done by scanning electron microscopy confirm that smaller blast-furnace slag particles react totally while the larger ones react partially with alkaline activators and contribute to the formation of a composite microstructure.

  12. Behavior of multi-walled carbon nanotubes on the porosity and microstructure of cement-based materials

    Science.gov (United States)

    Nochaiya, Thanongsak; Chaipanich, Arnon

    2011-01-01

    The porosity and microstructure of a Portland cement-multi-walled carbon nanotube composite were investigated. Multi-walled carbon nanotubes (CNTs), up to 1 wt.% of cement, synthesized by infusion chemical vapor deposition, and Portland cement type I (PC) were used to produce pastes with a water to cement ratio of 0.5. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to characterize Portland cement-CNTs systems. MIP analysis of the results indicates that total porosity of the mixes with CNTs was found to decrease with increasing CNTs content. Moreover, an important effect of additional CNTs was a reduction in the number of mesopores, while SEM technique showed dispersion of CNTs between the hydration phases of Portland cement pastes.

  13. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2006-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  14. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2007-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  15. An RFID-Based Tracing and Tracking System for the Fresh Vegetables Supply Chain

    Directory of Open Access Journals (Sweden)

    Luca Mainetti

    2013-01-01

    Full Text Available The paper presents an innovative gapless traceability system able to improve the main business processes of the fresh vegetables supply chain. The performed analysis highlighted some critical aspects in the management of the whole supply chain, from the land to the table of the end consumer, and allowed us to reengineer the most important processes. In particular, the first steps of the supply chain, which include cultivation in greenhouses and manufacturing of packaged vegetables, were analyzed. The re-engineered model was designed by exploiting the potentialities derived from the combined use of innovative Radio Frequency technologies, such as RFID and NFC, and important international standards, such as EPCglobal. The proposed tracing and tracking system allows the end consumer to know the complete history of the purchased product. Furthermore, in order to evaluate the potential benefits of the reengineered processes in a real supply chain, a pilot project was implemented in an Italian food company, which produces ready-to-eat vegetables, known as IV gamma products. Finally, some important metrics have been chosen to carry out the analysis of the potential benefits derived from the use of the re-engineered model.

  16. Non-linear optical imaging and fibre-based spectroscopy of fresh colon biopsies

    Science.gov (United States)

    Cicchi, R.; Sturiale, A.; Nesi, G.; Kapsokalyvas, D.; Tonelli, F.; Pavone, F. S.

    2012-06-01

    Two-photon fluorescence (TPEF) microscopy is a powerful tool to image human tissues up to 200 microns depth without any exogenously added probe. TPEF can take advantage of the autofluorescence of molecules intrinsically contained in a biological tissue, as such NADH, elastin, collagen, and flavins. Two-photon microscopy has been already successfully used to image several types of tissues, including skin, muscles, tendons, bladder. Nevertheless, its usefulness in imaging colon tissue has not been deeply investigated yet. In this work we have used combined two-photon excited fluorescence (TPEF), second harmonic generation microscopy (SHG), fluorescence lifetime imaging microscopy (FLIM), and multispectral two-photon emission detection (MTPE) to investigate different kinds of human ex-vivo fresh biopsies of colon. Morphological and spectroscopic analyses allowed to characterize both healthy mucosa, polyp, and colon samples in a good agreement with common routine histology. Even if further analysis, as well as a more significant statistics on a large number of samples would be helpful to discriminate between low, mild, and high grade cancer, our method is a promising tool to be used as diagnostic confirmation of histological results, as well as a diagnostic tool in a multiphoton endoscope or colonoscope to be used in in-vivo imaging applications.

  17. Visualization and quantification of water movement in porous cement-based materials by real time thermal neutron radiography:Theoretical analysis and experimental study

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Water movement in porous cement-based materials is of great importance when studying their deterioration processes and durability.Many traditional methods based on mass changes,electricity or nuclear magnetic resonances are available for studying water transport in cement-based materials.In this research,an advanced technique i.e.thermal neutron radiography was utilized to achieve visualization and quantification of time dependent water movement including water penetration and moisture vapor in porous cement-based materials through theoretical analysis and experimental study.Because thermal neutrons ex-perience a strong attenuation by hydrogen,neutron radiography exhibits high sensitivity to small amounts of water.A neutron transmission analysis for quantitative evaluation of raw radiographic measurements was developed and optimized based on point scattered functions(PScF).The determinations of the real time and space dependent water penetration into uncracked and cracked mortar samples,as well as the drying process have been presented in this paper.It is illustrated that thermal neutron radiography can be a useful research tool for visualization and quantification of water movement in porous building materials.The obtained results will help us to better understand deteriorating processes of cement-based materials and to find ways to improve their durability.

  18. EFFECT OF PVA MODIFICATION ON PROPERTIES OF CEMENT COMPOSITES

    Directory of Open Access Journals (Sweden)

    Jaroslav Topič

    2015-02-01

    Full Text Available Polymers are used for modification of the cement-based composites and others building materials since the thirties of 20th century. Based on the conclusions of recent studies, it is assumed that even water soluble polymers could be used as an admixture for such modification. Currently, there exist and are exploited several possibilities for polymer modification of mortars, wood-based products or bituminous asphalts. Various options differ in the way of modification, which can be basically applied to the entire volume or just a surface, but also in the form of the polymer used – either in the form of solution or fibers. The aim of our study was to investigate the influence of volume modification by the water soluble polymers, such as polyvinyl alcohol (PVA, on the properties of cement paste and find an optimum additive. It turned out that the addition of PVA solution into fresh cement paste results in an increase of porosity and therefore a stiffness and compressive strength reduction. On the other hand, the bending strength of PVA-rich specimens was significantly higher and their water absorption decreased, which may consequently result in enhanced frost resistance.

  19. Rheological behaviour of aluminosilicate slurries for oil well cementing; Comportamento reologico de pastas a base de aluminossilicatos para a cimentacao de pocos de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Marinho, E.P.; Martinelli, A.E.; Melo, D.M.A.; Melo, M.A.F.; Garcia, R.B. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Araujo, R.G.S. [PETROBRAS, Natal/Fortaleza, RN/CE (Brazil)

    2004-07-01

    Steam injection is a technique used to stimulate wells to produce heavy oils, such as those commonly found in Rio Grande do Norte/Brazil. This procedure increases the temperature and the pressure in the well, thus affecting the integrity of its brittle cement. In this work, alternative oil well cements based on the polymerization of aluminosilicates in alkaline environments are proposed. These polymers are both heat- and fire-resistant due to their inorganic structure. However, the use of such materials in oil well cementing is limited due to their plastic viscosity. The results showed that the rheological behavior of the alternative slurries could be adjusted by setting appropriate SiO{sub 2}:Al{sub 2}O{sub 3} molar ratios as well as the nature of the alkali used. (author)

  20. Photocurable bioactive bone cement based on hydroxyethyl methacrylate-poly(acrylic/maleic) acid resin and mesoporous sol gel-derived bioactive glass

    Energy Technology Data Exchange (ETDEWEB)

    Hesaraki, S., E-mail: S-hesaraki@merc.ac.ir

    2016-06-01

    This paper reports on strong and bioactive bone cement based on ternary bioactive SiO{sub 2}-CaO-P{sub 2}O{sub 5} glass particles and a photocurable resin comprising hydroxyethyl methacrylate (HEMA) and poly(acrylic/maleic) acid. The as-cured composite represented a compressive strength of about 95 MPa but it weakened during soaking in simulated body fluid, SBF, qua its compressive strength reached to about 20 MPa after immersing for 30 days. Biodegradability of the composite was confirmed by reducing its initial weight (~ 32%) as well as decreasing the molecular weight of early cured resin during the soaking procedure. The composite exhibited in vitro calcium phosphate precipitation in the form of nanosized carbonated hydroxyapatite, which indicates its bone bonding ability. Proliferation of calvarium-derived newborn rat osteoblasts seeded on top of the composite was observed during incubation at 37 °C, meanwhile, an adequate cell supporting ability was found. Consequently, it seems that the produced composite is an appropriate alternative for bone defect injuries, because of its good cell responses, high compressive strength and ongoing biodegradability, though more in vivo experiments are essential to confirm this assumption. - Highlights: • Light cure cement based on SiO{sub 2}-CaO-P{sub 2}O{sub 5} glass and polymer-like matrix was formed. • The matrix includes poly(acrylic/maleic acid) and poly(hydroxyethyl methacrylate). • The cement is as strong as polymethylmethacrylate bone cement. • The cement exhibits apatite formation ability in simulated body fluid. • The cement is biodegradable and supports proliferation of osteoblastic cells.

  1. Fermentation Quality and in Vitro Nutrient Digestibility of Fresh Rice Straw-Based Silage Treated with Lactic Acid Bacteria

    Directory of Open Access Journals (Sweden)

    B. Santoso

    2014-08-01

    Full Text Available The aim of the experiment was to evaluate fermentation characteristics and in vitro nutrient digestibility of fresh rice straw-based silage ensiled with addition of epiphytic lactic acid bacteria (LAB inoculant. The experiment was arranged in a completely randomized design, with 2 × 2 factorial arrangement of treatments. The first factor was the ratio of fresh rice straw (FRS, tofu waste (TW and cassava waste (CW consisted of two levels i.e., 40 : 20 : 40 and 40 : 25 : 35, on dry matter (DM basis. The second factor was the level of LAB inoculant with two levels ie., 0 and 20 mL/kg FM. The treatments were (A FRS + TW + CW with the ratio of 40 : 20 : 40, without LAB inoculant; (B FRS + TW + CW with the ratio of 40 : 20 : 40 + LAB inoculant; (C FRS + TW + CW with the ratio of 40 : 25 : 35, without LAB inoculant; (D FRS + TW + CW with ratio of 40 : 25 : 35 + LAB inoculant. Results showed that addition of LAB inoculant in silage increased lactic acid concentration (P0.05 on chemical composition, fermentation quality of silage and in vitro digestibility. It was concluded that mixture silage with ratio of 40 : 20 : 40 with the addition of LAB inoculant had the best fermentation quality and nutrient digestibility than other silages.

  2. Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

    Science.gov (United States)

    Memon, Fareed Ahmed; Nuruddin, Muhd Fadhil; Shafiq, Nasir

    2013-02-01

    The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete (SCGC) was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid (W/Gs) ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

  3. Ca stabilized zirconia based composites by wet consolidation of zirconia and high alumina cement mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Bruni, Y.L.; Garrido, L.B.; Aglietti, E.F., E-mail: lgarrido@cetmic.unlp.edu.ar [Centro de Tecnologia de Recursos Minerales y Ceramica (CETMIC/CIC-CONICET La Plata), Buenos Aires (Argentina)

    2012-07-01

    Composites of the CaO-Al{sub 2}O{sub 3}-ZrO{sub 2} system are widely used in many industrial applications. In this study, porous Ca stabilized ZrO{sub 2} composites were developed from a starting mixture of m-ZrO{sub 2} and calcium aluminate cement. Ceramics were produced by wet consolidation of aqueous suspensions with and without corn starch as pore former agent and sintering at 1000-1500 °C. The influence of processing parameters on crystalline phases, sintering behavior and textural characteristics was examined. Stabilized c-ZrO{sub 2} formed with the composition of Ca{sub 0.15}Zr{sub 0.85}O{sub 1.85}. The sintering of the mixtures lead to porous composites materials. Textural properties were analyzed considering the initial composition and the present crystalline phases. (author)

  4. The long-term durability of low alkali cements. Evidence from new natural analog sites in Europe and North Africa

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, W. Russell [Bedrock Geosciences, Auenstein (Switzerland); Laine, Heini M. [Saanio and Riekkola Oy, Helsinki (Finland); Khoury, Hani [Jordan Univ., Amman (Jordan). Dept. of Geology

    2015-07-01

    The long-term durability of low alkali cements is of interest where they are under consideration as repository tunnel and exploration borehole seals and plugs. It is essential to have an appropriate understanding of their longevity to inform decisions on their potential use in a repository environment. Archaelogical analogues of low alkali cement have been studied for some time. Thomassin and Rassineux (1992), for example, reviewed some of the literature on Gallo-Roman cement-based materials and noted that one of the most impressive examples is the 1700 year old Roman mortar used in Hadrian's Wall (UK) which still contains substantial amounts of CSH (calcium silicate hydrate) compounds. These mortars were studied specifically with the behaviour of an ILW repository in mind (Jull and Lees 1990). However, plugs and seals will generally be required to be durable for longer than the few thousand years which can be accessed via archaeological analogues, so it is essential to turn to natural systems for evidence of longer term durability. To date, there have been no reported studies on natural low alkali cements. In principle, however, such cements should exist and the Bituminous Marl Formation, which hosts the natural OPC cements in Jordan (Pitty and Alexander, 2011), is a likely source. This Formation constitutes a widespread terrain which stretches from Syria in the north, through Israel and Jordan to Saudi Arabia in the south. The natural cement was formed by the combustion of organic rich limestones, a process which continues today. In Syria and northern Jordan, for example, the Formation is punctured by Late Oligocene to Quaternary volcanics so sites which include pozzolanic ash mixed with the Bituminous Marl exist and, on combustion, should produce natural low alkali cements. A site in northern Jordan is currently under investigation for evidence of long-term fresh groundwater/low alkali cement interaction and the preliminary results of the study will be

  5. Some durability aspects of hybrid alkaline cements

    Directory of Open Access Journals (Sweden)

    Donatello S.

    2014-04-01

    Full Text Available Blended cements that contain a high content of fly ash and a low content of Portland cement typically suffer from low early strength development and long setting times. Recently, one method of overcoming these problems has been to use an alkali activator to enhance the reactivity of fly ash particles at early ages. Such cements can be grouped under the generic term “hybrid alkaline cements”, where both cement clinker and fly ash, encouraged by the presence of alkalis, are expected to contribute to cementitious gel formation. The work presented here examines some of the durability aspects of high fly ash content hybrid alkaline cement. Specifically, the aspects investigated were: exposure at high temperatures (up to 1000°C, resistance to immersion in aggressive solutions and susceptibility to the alkali aggregate reaction. All tests were repeated with a commercially available sulfate resistant Portland cement for comparison. When exposed to high temperatures, the hybrid alkaline cement showed strikingly different behaviour compared to the control Portland cement, showing fewer micro-cracks and maintaining residual compressive strengths at least equal to original strengths. Beyond 700°C, the hybrid alkaline cement began to sinter, which resulted in shrinkage of around 5% and a 100% increase in residual compressive strengths. No such sintering event was noted in the control Portland cement, which showed a drastic loss in residual compressive strengths upon heating. In immersion tests, the hybrid alkaline cement possessed excellent resistance to sulfate and seawater attack, similar to the control sulfate resistant cement. Both cements were however severely degraded by immersion in 0.1M HCl for 90 days. Both binders complied with the accelerated alkali-aggregate test but when this test was extended, the hybrid alkaline binder showed much greater dimensional stability. Possible reasons for the differences in durability behaviour in both cements

  6. Rapid Classification of Hairtail Fish and Pork Freshness Using an Electronic Nose Based on the PCA Method

    Directory of Open Access Journals (Sweden)

    Yong-Ming Zhang

    2011-12-01

    Full Text Available We report a method for building a simple and reproducible electronic nose based on commercially available metal oxide sensors (MOS to monitor the freshness of hairtail fish and pork stored at 15, 10, and 5 °C. After assembly in the laboratory, the proposed product was tested by a manufacturer. Sample delivery was based on the dynamic headspace method, and two features were extracted from the transient response of each sensor using an unsupervised principal component analysis (PCA method. The compensation method and pattern recognition based on PCA are discussed in the current paper. PCA compensation can be used for all storage temperatures, however, pattern recognition differs according to storage conditions. Total volatile basic nitrogen (TVBN and aerobic bacterial counts of the samples were measured simultaneously with the standard indicators of hairtail fish and pork freshness. The PCA models based on TVBN and aerobic bacterial counts were used to classify hairtail fish samples as “fresh” (TVBN ≤ 25 g and microbial counts ≤ 106 cfu/g or “spoiled” (TVBN ≥ 25 g and microbial counts ≥ 106 cfu/g and pork samples also as “fresh” (TVBN ≤ 15 g and microbial counts ≤ 106 cfu/g or “spoiled” (TVBN ≥ 15 g and microbial counts ≥ 106 cfu/g. Good correlation coefficients between the responses of the electronic nose and the TVBN and aerobic bacterial counts of the samples were obtained. For hairtail fish, correlation coefficients were 0.97 and 0.91, and for pork, correlation coefficients were 0.81 and 0.88, respectively. Through laboratory simulation and field application, we were able to determine that the electronic nose could help ensure the shelf life of hairtail fish and pork, especially when an instrument is needed to take measurements rapidly. The results also showed that the electronic nose could analyze the process and level of spoilage for hairtail fish and pork.

  7. Microbial analysis of biofilms on cement surfaces: An investigation in cement-associated peri-implantitis.

    Science.gov (United States)

    Korsch, Michael; Walther, Winfried; Marten, Silke-Mareike; Obst, Ursula

    2014-09-05

    The cementation of implant-supported restorations always poses the risk of excess cement retained in the peri-implant sulcus despite careful clinical control. Excess cement can become the basis of colonization by oral microorganisms. As a result of the biofilm formation peri-mucositis or peri-implantitis may develop. Complications were observed in the routine prosthetic restoration of implants when a methacrylate-based cement was used. These developed a few weeks after cementation of the suprastructure and caused bleeding on probing as well as suppuration from the peri-implant tissue. In the revision therapy, excess cement in the peri-implant sulcus was found in many cases. This excess cement was sampled from ten patients and investigated for biofilm formation. For this purpose, the cement samples were collected and analyzed for bacterial in situ colonization by 16S rDNA-based methods. In laboratory experiments, the methacrylate-based cement and two other dental cements were then investigated for their proneness to form biofilm. The results of the in situ and in vitro investigations revealed a strong tendency towards bacterial invasion of the methacrylate-based cement by opportunistic species and pathogens.

  8. Re-use of stabilised flue gas ashes from solid waste incineration in cement-treated base layers for pavements

    DEFF Research Database (Denmark)

    Cai, Zuansi; Jensen, Dorthe Lærke; Christensen, Thomas Højlund

    2003-01-01

    . Two types of FGA were treated by the Ferrox-process, which removes the majority of the easily soluble salts in the FGA and provides binding sites for heavy metals in terms of ferrihydrite. Cubes of cement treated base layer materials containing 5% stabilised FGA were cast, sealed and cured for two...... weeks. Cylinders (diameter 100 mm, length 150 mm) were drilled from these cubes for tank leaching experiments. Duplicate specimens were subject to compression strength testing and to tank leaching experiments. The compressive strength of the CTB fulfilled the Danish requirements for CTB, i.e. strength...... more than 5 MPa after 7 days. The tank leaching tests revealed that leaching of heavy metals was not significantly affected by the use of chemically stabilised flue gas ashes from waste incineration. Assuming that diffusion controls the leaching process it was calculated that less than 1% of the metals...

  9. Effects of the Component and Fiber Gradient Distributions on the Strength of Cement-based Composite Materials

    Institute of Scientific and Technical Information of China (English)

    YANG Jiu-jun; HAI Ran; DONG Yan-ling; WU Ke-ru

    2003-01-01

    The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied.The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved.The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C).To obtain the same strength,therefore,a smaller fiber volume content in FGDM/C is needed than that in FHDM/C.The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.

  10. Thermo-hydro-mechanical modeling and analysis of cement-based energy storages for small-scale dwellings

    Science.gov (United States)

    Hailemariam, Henok; Wuttke, Frank

    2016-04-01

    One of the common technologies for balancing the energy demand and supply in district heating, domestic hot water production, thermal power plants and thermal process industries in general is thermal energy storage. Thermal energy storage, in particular sensible heat storage as compared to latent heat storage and thermo-chemical storage, has recently gained much interest in the renewable energy storage sector due to its comparatively low cost and technical development. Sensible heat storages work on the principle of storing thermal energy by raising or lowering the temperature of liquid (commonly water) or solid media, and do not involve material phase change or conversion of thermal energy by chemical reactions or adsorption processes as in latent heat and thermo-chemical storages, respectively. In this study, the coupled thermo-hydro-mechanical behaviour of a cement-based thermal energy storage system for domestic applications has been modeled in both saturated as well as unsaturated conditions using the Finite Element method along with an extensive experimental analysis program for parameter detection. For this purpose, a prototype model is used with three well-known thermal energy storage materials, and the temperature and heat distribution of the system were investigated under specific thermo-hydro-mechanical conditions. Thermal energy samples with controlled water to solids ratio and stored in water for up to 28 days were used for the experimental program. The determination of parameters included: thermal conductivity, specific heat capacity and linear coefficient of thermal expansion (CTE) using a transient line-source measurement technique as well as a steady-state thermal conductivity and expansion meter; mechanical strength parameters such as uni-axial strength, young's modulus of elasticity, poisson's ratio and shear parameters using uniaxial, oedometer and triaxial tests; and hydraulic properties such as hydraulic permeability or conductivity under

  11. A fluoroscopy-based planning and guidance software tool for minimally invasive hip refixation by cement injection

    NARCIS (Netherlands)

    Malan, D.F.; Van der Walt, S.J.; Raidou, R.G.; Van den Berg, B.; Stoel, B.C.; Botha, C.P.; Nelissen, R.G.H.H.; Valstar, E.R.

    2015-01-01

    Purpose In orthopaedics, minimally invasive injection of bone cement is an established technique. We present HipRFX, a software tool for planning and guiding a cement injection procedure for stabilizing a loosening hip prosthesis. HipRFX works by analysing a pre-operative CT and intraoperative C-arm

  12. The characterisation, improvement and modelling aspects of Frost Salt Scaling of Cement-Based Materials with a High Slag Content

    NARCIS (Netherlands)

    Copuroglu, O.

    2006-01-01

    Blast furnace slag cement concrete is used extensively in a number of countries. In comparison with OPC, it is particularly well known for its excellent performance in marine environments. One dis-advantage of slag cement is its vulnerability to scaling under the combined load of freezing-thawing

  13. Continuous and embedded solutions for SHM of concrete structures using changing electrical potential in self-sensing cement-based composites

    Science.gov (United States)

    Downey, Austin; Garcia-Macias, Enrique; D'Alessandro, Antonella; Laflamme, Simon; Castro-Triguero, Rafael; Ubertini, Filippo

    2017-04-01

    Interest in the concept of self-sensing structural materials has grown in recent years due to its potential to enable continuous low-cost monitoring of next-generation smart-structures. The development of cement-based smart sensors appears particularly well suited for monitoring applications due to their numerous possible field applications, their ease of use and long-term stability. Additionally, cement-based sensors offer a unique opportunity for structural health monitoring of civil structures because of their compatibility with new or existing infrastructure. Particularly, the addition of conductive carbon nanofillers into a cementitious matrix provides a self-sensing structural material with piezoresistive characteristics sensitive to deformations. The strain-sensing ability is achieved by correlating the external loads with the variation of specific electrical parameters, such as the electrical resistance or impedance. Selection of the correct electrical parameter for measurement to correlate with features of interest is required for the condition assessment task. In this paper, we investigate the potential of using altering electrical potential in cement-based materials doped with carbon nanotubes to measure strain and detect damage in concrete structures. Experimental validation is conducted on small-scale specimens including a steel-reinforced beam of conductive cement paste. Comparisons are made with constant electrical potential and current methods commonly found in the literature. Experimental results demonstrate the ability of the changing electrical potential at detecting features important for assessing the condition of a structure.

  14. First study on gene expression of cement proteins and potential adhesion-related genes of a membranous-based barnacle as revealed from Next-Generation Sequencing technology

    KAUST Repository

    Lin, Hsiu Chin

    2013-12-12

    This is the first study applying Next-Generation Sequencing (NGS) technology to survey the kinds, expression location, and pattern of adhesion-related genes in a membranous-based barnacle. A total of 77,528,326 and 59,244,468 raw sequence reads of total RNA were generated from the prosoma and the basis of Tetraclita japonica formosana, respectively. In addition, 55,441 and 67,774 genes were further assembled and analyzed. The combined sequence data from both body parts generates a total of 79,833 genes of which 47.7% were shared. Homologues of barnacle cement proteins - CP-19K, -52K, and -100K - were found and all were dominantly expressed at the basis where the cement gland complex is located. This is the main area where transcripts of cement proteins and other potential adhesion-related genes were detected. The absence of another common barnacle cement protein, CP-20K, in the adult transcriptome suggested a possible life-stage restricted gene function and/or a different mechanism in adhesion between membranous-based and calcareous-based barnacles. © 2013 © 2013 Taylor & Francis.

  15. Intelligent Fish Freshness Assessment

    Directory of Open Access Journals (Sweden)

    Hamid Gholam Hosseini

    2008-01-01

    Full Text Available Fish species identification and automated fish freshness assessment play important roles in fishery industry applications. This paper describes a method based on support vector machines (SVMs to improve the performance of fish identification systems. The result is used for the assessment of fish freshness using artificial neural network (ANN. Identification of the fish species involves processing of the images of fish. The most efficient features were extracted and combined with the down-sampled version of the images to create a 1D input vector. Max-Win algorithm applied to the SVM-based classifiers has enhanced the reliability of sorting to 96.46%. The realisation of Cyranose 320 Electronic nose (E-nose, in order to evaluate the fish freshness in real-time, is experimented. Intelligent processing of the sensor patterns involves the use of a dedicated ANN for each species under study. The best estimation of freshness was provided by the most sensitive sensors. Data was collected from four selected species of fishes over a period of ten days. It was concluded that the performance can be increased using individual trained ANN for each specie. The proposed system has been successful in identifying the number of days after catching the fish with an accuracy of up to 91%.

  16. Matching-based fresh-slice method for generating two-color x-ray free-electron lasers

    Directory of Open Access Journals (Sweden)

    Weilun Qin

    2017-09-01

    Full Text Available Two-color high intensity x-ray free-electron lasers (FELs provide powerful tools for probing ultrafast dynamic systems. A novel concept of realizing fresh-slice two-color lasing through slice-dependent transverse mismatch has been proposed by one of the authors [Y. Chao, SLAC Report No. SLAC-PUB-16935, 2016]. In this paper we present a feasible example following this concept based on the Linac Coherent Light Source parameters. Time-dependent mismatch along the bunch is generated by a passive dechirper module and controlled by downstream matching sections, enabling FEL lasing at different wavelength with a split undulator configuration. Simulations for soft x-ray FELs show that tens of gigawatts pulses with femtosecond duration can be generated.

  17. Composite cement mortars based on marine sediments and oyster shell powder

    Directory of Open Access Journals (Sweden)

    Ez-zaki, H.

    2016-03-01

    Full Text Available Additions of dredged marine sediments and oyster shell powder (OS as cement substitute materials in mortars are examined by several techniques. The sediments have high water and chloride contents and calcite, quartz, illite and kaolinite as principal minerals. The OS powders are entirely composed of calcium carbonate and traces of other impurities. Four mixtures of treated sediments and OS powders at 650 °C and 850 °C are added to Portland cement at 8%, 16% and 33% by weight. The hydration of composite pastes is followed by calorimetric tests, the porosity accessible to water, the bulk density, the permeability to gas, the compressive strength and the accelerated carbonation resistance are measured. In general, the increase of addition amounts reduced the performance of mortars. However, a reduction of gas permeability was observed when the addition was up to 33%. Around 16% of addition, the compressive strength and carbonation resistance were improved.En este trabajo se ha valorado la sustitución de cemento en morteros por sedimentos marinos dragados y polvo de concha de ostra (OS. Los sedimentos tienen altos contenidos de agua, cloruros, calcita, cuarzo, illita y caolinita como minerales principales. Los polvos OS están compuestos de carbonato cálcico y trazas de otras impurezas. Se añadieron a un cemento Portland, cuatro mezclas de los sedimentos y polvos de OS tratados a 650 °C y 850 °C en proporciones del 8%, 16% y 33% en peso. La hidratación de pastas se estudió a través de calorimetría. Se estudió además la porosidad accesible al agua, densidad aparente, permeabilidad al gas, resistencia a compresión y carbonatación acelerada. En general, un aumento en la adición produjo una reducción del rendimiento de los morteros. Se observó, sin embargo, una reducción de la permeabilidad a los gases con porcentajes de adición de hasta el 33%. Con valores del 16% de sustitución, mejoraron las resistencias mecánicas y la

  18. Novel bone wax based on poly(ethylene glycol)-calcium phosphate cement mixtures.

    Science.gov (United States)

    Brückner, Theresa; Schamel, Martha; Kübler, Alexander C; Groll, Jürgen; Gbureck, Uwe

    2016-03-01

    Classic bone wax is associated with drawbacks such as the risk of infection, inflammation and hindered osteogenesis. Here, we developed a novel self-setting bone wax on the basis of hydrophilic poly(ethylene glycol) (PEG) and hydroxyapatite (HA) forming calcium phosphate cement (CPC), to overcome the problems that are linked to the use of conventional beeswax systems. Amounts of up to 10 wt.% of pregelatinized starch were additionally supplemented as hemostatic agent. After exposure to a humid environment, the PEG phase dissolved and was exchanged by penetrating water that interacted with the HA precursor (tetracalcium phosphate (TTCP)/monetite) to form highly porous, nanocrystalline HA via a dissolution/precipitation reaction. Simultaneously, pregelatinized starch could gel and supply the bone wax with liquid sealing features. The novel bone wax formulation was found to be cohesive, malleable and after hardening under aqueous conditions, it had a mechanical performance (∼2.5 MPa compressive strength) that is comparable to that of cancellous bone. It withstood systolic blood pressure conditions for several days and showed antibacterial properties for almost one week, even though 60% of the incorporated drug vancomycin hydrochloride was already released after 8h of deposition by diffusion controlled processes. The study investigated the development of alternative bone waxes on the basis of a hydroxyapatite (HA) forming calcium phosphate cement (CPC) system. Conventional bone waxes are composed of non-biodegradable beeswax/vaseline mixtures that are often linked to infection, inflammation and hindered osteogenesis. We combined the usage of bioresorbable polymers, the supplementation with hemostatic agents and the incorporation of a mineral component to overcome those drawbacks. Self-setting CPC precursors (tetracalcium phosphate (TTCP), monetite) were embedded in a resorbable matrix of poly(ethylene glycol) (PEG) and supplemented with pregelatinized starch. This

  19. The cement solidification systems at LANL

    Energy Technology Data Exchange (ETDEWEB)

    Veazey, G.W.

    1990-01-01

    There are two major cement solidification systems at Los Alamos National Laboratory. Both are focused primarily around treating waste from the evaporator at TA-55, the Plutonium Processing Facility. The evaporator receives the liquid waste stream from TA-55's nitric acid-based, aqueous-processing operations and concentrates the majority of the radionuclides in the evaporator bottoms solution. This is sent to the TA-55 cementation system. The evaporator distillate is sent to the TA-50 facility, where the radionuclides are precipitated and then cemented. Both systems treat TRU-level waste, and so are operated according to the criteria for WIPP-destined waste, but they differ in both cement type and mixing method. The TA-55 systems uses Envirostone, a gypsum-based cement and in-drum prop mixing; the TA-50 systems uses Portland cement and drum tumbling for mixing.

  20. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  1. Effects of surface treatments and storage times on the tensile bond strength of adhesive cements to noble and base metal alloys.

    Science.gov (United States)

    Burmann, Paulo Afonso; Santos, Jose Fortunato Ferreira; May, Liliana Gressler; Pereira, Joao Eduardo da Silva; Cardoso, Paulo Eduardo Capel

    2008-01-01

    This work evaluated two resin cements and a glass-ionomer cement and their bond strength to gold-palladium (Au-Pd), silver-palladium (Ag-Pd), and nickel-chromium-beryllium (Ni-Cr-Be) alloys, utilizing three surface treatments over a period of six months. Eight hundred ten pieces were cast (in a button shape flat surfaces) in one of three alloys. Each alloy group was assigned to three other groups, based on the surface treatment utilized. Specimens were fabricated by bonding similar buttons in using one of three adhesive cements. The 405 pairs were thermocycled and stored in saline solution (0.9% NaCl) at 37 degrees C. The tensile bond strengths were measured in a universal testing machine after storage times of 2, 90, or 180 days. The highest mean bond strength value was obtained with the base metal alloy (10.9 +/- 8.6 MPa). In terms of surface treatment, oxidation resulted in the highest mean bond strength (13.7 +/- 7.3 MPa), followed by sandblasting (10.3 +/- 5.5 MPa) and polishing (3.0 +/- 6.4 MPa). Panavia Ex (13.2 +/- 9.3 MPa) showed significantly higher bond strengths than the other two cements, although the storage time reduced all bond strengths significantly.

  2. Experimental ex-vivo validation of PMMA-based bone cements loaded with magnetic nanoparticles enabling hyperthermia of metastatic bone tumors

    Science.gov (United States)

    Harabech, Mariem; Kiselovs, Normunds Rungevics; Maenhoudt, Wim; Crevecoeur, Guillaume; Van Roost, Dirk; Dupré, Luc

    2017-05-01

    Percutaneous vertebroplasty comprises the injection of Polymethylmethacrylate (PMMA) bone cement into vertebrae and can be used for the treatment of compression fractures of vertebrae. Metastatic bone tumors can cause such compression fractures but are not treated when injecting PMMA-based bone cement. Hyperthermia of tumors can on the other hand be attained by placing magnetic nanoparticles (MNPs) in an alternating magnetic field (AMF). Loading the PMMA-based bone cement with MNPs could both serve vertebra stabilization and metastatic bone tumor hyperthermia when subjecting this PMMA-MNP to an AMF. A dedicated pancake coil is designed with a self-inductance of 10 μH in series with a capacitance of 0.1 μF that acts as resonant inductor-capacitor circuit to generate the AMF. The thermal rise is appraised in beef vertebra placed at 10 cm from the AMF generating circuit using optical temperatures sensors, i.e. in the center of the PMMA-MNP bone cement, which is located in the vicinity of metastatic bone tumors in clinical applications; and in the spine, which needs to be safeguarded to high temperature exposures. Results show a temperature rise of about 7 °C in PMMA-MNP whereas the temperature rise in the spine remains limited to 1 °C. Moreover, multicycles heating of PMMA-MNP is experimentally verified, validating the technical feasibility of having PMMA-MNP as basic component for percutaneous vertebroplasty combined with hyperthermia treatment of metastatic bone tumors.

  3. Freeze-Thaw Performance and Moisture-Induced Damage Resistance of Base Course Stabilized with Slow Setting Bitumen Emulsion-Portland Cement Additives

    Directory of Open Access Journals (Sweden)

    Mojtaba Shojaei Baghini

    2015-01-01

    Full Text Available Freeze-thaw (FT cycles and moisture susceptibility are important factors influencing the geotechnical characteristics of soil-aggregates. Given the lack of published information on the behavior of cement-bitumen emulsion-treated base (CBETB under environmental conditions, especially freezing and thawing, this study investigated the effects of these additives on the CBETB performance. The primary goal was to evaluate the resistance of CBETB to moisture damage by performing FT, Marshall conditioning, and AASHTO T-283 tests and to evaluate the long-term stripping susceptibility of CBETB while also predicting the liquid antistripping additives to assess the mixture’s durability and workability. Specimens were stabilized with Portland cement (0%–6%, bitumen emulsion (0%–5%, and Portland cement-bitumen emulsion mixtures and cured for 7 days, and their short- and long-term performances were studied. Evaluation results of both the Marshall stability ratio and the tensile strength ratio show that the additions of additives increase the resistance of the mixtures to moisture damage. Results of durability tests performed for determining the resistance of compacted specimens to repeated FT cycles indicate that the specimen with the 4% cement-3% bitumen emulsion mixture significantly improves water absorption, volume changes, and weight losses. This indicates the effectiveness of this additive as a road base stabilizer with excellent engineering properties for cold regions.

  4. Mechanical Behavior and Thermal Stability of Acid-Base Phosphate Cements and Composites Fabricated at Ambient Temperature

    Science.gov (United States)

    Colorado Lopera, Henry Alonso

    This dissertation presents the study of the mechanical behavior and thermal stability of acid-base phosphate cements (PCs) and composites fabricated at ambient temperature. These materials are also known as chemically bonded phosphate ceramics (CBPCs). Among other advantages of using PCs when compared with traditional cements are the better mechanical properties (compressive and flexural strength), lower density, ultra-fast (controllable) setting time, controllable pH, and an environmentally benign process. Several PCs based on wollastonite and calcium and alumino phosphates after thermal exposure up to 1000°C have been investigated. First, the thermo-mechanical and chemical stability of wollastonite-based PC (Wo-PC) exposed to temperatures up to 1000°C in air environment were studied. The effects of processing conditions on the curing and shrinkage of the wollastonite-based PC were studied. The chemical reactions and phase transformations during the fabrication and during the thermal exposure are analyzed in detail using scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA Then, the thermo-mechanical and chemical stability of glass, carbon and basalt fiber reinforced Wo-PC composites, were studied using SEM, XRD, TGA. The flexural strength and Weibull statistics were analyzed. A significant strength degradation in the composites were found after the thermal exposure at elevated temperatures due to the interdifusion and chemical reactions across the fibers and the matrix at temperatures over 600°C. To overcome this barrier, we have developed a new PC based on calcium and alumino-phosphates (Ca-Al PCs). The Ca-Al PCs were studied in detail using SEM, XRD, TGA, curing, shrinkage, Weibull statistics, and compression tests. Our study has confirmed that this new composite material is chemically and mechanically stable at temperatures up to 1000°C. Moreover, the compression strength increases after exposure to 1000

  5. Evaluation of the leachability of heavy metals from cement-based materials.

    Science.gov (United States)

    Dell'Orso, Marcello; Mangialardi, Teresa; Paolini, Antonio Evangelista; Piga, Luigi

    2012-08-15

    A new leaching test on comminuted (0.125-2.0mm gradation) cementitious matrices, designated as Modified-Pore Water (M-PW) test, was developed to evaluate the effect of varying leachate pH (4-12.8) and/or liquid-to-solid, L/S, ratio (0.6-50 dm(3)/kg) on the availability factor, F(AV), of heavy metals. The M-PW test was applied to leaching of lead and zinc ions from ground Portland cement mortar incorporating Municipal Solid Waste Incinerator (MSWI) fly ash. Correlation of M-PW test results (F(AV)-L/S data) allowed the determination of the pore-liquid availability factor, F(AVP), at different leachate pHs. These F(AVP) values were utilized, in conjunction with a kinetic pseudo-diffusional model, to evaluate the leaching behavior of monolithic mortar specimens subjected to dynamic leaching tests (constant leachant pH 4 or 6).A good agreement was found between the effective diffusion coefficients, D(e), of lead and zinc ions calculated by such a methodological approach and those obtained from recognized microstructural models. In contrast, no satisfactory agreement was found when these D(e) values were compared with the ones calculated from the results of other availability tests on granular solid samples (NEN 7341 and AAT tests).

  6. Utilization of Baggase Waste Based Materials as Improvement for Thermal Insulation of Cement Brick

    Directory of Open Access Journals (Sweden)

    Aminudin Eeydzah

    2017-01-01

    Full Text Available Building materials having low thermal load and low thermal conductivity will provide thermal comforts to the occupants in building. In an effort to reduce the use of high energy and waste products from the agricultural industry, sugarcane bagasse and banana bagasse has been utilize as an additive in the manufacture of cement brick. The aim of this study is to investigate the insulation and mechanical properties of brick that has been mixed with bagasse and its effectiveness as thermal insulation using heat flow meter. Waste bagasse is being treated using sodium hydroxide (NaOH and is characterized using SEM and XRF. The samples produced with two different dimensions of 50 mm × 50 mm × 50 mm and 215mm × 102.5mm × 65mm for thermal conductivity test. Next, the sample varies from 0% (control sample, 2%, 4%, 6%, 8% and 10% in order to determine the best mix proportion. The compressive strength is being tested for 7, 14 and 28 days of water curing. Results showed that banana bagasse has lower thermal conductivity compared to sugarcane bagasse used, with compressive strength of 15.6MPa with thermal conductivity 0.6W/m.K.

  7. Effect of the strontium aluminate and hemihydrate contents on the properties of a calcium sulphoaluminate based cement

    Directory of Open Access Journals (Sweden)

    Velazco, G.

    2014-09-01

    Full Text Available The effect of strontium aluminate (SrAl2O4 on the hydration process of a calcium sulphoaluminate (C4A3Ŝ cement was investigated. Cement pastes were prepared by mixing C4A3Ŝ , hemihydrate (CaSO4· ½H2O, CŜH0.5 and 0, 10 or 20wt% of SrAl2O4 (SrA. The amount of CŜH0.5 was 15, 20 or 25wt% based on the C4A3Ŝ quantity. The cement pastes were hydrated using water to cement ratios (w/c of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa after 28 d of curing. The main product after hydration was ettringite (C6AŜ3H32. The morphology of this phase consisted of thin needle-shaped crystals.Se investigó el efecto de la adición de aluminato de estroncio (SrAl2O4 sobre las propiedades de un cemento de sulfoaluminato de calcio (C4A3Ŝ. Se prepararon muestras mezclando C4A3Ŝ, hemihidrato (CaSO4· ½H2O, CŜH0.5 y 0, 10 o 20% e.p de SrAl2O4 (SrA. La cantidad de CŜH0.5 fue de 15, 20 o 25% e.p. basado en la cantidad de C4A3Ŝ. Las relaciones agua/cemento utilizadas fueron 0.4 y 0.5. Las muestras fueron curadas hasta 28 d. Se evaluó el tiempo de fraguado y la resistencia a la compresión. Los productos de hidratación se caracterizaron mediante DRX y MEB. El tiempo de fraguado se retardó hasta 42 minutos con la adición del SrAl2O4 comparado con las muestras sin adiciones. Las muestras con 25% e.p. de yeso y 20% e.p. de SrAl2O4 desarrollaron la mayor resistencia a la compresión alcanzando 60 MPa a 28 d de curado. Los análisis por MEB y DRX muestran como principal producto de hidratación a la etringita (C6AŜ3H32, cuya morfología se observa como cristales aciculares.

  8. Grout cement. ; Grout cement to fill ground/grout cement to fill cracks. Chunyuyo cement. ; Jiban chunyuyo cement /hibiware chunyuyo cement

    Energy Technology Data Exchange (ETDEWEB)

    Okaue, H. (Nittetsu Cement Co. Ltd., Hokkaido (Japan))

    1991-09-01

    Ground grout cement is grouted into the ground under high pressure in high water ratio (100 to 1000%) in the form of milk differing from concrete in terms of the water-cement ratio. The grouted milk is governed by characteristics of the cement the milk itself possesses, resulting in variable grouting modes, which are divided in fracture grouting, permeation grouting and boundary grouting. Their applications include cutting off of water in dams, ground reinforcement, prevention of water gushing in tunnel excavation, natural ground reinforcement, improvement of sandy soil and prevention of its collapse, and stabilization of ground for urban civil engineering works such as subway, water supply and sewerage constructions. Grout cement to fill cracks in concrete structures is so grouted into cracks that the slurry fills up contiguous cracks to a certain level and goes upward while pushing out air or water existing in the cracks. The slurry filled into the cracks solidifies and hardens while being absorbed into the concrete, and finally integrates with the concrete. The grout cement is used to rework such concrete structures as dams, tunnels, and bridge bases. 6 figs., 4 tabs.

  9. Discrimination methods of biological contamination on fresh-cut lettuce based on VNIR and NIR hyperspectral imaging

    Science.gov (United States)

    Multispectral imaging algorithms were developed using visible-near-infrared (VNIR) and near-infrared (NIR) hyperspectral imaging (HSI) techniques to detect worms on fresh-cut lettuce. The optimal wavebands that detect worm on fresh-cut lettuce for each type of HSI were investigated using the one-way...

  10. The influence of cement type and temperature on chloride binding in cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

    1998-01-01

    This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  11. Establishment and Analysis of the Sales Model of Fresh Agriculture Food Based on Business to Business E-commerce Platform

    Directory of Open Access Journals (Sweden)

    Xuehui Jiang

    2015-08-01

    Full Text Available This study introduced the network sales model of agricultural products from the view of business to business e-commerce and analyzed the features, we found the sales model was featured by pattern diversity which was however of low level; the existing e-commerce operation scale of agricultural products is small and the anti-risk capacity is weak; its resource integration capacity is insufficient and thus it can’t make full use of the advantages of e-commerce. Based on this, this study established sales chain of fresh agriculture products based on business to business e-commerce, i.e., to trade on the internet; the products are delivered to consumers by third-party according to the delivery of producing area and wholesale market of sales area and then collected by consumers themselves. Meanwhile, we should establish information center of price demand for online trading market and modern refrigeration base of wholesale market, accelerate the development of specialized rural cooperative or industrial company and assure the long-term operation of e-commerce of agricultural products circulation in the future.

  12. Design of smartphone-based spectrometer to assess fresh meat color

    Science.gov (United States)

    Jung, Youngkee; Kim, Hyun-Wook; Kim, Yuan H. Brad; Bae, Euiwon

    2017-02-01

    Based on its integrated camera, new optical attachment, and inherent computing power, we propose an instrument design and validation that can potentially provide an objective and accurate method to determine surface meat color change and myoglobin redox forms using a smartphone-based spectrometer. System is designed to be used as a reflection spectrometer which mimics the conventional spectrometry commonly used for meat color assessment. We utilize a 3D printing technique to make an optical cradle which holds all of the optical components for light collection, collimation, dispersion, and a suitable chamber. A light, which reflects a sample, enters a pinhole and is subsequently collimated by a convex lens. A diffraction grating spreads the wavelength over the camera's pixels to display a high resolution of spectrum. Pixel values in the smartphone image are translated to calibrate the wavelength values through three laser pointers which have different wavelength; 405, 532, 650 nm. Using an in-house app, the camera images are converted into a spectrum in the visible wavelength range based on the exterior light source. A controlled experiment simulating the refrigeration and shelving of the meat has been conducted and the results showed the capability to accurately measure the color change in quantitative and spectroscopic manner. We expect that this technology can be adapted to any smartphone and used to conduct a field-deployable color spectrum assay as a more practical application tool for various food sectors.

  13. Solidification of ion exchange resins saturated with Na+ ions: Comparison of matrices based on Portland and blast furnace slag cement

    Science.gov (United States)

    Lafond, E.; Cau dit Coumes, C.; Gauffinet, S.; Chartier, D.; Stefan, L.; Le Bescop, P.

    2017-01-01

    This work is devoted to the conditioning of ion exchange resins used to decontaminate radioactive effluents. Calcium silicate cements may have a good potential to encapsulate spent resins. However, certain combinations of cement and resins produce a strong expansion of the final product, possibly leading to its full disintegration. The focus is placed on the understanding of the behaviour of cationic resins in the Na+ form in Portland or blast furnace slag (CEM III/C) cement pastes. During hydration of the Portland cement paste, the pore solution exhibits a decrease in its osmotic pressure, which causes a transient expansion of small magnitude of the resins. At 20 °C, this expansion takes place just after setting in a poorly consolidated material and is sufficient to induce cracks. In the CEM III/C paste, swelling of the resins also occurs, but before the end of setting, and induces limited stress in the matrix which is still plastic.

  14. Thermal Properties of Cement Based Composites with Municipal Solid Waste Incinerator Fly Ash Accessed by Two Different Transient Methods

    Directory of Open Access Journals (Sweden)

    Jan FOŘT

    2016-05-01

    Full Text Available Thermal properties of cement composite with Mixed Fly Ash (MFA from different parts of Municipal Solid Waste Incineration (MSWI process as a partial replacement of Portland cement are researched in the paper. MFA is applied in the amount of 10 %, 20 % and 30 % of the mass of cement, while sand and water quantities are kept constant. For the sake of comparison, a reference mixture with Portland cement as the only binder is studied as well. For the characterization of studied materials, their basic physical properties as bulk density, matrix density and total open porosity are measured using gravimetric method combined with helium pycnometry. Among the thermal properties, thermal conductivity, thermal diffusivity and specific heat capacity are accessed by two transient methods having different experimental arrangement and time of measurement. The measured data obtained by the particular methods are compared and the applicability of the methods for the measurement of thermal properties of solid building materials is discussed.

  15. A fresh look at runway incursions: onboard surface movement awareness and alerting system based on SVS

    Science.gov (United States)

    Vernaleken, Christoph; Mihalic, Lamir; Güttler, Mathias; Klingauf, Uwe

    2006-05-01

    Increasing traffic density on the aerodrome surface due to the continuous worldwide growth in the number of flight operations does not only cause capacity and efficiency problems, but also increases the risk of serious incidents and accidents on the airport movement area. Of these, Runway Incursions are the by far most safety-critical. In fact, the worst-ever accident in civil aviation, the collision of two Boeing B747s on Tenerife in 1977 with 583 fatalities, was caused by a Runway Incursion. Therefore, various Runway Safety programs have recently been initiated around the globe, often focusing on ground-based measures such as improved surveillance. However, as a lack of flight crew situational awareness is a key causal factor in many Runway Incursion incidents and accidents, there is a strong need for an onboard solution, which should be capable of interacting cooperatively with ground-based ATM systems, such as A-SMGCS where available. This paper defines the concept of preventive and reactive Runway Incursion avoidance and describes a Surface Movement Awareness & Alerting System (SMAAS) designed to alert the flight crew if they are at risk of infringing a runway. Both the SVS flight deck displays and the corresponding alerting algorithms utilize an ED 99A/RTCA DO-272A compliant aerodrome database, as well as airport operational, traffic and clearance data received via ADS-B or other data links, respectively. The displays provide the crew with enhanced positional, operational, clearance and traffic awareness, and they are used to visualize alerts. A future enhancement of the system will provide intelligent alerting for conflicts caused by surrounding traffic.

  16. Biodegradable β-tricalcium phosphate cement with anti-washout property based on chelate-setting mechanism of inositol phosphate.

    Science.gov (United States)

    Konishi, Toshiisa; Takahashi, Shuhei; Zhuang, Zhi; Nagata, Kohei; Mizumoto, Minori; Honda, Michiyo; Takeuchi, Yasuhiro; Matsunari, Hitomi; Nagashima, Hiroshi; Aizawa, Mamoru

    2013-06-01

    Novel biodegradable β-tricalcium phosphate (β-TCP) cements with anti-washout properties were created on the basis of chelate-setting mechanism of inositol phosphate (IP6) using β-TCP powders. The β-TCP powders were ball-milled using ZrO₂ beads for 0-6 h in the IP6 solutions with concentrations from 0 to 10,000 ppm. The chelate-setting β-TCP cement with anti-washout property was successfully fabricated by mixing the β-TCP powder ball-milled in 3,000 ppm IP6 solution for 3 h and 2.5 mass% Na₂HPO₄ solution, and compressive strength of the cement was 13.4 ± 0.8 MPa. An in vivo study revealed that the above cement was directly in contact with host and newly formed bones without fibrous tissue layers, and was resorbed by osteoclast-like cells on the surface of the cement. The chelate-setting β-TCP cement with anti-washout property is promising for application as a novel injectable artificial bone with both biodegradability and osteoconductivity.

  17. [Study on modeling method of total viable count of fresh pork meat based on hyperspectral imaging system].

    Science.gov (United States)

    Wang, Wei; Peng, Yan-Kun; Zhang, Xiao-Li

    2010-02-01

    Once the total viable count (TVC) of bacteria in fresh pork meat exceeds a certain number, it will become pathogenic bacteria. The present paper is to explore the feasibility of hyperspectral imaging technology combined with relevant modeling method for the prediction of TVC in fresh pork meat. For the certain kind of problem that has remarkable nonlinear characteristic and contains few samples, as well as the problem that has large amount of data used to express the information of spectrum and space dimension, it is crucial to choose a logical modeling method in order to achieve good prediction result. Based on the comparative result of partial least-squares regression (PLSR), artificial neural networks (ANNs) and least square support vector machines (LS-SVM), the authors found that the PLSR method was helpless for nonlinear regression problem, and the ANNs method couldn't get approving prediction result for few samples problem, however the prediction models based on LS-SVM can give attention to the little training error and the favorable generalization ability as soon as possible, and can make them well synchronously. Therefore LS-SVM was adopted as the modeling method to predict the TVC of pork meat. Then the TVC prediction model was constructed using all the 512 wavelength data acquired by the hyperspectral imaging system. The determination coefficient between the TVC obtained with the standard plate count for bacterial colonies method and the LS-SVM prediction result was 0.987 2 and 0.942 6 for the samples of calibration set and prediction set respectively, also the root mean square error of calibration (RMSEC) and the root mean square error of prediction (RMSEP) was 0.207 1 and 0.217 6 individually, and the result was considerably better than that of MLR, PLSR and ANNs method. This research demonstrates that using the hyperspectral imaging system coupled with the LS-SVM modeling method is a valid means for quick and nondestructive determination of TVC of pork

  18. Cola à base de PVA e argamassa de solo-cimento como alternativas para o assentamento de alvenaria de tijolos maciços de solo-cimento PVA glue and cement soil mortars as alternatives for laying cement soil blocks masonry

    Directory of Open Access Journals (Sweden)

    Gisleiva C. dos S. Ferreira

    2011-04-01

    Full Text Available Neste trabalho, foi analisada a viabilidade de emprego de cola à base de PVA e argamassa de solo-cimento no assentamento de paredes de alvenaria de tijolos maciços de solo-cimento, em substituição à argamassa usual (cimento, cal e areia. Pequenos prismas, executados com quatro tijolos maciços de solo-cimento e assentados com as argamassas e a cola de PVA, foram ensaiados à compressão e à flexão. Os resultados dos ensaios dos prismas executados com a argamassa de assentamento usual foram tomados como padrão esperado de comportamento para os outros prismas executados com argamassa de solo-cimento e com cola de PVA. Os resultados obtidos nos ensaios dos prismas indicaram que tanto cola à base de PVA quanto argamassa de solo-cimento podem ser empregadas, satisfatoriamente, no assentamento de painéis de alvenaria de tijolos maciços de solo-cimento.This study presents the results of an experimental investigation in characterizing the properties of cement soil block masonry using cement-soil mortars and PVA glue. The study deals with the scantily explored area of tensile bond strength of soil-cement block masonry using cement-soil mortars and PVA glue. Flexural bond strength of masonry has been determined by testing stack-bonded prisms using a bond wrench test set-up. The study clearly demonstrates the superiority of cement-soil mortar over other conventional mortar such as cement mortar. The results of this study can be conveniently used to select a proportion for cement-soil mortar or PVA glue proportion for cement soil block masonry structures.

  19. Variation of the ultrasonic response of a dental implant embedded in tricalcium silicate-based cement under cyclic loading.

    Science.gov (United States)

    Vayron, Romain; Karasinski, Patrick; Mathieu, Vincent; Michel, Adrien; Loriot, Domitille; Richard, Gilles; Lambert, Gregory; Haiat, Guillaume

    2013-04-05

    The use of tricalcium silicate-based cement (TSBC) as bone substitute material for implant stabilization is promising. However, its mechanical behavior under fatigue loading in presence of a dental implant was not reported so far because of the difficulty of measuring TSBC properties around a dental implant in a nondestructive manner. The aim of this study is to investigate the evolution of the 10 MHz ultrasonic response of a dental implant embedded in TSBC versus fatigue time. Seven implants were embedded in TSBC following the same experimental protocol used in clinical situations. One implant was left without any mechanical solicitation after its insertion in TSBC. The ultrasonic response of all implants was measured during 24 h using a dedicated device deriving from previous studies. An indicator I based on the temporal variation of the signal amplitude was derived and its variation as a function of fatigue time was determined. The results show no significant variation of I as a function of time without mechanical solicitation, while the indicator significantly increases (pBiodentine-implant interface, which induces an increase of the impedance gap at the implant surface. The results are promising because they show the potentiality of ultrasonic methods to (i) investigate the material properties around a dental implant and (ii) optimize the conception of bone substitute materials in the context of dental implant surgery. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. A Solitary Wave-Based Sensor to Monitor the Setting of Fresh Concrete

    Directory of Open Access Journals (Sweden)

    Piervincenzo Rizzo

    2014-07-01

    Full Text Available We present a proof-of-principle study about the use of a sensor for the nondestructive monitoring of strength development in hydrating concrete. The nondestructive evaluation technique is based on the propagation of highly nonlinear solitary waves (HNSWs, which are non-dispersive mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional particle chains. A built-in transducer is adopted to excite and detect the HNSWs. The waves are partially reflected at the transducer/concrete interface and partially transmitted into the concrete. The time-of-flight and the amplitude of the waves reflected at the interface are measured and analyzed with respect to the hydration time, and correlated to the initial and final set times established by the penetration test (ASTM C 403. The results show that certain features of the HNSWs change as the concrete curing progresses indicating that it has the potential of being an efficient, cost-effective tool for monitoring strengths/stiffness development.

  1. Fresh look at the doppler changes in pregnancies with placental-based complications

    Directory of Open Access Journals (Sweden)

    S Dikshit

    2011-01-01

    Full Text Available Placental-based complications of pregnancy can be classified as acute and chronic. An example of acute placental complication is abruptio placenta. The chronic placental complications include pregnancy induced hypertension (PIH and idiopathic Intrauterine growth restriction (IUGR. The fetus is at risk for perinatal complications in both acute and chronic conditions. Here we take a look at the natural history of the Doppler parameters in chronic conditions. The techniques used for assessing the fetal well-being include, clinical methods, biophysical tests, conventional ultrasonography, and fetal Doppler studies. Arterial Doppler studies are used to assess the well-being of the fetus and to determine the timing of delivery. However, arterial Dopplers predict only the subset of fetuses at risk of having perinatal complications. Venous Dopplers have been used to improve upon the prognostication. However, by the time the commonly used venous Doppler signs, that is, ′A′ wave reversal in ductus venosus (DV is present, the fetus is likely to be already compromised. The fetus tries to adapt to the environment of deprivation by making a series of changes in the umbilical artery circulation, cerebral circulation, and hepatic circulation. As a result of these adaptations, the fetus overcomes the state of chronic hypoxia. This article takes a look at these changes and also the effect of these adaptations. It is suggested that serial comparisons of the venous flow characteristics of the DV and inferior vena cava (IVC can provide an early indication of the impending decompensation and can be used to predict the time the delivery.

  2. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    Directory of Open Access Journals (Sweden)

    Konstantin Sobolev

    2003-01-01

    Full Text Available The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and - at the same time - uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

  3. Sustainable development of the cement industry and blended cements to meet ecological challenges.

    Science.gov (United States)

    Sobolev, Konstantin

    2003-05-05

    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and--at the same time--uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

  4. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    speciation of silicon at pH 10 has a significant impact upon the solubility of montmorillonite and would thus constitute a logical choice of pH limit for cement-derived pore fluids, but it is unlikely that cement-based grouts could be developed to meet this limit. Control of mass transport by diffusion processes serves as a significant constraint over the amount of bentonite that can be degraded. Computer simulations indicate that porosity reduction is likely at the interface between cement and bentonite. However, it is not clear how the transport properties of bentonite may be modified due to mineral alteration processes. There are considerable uncertainties concerning the precise mechanism of the rate of montmorillonite dissolution at elevated pH. The rate of dissolution may be inhibited by the presence of dissolved Si (and perhaps Al), but this mechanism has yet to be confirmed at high pH. The type of secondary minerals assumed to form from cement-bentonite interaction will also have a significant impact upon the rate of montmorillonite dissolution. Low-pH cement systems have received little attention thus far regarding the development of models for the chemical evolution of pore fluids. Low Ca/Si CSH gels show preferential leaching of Si, which is in marked contrast with gels of greater Ca/Si ratio. Models apparently capable of predicting pore fluid composition coexisting with low Ca/Si CSH gels are a modified Berner model and a solid-solution model proposed by Sugiyama and Fujita. The solubility of silica in pore fluids coexisting with low Ca/Si gels may exceed that of amorphous silica, and may pose problems regarding the stability of montmorillonite in relation to framework silicates such as feldspars. However, the potential rate of conversion of montmorillonite to feldspar under repository conditions is uncertain. It is necessary to use additives such as super plasticiser to improve the workability of low-pH cements. These organic additives have the potential to

  5. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    speciation of silicon at pH 10 has a significant impact upon the solubility of montmorillonite and would thus constitute a logical choice of pH limit for cement-derived pore fluids, but it is unlikely that cement-based grouts could be developed to meet this limit. Control of mass transport by diffusion processes serves as a significant constraint over the amount of bentonite that can be degraded. Computer simulations indicate that porosity reduction is likely at the interface between cement and bentonite. However, it is not clear how the transport properties of bentonite may be modified due to mineral alteration processes. There are considerable uncertainties concerning the precise mechanism of the rate of montmorillonite dissolution at elevated pH. The rate of dissolution may be inhibited by the presence of dissolved Si (and perhaps Al), but this mechanism has yet to be confirmed at high pH. The type of secondary minerals assumed to form from cement-bentonite interaction will also have a significant impact upon the rate of montmorillonite dissolution. Low-pH cement systems have received little attention thus far regarding the development of models for the chemical evolution of pore fluids. Low Ca/Si CSH gels show preferential leaching of Si, which is in marked contrast with gels of greater Ca/Si ratio. Models apparently capable of predicting pore fluid composition coexisting with low Ca/Si CSH gels are a modified Berner model and a solid-solution model proposed by Sugiyama and Fujita. The solubility of silica in pore fluids coexisting with low Ca/Si gels may exceed that of amorphous silica, and may pose problems regarding the stability of montmorillonite in relation to framework silicates such as feldspars. However, the potential rate of conversion of montmorillonite to feldspar under repository conditions is uncertain. It is necessary to use additives such as super plasticiser to improve the workability of low-pH cements. These organic additives have the potential to

  6. A-mode ultrasound-based intra-femoral bone cement detection and 3D reconstruction in RTHR.

    Science.gov (United States)

    Heger, Stefan; Mumme, Thorsten; Sellei, Richard; De La Fuente, Matias; Wirtz, Dieter-C; Radermacher, Klaus

    2007-05-01

    Due to the difficulty of determining the 3D boundary of the cement-bone interface in Revision Total Hip Replacement (RTHR), the removal of the distal intra-femoral bone cement can be a time-consuming and risky operation. Within the framework of computer- and robot-assisted cement removal, the principles and first results of an automatic detection and 3D surface reconstruction of the cement-bone boundary using A-mode ultrasound are described. Sound propagation time and attenuation of cement were determined considering different techniques for the preparation of bone cement, such as the use of a vacuum system (Optivac, Biomet). A laboratory setup using a rotating, standard 5-MHz transducer was developed. The prototype enables scanning of bisected cement-prepared femur samples in a 90 degrees rotation range along their rotation axis. For system evaluation ex vivo, the distal femur of a human cadaver was prepared with bone cement and drilled (Ø 10 mm) to simulate the prosthesis cavity in a first approximation. The sample was cut in half and CT scanned (0.24 mm resolution; 0.5 mm distance; 0.5 mm thickness), and 3D voxel models of the manually segmented bone cement were reconstructed, providing the ground truth. Afterwards, 90 degrees segments of each ex-vivo sample were scanned by the A-mode ultrasound system. To obtain better ultrasound penetration, we used coded signal excitation and pulse compression filtering. A-mode ultrasound signal detection, filtering and segmentation were accomplished fully automatically. Subsequently, 3D voxel models of each sample were calculated. Accuracy evaluation of the measured ultrasound data was performed by ICP matching of each ultrasound dataset ( approximately 8000 points) to the corresponding CT dataset and calculation of the residual median distance error between the corresponding datasets. Prior to each ICP matching, an initial pre-registration was calculated using prominent landmarks in the corresponding datasets. This method

  7. Recommendations for the repair, the lining or the strengthening of concrete slabs or pavements with bonded cement-based material overlays

    OpenAIRE

    Courard, Luc; Bissonnette, Benoît; Beushausen, Hans; Fowler,David; Trevino, Manuel; Alex, Vaysburd; Johan, Silfwerbrand

    2013-01-01

    The recommendations presented in this publication are inspired by the State of the Art Report edited by the RILEM technical committee TC 193 RLS Bonded cement-based material overlays for the repair, the lining or the strengthening of slabs and pavements. The objective is to lay out all the practical aspects to be considered in the design of concrete overlays: bonded concrete overlay process, assessment of the existing structure, surface preparation, overlay materials, design methods, construc...

  8. 水泥基灌浆材料流动性能的研究%Study on the flow property of cement based grouting material

    Institute of Scientific and Technical Information of China (English)

    高汉青; 于大第; 杨晓光; 王炜; 潘美; 郑旗

    2014-01-01

    Two test methods were introduced for the flow property testing of cement based grouting material ,truncated cone method and flow cone method.Experiments were carried out to compare the flow performances of same cement based grouting material by the two dif-ferent test methods,and the result showed that the flow property of cement based grouting material with high fluidity could not be fully characterized only by the truncated method.Cement based material with excellent flow performance was prepared by using the self-made anti-settling agent,and it could meet the requirements of both GB/T 50448-2008 and ASTM-C939-2012.%介绍了国内标准与ASTM标准测试水泥基灌浆材料流动性能所采用的两种方法:截锥圆模法和流锥法,试验比较了水泥基灌浆材料在两种测试方法下的性能表现差异,结果表明国内标准仅采用截锥圆模法无法全面表征大流动度水泥基灌浆材料的流动特性。采用自制防沉剂,配制了同时满足GB/T 50448-2008和ASTM C939-2012要求的具有高流动性能的水泥基灌浆材料。

  9. An Electrochemical Microsensor Based on a AuNPs-Modified Microband Array Electrode for Phosphate Determination in Fresh Water Samples

    Directory of Open Access Journals (Sweden)

    Fangfang Wang

    2014-12-01

    Full Text Available This work describes the fabrication, characterization, and application of a gold microband array electrode (MAE for the determination of phosphate in fresh water samples. The working principle of this MAE is based on the reduction of a molybdophosphate complex using the linear sweep voltammetric (LSV method. The calibration of this microsensor was performed with standard phosphate solutions prepared with KH2PO4 and pH adjusted to 1.0. The microsensor consists of a platinum counter electrode, a gold MAE as working electrode, and an Ag/AgCl electrode as reference electrode. The microelectrode chips were fabricated by the Micro Electro-Mechanical System (MEMS technique. To improve the sensitivity, gold nanoparticles (AuNPs were electrodeposited on the working electrode. With a linear range from 0.02 to 0.50 mg P/L, the sensitivity of the unmodified microsensor is 2.40 µA per (mg P/L (R2 = 0.99 and that of the AuNPs-modified microsensor is 7.66 µA per (mg P/L (R2 = 0.99. The experimental results showed that AuNPs-modified microelectrode had better sensitivity and a larger current response than the unmodified microelectrode.

  10. Influence of the metakaolin on porous structure of matrixes based in mk/cement

    Directory of Open Access Journals (Sweden)

    Frías, M.

    2000-09-01

    Full Text Available The incorporation of pozzolanic materials in the manufacturing of blended cement has a positive effect on the improvement of blended mortar and concretes performances. These active additions modify porous structure, impeding or delaying the access of aggressive solutions and, therefore materials more durable are possible of obtaining. An increase or decrease on the durability of blended pastes, mortars and concretes will depend on chemical and mineralogical compositions, fineness and reaction kinetics of these pozzolans. The current work shows the results of a research carried out in blended pastes to know the effect of activated material (metakaolin on the microporosity of pastes elaborated with different amounts of mk (0-25%. A water/ binder ratio of 0,55 was used. Samples were cured at 20ºC for 360 days. The evolution of total, capilary and gel porosity as well as average pore size were carried out through mercury intrusion porosimeter (MIP. Also, the helium pycnometer as alternative method to obtain additional information about porosity above 1,4 Å was used. A good correlation between both methods has been obtained. In addition, it is proposed the best mk content for the elaboration of mk-blended pastes.

    La incorporación de materiales puzolánicos presenta un efecto positivo en la mejora de las prestaciones de los morteros y hormigones mixtos. Estos modifican la estructura porosa, impidiendo o retrasando el acceso de los medios agresivos y, por lo tanto, contribución a la obtención de materiales mixtos más durables. La mayor o menor durabilidad de las pastas, morteros y hormigones mixtos dependerá de la composición química, mineralógica, finura y de la cinética de reacción de estas adiciones activas. En el presente trabajo se recogen los resultados de una investigación llevada a cabo para conocer el efecto de un material activado (metacaolin en la microporosidad de pastas, elaboradas con diferentes contenidos de

  11. Topological calculation of key parameters of fibre for production of foam concrete based on cement-free nanostructured binder

    Directory of Open Access Journals (Sweden)

    KHARKHARDIN Anatoly Nikolaevich

    2016-08-01

    Full Text Available Fiber reinforcement is the process of introduction of fibers of different origins into binding system to enhance strength, stress-strain behavior of products and structures. Maximal effect of reinforcing process is possible when optimal parameters (length and consumption of fibre are determined. Moreover one need to consider particle-size composition and hardening process of binding system. In this paper the critical length of natural and sinthesized fibres as well as minimally required content in cellular systems is calculated with the mathematical apparatus of structural topology. As an example the foam concrete based on cement-free nanostructured binder with basalt fibre and microreinforcing constructional polymeric fibre is studied. Fiber diameter, refined with microstructure analysis, accomplished by SEM-microscopy and experimentally determined packing density in loose and compact state are applied as input parameters. Measurement of the fibre topological characteristics with acceptable is accomplished according to material porosity and pore size. So the minimal effective fibre length taking into account homogeneous distribution in bulk of composite matrix is less of 1 mm; minimal fibre consumption is 0,2–0,5 (by wt. %. Irrational optimization leads to unreasonable cost growth of final materials as well as formation of balling inclusions that negatively affects on final performance of composite.

  12. Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

    Science.gov (United States)

    Qureshi, T. S.; Al-Tabbaa, A.

    2016-08-01

    Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92-200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

  13. A prospective clinical trial on the influence of a triamcinolone/demeclocycline and a calcium hydroxide based temporary cement on pain perception

    Directory of Open Access Journals (Sweden)

    Willershausen Brita

    2012-03-01

    Full Text Available Abstract Introduction The aim of this clinical trial was to compare the degree of short term post-operative irritation after application of a triamcinolone/demeclocycyline based or a calcium hydroxide based provisional cement. Methods A total of 109 patients (55 female and 54 male; mean age: 51 ± 14 years with primary or secondary dentinal caries were randomly assigned to the two treatment groups of this biomedical clinical trial (phase III. Selection criteria were good systemic health and treated teeth, which were vital and showed no symptoms of pulpitis. Up to three teeth were prepared for indirect metallic restorations, and the provisional restorations were cemented with a triamcinolone/demeclocycyline (Ledermix or a calcium hydroxide (Provicol based material. The intensity of post-operative pain experienced was documented according to the VAS (4, 12, 20, 24, and 82 h and compared to VAS baseline. Results A total of 159 teeth were treated (Ledermix: 83 teeth, Provicol: 76 teeth. The minor irritation of the teeth, experienced prior to treatment, was similar in both groups; however, 4 h after treatment this value was significantly higher in the Provicol group than in the Ledermix group (p Conclusions The patients had no long term post-operative pain experience in both groups. However, within the first hours after cementation the sensation of pain was considerably higher in the Provicol group than in the Ledermix group.

  14. Production and characterization of setting hydraulic cements based on calcium phosphate; Obtencao e caracterizacao de cimentos de fosfato de calcio de pega hidraulica

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Luci C. de; Rigo, Eliana C.S.; Santos, Luis A dos; Boschi, Anselmo Ortega [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais; Carrodeguas, Raul G. [Universidad de La Habana, Habana (Cuba). Centro de Biomateriales

    1997-12-31

    Setting hydraulic cements based on calcium phosphate has risen great interest in scientific literature during recent years due to their total bio compatibility and to the fact that they harden `in situ`, providing easy handling and adaptation to the shape and dimensions of the defect which requires correction, differently from the predecessors, the calcium phosphate ceramics (Hydroxy apatite, {beta}-tri calcium phosphate, biphasic, etc) in the shape of dense or porous blocks and grains. In the work, three calcium-phosphate cement compositions were studied. The resulting compositions were characterized according to the following aspects: setting times, pH, mechanical resistance, crystalline phases, microstructure and solubility in SBF (Simulated Body Fluid). The results show a potential use for the compositions. (author) 6 figs., 4 tabs.

  15. Evaluation of global land-to-ocean fresh water discharge and evapotranspiration using space-based observations

    Science.gov (United States)

    Seo, Ki-Weon; Waliser, Duane E.; Tian, Baijun; Famiglietti, James S.; Syed, Tajdarul H.

    2009-07-01

    SummaryWe estimate global fresh water discharge from land-to-oceans ( Q) and evapotranspiration ( ET) on monthly time scales using a number of complimentary hydrologic data sets. This estimate is possible due to the new capability of measuring oceanic and land water mass changes from GRACE as well as the space-based measurements of oceanic and land precipitation ( P l) and oceanic evaporation. Monthly time series of Q show peaks in July and January, and those of ET show peaks in March, May and August. Our estimates of Q and ET are correlated with P l indicating qualitatively that our estimates capture temporal patterns of Q and ET reasonably well. Comparison of our Q with two other previous estimates based on the Global Runoff Data Centre (GRDC) river gauges network shows that our maximum peak in Q occurs about a month later than previous estimates. In addition, we compare our estimation of Q and ET to 20th century simulations from the WCRP CMIP3 multi-model archive assessed in the IPCC 4th Assessment Report. Runoff ( R) and ET from AOGCMs tend to only exhibit the annual cycle, but the Q estimated in this study exhibits additional semi-annual variations that exists in P l as well. In addition, R from the models shows a maximum peak 2 months earlier than the estimated Q, which is due partly to the river discharge time lag that most AOGCMs do not take into account. These results indicate that current AOGCMs exhibit basic shortcomings in simulating Q and ET accurately. The new method developed here can be a useful constraint on these models and can be useful to close budget of global water balance.

  16. Camera-Vision Based Oil Content Prediction for Oil Palm (Elaeis Guineensis Jacq Fresh Fruits Bunch at Various Recording Distances

    Directory of Open Access Journals (Sweden)

    Dinah Cherie

    2015-01-01

    Full Text Available In this study, the correlation between oil palm fresh fruits bunch (FFB appearance and its oil content (OC was explored. FFB samples were recorded from various distance (2, 7, and 10 m with different lighting spectrums and configurations (Ultraviolet: 280-380nm, Visible: 400-700nm, and Infrared: 720-1100nm and intensities (600watt and 1000watt lamps to explore the correlations. The recorded FFB images were segmented and its color features were subsequently extracted to be used as input variables for modeling the OC of the FFB. In this study, four developed models were selected to perform oil content prediction (OCP for intact FFBs. These models were selected based on their validity and accuracy upon performing the OCP. Models were developed using Multi-Linear-Perceptron-Artificial-Neural-Network (MLP-ANN methods, employing 10 hidden layers and 15 images features as input variables. Statistical engineering software was used to create the models. Although the number of FFB samples in this study was limited, four models were successfully developed to predict intact FFB’s OC, based on its images’ color features. Three OCP models developed for image recording from 10 m under UV, Vis2, and IR2 lighting configurations. Another model was successfully developed for short range imaging (2m under IR2 light. The coefficient of correlation for each model when validated was 0.816, 0.902, 0.919, and 0.886, respectively. For bias and error, these selected models obtained root-mean-square error (RMSE of 1.803, 0.753, 0.607, and 1.104, respectively.

  17. Re-use of stabilised flue gas ashes from solid waste incineration in cement-treated base layers for pavements.

    Science.gov (United States)

    Cai, Zuansi; Jensen, Dorthe L; Christensen, Thomas H; Bager, Dirch H

    2003-02-01

    Fly ash from coal-burning power plants has been used extensively as a pozzolan and fine filler in concrete for many years. Laboratory experiments were performed investigating the effect of substituting the coal-based fly ash with chemically stabilised flue gas ashes (FGA) from waste incineration. Two types of FGA were treated by the Ferrox-process, which removes the majority of the easily soluble salts in the FGA and provides binding sites for heavy metals in terms of ferrihydrite. Cubes of cement treated base layer materials containing 5% stabilised FGA were cast, sealed and cured for two weeks. Cylinders (diameter 100 mm, length 150 mm) were drilled from these cubes for tank leaching experiments. Duplicate specimens were subject to compression strength testing and to tank leaching experiments. The compressive strength of the CTB fulfilled the Danish requirements for CTB, i.e. strength more than 5 MPa after 7 days. The tank leaching tests revealed that leaching of heavy metals was not significantly affected by the use of chemically stabilised flue gas ashes from waste incineration. Assuming that diffusion controls the leaching process it was calculated that less than 1% of the metals would leach during a 100-year period from a 0.5 m thick concrete slab exposed to water on one side. Leaching of the common ions Ca, Cl, Na and SO4 was increased 3-20 times from the specimens with chemically stabilised flue gas ashes from waste incineration. However, the quantities leached were still modest. These experiments suggest that FGA from waste incineration after Ferrox-treatment could be re-used in CTB without compromising the strength and leaching from the base layer.

  18. Push-out Bond Strength of Fast-setting Mineral Trioxide Aggregate and Pozzolan-based Cements: ENDOCEM MTA and ENDOCEM Zr.

    Science.gov (United States)

    Silva, Emmanuel João Nogueira Leal; Carvalho, Nancy Kudsi; Guberman, Marta Reis da Costa Labanca; Prado, Marina; Senna, Plinio Mendes; Souza, Erick M; De-Deus, Gustavo

    2017-05-01

    The present study investigated the root canal dentin bond strength of 2 newly developed fast-setting mineral trioxide aggregate (MTA) and pozzolan-based cements: ENDOCEM MTA (Maruchi, Wonju, Korea) and ENDOCEM Zr (Maruchi). White MTA (Angelus, Londrina, Brazil) was used as the reference material for comparison. Root slices (1 mm ± 0.1 mm) were obtained from the middle third of 15 maxillary incisors previously selected. Three canal-like holes (0.8 diameter) were drilled perpendicularly on the axial surface of each root slice. A standardized irrigation protocol was applied for all samples, and after drying, each hole was filled with 1 of 3 test repair materials. Finally, slices were stored in contact with phosphate-buffered saline solution (pH = 7.2) for 7 days at 37°C before the push-out assay. Data were nonparametrically evaluated at α = 5%. The Friedman test was unable to confirm a significant dissimilarity in push-out ranks among the tested cements (P = .220). The new fast-setting MTA and pozzolan-based cements ENDOCEM MTA and ENDOCEM Zr present suitable bond strength performance, which is comparable with white MTA. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  19. Relation between the Rheology Characteristic and Initial Hydration Structure of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, the influence of cement kinds and the chemical admixtures on the initial rheology characteristic and structure forming and developing of cement hydration was studied. The relationship between the rheology characteristic, the initial hydration structure forming and the hydration process at very early ages was analyzed by macro properties and microstructure tests. The results showed that, the storage modulus, acted as S, could be described more subtle distinction accompanying with hydration of fresh paste model at very early period. Combining the resistivity alterations, a sudden change on structure forming emerged when the hydration of cement becoming inducing age. The rheology characteristic was interrelated to the hydration structure forming, development and the physical mechanics properties. The sudden change on storage modulus moved up due to the addition of retarder, but the structure forming and developing was retarded to a certain extent.

  20. Experimental ex-vivo validation of PMMA-based bone cements loaded with magnetic nanoparticles enabling hyperthermia of metastatic bone tumors

    Directory of Open Access Journals (Sweden)

    Mariem Harabech

    2017-05-01

    Full Text Available Percutaneous vertebroplasty comprises the injection of Polymethylmethacrylate (PMMA bone cement into vertebrae and can be used for the treatment of compression fractures of vertebrae. Metastatic bone tumors can cause such compression fractures but are not treated when injecting PMMA-based bone cement. Hyperthermia of tumors can on the other hand be attained by placing magnetic nanoparticles (MNPs in an alternating magnetic field (AMF. Loading the PMMA-based bone cement with MNPs could both serve vertebra stabilization and metastatic bone tumor hyperthermia when subjecting this PMMA-MNP to an AMF. A dedicated pancake coil is designed with a self-inductance of 10 μH in series with a capacitance of 0.1 μF that acts as resonant inductor-capacitor circuit to generate the AMF. The thermal rise is appraised in beef vertebra placed at 10 cm from the AMF generating circuit using optical temperatures sensors, i.e. in the center of the PMMA-MNP bone cement, which is located in the vicinity of metastatic bone tumors in clinical applications; and in the spine, which needs to be safeguarded to high temperature exposures. Results show a temperature rise of about 7 °C in PMMA-MNP whereas the temperature rise in the spine remains limited to 1 °C. Moreover, multicycles heating of PMMA-MNP is experimentally verified, validating the technical feasibility of having PMMA-MNP as basic component for percutaneous vertebroplasty combined with hyperthermia treatment of metastatic bone tumors.

  1. PMMA-based composite materials with reactive ceramic fillers: part III: radiopacifying particle-reinforced bone cements.

    Science.gov (United States)

    Abboud, M; Vol, S; Duguet, E; Fontanille, M

    2000-05-01

    New acrylic bone cements were prepared from alumina particles previously treated by 3-(trimethoxysilyl)propylmethacrylate (gamma-MPS), able to act both as radiopacifying and reinforcing agents. The present study deals with the handling characteristics and the compressive behavior of such cements. The influence of the particles morphology, their surface-modification by gamma-MPS bonding agent, their concentration in the cement, the powder-to-liquid ratio and the benzoyl peroxide concentration are reported. The role of grafted gamma-MPS molecules as coupling agent was confirmed. For several formulations, compressive strength and modulus reached 150 MPa and 3400 MPa respectively. Limitations in the use of such formulations are also comprehensively discussed.

  2. The case of Mugher cement facto

    African Journals Online (AJOL)

    Thomas

    based on emission test and mass balance performed. Yet it accounts for ... Hydraulic (chiefly portland) cement, the binding agent in concrete and most .... phenolphthalein were used for end-point detection of the acid-base titration. Materials.

  3. Comparison of Biocompatibility of Cemented vs. Cementless Hip Joint Endoprostheses Based on Postoperative Evaluation of Proinflammatory Cytokine Levels

    Science.gov (United States)

    Szypuła, Jan; Cabak, Anna; Kiljański, Marek; Boguszewski, Dariusz; Tomaszewski, Wiesław

    2016-01-01

    Background The yearly increase in the number of procedures involving implantation of hip joint endoprostheses forces prosthetics manufacturers to search for biologically neutral implants. The goal of this study was to assess the concentration of Interleukin-6 (IL-6) and its correlation with C-reactive protein (CRP), depending on the type of hip joint endoprosthesis (cemented or cementless endoprosthesis) in order to determine implant biotolerance during the early postoperative period. Material/Methods The sample comprised 200 patients [mean age=64 (31–81) years] with coxarthrosis. All patients underwent hip joint arthroplasty using a cemented or cementless endoprosthesis. Blood samples were collected 3 times: before the procedure, on the first day after the procedure, and after 6 weeks. IL-6 and CRP levels were assayed using immunoenzymatic methods. The results were subjected to statistical analysis using the Shapiro-Wilk test. Results On the 1st day after the procedure, CRP and IL-6 concentration increased rapidly after implantation of both cemented and cementless endoprostheses. At 6 weeks postoperatively, the CRP value remained at a similar level in patients after cemented arthroplasty and was almost 2-fold lower in patients who underwent cementless arthroplasty. The IL-6 value returned to the baseline level in patients after cementless arthroplasty and showed an ongoing increasing tendency in patients after cemented arthroplasty. Conclusions 1. The measurement of C-reactive protein and Interleukin-6 is a high-sensitivity test, assessing implant biotolerance. 2. The implantation of a cemented endoprosthesis induces a higher increase in the level of proinflammatory cytokines as compared with a cementless endoprosthesis. 3. For a complete assessment of both early and later body responses to implantation and the related surgical procedure, further studies using available approaches and tools are recommended. PMID:27935873

  4. Biospeckle technique for the non-destructive differentiation of bruised and fresh regions of an Indian apple using intensity-based algorithms

    Science.gov (United States)

    Kumari, S.; Nirala, A. K.

    2016-11-01

    In the present paper intensity-based algorithms have been applied to differentiate the bruised and fresh regions of an Indian apple through biospeckle technique during its 9 day shelf life. Existing algorithms such as the co-occurrence matrix, inertia moment, absolute value difference, generalized difference, parameterized Fujii, biospeckle activity (BA) value, granulometric size distribution (GSD) and grey-level co-occurrence matrix (GLCM), as well as three new proposed algorithms namely parameterized generalized difference, alternative generalized difference (AGD) and parameterized global average Fujii, have been used for qualitative and quantitative analysis. Co-occurrence matrix and activity level spectral maps have been used for qualitative analysis, whereas mean activity plots, curve of the BA index, GSD plots and texture features have been used for quantitative analysis. The experimental results suggest that overall difference in biospeckle activity between the bruised and fresh regions is maximum for the inertia moment method (521.99). Of the three proposed algorithms AGD gives the maximum overall difference in biospeckle activity (42.35). In addition, the BA value and parameters of the GLCM have also been applied for the first time to distinguish between the bruised and fresh regions of an Indian apple, and it is concluded that both the methods may be used for good differentiation between the bruised and fresh regions of apples.

  5. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  6. Inference of the phase-to-mechanical property link via coupled X-ray spectrometry and indentation analysis: Application to cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Krakowiak, Konrad J.; Wilson, William [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States); James, Simon [Schlumberger Riboud Product Center, 1 Rue Henri Becquerel, Clamart 92140 (France); Musso, Simone [Schlumberger-Doll Research Center, 1 Hampshire St., Cambridge, MA 02139-1578 (United States); Ulm, Franz-Josef, E-mail: ulm@mit.edu [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States)

    2015-01-15

    A novel approach for the chemo-mechanical characterization of cement-based materials is presented, which combines the classical grid indentation technique with elemental mapping by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). It is illustrated through application to an oil-well cement system with siliceous filler. The characteristic X-rays of major elements (silicon, calcium and aluminum) are measured over the indentation region and mapped back on the indentation points. Measured intensities together with indentation hardness and modulus are considered in a clustering analysis within the framework of Finite Mixture Models with Gaussian component density function. The method is able to successfully isolate the calcium-silica-hydrate gel at the indentation scale from its mixtures with other products of cement hydration and anhydrous phases; thus providing a convenient means to link mechanical response to the calcium-to-silicon ratio quantified independently via X-ray wavelength dispersive spectroscopy. A discussion of uncertainty quantification of the estimated chemo-mechanical properties and phase volume fractions, as well as the effect of chemical observables on phase assessment is also included.

  7. Shrinkage Properties of Cement Stabilized Gravel

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard

    2014-01-01

    Cement stabilized gravel is an attractive material in road construction because its strength prop-erties are accommodating the increasingly higher requirements to the bearing capacity of a base course. However, reflection cracking of cement stabilized gravel is a major concern. In this pa......-per the shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...... for the two cement contents is 9.9 × 10-6 ⁰C-1 and 11.3 × 10-6 ⁰C-1, respectively. Furthermore, it is found that reflecting cracking can mainly be explained by temperature dependent shrinkage rather than moisture dependent shrinkage....

  8. 掺合料和水胶比对水泥基材料水化产物和力学性能的影响%Influence of admixture and water-cement ratio on hydration products and mechanical properties of cement-based materials

    Institute of Scientific and Technical Information of China (English)

    吴福飞; 侍克斌; 董双快; 陈亮亮; 慈军; 王欣; 张凯

    2016-01-01

    Admixture and water-cement ratio are important factors affecting the development of properties of cement mortar or concrete. In order to study the influence of admixtures and water-cement ratio on the hydration products and the mechanical properties of cement-based materials, the study combined hydration reaction mechanism of pure cement and silicate admixture, derived the formulae of hydration products, theoretical maximum mixing amount and total porosity of composite cement-based materials, and investigated the effects of mixing amount of cement mortar with fly ash, steel slag and lithium slag on total porosity, mechanical properties and hydration products. This paper designed 3 gradients of water-cement ratio (0.50, 0.42 and 0.34), 3 kinds of admixtures (lithium slag, fly ash and steel slag) and 2 contents (20% and 60%); the ratio of cementitious material to sand was 1:2.5, and then, molding specimen accorded with the mix of mortar in the triple mold and the mechanical properties of mortar were tested when specimen was cured to 1, 3, 7, 28 and 90 d. The results showed that, after the same content of fly ash, steel slag and lithium slag incorporation, the contents of hydration products of composite cementitious materials, i.e. calcium hydroxide (CH) and calcium silicate hydrate (CSH), and the total porosity were smaller than those of pure cement; when the water-cement ratio decreased from 0.50 to 0.34, the total porosity of cement mortar decreased from 16.0% to 9.3%, and the contents of CH and CSH increased for the compound cement-based materials with mixing amount of 5%, but the increments were not big; the porosity of fly ash, steel slag and lithium slag cement-based composite materials reduced from 16.6%, 17.2% and 16.0% to 9.9%, 10.9% and 9.3%, respectively. When the admixture amount increased to 10%, the variation of porosity and hydration products of the 3 kinds of mortar was different. The content of hydration products (CH and CSH) of composite

  9. Effect of addition of sugar cane biomass ash in properties of fresh state in cement slurries for oil wells; Efeito da adicao de cinza de biomassa de cana-de-acucar nas propriedades no estado fresco de pastas de cimento para pocos de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Galvao, Lornna L.A.; Santos, Herculana T.; Souza, Pablo Diego Pinheiro; Freitas, Julio Cezar Oliveira [Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil); Nascimento, Julio Cesar S. [Universidade Federal da Bahia (UFBA), BA (Brazil); Amorim, Natalia M.M. [Universidade Potiguar (UNP), RN (Brazil); Martinell, Antonio E. [Mcgill University (MCGILL) (Canada); Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil)

    2012-07-01

    Recent studies have shown that ashes from biomass, in particular those generated by the alcohol industry have pozzolanic activity and can replace cement in many applications, reducing the consumption of cement and, consequently, the environmental impact caused by the production of this material. The present work evaluated the behavior of ash sugarcane biomass partially replacing Portland cement in concentrations of 10, 20 and 40% BWOC in oil well slurries. The results of rheology, thickening time and stability showed that the addition of 40% of biomass ash in oil well slurries significantly improves their properties, enabling the replacement of cement by ash. (author)

  10. Occurrence of natural Bacillus thuringiensis contaminants and residues of Bacillus thuringiensis-based insecticides on fresh fruits and vegetables

    DEFF Research Database (Denmark)

    Frederiksen, Kristine; Rosenquist, Hanne; Jørgensen, Kirsten

    2006-01-01

    A total of 128 Bacillus cereus-like strains isolated from fresh fruits and vegetables for sale in retail shops in Denmark were characterized. Of these strains, 39% (50/128) were classified as Bacillus thuringiensis on the basis of their content of cry genes determined by PCR or crystal proteins...

  11. Discrimination methods for biological contaminants in fresh-cut lettuce based on VNIR and NIR hyperspectral imaging

    Science.gov (United States)

    Mo, Changyeun; Kim, Giyoung; Kim, Moon S.; Lim, Jongguk; Lee, Seung Hyun; Lee, Hong-Seok; Cho, Byoung-Kwan

    2017-09-01

    The rapid detection of biological contaminants such as worms in fresh-cut vegetables is necessary to improve the efficiency of visual inspections carried out by workers. Multispectral imaging algorithms were developed using visible-near-infrared (VNIR) and near-infrared (NIR) hyperspectral imaging (HSI) techniques to detect worms in fresh-cut lettuce. The optimal wavebands that can detect worms in fresh-cut lettuce were investigated for each type of HSI using one-way ANOVA. Worm-detection imaging algorithms for VNIR and NIR imaging exhibited prediction accuracies of 97.00% (RI547/945) and 100.0% (RI1064/1176, SI1064-1176, RSI-I(1064-1173)/1064, and RSI-II(1064-1176)/(1064+1176)), respectively. The two HSI techniques revealed that spectral images with a pixel size of 1 × 1 mm or 2 × 2 mm had the best classification accuracy for worms. The results demonstrate that hyperspectral reflectance imaging techniques have the potential to detect worms in fresh-cut lettuce. Future research relating to this work will focus on a real-time sorting system for lettuce that can simultaneously detect various defects such as browning, worms, and slugs.

  12. Antimicrobial Effects of Dental Luting Glass Ionomer Cements on Streptococcus mutans

    OpenAIRE

    2014-01-01

    Objective. To reduce secondary caries, glass ionomer luting cements are often used for cementing of indirect restorations. This is because of their well-known antimicrobial potential through the release of fluoride ions. The aim of this in vitro study was to investigate the antimicrobial effect of five dental luting cements which were based on glass ionomer cement technology. Methods. Five different glass ionomer based luting cements were tested for their antimicrobial effects on Streptococcu...

  13. 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

    ) was conducted to describe the impact of water-to-cement ratio and corrosion current density (i.e., corrosion rate) on the reinforcement corrosion process. Focus was placed, in particular on the determination of the corrosion accommodating region (CAR) and time to corrosion-induced cracking. Experimental results...

  14. ASSESSMENT OF DEFORMATION AND STRENGTH OF SOILS STRENGTHENED BY CEMENTING

    Directory of Open Access Journals (Sweden)

    Sainov Mihail Petrovich

    2014-09-01

    Full Text Available Currently there are few studies of deformation and strength properties of loose soils strengthened by cementing. Based on the data of already arranged grout curtains it was determined that in cemented gravel-pebble soil there are 7...9 % of cement, which is less than in concrete. To assess deformation and strength of such soils it is possible to use the data of tests conducted by other authors, where the effect of cement contents on sand-cement mix properties was studied. Analysis of experimental data showed that cemented soil may be identified with concrete only with high content of cement (more than 10 %. At cement content 7...9 % in soil the strength deformation of cemented soil varies to a small extent. Its deformation becomes 2-3 times less. It greatly depends on compression stresses. The formulae are proposed which permit assessing the effect of compression and cement content on deformation of cemented soil. It is shown that strength of cemented soil is less than that even of the weakest concrete. It has a sufficiently high cohesion, but the friction angle is approximately the same as that of the initial soil.

  15. The suitability of a supersulfated cement for nuclear waste immobilisation

    Science.gov (United States)

    Collier, N. C.; Milestone, N. B.; Gordon, L. E.; Ko, S.-C.

    2014-09-01

    Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  16. Control of in vivo mineral bone cement degradation.

    Science.gov (United States)

    Kanter, Britta; Geffers, Martha; Ignatius, Anita; Gbureck, Uwe

    2014-07-01

    The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation.

  17. 18-year survival of posterior composite resin restorations with and without glass ionomer cement as base.

    NARCIS (Netherlands)

    Sande, F.H. van de; Rosa Rodolpho, P.A. Da; Basso, G.R.; Patias, R.; Rosa, Q.F. da; Demarco, F.F.; Opdam, N.J.M.; Cenci, M.S.

    2015-01-01

    OBJECTIVE: Advantages and disadvantages of using intermediate layers underneath resin-composite restorations have been presented under different perspectives. Yet, few long-term clinical studies evaluated the effect of glass-ionomer bases on restoration survival. The present study investigated the i

  18. Lithological and land-use based assessment of heavy metal pollution in soils surrounding a cement plant in SW Europe.

    Science.gov (United States)

    Cutillas-Barreiro, Laura; Pérez-Rodríguez, Paula; Gómez-Armesto, Antía; Fernández-Sanjurjo, María José; Álvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino; Arias-Estévez, Manuel; Nóvoa-Muñoz, Juan Carlos

    2016-08-15

    We study the influence of phasing out a cement plant on the heavy metal (Hg, Pb and Cr) content in the surrounding soils, taking into account factors often neglected, such as contributions due to local lithology or land use. The range of total Hg was 10-144µg kg(-1), reaching up to 41 and 145mgkg(-1) for total contents of Pb and Cr, respectively. Forest soils showed higher concentration of Hg than prairie soils, indicating the importance of land use on the accumulation of volatile heavy metals in soils. In forest soils, total Hg showed a trend to decrease with soil depth, whereas in prairie soils the vertical pattern of heavy metal concentrations was quite homogeneous. In most cases, the distance to the cement plant was not a factor of influence in the soils content of the analyzed heavy metals. Total Pb and Cr contents in soils nearby the cement plant were quite similar to those found in the local lithology, resulting in enrichment factor values (EF's) below 2. This suggests that soil parent material is the main source of these heavy metals in the studied soils, while the contribution of the cement plant to Pb and Cr soil pollution was almost negligible. On the contrary, the soils surrounding the cement plant accumulate a significant amount of Hg, compared to the underlying lithology. This was especially noticeable in forest soils, where Hg EF achieved values up to 36. These results are of relevance, bearing in mind that Hg accumulation in soils may be an issue of environmental concern, particularly in prairie soils, where temporal flooding can favor Hg transformation to highly toxic methyl-Hg. In addition, the concurrence of acid soils and total-Cr concentrations in the range of those considered phytotoxic should be also stressed.

  19. Slagment Cement Improve the Cement Resistance Toward Acids Attack During Acidizing Treatment

    Directory of Open Access Journals (Sweden)

    Nik Khairul Irfan Bin Nik Ab. Lah.

    2013-05-01

    Full Text Available Acidizing treatment in past experience shows several zonal isolation problems after the treatment. This study presents the effect of the acid treatment toward class G cement and slagment cement as the improvement method to improve the cement resistance toward the acid. Lab experiments were conducted by immerge the respective cement cubes into 12% HCl/3% HF solution for 40 min before several analysis were conducted. Based on the result, the mass loss and compressive strength loss of the cement cubes decrease as the curing temperature and pressure increase due to more evenly distributed cement chemical composition crystal in high curing condition as shown in Scanning Electron Microscopy (SEM analysis. From X-Ray Diffraction (XRD and X-Ray Fluorescence (XRF analysis, only the first layer of the cement cubes shows chemical component change due to the reaction between the acid. This study found that, replacing class G cement to slagment cement can reduce the mass loss and compressive strength loss up to 72% and 82%, respectively.

  20. Bonding glass-ionomer cements to chemomechanically-prepared dentin.

    Science.gov (United States)

    McInnes-Ledoux, P M; Weinberg, R; Grogono, A

    1989-05-01

    The aim of this investigation was to compare the shear bond strengths of two commercially available glass-ionomer cement base materials to remaining dentin: (1) after conventional caries removal and polyacrylic acid conditioning; (2) after chemomechanical caries removal (Caridex); and (3) after chemomechanical caries removal and polyacrylic acid conditioning. Ninety freshly extracted carious teeth were randomly assigned for caries removal with either the chemomechanical technique (N = 60), or with conventional mechanical drilling (N = 30). Caries removal was continued until the remaining dentin surfaces were judged sound. The remaining dentin in 30 of the teeth prepared with the chemomechanical technique, and in all of the teeth prepared with mechanical drilling, was treated with 10% aqueous polyacrylic acid for 10 seconds. Groups of 15 teeth were assigned for bonding with either Ketac-Bond or Shofu Glasionomer Base Cement. All bonded specimens were stored in a humidor at 37 degrees C for 24 hr. Shear bond strength was tested by means of a mechanical testing machine at a cross-head speed of 0.05 cm/min. Analysis of variance indicated no significant difference (p greater than 0.05) in the mean bond strength among the groups.

  1. Recommended method for measurement of absorbency of superabsorbent polymers in cement-based materials

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro

    2015-01-01

    —laser diffraction particle size analysis, and it allows an easy and reliable measurement of the absorbency of superabsorbent polymers. It is shown in detail how both the definition of the exposure liquid and the definition of the system of SAP particles can be selected so that absorbency can be experimentally...... of superabsorbent polymers in cementitious environments is well determined. It is vital that a generalized agreement over which method should be utilized with this regard is obtained, so large-scale industrial applications can be developed with sufficient quality and safeguards. There ought to be a standard method...... so that the properties of concrete with superabsorbent polymers can be better controlled in practice. In this paper, a technique that can be potentially used as a standard method is developed. The method is based on a measurement technique validated through an international standard procedure...

  2. 3D printing cement based ink, and it’s application within the construction industry

    Directory of Open Access Journals (Sweden)

    Jianchao Zhu

    2017-01-01

    Full Text Available The 3D printing technology is the engine key of the third industrial revolution, after introduction of the automation in the eighteenth century and the concept of mass production in early of twentieth century. 3D printing technology now offers the magic solution to balance both the benefits, and overcome the major associated problem with the previous concept which was the need of repetition. The 3D printing technology has two main critical success factors: the printing machine and the printing material (ink. This paper focusses on cementitious-based materials and the ability to utilize the technology in the construction industry. The research took a qualitative approach based on previous literature reviews as well as in-house research results carried out by the authors’ employer Research and Development Center. The paper summarizes the approach towards to an appropriate mix design which can achieve the requirement of the printing process, and overcome the current constraints which are hindering the wide application of 3D print in construction industry. The authors believe that the research topic and result will have great impact on pushing the construction industry forward towards achieving the UAE Government’s strategy and target to achieve twenty-five percent (25% of the buildings in Dubai by the year of 2030 relying on the 3D printing methodology. The research also concluded that even though the technology is adding a great value to the construction industry, it must be remembered that the technology is still in its infancy, and further research is required to achieve even higher strength printing materials that would be workable in multi-story buildings without the need of additional steel reinforcement.

  3. Cemented backfilling technology with unclassified tailings based on vertical sand silo

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new technology characterized by rapidly non-mechanical settlement of unclassified tailings was developed based on a large number of tests,and dynamic settlement and continual slurry preparation without hardening in vertical sand silo were eventually realized by the addition of an effective flocculating agent (NPA).The results show that the sedimentation velocity of interface between unclassified tailings and water after the addition of NPA increases by 10-20 times,the sedimentation mass fraction of unclassified tailings at the bottom of vertical sand silo is up to 64%,the solid particle content of waste water meets the national standard,and the side influences of NPA can be removed by the addition of fly ash.The industrial test result shows that the system,the addition manner and the equipments are rational,and the vertical sand silo is used efficiently.This developed system is simple with large throughput,and the processing cost is 2.2 yuan(RMB)/m3,only 10%-20% of that by mechanical settlement.

  4. The suitability of a supersulfated cement for nuclear waste immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C., E-mail: nick.collier@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Milestone, N.B. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Callaghan Innovation, 69 Gracefield Road, PO Box 31310, Lower Hutt 5040 (New Zealand); Gordon, L.E. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria 3010 (Australia); Ko, S.-C. [Holcim Technology Ltd, Hagenholzstrasse 85, CH-8050 Zurich (Switzerland)

    2014-09-15

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  5. Synkinematic quartz cementation in partially open fractures in sandstones

    Science.gov (United States)

    Ukar, Estibalitz; Laubach, Stephen E.; Fall, Andras; Eichhubl, Peter

    2014-05-01

    have recorded opening histories that lasted several tens of millions of years. Quartz bridges will form when the increase in fracture aperture is small for single fracture events, the rate of precipitation is greater than the rate of fracture aperture, and fresh non-euhedral nucleation surfaces continue to be created by fracturing. Because of the vast difference in growth rates between the c-axis (fast) and the a-axis (slow) of quartz crystals, the crystallographic orientation of quartz may play a role on the morphology and size of such bridges, and therefore degree of cement infill in fractures. SEM-based backscattered electron diffraction (EBSD) was used to explore the effect of the crystallographic orientation of quartz on the growth of quartz bridges in fractures from the Jurassic-Cretaceous Nikanassin Formation, northwestern Alberta Foothills, the Travis Peak Formation, East Texas, and the Cretaceous Mesaverde Group, Piceance Basin, Colorado. We find that, in all samples, most c-axes are oblique rather than perpendicular to the fracture wall, and well-developed bridges that are oriented at a low angle to the fracture wall are widespread. We conclude that precipitation on anhedral (fractured) surfaces exerts a larger control on the growth of quartz bridges than the orientation of the crystallographic c-axis.

  6. Shear bond strength evaluation of resin composite to resin-modified glass-ionomer cement using three different resin adhesives vs. glass-ionomer based adhesive

    Directory of Open Access Journals (Sweden)

    Mostafa Sadeghi

    2015-12-01

    Full Text Available Background: The clinical success of sandwich technique depends on the strength of resin-modified glass ionomer cement (RMGIC bonding to both dentin and resin composite. Therefore, the shear bond strength (SBS of resin composite bonded to RMGIC utilizing different resin adhesives versus a GIC-based adhesive was compared. Materials and methods: In this in vitro study, 84 holes (5×2 mm were prepared in acrylic blocks, randomly divided into seven groups (n=12 and filled with RMGIC (Light-Cured Universal Restorative, GC. In the Group I; no adhesive was applied on the RMGIC. In the Group II, non-etched and Group III was etched with phosphoric acid. In groups II and III, after rinsing, etch-and-rinse adhesive (OptiBond Solo Plus; in the Group IV; a two-step self-etch adhesive (OptiBond XTR and in Group V; a one-step self-etch (OptiBond All-in-One were applied on the cement surfaces. Group VI; a GIC-based adhesive (Fuji Bond LC was painted over the cement surface and cured. Group VII; the GIC-based adhesive was brushed over RMGIC followed by the placement of resin composite and co-cured. Afterward; resin composite (Point 4 cylinders were placed on the treated cement surfaces. The specimens were placed in 100% humidity at 37 ± 1°C and thermo cycled. The shear bond test was performed at a cross-head speed of 1 mm/min and calculated in MPa; the specimens were examined to determine mode of failure. The results were analyzed using one-way ANOVA and Tukey test. Results: The maximum (24.62±3.70 MPa and minimum (18.15±3.38 MPa SBS mean values were recorded for OptiBond XTR adhesive and the control group, respectively. The pairwise comparisons showed no significant differences between the groups that bonded with different adhesives. The adhesive failure was the most common failure mode observed. Conclusion: This study suggests that GIC-based adhesive could be applied over RMGIC as co-cure technique for sandwich restorations in lieu of employing the resin

  7. Analysis on Impacts and Co-Abatement Effects of Implementing the Low Carb on Cement Standard

    Institute of Scientific and Technical Information of China (English)

    PANG Jun; SHI Yuan-Chang; FENG Xiang-Zhao; WU Shi-Yu; SUN Wen-Long

    2014-01-01

    Based on the MAP-CGE model, this paper simulated the impacts on the output, energy consumption and pollutant emissions of different cement production processes when implementing a low carbon cement standard in China. It also calculated the impacts on the marginal abatement cost and equilibrium price of the cement industry, and analyzed the co-abatement effects of different pollutants. The results showed that implementing the low carbon cement standard will be beneficial in promoting an upgrading of cement production processes, and strengthening the energy conservation and emission reduction in the cement industry. If there is no change in the existing technology, the cement industry will reduce SO2 emissions by 1.17 kg and NOx emissions by 4.44 kg per ton of CO2 emission reduction. Implementing low carbon cement standard can also promote NOx abatement in the cement industry. However, the cement industry will bear the abatement costs, and their equilibrium price will increase slightly.

  8. Expansive Cements

    Science.gov (United States)

    1970-10-01

    sale: is disributici is unlimited = F’)RIWRD Seior Ignacio Soto, Rrecutive President, Instituto Mexicano del Cementc y Concreto , invited Mr. Bryant... Concreto , a.c., Kwidco, D. F., Mexico. Based on info.mation largely obtained from ACT Committee 223, Expansive ’ement. Concretes, ACI Journal, August 1Q70

  9. 水泥基材料表面渗透防护试验研究%Experimental Study on Cement-based Material Surface Permeability Protection

    Institute of Scientific and Technical Information of China (English)

    章岩; 王起才; 张忠元; 李韶瑜; 彭峰

    2014-01-01

    Harmful ions in environment can invade cement-based materials by the carrier of water, so improving the water resistance of the surface can improve anti-corrosion properties of harmful ions.Penetration protective material,which is different from the traditional means of additional thick protective surface coating,penetrates the surface of the substrate materials and forms water-repellent protective layer on the substrate surface so as to achieve the purpose of improving its anti-erosion ability to water containing harmful ion.The research results show that the surface of the cement-based materials achieves "super water-repellent"effect and the surface water absorp-tion of cement mortar test block is reduced 28.7 times after processed by the silicone surface pro-tection materials prepared.%水是环境中有害离子对水泥基材料构成侵害的载体,提高抗水性能就可提高抗有害离子侵蚀性能,渗透防护材料区别于在水泥基材料表面附加厚质防护涂层的传统手段,通过基材表面渗透,可在基材表层形成拒水防护层,以达到提高其抗水载有害离子侵蚀的能力的目的.研究结果表明,经研制出的有机硅类表面防护材料处理,可使水泥基材料的表面实现“超防水”效果,经防护处理后的水泥砂浆试块表面吸水率可降低28.7倍.

  10. Flexural strengthening of reinforced concrete beams with carbon fibers reinforced polymer (CFRP sheet bonded to a transition layer of high performance cement-based composite

    Directory of Open Access Journals (Sweden)

    V. J. Ferrari

    Full Text Available Resistance to corrosion, high tensile strength, low weight, easiness and rapidity of application, are characteristics that have contributed to the spread of the strengthening technique characterized by bonding of carbon fibers reinforced polymer (CFRP. This research aimed to develop an innovate strengthening method for RC beams, based on a high performance cement-based composite of steel fibers (macro + microfibers to be applied as a transition layer. The purpose of this transition layer is better control the cracking of concrete and detain or even avoid premature debonding of strengthening. A preliminary study in short beams molded with steel fibers and strengthened with CFRP sheet, was carried out where was verified that the conception of the transition layer is valid. Tests were developed to get a cement-based composite with adequate characteristics to constitute the layer transition. Results showed the possibility to develop a high performance material with a pseudo strain-hardening behavior, high strength and fracture toughness. The application of the strengthening on the transition layer surface had significantly to improve the performance levels of the strengthened beam. It summary, it was proven the efficiency of the new strengthening technique, and much information can be used as criteria of projects for repaired and strengthened structures.

  11. Synthesized mesoporous silica and calcium aluminate cement fillers increased the fluoride recharge and lactic acid neutralizing ability of a resin-based pit and fissure sealant.

    Science.gov (United States)

    Surintanasarn, Atikom; Siralertmukul, Krisana; Thamrongananskul, Niyom

    2017-07-12

    This study evaluated the effect of different types of filler in a resin-based pit and fissure sealant on fluoride release, recharge, and lactic acid neutralization. Resin-based sealant was incorporated with 5% w/w of the following fillers: calcium aluminate cement (CAC), synthesized mesoporous silica (SI), a CAC and SI mixture (CAC+SI), glass-ionomer powder (GIC), and acetic acid-treated GIC (GICA). Sealant without filler served as control. The samples were immersed in deionized water or a lactic acid solution and the concentration of fluoride in the water, before and after fluoride recharge, and the lactic acid pH change, respectively, were determined. The CAC+SI group demonstrated the highest fluoride release after being recharged with fluoride gel. The CAC+SI group also demonstrated increased lactic acid pH. These findings suggest that a resin-based sealant containing synthesized mesoporous silica and calcium aluminate cement may enhance remineralization due to fluoride release and higher pH.

  12. Concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) and Azaarenes in Runoff from Freshly Applied Coal-Tar-Based Pavement Sealcoat

    Science.gov (United States)

    Mahler, B. J.; Van Metre, P. C.

    2013-12-01

    Coal-tar-based sealcoat (CT-sealcoat) is extensively applied to asphalt parking lots and driveways in the U.S. and Canada. Toxicity to fish and invertebrates of runoff from pavement to which CT-sealcoat has been freshly applied has been reported, but relatively little is known about how concentrations of chemicals in runoff change in the hours to days following sealcoat application. We measured the concentrations of 16 U.S. Environmental Protection Agency Priority Pollutant polycyclic aromatic hydrocarbons (PAHs) and 7 azaarenes in 9 samples of simulated runoff from a coal-tar-sealed test plot collected at increasing intervals from 5 hours to 16 weeks following application. Azaarenes, several of which are common constituents in coal-tar pitch, and their oxidized derivatives, azaarones, are an emerging group of little-studied heterocyclic chemicals. Runoff samples were collected by spraying 25 L of a diluted groundwater to 10 m2 on sealed pavement and retrieving the runoff downgradient where the runoff pooled against spill berms. Unfiltered samples were analyzed by GC/MS following liquid-liquid extraction. In the first sample (t=5 hr), phenanthrene had the highest concentration (130 μg/L) among the 16 PAHs. Concentrations of the lower molecular weight (LMW) PAHs (2 and 3 ring) decreased during the 16 weeks following application, and concentrations of the higher molecular weight (HMW) PAHs (4 to 6 ring) increased, coincident with an increase in the concentration of suspended particulates. In the final sample (t=16 weeks), fluoranthene had the highest concentration (36 μg/L) among the 16 PAHs. Of the azaarenes measured, concentrations of acridine and carbazole (107 and 750 μg/L, respectively) in the initial sample exceeded those of any of the PAHs measured except phenanthrene; acridine and carbazole concentrations decreased over the 5 weeks to <5% of their initial values. Samples of dried sealcoat were analyzed the day of application and 5 weeks later. Samples were

  13. Color difference of composite resins after cementation with different shades of resin luting cement.

    Science.gov (United States)

    Cengiz, Esra; Kurtulmus-Yilmaz, Sevcan; Karakaya, Izgen; Aktore, Huseyin

    2017-07-26

    The purpose of this study was to evaluate the color difference of nanohybrid and ormocer-based composite resins with different thicknesses when 4 different shades of resin luting cement were used. 56 disc specimens of each composite resin (Aelite aesthetic enamel, Ceram-X mono) with 0.5 and 1 mm thicknesses were fabricated. Baseline color measurements were performed using a clinical spectrophotometer. The specimens of each thicknesses of each resin were randomly divided into 4 groups according to the shades of resin luting cement (white/A1, yellow/universal/A3, transparent and white opaque) (n = 7). Mixed resin cement was applied onto the resin specimens using a Teflon mold in 0.1 mm thickness. Color measurements of cemented composite resin specimens were repeated and color difference (∆E) between baseline and after cementation measurements was calculated. ANOVA and Tukey's test were used for statistical analysis. The opaque shade had significantly increased ∆E values as compared to the other shades (p resins in terms of ∆E values. The shade of resin cement and the type of the resin affected the final color; however, the thickness of composite resin had no influence on the final color of restoration. Selecting the shade of resin luting cement before cementation of indirect composite laminate restoration is important to achieve final color match.

  14. Plastic and free shrinkages cracking of blended white cement concrete

    Energy Technology Data Exchange (ETDEWEB)

    Rashad, A.M.; White, T.; Ariaratnam, S.; Knutson, K. [Housing and Building National Research Center, Cairo (Egypt)

    2007-07-01

    This paper presented the results of a study that investigated the plastic and free shrinkages of white portland cement concrete, concrete incorporating silica fume (SF) and concrete incorporating metakaolin (MK) compared to regular plain gray portland cement concrete. An experimental program was designed to investigate the plastic and free shrinkage of concrete containing gray and white blended cement. The paper discussed the experimental details including materials and cement types such as SF, MK, aggregate, and superplasticizer as well as concrete mixtures and specimen preparation including mixture proportions, preparation and curing of concrete specimens, and test specimens. It also presented the determination of concrete properties such as slump of fresh concrete, plastic shrinkage, and dry shrinkage. Test results and discussion of results were also provided. It was concluded that plain white portland cement concrete showed less number of plastic cracks but slightly higher average crack width compared to other concrete mixtures with MK or SF. In addition, free shrinkage behavior of plain white cement and plain gray cement matrix was comparable. 23 refs.

  15. Cement stratigraphy: Image probes of cathodoluminescent facies.

    OpenAIRE

    Vuillemin, Aurèle; Ndiaye, Mapathe; Martini, Rossana; Davaud, Eric Jean

    2011-01-01

    Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum em...

  16. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  17. Assessing the potential of ToF-SIMS as a complementary approach to investigate cement-based materials — Applications related to alkali–silica reaction

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, Laetitia, E-mail: laetitia.bernard@empa.ch [Laboratory for Nanoscale Materials Science, Empa, Swiss Federal Laboratories for Material Science and Technology, Ueberlandstr. 129, 8600 Duebendorf (Switzerland); Leemann, Andreas [Laboratory for Concrete/Construction Chemistry, Empa, Swiss Federal Laboratories for Material Science and Technology, Ueberlandstr. 129, 8600 Duebendorf (Switzerland)

    2015-02-15

    In this study, the potential of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for the application in cement-based materials is assessed in combination and comparison with scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Mortar, concrete and samples from model systems providing products formed by the alkali–silica reaction (ASR) were studied. ToF-SIMS provides qualitative data on alkalis in cases where EDX reaches its limits in regard to detectable concentration, lateral resolution and atomic number of the elements. Due to its high in-depth resolution of a few atomic monolayers, thin layers of reaction products can be detected on the surfaces and chemically analyzed with ToF-SIMS. Additionally, it delivers information on the molecular conformation within the ASR product, its hydrogen content and its isotope ratios, information not provided by EDX. Provided the samples are carefully prepared, ToF-SIMS opens up new possibilities in the analysis of cement-based materials.

  18. Application of Cement Stabilized Gravel in Road Base Course%水泥稳定砂砾在道路基层中的应用

    Institute of Scientific and Technical Information of China (English)

    史云龙

    2009-01-01

    水泥稳定砂砾基层具有强度高、造价低廉及原材料来源广等优点,能够很好地适应当前黑龙江省的交通条件、自然条件和经济条件.针对齐齐哈尔当地的天然砂砾,进行室内无侧限抗压强度试验、水稳定性试验和抗冻性试验,分析水泥稳定砂砾的强度变化规律,得出适合当地基层施工的合理配比.%Cement stabilized gravel base has advantages of high strength, low cost and wide material sources, and adapts well to the natural, economic and traffic conditions in Heilongjiang Province. Based on local crude sand gravel in Qiqihar, indoor unconfined compression test, water stability test and frost resistance teat were carried out to analyse strength change laws of cement stabilized sand gravel, and the reasonable proportion for bese course construction was concluded.

  19. Form and Mechanism of Sulfate Attack on Cement-based Material Made of Limestone Powder at Low Water-binder Ratio under Low Temperature Conditions

    Institute of Scientific and Technical Information of China (English)

    LIU Juanhong; SONG Shaomin; XU Guoqiang; XU Weiguo

    2012-01-01

    The development of strength and the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment were studied.The results indicate that when water-binder ratio is lower than 0.40,the cement-based material with limestone powder has insignificant change in appearance after being soaked in 10% magnesium sulfate solution at low temperature for 120 d,and has significant change in appearance after being soaked at the age of 200 d.Expansion damage and exfoliation occur on the surface of concrete test cube at different levels.When limestone powder accounts for about 28 percent of cementitious material,with the decrease of water-binder ratio,the compressive strength loss has gradually decreased after the material is soaked in the magnesium sulfate solution at low temperature at the age of 200 d.After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200 d,gypsum attack-led destruction is caused to the concrete test cube,without thaumasite sulfate attack.

  20. Comparative evaluation of shear bond strength and microleakage of tricalcium silicate-based restorative material and radioopaque posterior glass ionomer restorative cement in primary and permanent teeth: An in vitro study

    Directory of Open Access Journals (Sweden)

    Vignesh Guptha Raju

    2014-01-01

    Full Text Available Background: Restoration of carious primary molars is still a major concern while treating the young children that too in deep carious lesion which extends below the cemento-enamel junction (CEJ where pulp protection and achieving adequate marginal seal are very important to prevent secondary caries. The needs were met with the development of new materials. One such of new bioactive material is tricalcium silicate-based restorative material (Biodentine, recommended for restoring deep lesions. Aim: To evaluate and compare shear bond strength and microleakage of tricalcium silicate-based restorative material (Biodentine and glass ionomer cement (Fuji IX GP in primary and permanent teeth. Materials and Methods: Occlusal surface of crowns were ground flat. PVC molds were stabilized over flat dentin surface and filled with tricalcium silicate-based restorative material (Biodentine/glass ionomer cement (Fuji IX GP according to group ascertained. Shear bond strength was evaluated using universal testing machine (INSTRON. Standardized Class II cavities were prepared on both primary and permanent teeth, and then restored with tricalcium silicate-based restorative material (Biodentine/glass ionomer cement (Fuji IX GP according to group ascertained, over which composite resin material was restored using an open sandwich technique. Microleakage was assessed using dye penetration. Microleakage was examined using a stereomicroscope. Results: Results showed that glass ionomer cement (Fuji IX GP exhibited better shear bond strength than tricalcium silicate-based restorative material (Biodentine. Mean microleakage score for glass ionomer cement (Fuji IX GP in permanent teeth was 1.52 and for primary teeth was 1.56. The mean microleakage for tricalcium silicate-based restorative material (Biodentine in permanent teeth was 0.76 and for primary teeth was 0.60. Glass ionomer cement (Fuji IX GP exhibited more microleakage than tricalcium silicate-based restorative

  1. Comparative evaluation of shear bond strength and microleakage of tricalcium silicate-based restorative material and radioopaque posterior glass ionomer restorative cement in primary and permanent teeth: an in vitro study.

    Science.gov (United States)

    Raju, Vignesh Guptha; Venumbaka, Nilaya Reddy; Mungara, Jayanthi; Vijayakumar, Poornima; Rajendran, Sakthivel; Elangovan, Arun

    2014-01-01

    Restoration of carious primary molars is still a major concern while treating the young children that too in deep carious lesion which extends below the cemento-enamel junction (CEJ) where pulp protection and achieving adequate marginal seal are very important to prevent secondary caries. The needs were met with the development of new materials. One such of new bioactive material is tricalcium silicate-based restorative material (Biodentine), recommended for restoring deep lesions. To evaluate and compare shear bond strength and microleakage of tricalcium silicate-based restorative material (Biodentine) and glass ionomer cement (Fuji IX GP) in primary and permanent teeth. Occlusal surface of crowns were ground flat. PVC molds were stabilized over flat dentin surface and filled with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained. Shear bond strength was evaluated using universal testing machine (INSTRON). Standardized Class II cavities were prepared on both primary and permanent teeth, and then restored with tricalcium silicate-based restorative material (Biodentine)/glass ionomer cement (Fuji IX GP) according to group ascertained, over which composite resin material was restored using an open sandwich technique. Microleakage was assessed using dye penetration. Microleakage was examined using a stereomicroscope. RESULTS showed that glass ionomer cement (Fuji IX GP) exhibited better shear bond strength than tricalcium silicate-based restorative material (Biodentine). Mean microleakage score for glass ionomer cement (Fuji IX GP) in permanent teeth was 1.52 and for primary teeth was 1.56. The mean microleakage for tricalcium silicate-based restorative material (Biodentine) in permanent teeth was 0.76 and for primary teeth was 0.60. Glass ionomer cement (Fuji IX GP) exhibited more microleakage than tricalcium silicate-based restorative material (Biodentine), which was statistically significant

  2. A study of surfactant interaction in cement-based systems and the role of the surfactant in frost protection

    Science.gov (United States)

    Tunstall, Lori Elizabeth

    Air voids are deliberately introduced into concrete to provide resistance against frost damage. However, our ability to control air distribution in both traditional and nontraditional concrete is hindered by the limited amount of research available on air-entraining agent (AEA) interaction with both the solid and solution components of these systems. This thesis seeks to contribute to the information gap in several ways. Using tensiometry, we are able to quantify the adsorption capacity of cement, fly ash, and fly ash carbon for four commercial AEAs. These results indicate that fly ash interference with air entrainment is due to adsorption onto the glassy particles tucked inside carbon, rather than adsorption onto the carbon itself. Again using tensiometry, we show that two of the AEA show a stronger tendency to micellize and to interact with calcium ions than the others, which seems to be linked to the freezing behavior in mortars, since mortars made with these AEA require smaller dosages to achieve similar levels of protection. We evaluate the frost resistance of cement and cement/fly ash mortars by measuring the strain in the body as it is cooled and reheated. All of the mortars show some expansion at temperatures ≥ -42 °C. Many of the cement mortars are able to maintain net compression during this expansion, but none of the fly ash mortars maintain net compression once expansion begins. Frost resistance improves with an increase in AEA dosage, but no correlation is seen between frost resistance and the air void system. Thus, another factor must contribute to frost resistance, which we propose is the microstructure of the shell around the air void. The strain behavior is attributed to ice growth surrounding the void, which can plug the pores in the shell and reduce or eliminate the negative pore pressure induced by the ice inside the air void; the expansion would then result from the unopposed crystallization pressure, but this must be verified by future work

  3. PENGARUH RASIO TEPUNG BERAS DAN AIR TERHADAP KARAKTERISTIK KULIT LUMPIA BASAH [Effect of Flour to Water Ratio on Characteristics of Fresh Rice-Based Spring Rolls Wrappers

    Directory of Open Access Journals (Sweden)

    Anna Ingani Widjajaseputra1*

    2011-12-01

    Full Text Available Flour to water ratio in batter compositions affected water availability which was needed to provide physical and chemical changes during fresh rice-based spring rolls wrappers processing, such as gel forming of starches and heat-induced gels, flour’s components interactions in batter systems. Degree of water-starch, water-protein and protein–starch-water interactions were depend on water amount, temperature and duration of heating. The mechanical strength of spring rolls wrappers is one of problems when it is being used. The wrappers could be torn apart due to moisture absorption from the filling and the environment. The goal of this study was to determine the optimum flour to water ratio in formulation of fresh rice-based spring rolls wrappers. The investigation was provided by Randomized Completely Block Design with single factor and three replicates. The factor was rice flour to water ratio in six levels (3.0:4.5; 3.0:5.0;3.0:5.5; 3.0:6.0; 3.0:6.5; and 3.0:7.0 the data were analyzed by Analysis of Variance with 95% degree of confident. Flour to water ratio greatly influenced elongation at break which is important in the utilization of fresh rice-based spring rolls wrappers. Its ratio also influenced the size of swelled rice starch granules, pores size and moisture content of the products. Optimal ratio flour to water is 3.0:6.0 which produced the highest elongation at break.

  4. Efficacy of various protein-based coating on enhancing the shelf life of fresh eggs during storage.

    Science.gov (United States)

    Caner, Cengiz; Yüceer, Muhammed

    2015-07-01

    The effectiveness of various coatings (whey protein isolate [WPI], whey protein concentrate [WPC], zein, and shellac) on functional properties, interior quality, and eggshell breaking strength of fresh eggs were evaluated during storage at 24 °: C for 6 weeks. Coatings and storage time had significant effects on Haugh unit, yolk index, albumen pH, dry matter (DMA), relative whipping capacity (RWC), and albumen viscosity. Uncoated eggs had higher albumen pH (9.56) and weight loss, and lower albumen viscosity (5.73), Haugh unit (HU), and yolk index (YI) during storage. Among the coated eggs, the shellac and zein coated eggs had the highest value of albumen viscosity (27.26 to 26.90), HU (74.10 to 73.61), and YI (44.84 to 44.63) after storage. Shellac (1.44%) was more effective in preventing weight loss than WPC (4.59%), WPI (4.60%), and zein (2.13%) coatings. Uncoated eggs had the higest value (6.71%) of weight lost. All coatings increased shell strength (5.18 to 5.73 for top and 3.58 to 4.71 for bottom) significantly (P coated. The shellac and zein coatings were more effective for maintaining the internal quality of fresh eggs during storage. Fourier transform near infrared (FT-NIR) in the 800 to 2500 nm reflection spectra were used to quantify the contents of the fresh eggs at the end of storage. Eggs coated with shellac or zein displayed a higher absorbance at 970 and 1,197 nm respectively (OH vibration of water) compared with those coated with WPI or WPC and the uncoated group at the end of storage. The coatings improved functional properties and also shell strength and could be a viable alternative technology for maintaining the internal quality of eggs during long-term storage. This study highlights the promising use of various coatings to both enhance the functional properties and to reduce the breakage of eggs.

  5. Baryogensis in fresh inflation

    CERN Document Server

    Bellini, M

    2002-01-01

    I study the possibility of baryogenesis can take place in fresh inflation. I find that it is possible that violation of baryon number conservation can occur during the period out-of-equilibrium in this scenario. Indeed, baryogenesis could be possible before the thermal equilibrium is restored at the end of fresh inflation.

  6. Retentive strength of luting cements for stainless steel crowns: an in vitro study.

    Science.gov (United States)

    Subramaniam, Priya; Kondae, Sapna; Gupta, Kamal Kishore

    2010-01-01

    The present study evaluated and compared the retentive strength of three luting cements. A total of forty five freshly extracted human primary molars were used in this study. The teeth were prepared to receive stainless steel crowns. They were then randomly divided into three groups, of fifteen teeth each, so as to receive the three different luting cements: conventional glass ionomer resin modified glass ionomer and adhesive resin. The teeth were then stored in artificial saliva for twenty four hours. The retentive strength of the crowns was determined by using a specially designed Instron Universal Testing Machine (Model 1011). The data was statistically analyzed using ANOVA to evaluate retentive strength for each cement and Tukey test for pair wise comparison. It was concluded that retentive strength of adhesive resin cement and resin modified glass ionomer cement was significantly higher than that of the conventional glass ionomer cement.

  7. Assessment of the interaction of Portland cement-based materials with blood and tissue fluids using an animal model

    Science.gov (United States)

    Schembri Wismayer, P.; Lung, C. Y. K.; Rappa, F.; Cappello, F.; Camilleri, J.

    2016-01-01

    Portland cement used in the construction industry improves its properties when wet. Since most dental materials are used in a moist environment, Portland cement has been developed for use in dentistry. The first generation material is mineral trioxide aggregate (MTA), used in surgical procedures, thus in contact with blood. The aim of this study was to compare the setting of MTA in vitro and in vivo in contact with blood by subcutaneous implantation in rats. The tissue reaction to the material was also investigated. ProRoot MTA (Dentsply) was implanted in the subcutaneous tissues of Sprague-Dawley rats in opposite flanks and left in situ for 3 months. Furthermore the material was also stored in physiological solution in vitro. At the end of the incubation time, tissue histology and material characterization were performed. Surface assessment showed the formation of calcium carbonate for both environments. The bismuth was evident in the tissues thus showing heavy element contamination of the animal specimen. The tissue histology showed a chronic inflammatory cell infiltrate associated with the MTA. MTA interacts with the host tissues and causes a chronic inflammatory reaction when implanted subcutaneously. Hydration in vivo proceeds similarly to the in vitro model with some differences particularly in the bismuth oxide leaching patterns. PMID:27683067

  8. Ranking of Companies based on TOPSIS-DEA Approach Methods (Case Study of Cement Industry in Tehran Stock Exchange

    Directory of Open Access Journals (Sweden)

    Ali Mansory

    2014-08-01

    Full Text Available Ranking options has always been the main issue for managers. There are a lot of qualitative and quantitative approaches for ranking. However most of the approaches for separating and ranking corporations in stock market are less reliable and the results obtained will be invalid. While the evaluation obtained merely through qualitative or quantitative approaches alone, the advantages of integration will be ignored. Thus logically the efficiency of result will be questionable. Thus in this paper the advantages of qualitative and quantitative approaches are integrated which in turn bring about more precision in values of input and output indices. Hence in this paper the approaches, TOPSIS & DEA, have been introduced to rate active companies in cement industry accepted in Tehran stock market. The approach adopted in this paper is applicable and carried out during 2006-2011 and the population of the research includes accepted companies in stock market in cement industry (28 companies and at the end a precise ranking of the companies is presented by integrattive techniques.

  9. The contemporary cement cycle of the United States

    Science.gov (United States)

    Kapur, A.; Van Oss, H. G.; Keoleian, G.; Kesler, S.E.; Kendall, A.

    2009-01-01

    A country-level stock and flow model for cement, an important construction material, was developed based on a material flow analysis framework. Using this model, the contemporary cement cycle of the United States was constructed by analyzing production, import, and export data for different stages of the cement cycle. The United States currently supplies approximately 80% of its cement consumption through domestic production and the rest is imported. The average annual net addition of in-use new cement stock over the period 2000-2004 was approximately 83 million metric tons and amounts to 2.3 tons per capita of concrete. Nonfuel carbon dioxide emissions (42 million metric tons per year) from the calcination phase of cement manufacture account for 62% of the total 68 million tons per year of cement production residues. The end-of-life cement discards are estimated to be 33 million metric tons per year, of which between 30% and 80% is recycled. A significant portion of the infrastructure in the United States is reaching the end of its useful life and will need to be replaced or rehabilitated; this could require far more cement than might be expected from economic forecasts of demand for cement. ?? 2009 Springer Japan.

  10. Physicochemical properties and cytotoxicity of an experimental resin-based pulp capping material containing the quaternary ammonium salt and Portland cement.

    Science.gov (United States)

    Yang, Y W; Yu, F; Zhang, H C; Dong, Y; Qiu, Y N; Jiao, Y; Xing, X D; Tian, M; Huang, L; Chen, J H

    2017-04-04

    To evaluate in vitro the physicochemical properties, cytotoxicity and calcium phosphate nucleation of an experimental light-curable pulp capping material composed of a resin with antibacterial monomer (MAE-DB) and Portland cement (PC). The experimental material was prepared by mixing PC with a resin containing MAE-DB at a 2 : 1 ratio. Cured pure resin containing MAE-DB served as control resin. ProRoot MTA and Dycal served as commercial controls. The depth of cure, degree of monomer conversion, water absorption and solubility of dry samples, calcium release, alkalinizing activity, calcium phosphate nucleation and the cytotoxicity of materials were evaluated. Statistical analysis was carried out using anova followed by Tukey's HSD test (equal variance assumed) or Tamhane test (equal variance not assumed) and independent-samples t-tests. The experimental material had a cure depth of 1.19 mm, and the mean degree of monomer conversion was 70.93% immediately post-cure and 88.75% at 24 h post-cure. The water absorption of the experimental material was between those of MTA and Dycal, and its solubility was significantly less (P material exhibited continuous calcium release and an alkalinizing power between those of MTA and Dycal throughout the test period. Freshly set experimental material, control resin and all 24-h set materials had acceptable cytotoxicity. The experimental material, MTA and Dycal all exhibited the formation of apatite precipitates after immersion in phosphate-buffered saline. The experimental material possessed adequate physicochemical properties, low cytotoxicity and good calcium phosphate nucleation. © 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  11. In vitro antibacterial activity of a novel resin-based pulp capping material containing the quaternary ammonium salt MAE-DB and Portland cement.

    Directory of Open Access Journals (Sweden)

    Yanwei Yang

    Full Text Available BACKGROUND: Vital pulp preservation in the treatment of deep caries is challenging due to bacterial infection. The objectives of this study were to synthesize a novel, light-cured composite material containing bioactive calcium-silicate (Portland cement, PC and the antimicrobial quaternary ammonium salt monomer 2-methacryloxylethyl dodecyl methyl ammonium bromide (MAE-DB and to evaluate its effects on Streptococcus mutans growth in vitro. METHODS: The experimental material was prepared from a 2 : 1 ratio of PC mixed with a resin of 2-hydroxyethylmethacrylate, bisphenol glycerolate dimethacrylate, and triethylene glycol dimethacrylate (4 : 3 : 1 containing 5 wt% MAE-DB. Cured resin containing 5% MAE-DB without PC served as the positive control material, and resin without MAE-DB or PC served as the negative control material. Mineral trioxide aggregate (MTA and calcium hydroxide (Dycal served as commercial controls. S. mutans biofilm formation on material surfaces and growth in the culture medium were tested according to colony-forming units (CFUs and metabolic activity after 24 h incubation over freshly prepared samples or samples aged in water for 6 months. Biofilm formation was also assessed by Live/Dead staining and scanning electron microscopy. RESULTS: S. mutans biofilm formation on the experimental material was significantly inhibited, with CFU counts, metabolic activity, viability staining, and morphology similar to those of biofilms on the positive control material. None of the materials affected bacterial growth in solution. Contact-inhibition of biofilm formation was retained by the aged experimental material. Significant biofilm formation was observed on MTA and Dycal. CONCLUSION: The synthesized material containing HEMA-BisGMA-TEGDMA resin with MAE-DB as the antimicrobial agent and PC to support mineralized tissue formation inhibited S. mutans biofilm formation even after aging in water for 6 months, but had no inhibitory effect on

  12. Performance Analysis of Styrene Butadiene Rubber-Latex on Cement Concrete Mixes.

    Directory of Open Access Journals (Sweden)

    Er. Kapil Soni

    2014-03-01

    Full Text Available To improve the performance of concrete, polymers are mixed with concrete. It has been observed that polymer-modified concrete (PMC is more durable than conventional concrete due to superior strength and high durability. In this research, effect of Styrene-Butadiene Rubber (SBR latex on compressive strength and flexural strength of concrete has been studied and also the optimum polymer (SBR-Latex content for concrete is calculated. This research was carried out to establish the effects of polymer addition on compressive and flexural strength using concrete with mix design of constant water-cement ratio at local ambient temperature. The mixes were prepared with Styrene-Butadiene Rubber (SBR latex -cement ratio of 0 %, 5%, 10%, 15% and 20%. Slump test was conducted on fresh concrete while compressive strength and flexural strength were determined at different age. A locally available Perma-Latex is used as SBR Latex. It has been observed that SBR latex has negative effect at early age while at 28 days, the addition of SBR latex in concrete results in enhancement of compressive strength and Flexural Strength. Based on the results of this study, latex modified concrete made using Perma-Latex may be recommended to be used with various types of concrete structures. However, for the mixes rich in cement, the dosage of SBR latex needs to be adjusted to maintain required workability of concrete.

  13. Cement and concrete

    Science.gov (United States)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  14. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Hasan KAPLAN; Hanifi BİNİCİ

    1995-01-01

    Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, ce...

  15. Use of natural antimicrobials to improve the quality characteristics of fresh "Phyllo" - A dough-based wheat product - Shelf life assessment.

    Science.gov (United States)

    Tsiraki, Maria I; Karam, Layal; Abiad, Mohamad G; Yehia, Hany M; Savvaidis, Ioannis N

    2017-04-01

    This study explores the effects of chitosan and natamycin on the quality of fresh "Phyllo" - a dough-based wheat product, by monitoring the microbiological, physicochemical and sensory parameters. Four different lots of phyllo samples stored under aerobic packaging conditions, in the absence or presence of the aforementioned antimicrobials, were prepared and stored at 4 °C. Microbiological data suggested that, the combination of chitosan and natamycin resulted in significant reductions (1-3 log cfu/g) of the microbial species examined (mesophilic total viable counts; TVC), yeasts/molds, psychrotrophic and lactic acid bacteria (LAB), Enterobacteriaceae and coliforms) by day 10. The pH values of treated phyllo samples were lower on final day 10, as compared to the untreated phyllo, and of the Hunter color parameters (L*, b* and a*) that were evaluated, mostly the combined treatment of chitosan and natamycin maintained the original lightness (L*) and color (yellowness) stability (b*) of phyllo product during the storage period. Sensory data, based on overall acceptability (mean values of appearance and odor) scores confirmed the superiority of combined treatment of chitosan and natamycin, resulting in almost a doubling of the shelf-life of fresh phyllo, while retaining excellent sensorial characteristics (appearance and odor) even on final storage day (10). Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Design of the FRESH study: A randomized controlled trial of a parent-only and parent-child family-based treatment for childhood obesity.

    Science.gov (United States)

    Boutelle, Kerri N; Braden, Abby; Douglas, Jennifer M; Rhee, Kyung E; Strong, David; Rock, Cheryl L; Wilfley, Denise E; Epstein, Leonard; Crow, Scott

    2015-11-01

    Approximately 1 out of 3 children in the United States is overweight or obese. Family-based treatment (FBT) is considered the gold-standard treatment for childhood obesity, but FBT is both staff and cost intensive. Therefore, we developed the FRESH (Family, Responsibility, Education, Support, & Health) study to evaluate the effectiveness of intervening with parents, without child involvement, to facilitate and improve the child's weight status. Targeting parents directly in the treatment of childhood obesity could be a promising approach that is developmentally appropriate for grade-school age children, highly scalable, and may be more cost effective to administer. The current paper describes the FRESH study which was designed to compare the effectiveness of parent-based therapy for pediatric obesity (PBT) to a parent and child (FBT) program for childhood obesity. We assessed weight, diet, physical activity, and parenting, as well as cost-effectiveness, at baseline, post-treatment, and at 6- and 18-month follow-ups. Currently, all participants have been recruited and completed assessment visits, and the initial stages of data analysis are underway. Ultimately, by evaluating a PBT model, we hope to optimize available child obesity treatments and improve their translation into clinical settings. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Promotion of in vivo degradability, vascularization and osteogenesis of calcium sulfate-based bone cements containing nanoporous lithium doping magnesium silicate

    Science.gov (United States)

    Cao, Liehu; Weng, Weizong; Chen, Xiao; Zhang, Jun; Zhou, Qirong; Cui, Jin; Zhao, Yuechao; Shin, Jung-Woog; Su, Jiacan

    2017-01-01

    Nanoporous lithium doping magnesium silicate (nl-MS) was introduced into calcium sulfate hemihydrate to prepare calcium sulfate composite (nl-MSC) bone cements. The introduction of nl-MS improved the in vitro degradability of nl-MSC cements, which could neutralize acidic degradable products of calcium sulfate and prevented the pH from dropping. The cements were implanted into the bone defects of femur bone of rabbits, and the results of histological and immunohistochemical analysis revealed that massive new bone tissue formed in the defects while the cements were degradable, indicating that the osteogenesis and degradability of the nl-MSC cements were much better than the control calcium sulfate dihydrate (CSD) cements. Furthermore, the positive expression of vascular endothelial growth factor and collagen type I for nl-MSC cements was higher than CSD, indicating that addition of nl-MS into the cements enhanced vascularization and osteogenic differentiation. The results suggested that the nl-MSC cements with good biocompatibility and degradability could promote vascularization and osteogenesis, and had great potential to treat bone defects. PMID:28260883

  18. Non-conventional cement-based composites reinforced with vegetable fibers: A review of strategies to improve durability

    Directory of Open Access Journals (Sweden)

    Santos, S. F.

    2015-03-01

    Full Text Available The present review shows the state-of-art on the approachs about improving the processing, physical- mechanical performance and durability of non-conventional fiber-cement composites. The objective of this review is to show some of these strategies to mitigate the degradation of the vegetable fibers used as reinforcement in cost-effective and non-conventional fiber-cement and, consequently, to improve their mechanical and durability properties for applications in the housing construction. Beyond the introduction about vegetable fibers, the content of this review is divided in the following sections: (i surface modification of the fibers; (ii improving fiber-to-cement interface; (iii natural pozzolans; (iv accelerated carbonation; (v applications of nanoscience; and (vi principles of functionally graded materials and extrusion process were briefly discussed with focus on future research needs.La presente revisión explora la actualidad en el campo de los compuestos de fibrocemento no convencionales en relación a mejoras en el proceso productivo, el rendimiento físico-mecánico y la durabilidad. El objetivo de esta revisión es exponer algunas estrategias para mitigar la degradación de las fibras vegetales utilizadas como refuerzo en fibrocementos no convencionales y rentables, obteniendo en consecuencia una mejoría en el rendimiento de sus propiedades mecánicas y durabilidad para su aplicación en el área de la construcción de viviendas. Además de la introducción en relación a las fibras vegetales, el contenido de esta revisión se divide en las siguientes secciones: (i modificación de la superficie de las fibras; (ii mejoramiento de la interfaz fibra-cemento; (iii puzolanas naturales; (iv carbonatación acelerada; (v aplicaciones de la nanociencia; y (vi principios de los materiales funcionalmente graduados y el proceso de extrusión fueron discutidos brevemente con un enfoque a investigaciones futuras.

  19. Carbonate cementation in the late glacial outwash and beach deposits in northern Estonia

    Directory of Open Access Journals (Sweden)

    Maris Rattas

    2014-02-01

    Full Text Available The sedimentary environments, morphology and formation of carbonate cement in the late glacial glaciofluvial outwash and beach deposits in northern Estonia are discussed. Cementation is observed in well-drained, highly porous carbonaceous debris-rich gravel and sand-forming, resistant ledges in otherwise unconsolidated sediments. The cemented units occur as laterally continuous layers or as isolated lenticular patches with thicknesses from a few centimetres to 3 m. The cement is found in two main morphologies: (1 cement crusts or coatings around detrital grains and (2 massive cement almost entirely filling interparticle pores and intraparticle voids. It is exclusively composed of low-Mg calcite with angular equant to slightly elongated rhombohedral and scalenohedral or prismatic crystals, which indicate precipitation from meteoric or connate fresh surface (glacial lake water and/or near-surface groundwater under low to moderate supersaturation and flow conditions. The absence of organic structures within the cement suggests that cementation is essentially inorganic. The cement exhibits both meteoric vadose and phreatic features and most probably occurred close to the vadose–phreatic interface, where the conditions were transitional and/or fluctuating. Cementation has mainly taken place by CO2-degassing in response to fluctuations in groundwater level and flow conditions, controlled by the Baltic Ice Lake water level, and seasonal cold and/or dry climate conditions.

  20. 磷酸镁水泥基材料耐久性研究进展%Research Progresses on Durability of Magnesium Phosphate Cement Based Materials

    Institute of Scientific and Technical Information of China (English)

    常远; 史才军; 杨楠; 杨建明

    2014-01-01

    Magnesium phosphate cement based materials possess many advantages including small dry shrinkage,excellent re-sistance to abrasion and deicer-scaling or freezing and thawing,good resistance to steel corrosion and wetting-drying cycle and so on.It is suggested that dry shrinkage of magnesium phosphate cement based materials is greatly effected by water to binder ratio,surface activity of magnesium oxide,phosphate to magnesia ratio,retarder and addition of fly ash.Excellent resistance to deicer-scaling or freezing and thawing owe to small water to binder ratio and lots of enclosed pores inside.These enclosed pores may be caused by creation of carbon dioxide gas or evaporation of free water for hydration heat evolution.Magnesium phosphate cement based materials has weak resistance to water or acid and alkali corrosion which may be improved by improve-ment of retarder,increasing fineness of phosphate prolonging pre-curing time.%磷酸镁水泥基材料具有干缩小、耐磨性好、抗冻性和抗盐冻剥蚀性能优良、防钢筋锈蚀性能和抗干湿循环性能优良等特点。氧化镁活性、磷镁比、缓凝剂、水胶比以及粉煤灰掺量对磷酸镁水泥基材料干燥收缩有显著影响。水灰比低及基体内部存在大量均匀封闭气孔是磷酸镁水泥基材料基体抗冻性优良的主要原因,大量封闭气孔可能是基体内部发生化学反应生成二氧化碳气体造成或是由于水化放热过程中自由水蒸发受阻后经水化产物填充形成的。磷酸镁水泥基材料耐水性能和耐酸碱腐蚀性较差,但耐水性可通过改善缓凝剂、增大磷酸盐细度、增加预养护时间来改善。

  1. Propriedades e bioatividade de um cimento endodôntico à base de aluminato de cálcio Properties and bioactivity of endodontic calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2011-09-01

    Full Text Available Desde sua introdução na endodontia como um material retro-obturador e selador de defeitos da raiz dental, o agregado de trióxido mineral (MTA tem sido considerado como um material endodôntico revolucionário. Apesar disso, este material apresenta algumas propriedades limitantes, necessitando alterações em sua composição bem como desenvolvimento de novos materiais. Assim, o objetivo desse trabalho foi mostrar a influência de aditivos no desenvolvimento de um cimento endodôntico à base de cimento de aluminato de cálcio (ECAC. Além disso, foram avaliadas as propriedades do ECAC em comparação com o MTA, quando em contato com solução de fluido corporal simulado (SBF. Testes de manipulação e medidas de resistência à compressão, porosidade aparente, tempo de endurecimento, pH e condutividade iônica, foram realizados para os materiais MTA puro e ECAC contendo aditivos. Considerando as propriedades apresentadas pelo ECAC, este material alternativo pode ser indicado para múltiplas aplicações em endodontia.The mineral trioxide aggregate (MTA, a material primarily developed as a root-end filling has been extensively investigated as an innovative product for endodontic applications. However, changes in its formulation/composition involving its mineral aggregates and the development of alternatives of materials have been proposed in an attempt to overcome its negative physical-chemical characteristics. In this work, the influence of additives addition on the development of a novel endodontic cement based on calcium aluminate, has been evaluated. In addition, the properties of endodontic calcium aluminate cement (ECAC were compared with the gold standard mineral-trioxide-aggregate in contact with simulated body fluid (SBF. Manipulation tests and measurements of compressive strength, apparent porosity, setting time, pH and ionic conductivity were carried out on plain MTA and calcium aluminate cement with and without various additives

  2. Meteoric calcite cementation: diagenetic response to relative fall in sea-level and effect on porosity and permeability, Las Negras area, southeastern Spain

    Science.gov (United States)

    Li, Zhaoqi; Goldstein, Robert H.; Franseen, Evan K.

    2017-03-01

    A dolomitized Upper Miocene carbonate system in southeast Spain contains extensive upper and lower zones of calcite cementation that cut across the stratigraphy. Cement textures including isopachous and circumgranular, which are consistent with phreatic-zone cementation. Cements in the upper cemented zone are non-luminescent, whereas those in the lower cemented zone exhibit multiple bands of luminescent and non-luminescent cements. In the upper cemented zone, isotopic data show two meteoric calcite lines (MCL) with mean δ18O at - 5.1‰ and - 5.8‰ VPDB, whereas no clear MCL is defined in the lower cemented zone where mean δ18O for calcite cement is at - 6.7‰ VPDB. δ13C values in both cement zones are predominantly negative, ranging from - 10 to + 2‰ VPDB, suggestive of carbon from soil gas or decayed organics. Measurements of Tm ice in primary fluid inclusions yield a mode of 0.0 °C in both zones, indicating calcite cementation from fresh water. These two zones define the positions of two different paleo-water tables that formed during a relative sea-level fall and erosional downcutting during the Plio-Pleistocene. The upper cemented zone pre-dated the lower cemented zone on the basis of known relative sea-level history. Meteoric calcite cementation reduced porosity and permeability, but measured values are inconsistent with simple filling of open pore space. Each texture, boundstone, grainstone, packstone, wackestone, produces a different relationship between percent calcite cement and porosity/permeability. Distribution of cements may be predictable on the basis of known sea-level history, and the effect of the cementation can be incorporated into subsurface geomodels by defining surfaces of rock boundaries that separate cemented zones from uncemented zones, and applying texture-specific relationships among cementation, porosity and permeability.

  3. Chemical and physical properties of bone cement for vertebroplasty

    Directory of Open Access Journals (Sweden)

    Po-Liang Lai

    2013-08-01

    Full Text Available Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.

  4. Cements and adhesives for all-ceramic restorations.

    Science.gov (United States)

    Manso, Adriana P; Silva, Nelson R F A; Bonfante, Estevam A; Pegoraro, Thiago A; Dias, Renata A; Carvalho, Ricardo M

    2011-04-01

    Dental cements are designed to retain restorations, prefabricated or cast posts and cores, and appliances in a stable, and long-lasting position in the oral environment. Resin-based cements were developed to overcome drawbacks of nonresinous materials, including low strength, high solubility, and opacity. Successful cementation of esthetic restorations depends on appropriate treatment to the tooth substrate and intaglio surface of the restoration, which in turn, depends on the ceramic characteristics. A reliable resin cementation procedure can only be achieved if the operator is aware of the mechanisms involved to perform the cementation and material properties. This article addresses current knowledge of resin cementation concepts, exploring the bonding mechanisms that influence long-term clinical success of all-ceramic systems. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Exposure to cement dust at a Portland cement factory and the risk of cancer.

    Science.gov (United States)

    Vestbo, J; Knudsen, K M; Raffn, E; Korsgaard, B; Rasmussen, F V

    1991-01-01

    The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 14 cases of respiratory cancer were observed (observed/expected (O/E) 1.52, 95% confidence interval (95% CI) 0.90-2.57) when compared with all Danish men. Men with 1-20 years exposure had O/E 1.14 (95% CI 0.59-2.19) based on nine cases of cancer. After excluding all men with documented exposure to asbestos during employment in an asbestos cement factory no increased risk of overall cancer or respiratory cancer was found among cement workers compared with white collar workers from the local reference population, using a Cox regression model controlling for age and smoking habits. Relative risks were 0.5 (95% CI 0.1-1.5) and 1.0 (95% CI 0.4-2.6) for men with 1-20 and more than 20 years of exposure to cement dust respectively compared with white collar workers. PMID:1772795

  6. Production of cement requiring low energy expenditure. An industrial test

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, S.; Blanco, M.T.; Palomo, A.; Puertas, F. (Instituto de Ciencias de la Construccion, Madrid (Spain))

    1991-01-01

    A new method for making cement is proposed. It is based on the use of CaF{sub 2} and CaSO{sub 4} for partial replacement of the usual raw materials in cement manufacturing. This paper shows the feasibility of the proposed method on an industrial scale. A test carried out in a Spanish cement factory (1500 t yield of the new cement) has revealed that the mehtod can not only be adapted to the current technology but also requires a much lower energy expenditure. The final product is shown to have excellent properties in comparison with OPC. (orig.).

  7. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  8. Cementing and formation damage; Cimentacao e dano a formacao

    Energy Technology Data Exchange (ETDEWEB)

    Souza, David Soares de [PETROBRAS, BA (Brazil). Distrito de Perfuracao da Bahia. Div. de Tecnicas e Operacoes

    1994-07-01

    This work presents a general perspective on cementing and formation damage. Few relative experiments to the damage to the formation, that they involve the casing activity and cementing, consider all the factors that affect these operations. So that she can analyze the contribution of a primary cementing has in the formation damage , it should be considered, also, the contribution of the drilling fluid and of the operation of the perforation. With base in experimental data of several accomplished studies, it can be concluded that a primary cementing has small, or any, contribution in the decrease of the productivity of an oil well.

  9. Bone cement flow analysis by stepwise injection through medical cannulas.

    Science.gov (United States)

    Zderic, Ivan; Steinmetz, Philipp; Windolf, Markus; Richards, R Geoff; Boger, Andreas; Gueorguiev, Boyko

    2016-12-01

    Cement leakage is a serious adverse event potentially occurring during vertebroplasty. Pre-operative in-silico planning of the cement filling process can help reducing complication rates related to leakage. This requires a better understanding of the cement flow along the whole injection path. Therefore, the aim of the present study was to analyze bone cement flow behavior by stepwise injections through medical cannulas. Sixteen cannulas were assigned to four groups for stepwise injection of differently colored cement portions of 1ml volume. Each group differed in the amount of injected cement portions with a range of 1-4ml. After cement curing longitudinal cross-sections of the cannulas were performed and high-resolution pictures taken. Based on these pictures, quadratic polynomial interpolation was applied to the marked intersections between the last two injected cement portions to calculate the leading coefficients. Leading coefficients in the groups with three cement portions (0.287 ± 0.078), four portions (0.243 ± 0.041) and two portions (0.232 ± 0.050) were comparable and significantly higher than the group with one cement portion (0.0032 ± 0.0004), p ≤ 0.016. Based on these findings, cement flow through medical cannulas can be considered as predictable and can therefore be excluded as a source of risk for possible cement leakage complications during vertebroplasty procedures. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  10. Experimental investigation of influence of acid rain on leaching and hydraulic characteristics of cement-based solidified/stabilized lead contaminated clay.

    Science.gov (United States)

    Du, Yan-Jun; Jiang, Ning-Jun; Shen, Shui-Long; Jin, Fei

    2012-07-30

    Remediation of contaminated lands in China urban areas is of great concern. Degradation of construction facilities caused by acid rain is a serious environmental pollution issue in China. This paper presents an investigation of the effects of acid rain on leaching and hydraulic properties of cement-based solidified/stabilized lead contaminated soil. Laboratory tests including infiltration test and soaking test are conducted. It is found that the soil hydraulic conductivity decreases with increase in the pore volume of flow of permeant liquids (acid rain and distilled water). The decreasing rate in the case of the acid rain is lower than that in the case of the distilled water. The soaking test results show that pH and the presence of sulfate ions of acid rain have considerable influence on the leached concentrations and leaching rate of calcium.

  11. A model for discrimination freshness of shrimp

    Directory of Open Access Journals (Sweden)

    Linong Du

    2015-12-01

    Full Text Available The shrimp is popular for its nutrition and dainty, however, it is easy to decay, and its freshness degrades, so, it is important to assess its freshness. The shrimp gives off unpleasant odor with its freshness change, detecting its odor difference can evaluate its freshness. The feasibility of using electronic nose for evaluating the freshness of shrimp (Penaeus vanmamei is explored in this paper. The odor of shrimp, stored at 5 °C, was detected by the electronic nose. Combined with the sensory evaluation and TVBN, a model based on the electronic nose was constructed to evaluate the shrimp freshness. In principal components analysis, the first three principal components accounted for 86.97% of total variation, and they are used to establish a model to estimate the shrimp freshness with Fisher Liner Discriminant. The discriminant rates were 98.3% for 120 modeling sample data, and 91.7% for 36 testing sample data. The model could be easily used to evaluate the freshness of shrimp with better accuracy.

  12. 磷石膏基水泥的早期水化性能研究%Early hydration properties of phosphogypsum-based cement

    Institute of Scientific and Technical Information of China (English)

    袁继峰; 刘彬; 董晓进

    2014-01-01

    研究了原样磷石膏、200℃煅烧磷石膏、800℃煅烧磷石膏制备的磷石膏水泥的力学性能(对应编号分别为:MPC-1、MPC-2和MPC-3),进行了不同改性磷石膏基水泥早期水化放热速率及28 d水化产物的测试分析。结果表明:煅烧磷石膏尤其高温煅烧磷石膏可发挥更好的硫酸盐激发效果,有效提高磷石膏基水泥的强度,尤其是早期强度。800℃煅烧磷石膏水泥MPC-3试样3、28 d强度分别为20.1、44.7 MPa,达到42.5R水泥强度等级要求;煅烧磷石膏基水泥的早期水化进程明显加快,相对MPC-1试样,MPC-2、MPC-3第二放热峰出现时间分别提前约10 h和17 h;磷石膏基水泥的水化产物主要为钙矾石和C-S-H凝胶,高温煅烧磷石膏基水泥水化产物更为密集。%Influence of phosphogypsum,200 ℃ calcined phosphogypsum and 800 ℃ calcined phosphogypsum on paste strength of modified phosphogypsum-based cement(No.:MPC-1 MPC-2 and MPC-3) were tested;Furthermore,early hydration exothermic rate and 28 d hydration products were systematically compared.Results showed that calcined phosphogypsum ,especially high temperature calcined phosphogypsum can play better stimulate sulfate effect,effectively improve strength of MPC,especially early strength.800 ℃ calcined phosphogypsum-based cement with the compressive strength 20.1 MPa at 3 d and 44.7 MPa at 28 d can meet the standard of Portland ce-ment of 42.5R grade in strengths.Early hydration process of MPC accelerated markedly ,the second exothermic peak of MPC-2 and MPC-3 can respectively advance for 10 h and 17 h relative to MPC-1.Hydration products of phosphogypsum-based cement were mainly ettringite and C-S-H gel,which were more intensive for MPC-2 and MPC-3.

  13. Corrosion-resistant Foamed Cements for Carbon Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Gill, S.; Pyatina, T., Muraca, A.; Keese, R.; Khan, A.; Bour, D.

    2012-12-01

    The cementitious material consisting of Secar #80, Class F fly ash, and sodium silicate designed as an alternative thermal-shock resistant cement for the Enhanced Geothermal System (EGS) wells was treated with cocamidopropyl dimethylamine oxide-based compound as foaming agent (FA) to prepare numerous air bubble-dispersed low density cement slurries of and #61603;1.3 g/cm3. Then, the foamed slurry was modified with acrylic emulsion (AE) as corrosion inhibitor. We detailed the positive effects of the acrylic polymer (AP) in this emulsion on the five different properties of the foamed cement: 1) The hydrothermal stability of the AP in 200 and #61616;C-autoclaved cements; 2) the hydrolysis-hydration reactions of the slurry at 85 and #61616;C; 3) the composition of crystalline phases assembled and the microstructure developed in autoclaved cements; 4) the mechanical behaviors of the autoclaved cements; and, 5) the corrosion mitigation of carbon steel (CS) by the polymer. For the first property, the hydrothermal-catalyzed acid-base interactions between the AP and cement resulted in Ca-or Na-complexed carboxylate derivatives, which led to the improvement of thermal stability of the AP. This interaction also stimulated the cement hydration reactions, enhancing the total heat evolved during cement’s curing. Addition of AP did not alter any of the crystalline phase compositions responsible for the strength of the cement. Furthermore, the AP-modified cement developed the porous microstructure with numerous defect-free cavities of disconnected voids. These effects together contributed to the improvement of compressive-strength and –toughness of the cured cement. AP modification of the cement also offered an improved protection of CS against brine-caused corrosion. There were three major factors governing the corrosion protection: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS

  14. Chemo-physical modeling of cement mortar hydration: Role of aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jena, E-mail: jeong@profs.estp.fr [Université Paris-Est, Institut de Recherche en Constructibilité, ESTP, 28 Avenue Président Wilson, 94234 Cachan (France); Ramézani, Hamidréza, E-mail: hamidreza.ramezani@univ-orleans.fr [CRMD, CNRS FRE 3520-Research Center on Divided Materials, École Polytechnique de l’Université d’Orléans, 8 rue Léonrad de Vinci, 45072 Orléans Cedex 2 (France); Leklou, Nordine, E-mail: nordine.leklou@univ-nantes.fr [LUNAM Université, Université de Nantes-IUT Saint-Nazaire, GeM, CNRS UMR 6183, Research Institute in Civil Engineering and Mechanics, 58 rue Michel Ange BP 420 44606 Saint Nazaire Cedex (France); Mounanga, Pierre, E-mail: pierre.mounanga@univ-nantes.fr [LUNAM Université, Université de Nantes-IUT Saint-Nazaire, GeM, CNRS UMR 6183, Research Institute in Civil Engineering and Mechanics, 58 rue Michel Ange BP 420 44606 Saint Nazaire Cedex (France)

    2013-07-20

    Graphical abstract: - Abstract: After mixing of the cement with water, most of the anhydride products sustain the hydration process and this leads to the hydrate products, e.g. CSH, Ca(OH){sub 2}, Afm and Aft. The mentioned hydration process is a highly complex phenomenon involving the chemically based thermo-activation inside the cement mortars during the early age hydration process. The chemo-thermal hydration reactions drasticaly increase at the early age of hydration after the mixing action and then it becomes less important and turns to be nearly asymptotic. The progress of the hydration phenomenon drives the material properties change during the very early age of cement hydration. Regarding the mortar and concrete, such hydration process would not be homogeneous through the cement matrix due to the aggregates presence. These inclusions will affect the temperature distribution as well as degree of hydration. In the current contribution, the chemical and thermal hydration have been firstly investigated by means of SEM observations using replica method and secondly by the 3D-FEM numerical experiments including two different case studies using glass beads as aggregates. The numerical experiments match fairly good the experimental measurements obtained using a pseudo-adiabatic testing setup for the case studies herein. The scanning electron microscopy (SEM) images observation demonstrates the gap spaces around the glass beads next to the external surfaces. These gaps can be essentially seen for the multi-glass beads case study. The role of the temperature and degree of hydration gradients are clearly obtained using the numerical samples. Some fresh routes and outlooks have been afterwards discussed.

  15. Development of nanosilica bonded monetite cement from egg shells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: huanzhou@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu (China); Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Division of Dentistry, The University of Toledo, Toledo, OH (United States)

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement.

  16. Statistical Study on Cement-Soil Mixture Strength

    Institute of Scientific and Technical Information of China (English)

    YU Zhiqiang; CAO Yonghua; YAN Shuwang

    2005-01-01

    This paper presents an investigation on strength of cement deep mixing (CDM) mixture. Four typical works of offshore or land-based projects are introduced. With samples from these projects and laboratory tests, statistical analysis is made on the increment law of the strength of cement-soil mixture with different amount of cement, and strengths under different working conditions are compared. It is found that the amount of cement in the cement-soil mixture is closely related to the unconfined compressive strength of the mixture. At the age of 90 d,the unconfined compressive strength of the cement-soil mixture increased by 0.054 Mpa-0.124 Mpa with each cement increasing 10 kg/m3 in the cement-soil mixture, averagely increased by 0.085 Mpa, while that at the age of 120 d increased by 11% in comparison.The quality of the cement-soil mixture should be comprehensively evaluated in accordance with the trimmed average of strength, coefficient of variation and rock quality designation (RQD) indicators of sampling ratio.

  17. Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation

    DEFF Research Database (Denmark)

    Lura, Pietro; Couch, J.; Jensen, Ole Mejlhede

    2009-01-01

    In this study, the acoustic emission activity of cement pastes was investigated during the first day of hydration. Deaired, fresh cement pastes were cast in sealed sample holders designed to minimize friction and restraint. The majority of acoustic emission events occurred in lower water to cement....... According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs...

  18. Modeling and analyzing autogenous shrinkage of hardening cement paste

    NARCIS (Netherlands)

    Lu, T.; Koenders, E.A.B.

    2014-01-01

    In this paper, a conceptual model for analyzing the plastic part of autogenous deformation of cement paste based on the Arrhenius rate theory will be presented. The autogenous deformation will be calculated from the elastic deformations with inclusion of creep. Different kinds of cement paste with a

  19. Modeling and analyzing autogenous shrinkage of hardening cement paste

    NARCIS (Netherlands)

    Lu, T.; Koenders, E.A.B.

    2014-01-01

    In this paper, a conceptual model for analyzing the plastic part of autogenous deformation of cement paste based on the Arrhenius rate theory will be presented. The autogenous deformation will be calculated from the elastic deformations with inclusion of creep. Different kinds of cement paste with a

  20. Purification of Immune Cell Populations from Freshly Isolated Murine Tumors and Organs by Consecutive Magnetic Cell Sorting and Multi-parameter Flow Cytometry-Based Sorting.

    Science.gov (United States)

    Salvagno, Camilla; de Visser, Karin E