WorldWideScience

Sample records for cement based composites

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  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. 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.

  9. 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.

  10. 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...

  11. 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.

  12. 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 f...

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.%.

  2. 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.

  3. 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.

  4. 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.

  5. Mechanism of Functional Responses to Loading of Carbon Fiber Reinforced Cement-based Composites

    Institute of Scientific and Technical Information of China (English)

    JIANG Cuixiang; LI Zhuoqiu; SONG Xianhui; LU Yong

    2008-01-01

    Single fiber pull-out testing was conducted to study the origin of the functional responses to loading of carbon fiber reinforced cement-based composites.The variation of electrical resistance with the bonding force on the fiber-matrix interface was measured.Single fiber electromechanical testing was also conducted by measuring the electrical resistance under static tension.Comparison of the results shows that the resistance increasing during single fiber pull-out is mainly due to the changes at the interface.The conduction mechanism of the composite can be explained by the tunneling model.The interfacial stress causes the deformation of interfacial structure and the interfacial debonding.which have influences on the tunneling effect and result in the change of resistance.

  6. 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.

  7. 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

  8. Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

    Institute of Scientific and Technical Information of China (English)

    FAN Xiaoming; FANG Dong; SUN Mingqing; LI Zhuoqiu

    2011-01-01

    The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites(CFGCC) with carbon fiber content(l% by the weight of cement), graphite powder contents (0%-50% by the weight of cement) and CCCW(cementitious capillary crystalline waterproofing materials, 4% by the weight of cement) were studied. The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena. The percolation threshold was about 20%. A clear piezoresistive effect was observed in CFGCC with 1 wt% of carbon fibers, 20wt% or 30wt% of graphite powders under uniaxial compressive tests, indicating that this type of smart composites was a promising candidate for strain sensing. The measured gage factor (defined as the fractional change in resistance per unit strain) of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22, respectively. With the addition of CCCW, the mechanical properties of CFGCC were improved, which benefited CFGCC piezoresistivity of stability.

  9. 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.

  10. 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.

  11. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

    Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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.

  20. Dynamic properties of composite cemented clay

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 梁旭

    2004-01-01

    In this work,the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

  1. 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.

  2. 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.

  3. Development of monetite/phosphorylated chitosan composite bone cement.

    Science.gov (United States)

    Boroujeni, Nariman Mansouri; Zhou, Huan; Luchini, Timothy J F; Bhaduri, Sarit B

    2014-02-01

    In this article, we report the development of a biodegradable monetite [dicalcium phosphate anhydrous (DCPA), CaHPO4 ]/phosphorylated chitosan (p-chitosan) composite orthopedic cement. The cement pastes showed desirable handling properties, injectability, and washout resistance. The incorporation of p-chitosan powders at 5 wt % shortened the setting time of DCPA and significantly improved the mechanical performance of DCPA cement, increasing the compressive strength almost twice from 11.09 ± 1.85 MPa at 0% chitosan to 23.43 ± 1.47 MPa at 5 wt % p-chitosan. On the other hand, higher p-chitosan content or untreated chitosan incorporation lowered the performance of DCPA cements. The cytocompatibility of the composite cement was investigated in vitro using the preosteoblast cell line MC3T3-E1. An increase in cell proliferation was observed in both DCPA and DCPA-p-chitosan. The results show that both the materials are as cytocompatible as hydroxyapatite. Based on these results, DCPA-p-chitosan composite cement can be considered as potential bone repair material.

  4. Center for Cement Composite Materials

    Science.gov (United States)

    1990-01-31

    pastes have shown that the matrix is microporous; mesopores are absent unless the material is allowed to dry out. This results in water adsorption at low...only to water. When subsequently dried a portion of3 the porosity is converted to larger mesopores . • Only about one third of the cement reacts in a...Frictional sliding, in this case was characterized by a decreasing slope in the loading curve followed by hysteresis in the unload/reloading curves

  5. Composite Control of Precalciner Exit Temperature in Cement Rotary Kiln

    Institute of Scientific and Technical Information of China (English)

    赵晨; 诸静

    2003-01-01

    A composite control strategy for the precalciner exit temperature in cement kiln is introduced based on a mathematical model. In this model, the raw meal flow, coal powder flow and wind flow are taken as three input variables, the clinker fow and exit teperature of cement kiln are output variables, and other influencing factors are considered as disturbance. A composite control system is synthesied by integrating self-learning PID, fuzzy and feedforward function into a combined controller, and the arithmetics for the self-learning PID controller, fuzzy controller and feedforward controller are elaborated respectively. The control strategy has been realized by software in real practice at cement factory. Application results show that the composite control technology is superior to the general PID control in control effect, and is suitable to the industrial process control with slow parameter variation, nonlinearity and uncertainty.

  6. 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.

  7. DESIGN OF CEMENT COMPOSITES WITH INCREASED IMPERMEABILITY

    Directory of Open Access Journals (Sweden)

    Fedyuk Roman Sergeevich

    2016-05-01

    Full Text Available The paper deals with the development of composite binders for producing concrete with improved characteristics of gas, water and vapor permeability. The authors investigate the processes of composite materials formation in order of decreasing scale levels from macro to nanostructures. The criteria for optimization of the volume of dispersed additives in concrete are offered. The authors theoretically studied the technological features of the formation of hydrated cement stone structure. A positive effect of nanodispersed additives on the structure and physico-mechanical properties of cement composite materials are predicted. Thanks to its improved features, such as good ratio of strength and body density, high density and lifetime, the modified concrete may be used when solving various practical tasks of the construction branch.

  8. Possibility of Using Wood Pulp in the Preparation of Cement Composites

    Science.gov (United States)

    Kidalova, Lucia; Stevulova, Nadezda; Geffert, Anton

    2014-06-01

    Sustainable building materials are based on the use of renewable materials instead of non-renewable. Large group of renewable materials composes of plant fibres having high tensile strength are used as fillers into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic fillers, such as wood pulp. Wood pulp cellulose is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. Varying the producing technology (wood pulp and cement ratio in mixture) it is possible to obtain composites with density from 940 to 1260 kgm-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. Based on the experimental results, cement composites with using unbleached wood pulp reach higher values than composites based on bleached wood pulp. Volume ratio of unbleached wood pulp in composites influences water absorbability of cement composites

  9. Possibility of Using Wood Pulp in the Preparation of Cement Composites

    Directory of Open Access Journals (Sweden)

    Kidalova Lucia

    2014-06-01

    Full Text Available Sustainable building materials are based on the use of renewable materials instead of non-renewable. Large group of renewable materials composes of plant fibres having high tensile strength are used as fillers into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic fillers, such as wood pulp. Wood pulp cellulose is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. Varying the producing technology (wood pulp and cement ratio in mixture it is possible to obtain composites with density from 940 to 1260 kgm-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. Based on the experimental results, cement composites with using unbleached wood pulp reach higher values than composites based on bleached wood pulp. Volume ratio of unbleached wood pulp in composites influences water absorbability of cement composites

  10. Effect of Calcium Leaching on the Properties of Cement-based Composites

    Institute of Scientific and Technical Information of China (English)

    LLIN Weiting; CHENG An; HUANG Ran; CHEN Chuntao; ZHOU Xingang

    2011-01-01

    Leaching is one of the major factors that alter the mechanical properties of cementbased composites.This study is aimed to investigate the effect of leaching on the properties of cementbased composites.Specimens with two water/cementitious ratios and two mineral admixtures were tested.An electrical potential was applied to accelerate the leaching process.Compressive strength test,scanning electronic microscopy,thermogravimetric analysis and X-ray diffraction analysis were conducted.Test results demonstrated that the calcium leaching reduced compressive strengths of concrete specimens,and such effect was prominent on the specimens without mineral admixtures.The leaching resistance increased with a decrease in water/cementitious ratio and an increase in amount of mineral admixtures.The mineral admixtures would reduce the amount of calcium hydroxide and refine the pore structure through pozzolanic reactions.A fair relationship was found between the calcium leaching and the compressive strength.

  11. Durability of Cement Composites Reinforced with Sisal Fiber

    Science.gov (United States)

    Wei, Jianqiang

    This dissertation focuses mainly on investigating the aging mechanisms and degradation kinetics of sisal fiber, as well as the approaches to mitigate its degradation in the matrix of cement composites. In contrast to previous works reported in the literature, a novel approach is proposed in this study to directly determine the fiber's degradation rate by separately studying the composition changes, mechanical and physical properties of the embedded sisal fibers. Cement hydration is presented to be a crucial factor in understanding fiber degradation behavior. The degradation mechanisms of natural fiber consist of mineralization of cell walls, alkali hydrolysis of lignin and hemicellulose, as well as the cellulose decomposition which includes stripping of cellulose microfibrils and alkaline hydrolysis of amorphous regions in cellulose chains. Two mineralization mechanisms, CH-mineralization and self-mineralization, are proposed. The degradation kinetics of sisal fiber in the cement matrix are also analyzed and a model to predict the degradation rate of cellulose for natural fiber embedded in cement is outlined. The results indicate that the time needed to completely degrade the cellulose in the matrix with cement replacement by 30wt.% metakaolin is 13 times longer than that in pure cement. A novel and scientific method is presented to determine accelerated aging conditions, and to evaluating sisal fiber's degradation rate and durability of natural fiber-reinforced cement composites. Among the static aggressive environments, the most effective approach for accelerating the degradation of natural fiber in cement composites is to soak the samples or change the humidity at 70 °C and higher temperature. However, the dynamic wetting and drying cycling treatment has a more accelerating effect on the alkali hydrolysis of fiber's amorphous components evidenced by the highest crystallinity indices, minimum content of holocellulose, and lowest tensile strength. Based on the

  12. Development of Clinical Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new type of inorganicorganic biomimetic bone cement consisting of nanohydroxyapatite and polyamide 66 composite was investigated. This cement can be handled as paste and easily shaped into any contour. Nanoapatite and polyamide composite cement has a reasonable setting time, excellent washout resistance, high mechanical strength and bioactivity, and it is easily handled and shaped, which can be developed as a clinical cement. It can be predicted that nanoapatite/polymer composite cement would be a new trend of biomedical material, showing a promising prospect.

  13. 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.

  14. 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.

  15. 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

    In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag...... (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....

  16. DEVELOPING A NEW GENERATION OF HIGH PERFORMANCE COMPOSITE CEMENT

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper proposed a new generation of high performance composite cement which is designed according to the optimization of composition and structure of cement paste and is manufactured by blending the different components with special composite techniques. Each of these components has its different special property, and should be compatible with each other and match each other, and the properties of them are complementary mutually. At present, such kind of high performance composite cement can be manufactured with high reactivity cement clinker, ground granulated blast-furnace slag, high grade fly ash, silica fume etc.

  17. 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

  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. Test on Sensor Effect of Cement Matrix Piezoelectric Composite

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaoming; LI Zhongxian; DING Yang; LI Zongjin

    2005-01-01

    A novel cement matrix smart piezoelectric composite and its application as sensing element are presented.A cement matrix smart piezoelectric composite piece encapsulated in a cement mortar formed a practical sensor, and it was tested on material test system with cyclic loading.According to the theoretical analysis, the function of the cement matrix piezoelectric sensor output voltage was expressed in terms of the magnitude of the input cyclic loading amplitude and frequency.The curve fitting of gain function that is defined as sensor′s gain factor under different frequencies of input loading was carried out. From the results of curve fitting, it is found that the cement matrix smart piezoelectric composite has a simple relationship between input loading and output voltage.Therefore the cement matrix piezoelectric composite sensor is suitable to be applied in structural health monitoring.

  20. 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.

  1. 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.

  2. 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.

  3. Injectable Premixed Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new type of injectable premixed bone cement consisting of nano-hydroxyapatite (n-HA) and polyamide 66(PA66) composite is investigated. This cement can be handled as paste and easily shaped, which can set in air, in physiological saline solution and in blood. The setting time, injectability and compressive strength of the cement largely depend on the ratio of liquid to powder (L/P). Moreover, the content of n-HA in composite also affects the compressive strength and injectability of the cement. The premixed composite cement can remain stable in the package for a long period and harden only after delivery to the defects site. The results suggest that injectable premixed cement has a reasonable setting time, reasonable viscosity for injecting, excellent washout resistance and high mechanical strength, which can be developed for root canal filling, sealing and various bone defects augmentation.

  4. Cement compositions for cementing wells, allowing pressure gas-channeling in the cemented annulus to be controlled

    Energy Technology Data Exchange (ETDEWEB)

    Parcevaux, P.A.; Piot, B.M.; Vercaemer, C.J.

    1987-01-27

    The invention relates to cement compositions for cementing oil and geothermal wells. These compositions allow pressure gas-channeling to be effectively controlled up to more than about 485/sup 0/F. The compositions according to the invention comprise four essential constituents: a cement, a styrene-butadiene latex, a latex stabilizer, and water. The cement is a hydraulic cement belonging to any class among those currently used for cementing oil wells. The useful stabilizers according to the invention are anionic polyelectrolytes such as lignosulfanates and their desulfonated and/or resulfonated derivatives; sulfonated lignin-Kraft products; melamine-formaldehyde resins modified by a sulfonic acid or sulfite; formaldehyde/sulfonated naphthalene resins; or the condensation products of bi-nuclear sulfonated phenols and of formaldehyde. Preferred are the sodium salts of the condensation product of mononaphthalenesulfonic acid and of formaldehyde. The patent also includes a description of tests of various cement compositions of the invention, plus scanning electron microscope observations. 10 figs., 7 tabs.

  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. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    Directory of Open Access Journals (Sweden)

    Adriana Eštoková

    2013-12-01

    Full Text Available The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

  7. Transport Properties of Carbon-Nanotube/Cement Composites

    NARCIS (Netherlands)

    Han, B.; Yang, Z.; Shi, X.; Yu, X.

    2012-01-01

    This paper preliminarily investigates the general transport properties (i.e., water sorptivity, water permeability, and gas permeability) of carbon-nanotube/cement composites. Carboxyl multi-walled carbon nanotubes (MWNTs) are dispersed into cement mortar to fabricate the carbon nanotubes (CNTs) rei

  8. 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.

  9. 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.

  10. TECHNICAL NOTE: Dielectric and piezoelectric properties of piezoelectric ceramic sulphoaluminate cement composites

    Science.gov (United States)

    Cheng, Xin; Huang, Shifeng; Chang, Jun; Lu, Lingchao; Liu, Futian; Ye, Zengmao; Wang, Shoude

    2005-10-01

    Using cement as the matrix of piezoelectric smart composites can solve the problem of mismatch of smart composites and concrete structure in civil engineering. 0 3 cement based piezoelectric composites were fabricated by a compression technique using PMN and sulphoaluminate cement as raw materials. The influence of the PMN content on the dielectric and piezoelectric properties of the composites was investigated. The temperature dependence of the dielectric properties of the composites was discussed in detail. The results indicate that the dielectric constants are almost constant in the temperature range from -30 to 50 °C, which shows excellent dielectric temperature stability. With increasing PMN content, the piezoelectric and dielectric properties of the composites increase. The theoretical values of the dielectric constants show good agreement with the experimental values for the composites.

  11. Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement

    Directory of Open Access Journals (Sweden)

    Mark Bediako

    2015-01-01

    Full Text Available The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC and Portland limestone cement (PLC, CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The chemical compositions were analyzed with X-Ray Fluorescence (XRF spectrometer. Student’s t-test was used to test the significance of the variation in chemical composition between standard literature values and each of the commercial cement brands. Analysis of variance (ANOVA was also used to establish the extent of variations between chemical compositions and brand name of the all commercial Portland cement brands. Student’s t-test results showed that there were no significant differences between standard chemical composition values and that of commercial Portland cement. The ANOVA results also indicated that each brand of commercial Portland cement varies in terms of chemical composition; however, the specific brands of cement had no significant differences. The study recommended that using any brand of cement in Ghana was good for any construction works be it concrete or mortar formation.

  12. Modeling of properties of fiber reinforced cement composites

    Directory of Open Access Journals (Sweden)

    Jevtić Dragica

    2008-01-01

    Full Text Available This paper presents the results of authors' laboratory testing of the influence of steel fibers as fiber reinforcement on the change of properties of cement composite mortar and concrete type materials. Mixtures adopted - compositions of mortars had identical amounts of components: cement, sand and silica fume. The second type of mortar contained 60 kg/m3 of fiber reinforcement, as well as the addition of the latest generation of superplasticizer. Physical and mechanical properties of fiber reinforced mortars and etalon mixtures (density, flexural strength, compressive strength were compared. Tests on concrete type cement composites included: density, mechanical strengths and the deformation properties. The tests showed an improvement in the properties of fiber reinforced composites.

  13. Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior

    Directory of Open Access Journals (Sweden)

    Rongda Ye

    2015-11-01

    Full Text Available Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28/expanded perlite (EP composite phase change materials (PCMs. The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%–35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings.

  14. Structure, properties and animal study of a calcium phosphate/calcium sulfate composite cement.

    Science.gov (United States)

    Chen, Wei-Luen; Chen, Chang-Keng; Lee, Jing-Wei; Lee, Yu-Ling; Ju, Chien-Ping; Lin, Jiin-Huey Chern

    2014-04-01

    In-vitro and in-vivo studies have been conducted on an in-house-developed tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH)-derived composite cement. Unlike most commercial calcium-based cement pastes, the investigated cement paste can be directly injected into water and harden without dispersion. The viability value of cells incubated with a conditioned medium of cement extraction is >90% that of Al2O3 control and >80% that of blank medium. Histological examination reveals excellent bonding between host bone and cement without interposition of fibrous tissues. At 12 weeks-post implantation, significant remodeling activities are found and a new bone network is developed within the femoral defect. The 26-week samples show that the newly formed bone becomes more mature, while the interface between residual cement and the new bone appears less identifiable. Image analysis indicates that the resorption rate of the present cement is much higher than that of TTCP or TTCP/DCPA-derived cement under similar implantation conditions.

  15. Full factorial design analysis of carbon nanotube polymer-cement composites

    Directory of Open Access Journals (Sweden)

    Fábio de Paiva Cota

    2012-08-01

    Full Text Available The work described in this paper is related to the effect of adding carbon nanotubes (CNT on the mechanical properties of polymer-cement composites. A full factorial design has been performed on 160 samples to identify the contribution provided by the following factors: polymeric phase addition, CNT weight addition and water/cement ratio. The response parameters of the full factorial design were the bulk density, apparent porosity, compressive strength and elastic modulus of the polymer-cement-based nanocomposites. All the factors considered in this analysis affected significantly the bulk density and apparent porosity of the composites. The compressive strength and elastic modulus were affected primarily by the cross-interactions between polymeric phase and CNT additions, and the water/cement ratio with polymeric phase factors.

  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. Crack path and fracture surface modifications in cement composites

    Directory of Open Access Journals (Sweden)

    Sajjad Ahmad

    2015-10-01

    Full Text Available There is a tremendous increase in the use of high strength and high performance self-consolidating cementitious composites due to their superior workability and mechanical strengths. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to the low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. The present paper reports the modifications in the crack growth pattern of the high performance cement composites to achieve enhanced ductility and toughness. The objective was accomplished by the incorporation of the micro sized inert particulates in the cement composite matrix. The results indicate that the incorporation of micro sized inert particles acted as the obstacles in the growth of the cracks thus improving the ductility and the energy absorption capacity of the self-consolidating cementitious composites.

  18. A Study of Metal-Cement Composites with Additives

    Directory of Open Access Journals (Sweden)

    Mironov Victor

    2014-12-01

    Full Text Available The application of small-sized metal fillers (SMF provides a combination of high bulk density, increased durability and ferromagnetic properties of composite materials on the cement basis. However, the total strength of the composite can be compromised by poor adhesion of metal particles with the cement matrix. The use of versatile additives like microsilica and metakaolin is able to improve the structural integrity and mechanical properties of heavy concretes. The paper considers the results of a study using specimens of heavy concretes with SMF aiming to estimate its strength, structural features and ultrasonic parameters. It was found that the contact of SMF particles with the cement was not perfect, since the voids appeared between them and the cement matrix during the cement hydration process (exothermal reaction. Due to the border porosity, the specimens with the metal fillers have lower compressive strength, lower ultrasound velocity and increased frequency slope of attenuation. Microsilica and metakaolin additives facilitate better contact zone between the cement matrix and metal fillers.

  19. High Performance Fiber Reinforced Cement Composites 6 HPFRCC 6

    CERN Document Server

    Reinhardt, Hans; Naaman, A

    2012-01-01

    High Performance Fiber Reinforced Cement Composites (HPFRCC) represent a class of cement composites whose stress-strain response in tension undergoes strain hardening behaviour accompanied by multiple cracking, leading to a high strain prior to failure. The primary objective of this International Workshop was to provide a compendium of up-to-date information on the most recent developments and research advances in the field of High Performance Fiber Reinforced Cement Composites. Approximately 65 contributions from leading world experts are assembled in these proceedings and provide an authoritative perspective on the subject. Special topics include fresh and hardening state properties; self-compacting mixtures; mechanical behavior under compressive, tensile, and shear loading; structural applications; impact, earthquake and fire resistance; durability issues; ultra-high performance fiber reinforced concrete; and textile reinforced concrete. Target readers: graduate students, researchers, fiber producers, desi...

  20. Streptococcus mutans counts in plaque adjacent to orthodontic brackets bonded with resin-modified glass ionomer cement or resin-based composite

    Directory of Open Access Journals (Sweden)

    Solange Machado Mota

    2008-03-01

    Full Text Available This study investigated the number of Streptococcus mutans CFU (colony forming units in the saliva and plaque adjacent to orthodontic brackets bonded with a glass ionomer cement - GIC (Fuji Ortho or a resin-based composite - RC (Concise. Twenty male and female patients, aged 12 to 20 years, participated in the study. Saliva was collected before and after placement of appliances. Plaque was collected from areas adjacent to brackets and saliva was again collected on the 15th, 30th, and 45th day after placement. On the 30th day, 0.4% stannous fluoride gel was applied for 4 minutes. No significant modification in the number of Streptococcus mutans CFU in saliva was observed after placement of the fixed orthodontic appliances. On the 15th day, the percentage of Streptococcus mutans CFU in plaque was statistically lower in sites adjacent to GIC-bonded brackets (mean = 0.365 than in those adjacent to RC-bonded brackets (mean = 0.935. No evidence was found of a contribution of GIC to the reduction of CFU in plaque after the 15th day. Topical application of stannous fluoride gel on the 30th day reduced the number of CFU in saliva, but not in plaque. This study suggests that the antimicrobial activity of GIC occurs only in the initial phase and is not responsible for a long-term anticariogenic property.

  1. The Smart Behavior of Cement-based Composite Containing Carbon Fibers under Three-point-bending Load

    Institute of Scientific and Technical Information of China (English)

    CHEN Bing; WU Keru; YAO Wu

    2005-01-01

    The influences of the fiber volume fraction on the electrical conductivity and the fraction change of electrical resistance under three-point- bending test were discussed. It is found that the relationship between the electrical conductivity of composites and the fiber volume fraction can be explained by the percolation theory and the change of electrical resistance of specimens reflects to the process of loading. The sensitivity and the response of the change of electrical resistance to the load for specimens with different fiber volume fractions are quite different,which provide an important guide for the manufacture of conductive and intrinsically smart carbon fiber composite.

  2. Utilizing wood wastes as reinforcement in wood cement composite bricks

    Directory of Open Access Journals (Sweden)

    Nusirat Aderinsola Sadiku

    2015-07-01

    Full Text Available This paper presents the research work undertaken to study the properties of Wood Cement Composite Bricks (WCCB from different wood wastes and cement / wood content. The WCBBs with nominal density of 1200 kg m-3 were produced from three tropical wood species and at varying cement and wood content of 2:1, 2.5:1 and 3:1 on a weight to weight basis. The properties evaluated were compressive strength, Ultra Pulse Velocity (UPV, water absorption (WA and thickness swelling (TS. The Compressive strength values ranged from 0.25 to 1.13 N mm-2 and UPV values ranged from 18753 to 49992 m s-1. The mean values of WA after 672 hours (28 days of water soaking of the WCCBs ranged from 9.50% to 47.13% where there were no noticeable change in the TS of the bricks. The observed density (OD ranged from 627 to 1159 kg m-3. A. zygia from the three wood/cement content were more dimensionally stable and better in compressive strength than the other two species where T. scleroxylon had the best performance in terms of UPV. All the properties improved with increasing cement content. WCCBs at 3.0:1 cement/wood content are suitable for structural application such as panelling, ceiling and partitioning

  3. Biological Evaluation of α-TCP/TTCP Composite Bone Cement

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    α-tricalcium phosphate(α-TCP)/tetracalcium phosphate(TTCP) composite bone cement had good hydration characteristic.In our system,α-TCP/TTCP powder mixture was mixed with water at a powder/liquid (P/L) ratio of 1.50g*mL-1.The setting time could be adjusted,the maximum compressive strength was 45.36MPa,and the hydration product was hydroxyapatite (HAP).In vitro biological simulated experiments indicate that α-TCP/TTCP bone cement has α certain dissolubility.The hardened product is mainly HAP after soaking in simulated body fluid (SBF) for 10 weeks.The results of in vitro test and animal experiments and SEM analyses show that no local or general toxicity response,no muscle stimulation,no haemolysis,no cruor,no inflammatory reaction and no exclusion response are caused by α-TCP/TTCP cement, which can be contributed to bone tissue spreading and impinging.α-TCP/TTCP cement hydrated and hardened continually in vivo.The materials fused with host bone together with implanting time prolonging.Therefore,it is believed that α-TCP/TTCP composite bone cement has a high biocompatibility and bioactivity,a certain biodegradation and good osteogenesis as well.

  4. Tensile and Flexural Properties of Cement Composites Reinforced with Flax Nonwoven Fabrics

    Directory of Open Access Journals (Sweden)

    Josep Claramunt

    2017-02-01

    Full Text Available The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility.

  5. Preparation and Properties of a New Composite of Epoxy Emulsion(EEM)Modified Cement

    Institute of Scientific and Technical Information of China (English)

    XIAO Liguang; JIN Yujie; GU Lixia

    2009-01-01

    High performance cement based composite materials was prepared by adding epoxy emulsion.The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory.This epoxy emulsion has advantages over other emulsion,such as dehydrated slightly,and well film formation abilities.The mechanical properties, corruptness resistance and structure of ep-oxy emulsion modified cement mortars were studied.Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength.The corruptness resistance of all modified mortars is better than the unmodified mortar.The polymer film forms the bridge phases between the matrix and the aggregate regions,and forms a three-dimension structure in the cement hydration system,which improves the mechanical properties of modified mortars.

  6. Application of Granulated Blast Furnace Slag in Cement Composites Exposed to Biogenic Acid Attack

    Science.gov (United States)

    Kovalcikova, M.; Estokova, A.; Luptakova, A.

    2015-11-01

    The deterioration of cement-based materials used for the civil infrastructure has led to the realization that cement-based materials, such as concrete, must be improved in terms of their properties and durability. 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 corrosion of concrete. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to deterioration by aggressive chemicals. The paper is focused on the investigation of the influence of biogenic acid attack on the cement composites affected by bacteria Acidithiobacillus thiooxidans. The concrete specimens with 65 wt. % addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were studied. The experiments proceeded during 150 days under model laboratory conditions. The pH values and chemical composition of leachates were measured after each 30- day cycle. The calcium and silicon contents in leachates were evaluated using X - ray fluorescence method (XRF). Summarizing the results, the 65% wt. addition of antimicrobial activated granulated blast furnace slag was not confirmed to be more resistant.

  7. 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.

  8. 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.

  9. Constraining the Texture and Composition of Pore-Filling Cements at Gale Crater, Mars

    Science.gov (United States)

    Siebach, K. L.; Grotzinger, J. P.; McLennan, S. M.; Hurowitz, J. A.; Ming, D. W.; Vaniman, D. T.; Rampe, E. B.; Blaney, D. L.; Kah, L. C.

    2015-01-01

    The Mars Science Laboratory (MSL) rover Curiosity has encountered a wide variety of sedimentary rocks deposited in fluvio-lacuestrine sequences at the base of Gale Crater. The presence of sedimentary rocks requires that initial sediments underwent diagenesis and were lithified. Lithification involves sediment compaction, cementation, and re-crystallization (or authigenic) processes. Analysis of the texture and composition of the cement can reveal the environmental conditions when the cements were deposited, enabling better understanding of early environments present within Gale Crater. The first step in lithification is sediment compaction. The Gale crater sediments do not show evidence for extensive compaction prior to cementation; the Sheepbed mudstone in Yellowknife Bay (YKB) has preserved void spaces ("hollow nodules"), indicating that sediments were cemented around the hollow prior to compaction, and conglomerates show imbrication, indicating minimal grain reorganization prior to lithification. Furthermore, assuming the maximum burial depth of these sediments is equivalent to the depth of Gale Crater, the sediments were never under more than 1 kb of pressure, and assuming a 15 C/km thermal gradient in the late Noachian, the maximum temperature of diagenesis would have been approximately 75 C. This is comparable to shallow burial diagenetic conditions on Earth. The cementation and recrystallization components of lithification are closely intertwined. Cementation describes the precipitation of minerals between grains from pore fluids, and recrystallization (or authigenesis) is when the original sedimentary mineral grains are altered into secondary minerals. The presence of authigenic smectites and magnetite in the YKB formation suggests that some recrystallization has taken place. The relatively high percentage of XRD-amorphous material (25-40%) detected by CheMin suggests that this recrystallization may be limited in scope, and therefore may not contribute

  10. 电磁改性谐振水泥基复合材料的吸波性能研究%Research on absorbing properties of electromagnetic modified resonance-cement-based composite

    Institute of Scientific and Technical Information of China (English)

    国爱丽; 高日

    2012-01-01

    利用涂挂法,分别在粉煤灰漂珠和闭孔珍珠岩表面涂挂石墨和铁氧体,通过扫描电镜对比改性前后漂珠和珍珠岩表面的微观变化.研究表明石墨和铁氧体在连续釉化面与特殊蜂窝结构的相间的珍珠岩颗粒表面分布均匀,形成了谐振腔吸波体.改性漂珠和珍珠岩分别与水泥基材料复合,形成吸波水泥基复合材料.采用RCS法测量各复合水泥基材料对S~C波段和X~Ku波段的电磁波反射率,研究复合水泥基材料的吸波效能.研究表明与涂挂法改性漂珠相比,涂挂法改性闭孔珍珠岩能有效提高水泥基材料的吸波效能,拓宽了一10dB带宽,具有进一步实际应用研究的意义.%Fly ash floating beads and closed cell perlite were coated by graphite and ferrite respectively, and then it was compared of the microscopic changes of the surface of fly ash floating beads and closed cell before and after modification by SEM. Results show that graphite and ferrite, respectively, distributed uniformly on closed cell perlite surface, in which continuous glaze surface and special honeycomb structures distribute alternately and formed the good performance resonant absorber. Modified ash floating beads and closed cell perlite mixed with cement-based materials to form cement-based absorbing composites, and then it was measured that radar reflectivity of the cement-based absorbing composites in S-C and X-Ku by using RCS to study the absorbing performance. The results show that compared with the modified fly ash floating beads by coating, the modified closed cell perlite by coating was more effective to improve the absorbing properties of the cement-based composites, and broadened —10dB bandwidth. It is significance to further the practical application of the cement-based composites.

  11. The effect of composition on mechanical properties of brushite cements.

    Science.gov (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan

    2014-01-01

    Due to a fast setting reaction, good biological properties, and easily available starting materials, there has been extensive research within the field of brushite cements as bone replacing material. However, the fast setting of brushite cement gives them intrinsically low mechanical properties due to the poor crystal compaction during setting. To improve this, many additives such as citric acid, pyrophosphates, and glycolic acid have been added to the cement paste to retard the crystal growth. Furthermore, the incorporation of a filler material could improve the mechanical properties when used in the correct amounts. In this study, the effect of the addition of the two retardants, disodium dihydrogen pyrophosphate and citric acid, together with the addition of β-TCP filler particles, on the mechanical properties of a brushite cement was investigated. The results showed that the addition of low amounts of a filler (up to 10%) can have large effects on the mechanical properties. Furthermore, the addition of citric acid to the liquid phase makes it possible to use lower liquid-to-powder ratios (L/P), which strongly affects the strength of the cements. The maximal compressive strength (41.8MPa) was found for a composition with a molar ratio of 45:55 between monocalcium phosphate monohydrate and beta-tricalcium phosphate, an L/P of 0.25ml/g and a citric acid concentration of 0.5M in the liquid phase.

  12. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. 21 CFR 888.3100 - Ankle joint metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... cemented prosthesis. 888.3100 Section 888.3100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF... Ankle joint metal/composite semi-constrained cemented prosthesis. (a) Identification. An ankle joint metal/composite semi-constrained cemented prosthesis is a device intended to be implanted to replace...

  15. 21 CFR 888.3340 - Hip joint metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... cemented prosthesis. 888.3340 Section 888.3340 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF... Hip joint metal/composite semi-constrained cemented prosthesis. (a) Identification. A hip joint metal/composite semi-constrained cemented prosthesis is a two-part device intended to be implanted to replace...

  16. Use of coir pith particles in composites with Portland cement.

    Science.gov (United States)

    Brasileiro, Gisela Azevedo Menezes; Vieira, Jhonatas Augusto Rocha; Barreto, Ledjane Silva

    2013-12-15

    Brazil is the fourth largest world's producer of coconut (Cocos nucifera L.). Coconut crops generate several wastes, including, coir pith. Coir pith and short fibers are the byproducts of extracting the long fibers and account for approximately 70% of the mature coconut husk. The main use of coir pith is as an agricultural substrate. Due to its shape and small size (0.075-1.2 mm), this material can be considered as a particulate material. The aim of this study was to evaluate the use of coir pith as an aggregate in cementitious composites and to evaluate the effect of the presence of sand in the performance of these composites. Some composites were produced exclusively with coir pith particles and other composites with coir pith partially substituting the natural sand. The cementitious composites developed were tested for their physical and mechanical properties and characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy to evaluate the effect of coir pith particles addition in cement paste and sand-cement-mortar. The statistical significance of the results was evaluated by one-way analysis of variance (ANOVA) test followed by multiple comparisons of the means by Tukey's test that showed that the composites with coir pith particles, with or without natural sand, had similar mechanical results, i.e., means were not statistically different at 5% significance level. There was a reduction in bulk density and an improved post-cracking behavior in the composites with coir pith particles compared to conventional mortar and to cement paste. These composites can be used for the production of lightweight, nonstructural building materials, according to the values of compressive strength (3.97-4.35 MPa) and low bulk density (0.99-1.26 g/cm(3)).

  17. Polymer-Cement Composites Containing Waste Perlite Powder

    Directory of Open Access Journals (Sweden)

    Paweł Łukowski

    2016-10-01

    Full Text Available Polymer-cement composites (PCCs are materials in which the polymer and mineral binder create an interpenetrating network and co-operate, significantly improving the performance of the material. On the other hand, the need for the utilization of waste materials is a demand of sustainable construction. Various mineral powders, such as fly ash or blast-furnace slag, are successfully used for the production of cement and concrete. This paper deals with the use of perlite powder, which is a burdensome waste from the process of thermal expansion of the raw perlite, as a component of PCCs. The results of the testing of the mechanical properties of the composite and some microscopic observations are presented, indicating that there is a possibility to rationally and efficiently utilize waste perlite powder as a component of the PCC. This would lead to creating a new type of building material that successfully meets the requirements of sustainable construction.

  18. Piezoelectric, dielectric, and ferroelectric properties of 0-3 ceramic/cement composites

    Science.gov (United States)

    Xin, Cheng; Shifeng, Huang; Jun, Chang; Zongjin, Li

    2007-05-01

    The sulphoaluminate cement and a piezoelectric ceramic, 0.08Pb(Li1/4Nb3/4)O3.0.47PbTiO3.0.45PbZrO3[P(LN)ZT], were used to fabricate 0-3 cement based piezoelectric composites. The piezoelectric, dielectric, and ferroelectric properties of the composites were mainly investigated. The results indicate that the piezoelectric strain factor d33 increases as the P(LN)ZT volume fraction increases, which follows the cube model well. The dielectric constant ɛx and dielectric loss tan δ show similar trends with the d33. In the frequency range of 40-100 kHz, the dielectric constants of the composites decrease sharply, which is mainly attributed to interfacial polarization in the composite. Above 200 kHz, the cement-based piezoelectric composites exhibit good dielectric-frequency stability. Hysteresis measurements indicate that the composites exhibit typical ferroelectric hysteresis loops at room temperature. The remanent polarization Pr and the coercive field Ec of the composites increase as the P(LN)ZT volume fraction increases. Meanwhile, the remnant polarizations Pr shows little asymmetric characterization.

  19. 防水剂对受荷开裂下PVA-SHCC渗透性能的影响%Influences by waterproofing agent on impermeability of strain hardening cement-based composite on the loading state

    Institute of Scientific and Technical Information of China (English)

    高嵩; 李秋义; 金祖权; 吴本清

    2014-01-01

    受荷载时产生的多重裂缝是SHCC的薄弱部位和外界介质侵入的通路,会加速了结构的耐久性劣化。而对SHCC进行防水处理是提高耐久性的有效措施,研究了防水剂对PVA-SHCC试件抗氯离子渗透性能和受荷开裂下的试件水毛细吸收系数的影响。试验结果表明:对PVA-SHCC进行防水处理可以显著降低试件中的氯离子扩散系数,外涂防水剂试件的氯离子扩散系数只是不掺防水剂的试样的8%到20%,内掺防水剂的试件的氯离子扩散系数只是不掺防水剂试件的60%左右。试件在受荷开裂下的抗渗性比未施加应力试件的抗渗性差,采取防水处理可以有效提高受荷试件的抗渗性能,外涂和内掺处理方式对提高抗渗的效果相差不大。SHCC渗透性能的研究可以为SHCC结构耐久性研究和服役寿命预测提供重要参考。%Cracks in strain hardening cement-based composite(SHCC)structures caused by mechanical load are the weakness under ser-vice condition,and they provide pathways for access of water and solution containing chloride into strain hardening cement-based com-posite. In the present paper,the influences by waterproofing agent to chloride resisting performances and capillary suction coefficient of specimen on the loading state are experimental studied.The experimental results indicate that water proof treatment can significantly reduce the chloride diffusion coefficient.The chloride diffusion coefficient of the specimen by external application of waterproofing agent is only between 8%and 20%of normal strain hardening cement-based composite specimen. And which of blended with waterproofing agent is ap-proximately 60%of normal strain hardening cement-based composite.Furthermore,the impermeability of strain hardening cement-based composite specimen under the loading state is much worse than that of unloaded strain hardening cement-based composite specimen.The water proofing treatments are

  20. 水泥基复合保温材料的防水性能研究%Study on the waterproofing properties of thermal insulation cement-based composite materials

    Institute of Scientific and Technical Information of China (English)

    李静; 李国忠

    2015-01-01

    Polystyrene granules (EPS) for lightweight aggregate and cement for cementing material, while adding a variety of additives, were used to prepare cement-based composite thermal insulation materials by the method of vibration molding. The effects of different waterproof agent on water absorption, flexural softening resistance coefficient and strength of cement-based composite thermal insulation materials were studied contrastively by adding emulsified stearic acid and emulsified composite waterproofing agent, and the related mechanisms were analyzed. Results showed that the waterproofing effect and strengthen effect of emulsified composite waterproofing agent is superior to emulsified stearic acid, when the content of emulsified stearic acid and emulsified composite waterproofing agent are 5% and 5%, respectively, the 2h, 24h water absorption of samples are 20.59%, 47.64%and 15.53%, 34.53%, the flexural softening resistance coefficient of samples are 0.71 and 0.75, the flexural and compressive strength of samples are 0.32MPa, 0.42MPa and 0.35MPa, 0.47MPa respectively.%以聚苯乙烯颗粒(EPS)为轻骨料、水泥为胶凝材料,同时掺加多种外加剂,经振动成型制备水泥基复合保温材料,通过掺加乳化硬脂酸和乳化复合防水剂,对比研究了不同防水剂对水泥基复合保温材料吸水率、抗折软化系数和强度的影响,并对其相关作用机理进行了分析。结果表明:乳化复合防水剂的防水效果和增强效果均明显优于乳化硬脂酸,当乳化硬脂酸和乳化复合防水剂掺量分别为5%和5%时,试样的2 h、24 h吸水率分别为20.59%、47.64%和15.53%、34.53%,试样的抗折软化系数分别为0.71和0.75,试样的抗折、抗压强度分别为0.32 MPa、0.42 MPa和0.35 MPa、0.47 MPa。

  1. 利用原状磷石膏制备石膏基复合胶凝材料的力学性能%Mechanical property of phosphogypsum based composite cementing material prepared with original phosphogypsum

    Institute of Scientific and Technical Information of China (English)

    张毅; 王小鹏; 李东旭

    2011-01-01

    Original untreated phosphogypsum was used to prepare a kind of phosphogypsum based cementing material, the mechanical property of the prepared material was tested and effects of quicklime content, water/cement ratio and molding pressure on the mechanical property were investigated. The results showed that with the quicklime content of 4%, the phosphogypsum slag composite cementing material had a good mechanical property, slag power had a positive correlation with the mechanical property of the phosphogypsum fly ash composite cementing material, and the mechanical property of the phosphogypsum slag boiler slag composite cementing material decreased as the molding pressure was greater than 3 MPa. Compared with the specimens prepared by casting molding method, the total porosity value of the specimens prepared under 5 MPa molding pressure was larger, especially for the volume fraction of more than 200 nm pore. Its microstructure would be destroyed, thus its mechanical property was decreased.%以未经处理的原状磷石膏制备磷石膏基复合胶凝材料,测试磷石膏基复合胶凝材料的力学性能,考察生石灰的掺量、水灰比以及成型压力对磷石膏基复合胶凝材料力学性能的影响.结果表明:当生石灰掺量为4%时,磷石膏-矿渣复合胶凝材料具有较好的力学性能,矿渣微粉对磷石膏-粉煤灰复合胶凝材料的力学性能有增强作用.对于磷石膏-矿渣-炉渣复合胶凝材料,当成型压力超过3MPa时,制备的材料力学性能明显下降.同浇注成型试样相比较,在5MPa成型压力下的压实成型试样,材料孔隙率提高,特别对于200nm以上孔所占体积分数来说,其所占体积分数要远远高于浇注成型试样,导致了材料微观结构劣化,力学性能变差.

  2. Antibacterial and bioactive composite bone cements containing surface silver-doped glass particles.

    Science.gov (United States)

    Miola, Marta; Fucale, Giacomo; Maina, Giovanni; Verné, Enrica

    2015-10-20

    A bioactive silica-based glass powder (SBA2) was doped with silver (Ag(+)) ions by means of an ion-exchange process. Scanning electron microscopy (SEM), energy dispersion spectrometry (EDS) and x-ray diffraction (XRD) evidenced that the glass powder was enriched with Ag(+) ions. However, a small amount of Ag2CO3 precipitated with increased Ag concentrations in the exchange solution. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of Ag-SBA2 towards Staphylococcus aureus were also evaluated and were respectively 0.05 mg ml(-1) and 0.2 mg ml(-1). Subsequently, Ag-SBA2 glass was used as filler (30%wt) in a commercial formulation of bone cement (Simplex(™) P) in order to impart both antibacterial and bioactive properties. The composite bone cement was investigated in terms of morphology (using SEM) and composition (using EDS); the glass powder was well dispersed and exposed on the cement surface. Bioactivity tests in simulated body fluid (SBF) evidenced the precipitation of hydroxyapatite on sample surfaces. Composite cement demonstrated antibacterial properties and a compressive strength comparable to the commercial formulation.

  3. Microshear bond strength between restorative composites and resin cements

    Directory of Open Access Journals (Sweden)

    Rubens Nazareno GARCIA

    2008-08-01

    Full Text Available Introduction and objective: The techniques of adhesive cementationhave been widely used in dental restoration. The purpose of this studywas to evaluate the microshear bond strength between restorativecomposites and resin cements. Material and methods: Twenty composites blocks were prepared in order to obtain a flat surface, using 600-grid sandpaper. The samples were randomly divided in four groups(n=15 according to the experimental groups: [1] Z250 block + Single Bond + cylinder of RelyX ARC; [2] Z250 block + Single Bond + cylinder of Panavia F; [3] Clearfil AP-X block + Clearfil SE Bond adhesive + cylinder of RelyX ARC; [4] Clearfil AP-X block + Clearfil SE Bond adhesive + cylinder of Panavia F. The adhesive systems and the resin cements were applied according to the experimental groups, using a Tygon matrix.The samples were stored in distilled water at 37±2ºC for 24 hours.Microshear bond strengths were determined using an apparatus attached to an Instron universal testing machine at a crosshead speed of 0.5 mm/minute. Results: The results obtained in MPa (SD were statistically analyzed (ANOVA and Tukey test, p<0.05, and showed the following results: [1] 39.76 (5.34; [2] 45.01 (8.53; [3] 46.39 (9.22; [4]45.78 (9.06.There was no statistically significant difference between groups [1] and [2]; and between groups [3] and [4]. However, there was statistically significant difference between groups [1] and [3]. Conclusion:When Clearfil AP-X block was used with Clearfil SE Bond adhesive or RelyX resin cement, the microshear bond strength values were higher.The results suggest that in the union of the resin cements to the restorative composites, hydrophobic adhesives are necessary.

  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. Production of bone cement composites: effect of fillers, co-monomer and particles properties

    Energy Technology Data Exchange (ETDEWEB)

    Santos Junior, J.G.F.; Melo, P.A.; Pinto, J.C., E-mail: jjunior@peq.coppe.ufrj.b, E-mail: melo@peq.coppe.ufrj.b, E-mail: pinto@peq.coppe.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia. (PEQ/COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Quimica; Pita, V.J.R.R., E-mail: vjpita@ima.ufrj.b [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Eloisa Mano; Nele, M. [Universidade Federal do Rio de Janeiro (EQ/UFRJ), RJ (Brazil). Escola de Quimica

    2011-04-15

    Artificial bone cements (BCs) based on poly(methyl methacrylate) (PMMA) powders and methyl methacrylate (MMA) liquid monomer also present in their formulation small amounts of other substances, including a chemical initiator compound and radiopaque agents. Because inadequate mixing of the recipe components during the manufacture of the bone cement may compromise the mechanical properties of the final pieces, new techniques to incorporate the fillers into the BC and their effect upon the mechanical properties of BC pieces were investigated in the present study. PMMA powder composites were produced in situ in the reaction vessel by addition of X-ray contrasts to the reacting MMA mixture. It is shown that this can lead to much better mechanical properties of test pieces, when compared to standard bone cement formulations, because enhanced dispersion of the radiopaque agents can be achieved. Moreover, it is shown that the addition of hydroxyapatite (HA) and acrylic acid (AA) to the bone cement recipe can be beneficial for the mechanical performance of the final material. It is also shown that particle morphology can exert a tremendous effect upon the performance of test pieces, indicating that the suspension polymerization step should be carefully controlled when optimization of the bone cement formulation is desired. (author)

  6. 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.

  7. 21 CFR 888.3500 - Knee joint femorotibial metal/composite semi-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/composite semi... § 888.3500 Knee joint femorotibial metal/composite semi-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite semi-constrained cemented prosthesis is a...

  8. 21 CFR 888.3490 - Knee joint femorotibial metal/composite non-constrained cemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Knee joint femorotibial metal/composite non... § 888.3490 Knee joint femorotibial metal/composite non-constrained cemented prosthesis. (a) Identification. A knee joint femorotibial metal/composite non-constrained cemented prosthesis is a...

  9. Characterization of a new composite PMMA-HA/Brushite bone cement for spinal augmentation.

    Science.gov (United States)

    Aghyarian, Shant; Rodriguez, Lucas C; Chari, Jonathan; Bentley, Elizabeth; Kosmopoulos, Victor; Lieberman, Isador H; Rodrigues, Danieli C

    2014-11-01

    Calcium phosphate fillers have been shown to increase cement osteoconductivity, but have caused drawbacks in cement properties. Hydroxyapatite and Brushite were introduced in an acrylic two-solution cement at varying concentrations. Novel composite bone cements were developed and characterized using rheology, injectability, and mechanical tests. It was hypothesized that the ample swelling time allowed by the premixed two-solution cement would enable thorough dispersion of the additives in the solutions, resulting in no detrimental effects after polymerization. The addition of Hydroxyapatite and Brushite both caused an increase in cement viscosity; however, these cements exhibited high shear-thinning, which facilitated injection. In gel point studies, the composite cements showed no detectable change in gel point time compared to an all-acrylic control cement. Hydroxyapatite and Brushite composite cements were observed to have high mechanical strengths even at high loads of calcium phosphate fillers. These cements showed an average compressive strength of 85 MPa and flexural strength of 65 MPa. A calcium phosphate-containing cement exhibiting a combination of high viscosity, pseudoplasticity and high mechanical strength can provide the essential bioactivity factor for osseointegration without sacrificing load-bearing capability.

  10. Effect of carbon nanotube on physical and mechanical properties of natural fiber/glass fiber/cement composites

    Institute of Scientific and Technical Information of China (English)

    Hamed Younesi Kordkheili; Shokouh Etedali Shehni; Ghorban Niyatzade

    2015-01-01

    The objective of this investigation was to introduce a cement-based composite of higher quality. For this purpose new hybrid nanocomposite from bagasse fiber, glass fiber and multi-wall carbon nanotubes (MWCNTs) were manufactured. The physical and mechanical proper-ties of the manufactured composites were measured according to standard methods. The properties of the manufactured hybrid nanocomposites were dramatically better than traditional composites. Also all the reinforced composites with carbon nanotube, glass fiber or bagasse fiber exhibited better properties rather than neat cement. The results indicated that bagasse fiber proved suitable for substitution of glass fiber as a reinforcing agent in the cement composites. The hybrid nanocomposite containing 10%glass fiber, 10%bagasse fiber and 1.5%MWCNTs was selected as the best compound.

  11. Laboratory Investigation on the Strength Gaining of Brick Aggregate Concrete Using Ordinary Portland Cement and Portland Composite Cement

    Directory of Open Access Journals (Sweden)

    Hoque M H, Numen E H, Islam N., Mohammed

    2014-05-01

    Full Text Available This study focused on the laboratory investigation of strength variation of brick aggregate concrete made with ordinary Portland cement (OPC and Portland composite cement (PCC.The investigation was conducted by testing concrete cylinder specimens at different ages of concrete with concrete mix ratios: 1:1.5:3 and 1:2:4 by volume and with water cement ratios=0.45 and 0.60. The test result reveals that at the early age, concrete composed with OPC attained larger compressive strength than the concrete made of PCC. However, in the later age concrete made with PCC achieved higher strength than OPC.

  12. 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.

  13. Interface and internal compatibility in a copper fibre cement composite

    Directory of Open Access Journals (Sweden)

    Kittl, P.

    1993-09-01

    Full Text Available This paper presents the mechanical behaviour of a compacted composite formed by short ductile copper fibres randomly distributed in portland cement matrix. The samples, a half with fibres and the other without them, were subjected to compression fatigue. So, 1 hertz and the value of stress corresponding to the 1% of the probability of fracture by gradual load were used. Diagrams of cumulative probability of fracture against cycles are obtained for both types of samples. Scanning electron microscopy shows that the mechanisms of fracture are different in each case. Samples of compacted neat-cement paste finish their life with a catastrophic fracture whereas samples of composite behave like a pseudoductile material devoid of catastrophic failure. The results are discussed and compared with the ones obtained by thermal shock and by the interface brittleness theory, as well as with the statistical theory of time-dependent fracture for cementitious materials subjected to cyclic loading. So, in the thermal shock microcracks are generated in the interface matrix-fibre which simultaneously act as emmitings and sumps of cracks whereas this does not occur in mechanical fatigue.

    Este trabajo presenta el comportamiento mecánico de un compuesto fabricado por compactación y constituido por fibras de cobre distribuidas aleatoriamente en una matriz de cemento portland. Las muestras, la mitad con fibras y la otra sin ellas, se sometieron a fatiga por compresión. El ciclo de carga fue de 1 hertz y la carga aplicada aquella correspondiente a la tensión asociada a un 1% de probabilidad de fractura cuando la carga se aplica gradualmente. Para ambos tipos de muestras se graficaron los diagramas de probabilidad acumulativa de fractura en función del número de ciclos. Con microscopía electrónica de barrido se observó que el mecanismo de fractura es diferente para cada tipo de muestras. Aquellas de pasta pura de cemento compactada terminaron su ciclo de

  14. Porous calcium phosphate-poly (lactic-co-glycolic) acid composite bone cement: A viable tunable drug delivery system.

    Science.gov (United States)

    Roy, Abhijit; Jhunjhunwala, Siddharth; Bayer, Emily; Fedorchak, Morgan; Little, Steve R; Kumta, Prashant N

    2016-02-01

    Calcium phosphate based cements (CPCs) are frequently used as bone void fillers for non-load bearing segmental bone defects due to their clinically relevant handling characteristics and ability to promote natural bone growth. Macroporous CPC scaffolds with interconnected pores are preferred for their ability to degrade faster and enable accelerated bone regeneration. Herein, a composite CPC scaffold is developed using newly developed resorbable calcium phosphate cement (ReCaPP) formulation containing degradable microspheres of bio-compatible poly (lactic-co-glycolic acid) (PLGA) serving as porogen. The present study is aimed at characterizing the effect of in-vitro degradation of PLGA microspheres on the physical, chemical and structural characteristics of the composite cements. The porosity measurements results reveal the formation of highly interconnected macroporous scaffolds after degradation of PLGA microspheres. The in-vitro characterizations also suggest that the degradation by products of PLGA reduces the pH of the local environment thereby increasing the dissolution rate of the cement. In addition, the in-vitro vancomycin release from the composite CPC scaffold suggests that the drug association with the composite scaffolds can be tuned to achieve control release kinetics. Further, the study demonstrates control release lasting for longer than 10weeks from the composite cements in which vancomycin is encapsulated in PLGA microspheres.

  15. Effect of surfactants on pressure-sensitivity of CNT filled cement mortar composites

    Science.gov (United States)

    Han, Baoguo; Yu, Xun

    2014-11-01

    Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) were used as surfactants to disperse multi-walled carbon nanotubes (MWNT) in cement mortar and fabricate pressure-sensitive carbon nanotubes filled cement mortar composites. The pressure-sensitivity of cement mortar composites with different concentrations of MWNT and different surfactants was explored under repeated loading and impulsive loading, respectively. Experimental results indicate that the response of the electrical resistance of composites with NaDDBS to external force is more stable and sensitive than that of composites with SDS. Therefore, NaDDBS has higher efficiency than SDS for the dispersion of MWNT in cement mortar, and it is an effective surfactant for fabricating MWNT filled cement mortar composites with superior pressure-sensitivity.

  16. Osteogenesis Capacity of a Novel BMP/α-TCP Bioactive Composite Bone Cement

    Institute of Scientific and Technical Information of China (English)

    YANG Wei-zhong; ZHOU Da-li; YIN Shao-ya; YIN Guang-fu; GAO Li-da; ZHANG Yun

    2004-01-01

    To improve the osteogenesis ability of α-tricalcium phosphate (α-TCP) bone cement,a novel BMP/α-TCP composite bone cement was prepared.By measuring the setting time and compressive strength,the hydration characteristic of bone cement was evaluated.Animal experiments including histological observation,radiographic investigation as well as digital image analyses reveal the difference of osteogenesis ability among BMP,α-TCP bone cement and BMP/α-TCP composite bone cement.Results show that α-TCP bone cement possesses excellent hydration and setting properties as well as high mechanical property.Comparison experiments show that BMP/α-TCP composite bone cement has a stronger osteogenesis ability.The gross observation of the implant site does not exhibit any inflammation or necrosis.Histological analyses reveal that the material has good osteointegration with host bone,and new bone formation is detected within the materials,which are degrading.Strong osteogenesis ability of the composite is due to not only the excellent osteoconductive potential but also the osteoinductive potential contributed by active BMP releasing and the material degradation.Large skull defect could be well-healed by filling BMP/α-TCP composite bone cement.This novel material proves itself to be an absorbable and bioactive bone cement with an osteogenesis ability.

  17. 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.

  18. 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...

  19. 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.

  20. 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...

  1. Electrical resistance stability of high content carbon fiber reinforced cement composite

    Institute of Scientific and Technical Information of China (English)

    YANG Zai-fu; TANG Zu-quan; LI Zhuo-qiu; QIAN Jue-shi

    2005-01-01

    The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50℃C, increases relatively by 4% when ambient temperature decreases from 15℃ to-20℃, and decreases relatively by 13% with temperature increasing by 88℃. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

  2. Microindentation of Polymethyl Methacrylate (PMMA Based Bone Cement

    Directory of Open Access Journals (Sweden)

    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.

  3. Optimization of fly ash as sand replacement materials (SRM) in cement composites containing coconut fiber

    Science.gov (United States)

    Nadzri, N. I. M.; Jamaludin, S. B.; Mazlee, M. N.; Jamal, Z. A. Z.

    2016-07-01

    The need of utilizing industrial and agricultural wastes is very important to maintain sustainability. These wastes are often incorporated with cement composites to improve performances in term of physical and mechanical properties. This study presents the results of the investigation of the response of cement composites containing coconut fiber as reinforcement and fly ash use as substitution of sand at different hardening days. Hardening periods of time (7, 14 and 28 days) were selected to study the properties of cement composites. Optimization result showed that 20 wt. % of fly ash (FA) is a suitable material for sand replacement (SRM). Meanwhile 14 days of hardening period gave highest compressive strength (70.12 MPa) from the cement composite containing 9 wt. % of coconut fiber and fly ash. This strength was comparable with the cement without coconut fiber (74.19 MPa) after 28 days of curing.

  4. Effect of retardants on the heat release during setting of bone cement-type composites

    Directory of Open Access Journals (Sweden)

    D. Pijocha

    2011-12-01

    Full Text Available Purpose: The aim of this work was to investigate the influence of retardants on the heat release during setting of the new hydroxyapatite (HA - magnesium phosphate cement (MPC - calcium sulphate hemihydrate (CSH composites.Design/methodology/approach: We used the calorimetric method to measure the temperature effect of setting reaction in these new composites. Microstructure observations by means of scanning electron microscopy was also performed.Findings: The decrease in maximum temperature reached during hardening process with use of different retardants was confirmed.Research limitations/implications: Biological evaluation and in vitro physico-chemical tests of the novel composites need to be done.Practical implications: The highly exothermic setting reaction of cement composites based on MPC can be lowered to avoid harmful necrosis of the tissues surrounding the implant material.Originality/value: Detailed studies on the heat release during setting of HA - MPC - CSH composites were performed for a first time, giving an opportunity to choose the best composition for further studies.

  5. Microstructure of a cement matrix composite reinforced with polypropylene fibers

    Directory of Open Access Journals (Sweden)

    Rincón, J. M.

    2004-06-01

    Full Text Available The present investigation deals with the microstructural characterization of a composite material, which is comprised of polypropylene fibers in an cement matrix, by means of environmental scanning electron microscopy (ESEM and field emission scanning electron microscopy (FESEM. The microstructure of the different phases that compose the matrix is very heterogeneous, though there is a uniform distribution of the fibers inside it. The surface of this composite is different after setting, cured and hardening depending if the zone is or not in touch with the walls of the mould. The interface between the different crystalline regions of the cement matrix and the dispersed fibers shows compatibility between the matrix and the polymeric fibers. The mechanical properties (compression and bending strength have also been evaluated. The use of melamine formaldehyde as additive leads to a reinforcement of the cement matrix and to the improvement of the mechanical properties.

    Se ha llevado a cabo una observacíón microestructural detallada de un material compuesto de fibras de polipropileno embebidas en una matriz de cemento usando los nuevos tipos de microscopía electrónica de barrido, tales como: un microscopio electrónico medioambiental (acrónimo en inglés: ESEM y uno de emisión de campo (acrónimo en inglés: FESEM. La microestructura de las diferentes fases que componen la matriz es muy heterogénea, aunque hay una distribución uniforme de las fibras dentro de ellas. La superficie de este material compuesto es diferente después del fraguado, curado y endurecimiento según qué zonas estén o no en contacto con las paredes del molde. La interfase entre las diferentes fases cristalinas de la matriz de cemento y las fibras dispersadas se ha observado a diferentes aumentos, comprobándose compatibilidad entre la matriz y las fibras poliméricas. Las propiedades de resistencia mecánica (tanto a flexión como a compresión han sido tambi

  6. Electrical Resistance and Microstructure of Latex Modified Carbon Fiber Reinforced Cement Composites

    Institute of Scientific and Technical Information of China (English)

    WEI Jian; CHENG Feng; YUAN Hudie

    2012-01-01

    The electrical resistance,flexural strength,and microstructure of carbon fiber reinforced cement composites (CFRC) were improved greatly by adding water-redispersible latex powder.The electrical resistance of CFRC was investigated by two-probe method.The input range of CFRC based strain sensors was therefore increased,whereas electrical resistance was increased and remained in the perfect range of CFRC sensors.The analysis of scanning electron microscopy indicated that elastic latex bridges and a latex layer existed among the interspaces of the adjacent cement hydration products which were responsible for the enhancement of the flexural strength and electrical resistance.The formation mechanism of the elastic latex bridges was also discussed in detail.The continuous moving of two opposite interfaces of the latex solution-air along the interspaces of the adjacent hydrated crystals or colloids was attributed to the formation of the elastic latex bridges.

  7. Effect of surface treatment of carbon nanotubes on mechanical properties of cement composite

    Directory of Open Access Journals (Sweden)

    KONDAKOV Alexander Igorevich

    2014-08-01

    Full Text Available The aim of the paper is to explore the influence of the carbon nanotubes functionalized by oxygen groups on the physical and mechanical properties of cement composites. Advantages and disadvantages of the main methods for the homogeneous distribution of carbon nanotubes (CNTs in solution are discussed. A method for covalent functionalization of CNTs is described. An acid-base titration and dispersion analysis of solutions containing functionalized carbon nanotubes (f-CNTs was performed. The research data made it possible to propose new technology of preparation of modified concrete. The results of the work can be used for designing of the additives commonly used in the construction industry, as well as for further studies of the effects of CNTs on the physical and mechanical and structural properties of building materials. Efficient modification of cement composite with f-CNTs was achieved at the concentration of f-CNTs ranging from 0.0004% to 0.0008% by weight of the binder. The observed increase of the concrete mechanical properties is explained by the fact that the CNTs act as nucleation centers for the cement hydration products.

  8. Simulations reveal the role of composition into the atomic-level flexibility of bioactive glass cements.

    Science.gov (United States)

    Tian, Kun Viviana; Chass, Gregory A; Di Tommaso, Devis

    2016-01-14

    Bioactive glass ionomer cements (GICs), the reaction product of a fluoro-alumino-silicate glass and polyacrylic acid, have been in effective use in dentistry for over 40 years and more recently in orthopaedics and medical implantation. Their desirable properties have affirmed GIC's place in the medical materials community, yet are limited to non-load bearing applications due to the brittle nature of the hardened composite cement, thought to arise from the glass component and the interfaces it forms. Towards helping resolve the fundamental bases of the mechanical shortcomings of GICs, we report the 1st ever computational models of a GIC-relevant component. Ab initio molecular dynamics simulations were employed to generate and characterise three fluoro-alumino-silicate glasses of differing compositions with focus on resolving the atomic scale structural and dynamic contributions of aluminium, phosphorous and fluorine. Analyses of the glasses revealed rising F-content leading to the expansion of the glass network, compression of Al-F bonding, angular constraint at Al-pivots, localisation of alumino-phosphates and increased fluorine diffusion. Together, these changes to the structure, speciation and dynamics with raised fluorine content impart an overall rigidifying effect on the glass network, and suggest a predisposition to atomic-level inflexibility, which could manifest in the ionomer cements they form.

  9. The effect of porosity on drug release kinetics from vancomycin microsphere/calcium phosphate cement composites.

    Science.gov (United States)

    Schnieders, Julia; Gbureck, Uwe; Vorndran, Elke; Schossig, Michael; Kissel, Thomas

    2011-11-01

    The influence of porosity on release profiles of antibiotics from calcium phosphate composites was investigated to optimize the duration of treatment. We hypothesized, that by the encapsulation of vancomycin-HCl into biodegradable microspheres prior admixing to calcium phosphate bone cement, the influence of porosity of the cement matrix on vancomycin release could be reduced. Encapsulation of vancomycin into a biodegradable poly(lactic co-glycolic acid) copolymer (PLGA) was performed by spray drying; drug-loaded microparticles were added to calcium phosphate cement (CPC) at different powder to liquid ratios (P/L), resulting in different porosities of the cement composites. The effect of differences in P/L ratio on drug release kinetics was compared for both the direct addition of vancomycin-HCl to the cement liquid and for cement composites modified with vancomycin-HCl-loaded microspheres. Scanning electron microscopy (SEM) was used to visualize surface and cross section morphology of the different composites. Brunauer, Emmett, and Teller-plots (BET) was used to determine the specific surface area and pore size distribution of these matrices. It could be clearly shown, that variations in P/L ratio influenced both the porosity of cement and vancomycin release profiles. Antibiotic activity during release study was successfully measured using an agar diffusion assay. However, vancomycin-HCl encapsulation into PLGA polymer microspheres decreased porosity influence of cement on drug release while maintaining antibiotic activity of the embedded substance.

  10. PLGA microsphere/calcium phosphate cement composites for tissue engineering: in vitro release and degradation characteristics.

    NARCIS (Netherlands)

    Habraken, W.J.E.M.; Wolke, J.G.C.; Mikos, A.G.; Jansen, J.A.

    2008-01-01

    Bone cements with biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres have already been proven to provide a macroporous calcium phosphate cement (CPC) during in situ microsphere degradation. Furthermore, in vitro/in vivo release studies with these PLGA microsphere/CPC composites (PLGA/CP

  11. Study of the relation between hydrated portland cement composition and leaching resistance

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    1998-01-01

    The present paper addresses cement compositions that have an optimal resistance against acid attack and hence, low leaching rates and optimal waste containment. To this end a shrinking core leaching model is used that describes the leaching of metals from a cement sample. This process is directly re

  12. Research on the nanolevel influence of surfactants on structure formation of the hydrated Portland cement compositions

    Directory of Open Access Journals (Sweden)

    Guryanov Alexander

    2016-01-01

    Full Text Available The research of the structure formation process on a nanolevel of the samples of hydrated Portland cement compositions containing the modifying additives has been conducted with the help of small angle neutron scattering method. Carbonate and aluminum alkaline slimes as well as the complex additives containing surfactants were used as additives. The influence of slimes and surfactants on structural parameters change of Portland cement compositions of the average size of the disseminating objects, fractal dimension samples is considered. These Portland cement compositions are shown to be fractal clusters.

  13. Concretes with ternary composite cements. Part III: multicriteria optimization

    Directory of Open Access Journals (Sweden)

    Irassar, E. F.

    2007-06-01

    Full Text Available Optimization methods are tools of vital importance in composite material design, where large numbers of components and design criteria must be taken into account. The formulation of today’s separately milled custommade cements is a clear example of just such a case, for the components must be proportioned to yield mortars and concretes with the proper balance of durability, strength, financial and environmental features. Multicriteria optimization has been used to develop many materials, although its application in cement formulation has yet to be explored. The present paper discusses the use of an objective function to jointly optimize sorptivity and compressive strength in limestone- (up to 20% and/or granulated blast furnace slag- (up to 20% additioned Portland cement concrete.Los métodos de optimización constituyen una herramienta de vital importancia en el diseño de materiales compuestos, donde la cantidad de componentes de la mezcla y los criterios de diseño que deben tenerse en cuenta en el proceso de fabricación son numerosos. En la actualidad, la formulación de un cemento a medida (tailor made a partir del proceso de molienda separada es un claro ejemplo de ello, pues las proporciones relativas de las componentes de la mezcla deben permitir luego obtener morteros y hormigones con el equilibrio justo entre los requerimientos durables, mecánicos, económicos y ecológicos que se soliciten. La optimización por multicriterios ha sido empleada en el desarrollo de diversos materiales, sin embargo, su aplicación en la formulación del cemento no ha sido aún explorada. En este trabajo se presenta la optimización conjunta de la capacidad de absorción y la resistencia a compresión de hormigones elaborados con cemento Portland con caliza (hasta un 20% y/o escoria granulada de alto horno (hasta un 20% utilizando la función objetivo.

  14. Reinforcing graphene oxide/cement composite with NH$_2$ functionalizing group

    Indian Academy of Sciences (India)

    M EBRAHIMIZADEH ABRISHAMI; V ZAHABI

    2016-08-01

    In this study, pure and NH$_2$-functionalized graphene oxide (GO) nanosheets have been added to the cement mortar with different weight percents (0.05, 0.10, 0.15, 0.20 and 0.25 wt%). In addition, the effects of functionalizing GO on the microstructure and mechanical properties (flexural/compressive strengths) of cement composite have been investigated for the first time. Scanning electron microscopy (SEM) images showed that GO filledthe pores and well dispersed in concrete matrix, whereas exceeding GO additive from 0.10 wt% caused the formation of agglomerates and microcracks. In addition, mercury intrusion porosimetry confirmed the significant effects of GO and functionalizing groups on filling the pores. NH2-functionalizing helped to improve the cohesion between GO nanosheets and cement composite. Compressive strengths increased from 39 MPa for the sample without GO to54.23 MPa for the cement composites containing 0.10 wt% of NH$_2$-functionalized GO. Moreover, the flexural strength increased to 23.4 and 38.4% by compositing the cement paste with 0.10 wt% of pure and NH$_2$-functionalized GO, compared to the sample without GO, respectively. It was shown that functionalizing considerably enhanced the mechanical properties of GO/cement composite due to the interfacial strength between calcium silicatehydrates (C-S-H) gel and functionalized GO nanosheets as observed in SEM images. The morphological results were in good agreement with the trend obtained in mechanical properties of GO/cement composites.

  15. Effect of indirect composite treatment microtensile bond strength of self-adhesive resin cements

    Science.gov (United States)

    Escribano, Nuria; Baracco, Bruno; Romero, Martin; Ceballos, Laura

    2016-01-01

    Background No specific indications about the pre-treatment of indirect composite restorations is provided by the manufacturers of most self-adhesive resin cements. The potential effect of silane treatment to the bond strength of the complete tooth/indirect restoration complex is not available.The aim of this study was to determine the contribution of different surface treatments on microtensile bond strength of composite overlays to dentin using several self-adhesive resin cements and a total-etch one. Material and Methods Composite overlays were fabricated and bonding surfaces were airborne-particle abraded and randomly assigned to two different surface treatments: no treatment or silane application (RelyX Ceramic Primer) followed by an adhesive (Adper Scotchbond 1 XT). Composite overlays were luted to flat dentin surfaces using the following self-adhesive resin cements: RelyX Unicem, G-Cem, Speedcem, Maxcem Elite or Smartcem2, and the total-etch resin cement RelyX ARC. After 24 h, bonded specimens were cut into sticks 1 mm thick and stressed in tension until failure. Two-way ANOVA and SNK tests were applied at α=0.05. Results Bond strength values were significantly influenced by the resin cement used (p0.05). All self-adhesive resin cements showed lower bond strength values than the total-etch RelyX ARC. Among self-adhesive resin cements, RelyX Unicem and G-Cem attained statistically higher bond strength values. Smartcem2 and Maxcem Elite exhibited 80-90% of pre-test failures. Conclusions The silane and adhesive application after indirect resin composite sandblasting did not improve the bond strength of dentin-composite overlay complex. Selection of the resin cement seems to be a more relevant factor when bonding indirect composites to dentin than its surface treatment. Key words:Bond strength, self-adhesive cement, silane, dentin, indirect composite. PMID:26855700

  16. Curing units' ability to cure restorative composites and dual-cured composite cements under composite overlay.

    Science.gov (United States)

    Park, Sung-Ho; Kim, Su-Sun; Cho, Yong-Sik; Lee, Chang-Kyu; Noh, Byng-Duk

    2004-01-01

    This study compared the efficacy of using conventional low-power density QTH (LQTH) units, high-power density QTH (HQTH) units, argon (Ar) laser and Plasma arc curing (PAC) units for curing dual-cured resin cements and restorative resin composites under a pre-cured resin composite overlay. The microhardness of the two types of restorative resins (Z100 and Tetric Ceram) and a dual-cured resin cement (Variolink II) were measured after they were light cured for 60 seconds in a 2 mm Teflon mold. The recorded microhardness was determined to be the optimum microhard-ness (OM). Either one of the two types of restorative resins (Z100, Tetric Ceram) or the dual cured resin cement (Variolink II) were placed under a 1.5-mm thick and 8 mm diameter pre-cured Targis (Vivadent/Ivoclar AG, Schaan, Liechtenstein) overlay. The specimens that were prepared for each material were divided into four groups depending upon the curing units used (HQTH, PAC, Laser or LQTH) and were further subdi-vided into subgroups according to light curing time. The curing times used were 30, 60, 90 and 120 seconds for HQTH; 12, 24, 36 and 48 seconds for the PAC unit; 15, 30, 45 and 60 for the Laser and 60, 120 or 180 seconds for the LQTH unit. Fifteen specimens were assigned to each sub- group. The microhardness of the upper and and lower composite surfaces under the Targis overlay were measured using an Optidur Vickers hardness-measuring instrument (Göttfert Feinwerktechnik GmbH, Buchen, Germany). In each material, for each group, a three-way ANOVA with Tukey was used at the 0.05 level of significance to compare the microhardnesses of the upper and lower composite surfaces and the previously measured OM of the material. From the OM of each material, 80% OM was calculated and the time required for the microhardness of the upper and lower surface of the specimen to reach 100% and 80% of OM was determined. In Z100 and Tetric Ceram, when the composites were light cured for 120 seconds using the HQTH lamp

  17. Synthesis of Chitosan-Hydroxyapatite Composites and Its Effect on the Properties of Bioglass Bone Cement

    Institute of Scientific and Technical Information of China (English)

    Jingxiao Liu; Fei Shi; Ling Yu; Liting Niu; Shanshan Gao

    2009-01-01

    Chitosan-hydroxyapatite (CS-HA) composite powders were synthesized via in situ co-precipitation method, through the reaction of Ca(NO3)2 and H3PO4 in the simulated body fluid (SBF) containing appropriate amount of chitosan. The thermal evolution, microstructure and morphology were studied by TG-DTA (thermogravimetry-differential thermal analysis), XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy) and TEM (transmission electron microscopy). The in vitro bioactivity test showed that the obtained CS-HA composites had higher capability of inducing calcium ions deposition. Effects of CS-HA composites on the bioactivity and compressive strength of bioglass bone cement were investigated. The results indicated that the bioactivity of bioglass bone cement could be improved further when CS-HA composite powders were added into the cement, and appropriate amount of CS-HA additive was favorable for compressive strength improvement of bioglass bone cement.

  18. 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.

  19. Composite bone cements loaded with a bioactive and ferrimagnetic glass-ceramic: Leaching, bioactivity and cytocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Verné, Enrica, E-mail: enrica.verne@polito.it [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Bruno, Matteo [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Miola, Marta [Institute of Materials Physics and Engineering, Applied Science and Technology Department, Politecnico di Torino, C. so Duca degli Abruzzi 24, 10129 Torino (Italy); Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Maina, Giovanni; Bianco, Carlotta [Traumatology Orthopedics and Occupational Medicine Dept., Università di Torino, Via G. Zuretti 29, 10126 Torino (Italy); Cochis, Andrea [Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Rimondini, Lia [Department of Health Sciences, Università del Piemonte Orientale “Amedeo Avogadro”, Via Solaroli 17, 28100 Novara (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, Via G. Giusti, 9, 50121 Firenze (Italy)

    2015-08-01

    In this work, composite bone cements, based on a commercial polymethylmethacrylate matrix (Palamed®) loaded with ferrimagnetic bioactive glass-ceramic particles (SC45), were produced and characterized in vitro. The ferrimagnetic bioactive glass-ceramic belongs to the system SiO{sub 2}–Na{sub 2}O–CaO–P{sub 2}O{sub 5}–FeO–Fe{sub 2}O{sub 3} and contains magnetite (Fe{sub 3}O{sub 4}) crystals into a residual amorphous bioactive phase. Three different formulations (containing 10, 15 and 20 wt.% of glass-ceramic particles respectively) have been investigated. These materials are intended to be applied as bone fillers for the hyperthermic treatment of bone tumors. The morphological, compositional, calorimetric and mechanical properties of each formulation have been already discussed in a previous paper. The in vitro properties of the composite bone cements described in the present paper are related to iron ion leaching test (by graphite furnace atomic absorption spectrometer), bioactivity (i.e. the ability to stimulate the formation of a hydroxyapatite – HAp – layer on their surface after soaking in simulated body fluid SBF) and cytocompatibility toward human osteosarcoma cells (ATCC CRL-1427, Mg63). Morphological and chemical characterizations by scanning electron microscopy and energy dispersion spectrometry have been performed on the composite samples after each test. The iron release was negligible and all the tested samples showed the growth of HAp on their surface after 28 days of immersion in a simulated body fluid (SBF). Cells showed good viability, morphology, adhesion, density and the ability to develop bridge-like structures on all investigated samples. A synergistic effect between bioactivity and cell mineralization was also evidenced. - Highlights: • An in vitro biological characterization was carried out on ferromagnetic and bioactive composite cements. • No release of iron was revealed in the physiological solution. • Bioactivity tests

  20. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

  1. 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

  2. Strain and damage self-sensing cement composites with conductive graphene nanoplatelet

    Science.gov (United States)

    Pang, Sze Dai; Gao, Hongchen J.; Xu, Chunying; Quek, Ser Tong; Du, Hongjian

    2014-04-01

    A novel cement composite containing graphene nanoplatelet (GNP) which can sense its own strain and damage is introduced in this paper. Piezoresistive strain sensing was investigated for mortar specimens with GNP under both cyclic and monotonically increasing compressive and tensile strain. Under compression, the electrical resistance decreased with increasing strain and the normalized resistance can be described by a bilinear curve with a kink at about 400 microstrain. At low strain, a high gauge factor exceeding 103 in magnitude was obtained and it increased almost linearly with the GNP content. This can be attributed primarily to the reducing interfacial distance and forming of better contacts between GNP and cement paste when the composite was initially loaded. At higher compressive strain beyond 400 microstrain, the gauge factor is consistently about 102 for GNP content exceeding the percolation threshold. A different response was observed for specimens under tension due to the formation and propagation of microcracks even at low tensile strain due to the brittleness of the material. The initial gauge factor is of the order 102 for tensile strain up to 100 microstrain and it increases exponentially beyond that. The damage self-sensing capability of this conductive cement composites is explored using electric potential method. Closed form expression for the assessment of damage are derived based on the mathematical analogy between the electrostatic field and the elastostatic field under anti-plane shear loading. The derived expression provide a quick and accurate assessment of the damage of this conductive material which is characterized by its change in compliance.

  3. 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.

  4. Investigation of the Mechanical Properties and Microstructure of Graphene Nanoplatelet-Cement Composite

    Directory of Open Access Journals (Sweden)

    Baomin Wang

    2016-11-01

    Full Text Available In this work, graphene nanoplatelets (GNPs were dispersed uniformly in aqueous solution using methylcellulose (MC as a dispersing agent via ultrasonic processing. Homogenous GNP suspensions were incorporated into the cement matrix to investigate the effect of GNPs on the mechanical behavior of cement paste. The optimum concentration ratio of GNPs to MC was confirmed as 1:7 by ultraviolet visible spectroscopy (UV-Vis, and the optical microscope and transmission electron microscopy (TEM images displayed remarkable dispersing performance. The GNP–cement composite exhibited better mechanical properties with the help of surface-modified GNPs. The flexural strength of cement paste increased up to 15%–24% with 0.05 wt % GNPs (by weight of cement. Meanwhile, the compressive strength of the GNP–cement composite increased up to 3%–8%. The X-ray diffraction (XRD and thermal analysis (TG/DTG demonstrated that the GNPs could accelerate the degree of hydration and increase the amount of hydration products, especially at an early age. Meanwhile, the lower porosity and finer pore size distribution of GNP–cement composite were detected by mercury intrusion porosimetry (MIP. In addition, scanning electron microscope (SEM analysis showed the introduction of GNPs could impede the development of cracks and preserve the completeness of the matrix through the plicate morphology and tortuous behavior of GNPs.

  5. 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 %.

  6. Thermogravimetric analysis of phase transitions in cement compositions mixed by sodium silicate solution

    Directory of Open Access Journals (Sweden)

    Fedosov Sergey Viktorovich

    2014-01-01

    Full Text Available This paper presents a study of the capability to modify cement by mechanical activation of sodium silicate water solution. Admixtures or blends of binding agents were employed for modifying concrete properties. The liquid glass is applied to protect from chemically or physically unfavorable environmental impacts, such as acidic medium and high temperature. The sodium silicate is a high-capacity setting accelerator. The increasing of the liquid glass proportion in the mix leads to the degradation of the cement paste plasticity and for this reason it is necessary to reduce the amount of liquid glass in the cement paste. The activation of dilute water solution of sodium silicate into rotary pulsating apparatus directly before tempering of the cement paste is an effective way to decrease mass fraction of liquid glass in the cement paste. The results of the combined influence of liquid glass and mechanical activation on physicochemical processes taking place in cement stone are represented in this research. Thermogravimetric analysis was used in order to study cement blends. Thermogravimetric analysis of modified cement stone assays was performed by thermo analyzer SETARAM TGA 92-24. The results of the analysis of phase transition taking place under high-temperature heating of cement stone modified by the mechanical activation of the water solution of the sodium silicate were introduced. Thermograms of cement stone assays were obtained at different hardening age. The comparison of these thermograms allows us to come to a conclusion on the formation and the retention during long time of a more dense structure of the composite matrix mixed by the mechanical activation of sodium silicate water solution. The relation between the concrete composition and its strength properties was stated. Perhaps, the capability of modified concrete to keep calcium ions in sparingly soluble hydrosilicates leads to the increase in its durability and corrosion resistance.

  7. Bond strength of a resin cement to a cured composite inlay material.

    Science.gov (United States)

    Latta, M A; Barkmeier, W W

    1994-08-01

    Although resin cements have been effectively bonded to mineralized tooth structures, bonding to a cured composite material has remained a challenge. This study evaluated the shear bond strength of a resin cement bonded to a cured composite inlay material by use of a variety of composite surface treatments: (1) hydrofluoric acid/60 seconds, (2) ammonium bifluoride/60 seconds, (3) resin adhesive, (4) microabrasion with 50 microns aluminum oxide, and (5) microabrasion with 50 microns aluminum oxide and application of a resin adhesive. The resin cement was also bonded to human enamel that was etched with phosphoric acid. Scanning electron microscopy examinations were completed to evaluate the effects of the composite surface treatments. The results indicated that microabrasion of a cured composite enhances bonding of a resin cement. The bond strength of a resin cement to a composite surface that was air abraded with aluminum oxide, with or without the application of a resin adhesive, was higher than surface treatments with hydrofluoric acid or ammonium bifluoride. Scanning electron microscopy indicated that an irregular surface on the composite was created with aluminum oxide air abrasion.

  8. Surface roughness of orthodontic band cements with different compositions

    Directory of Open Access Journals (Sweden)

    Françoise Hélène van de Sande

    2011-06-01

    Full Text Available OBJECTIVES: The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions. MATERIAL AND METHODS: Eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP, compomer (C, resin-modified glass ionomer cement (RMGIC and resin cement (RC. Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0 or 0.1 M lactic acid solution (pH 4.0 for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200 before and after the storage period. Data were analyzed by two-way ANOVA and Tukey's test (comparison among cements and storage solutions or paired t-test (comparison before and after the storage period at 5% significance level. RESULTS: The values for average surface roughness were statistically different (pRMGIC>C>R (p0.05. Compared to the current threshold (0.2 µm related to biofilm accumulation, both RC and C remained below the threshold, even after acidic challenge by immersion in lactic acid solution. CONCLUSIONS: Storage time and immersion in lactic acid solution increased the surface roughness of the majority of the tested cements. RC presented the smoothest surface and it was not influenced by storage conditions.

  9. Fire experience temperature detected experiment of ecological cement-based composite material%轻质水泥基结构火灾经历温度的红外热像检测实验

    Institute of Scientific and Technical Information of China (English)

    王海蓉; 陈振中; 梁栋

    2011-01-01

    以轻质水泥基结构为研究对象,利用红外热像和多通路温度传感器检测材料在火灾中经历的最高温度.在红外热像温升随时间的变化关系的基础上,建立了轻质水泥基材料的红外热像平均温升与其受火温度及强度损失的回归方程,得到该结构的火灾损伤的检测和评估模型.结果表明:(1)作为含有气泡状有机质的新型建筑材料,其高温作用后的红外热像温升明显较混凝土结构高;(2)材料的受火温度和材料强度损失的检测模型分别为:T=472.734 458x-587.909 642和f(T)/f0=110.662 138-0.154 507x;(3)通过红外热像检测模型,可评估火灾后的轻质水泥基材料的损伤程度,获得结构破坏前兆信息.%Ecological lightweight cement-based structure was studied , using infrared thermal imaging and inclusions burst the maximum temperature of the material experienced by the fire was detected.Based on Infrared thermal imaging in the variation of temperature over time, average temperature rise of Infrared thermal imaging with fire temperature and intensity loss by the regression equation was established, the structure of the fire damage detection and evaluation model was found.The results showed that: (1) As a new type of building materials with bubble-like organic matter, the infrared thermal imaging temperature significantly higher than the concrete structure , after high temperature ; (2) burst temperature and Infrared thermal imaging test was basically the same; (3) through the infrared thermal image detection model, the damage of ecological lightweight cement-based composite material after fire could be evaluated, precursor information of broken ring structure would be get.

  10. 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.

  11. 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.

  12. Propriedades mecânicas de materiais compósitos à base de cimento Portland e resina epoxi Mechanical properties of composite materials based on portland cement and epoxy resin

    Directory of Open Access Journals (Sweden)

    T. H. Panzera

    2010-03-01

    Full Text Available O estudo de materiais de alto desempenho e multifuncionais, como os compósitos poliméricos cimentícios, tem sido o foco de inúmeras pesquisas na indústria da construção civil. Este trabalho investiga o efeito da combinação de uma fase polimérica termorrígida, uma resina epóxi, com cimento Portland branco estrutural, seguido da avaliação da resistência à compressão e módulo de elasticidade. Este compósito, quando comparado individualmente com as suas matérias-prima originais, promove um aumento da resistência mecânica à compressão, redução da massa específica e, também uma mudança significativa do comportamento mecânico. As mudanças nas propriedades mecânicas estão associadas à hidratação da fase cimentícia na presença da resina, fato comprovado através da análise espectroscópica na região do infravermelho.The study of multi-functional materials of high performance, as the polymeric-cementitious composites, has been the focus of several researches in the industry of the civil engineering. This work investigates the effect of the combination of a thermorigid epoxy phase and the white Portland cement, followed by the evaluation of its compressive strength and modulus of elasticity. This composite, when the phases are individually compared, provides an increase of the compressive strength, a reduction of the density, and a significant change of the mechanical behaviour. The changes in mechanical behaviour are associated with the hydration of cement in the presence of resin, which was evident after infrared spectroscopy analysis.

  13. 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.

  14. Evaluation of the biphasic calcium composite (BCC), a novel bone cement, in a minipig model of pulmonary embolism.

    Science.gov (United States)

    Qin, Yi; Ye, Jichao; Wang, Peng; Gao, Liangbin; Jiang, Jianming; Wang, Suwei; Shen, Huiyong

    2016-01-01

    Polymethylmethacrylate (PMMA) bone cement, which is used as a filler material in vertebroplasty, is one of the major sources of pulmonary embolism in patients who have undergone vertebroplasty. In the present study, we established and evaluated two animal models of pulmonary embolism by injecting PMMA or biphasic calcium composite (BCC) bone cement with a negative surface charge. A total of 12 adults and healthy Wuzhishan minipigs were randomly divided into two groups, the PMMA and BBC groups, which received injection of PMMA bone cement and BBC bone cement with a negative surface charge in the circulation system through the pulmonary trunk, respectively, to construct animal models of pulmonary embolism. The hemodynamics, arterial blood gas, and plasma coagulation were compared between these two groups. In addition, morphological changes of the lung were examined using three-dimensional computed tomography. The results showed that both PMMA and BCC injections induced pulmonary embolisms in minipigs. Compared to the PMMA group, the BCC group exhibited significantly lower levels of arterial pressure, pulmonary artery pressure, blood oxygen pressure, blood carbon dioxide pressure, blood bicarbonate, base excess, antithrombin III and D-dimer. In conclusion, BCC bone cement with a negative surface charge is a promising filler material for vertebroplasty.

  15. 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.

  16. 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.

  17. 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

  18. Preparation of in situ hardening composite microcarriers: calcium phosphate cement combined with alginate for bone regeneration.

    Science.gov (United States)

    Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C; Kim, Hae-Won

    2014-03-01

    Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8-1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement-alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate-hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement-alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone.

  19. Polymeric-Calcium Phosphate Cement Composites-Material Properties: In Vitro and In Vivo Investigations

    Science.gov (United States)

    Khashaba, Rania M.; Moussa, Mervet M.; Mettenburg, Donald J.; Rueggeberg, Frederick A.; Chutkan, Norman B.; Borke, James L.

    2010-01-01

    New polymeric calcium phosphate cement composites (CPCs) were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement. In vitro cytotoxicity and in vivo biocompatibility of the two CPCs and hydroxyapatite cement were assessed. The setting time of the cements was 5–15 min. CPC-1 and CPC-2 showed significantly higher compressive and diametral strength values compared to hydroxyapatite cement. CPC-1 and CPC-2 were equivalent to Teflon controls after 1 week. CPC-1, CPC-2, and hydroxyapatite cement elicited a moderate to intense inflammatory reaction at 7 days which decreased over time. CPC-1 and CPC-2 show promise for orthopedic applications. PMID:20811498

  20. Polymeric-Calcium Phosphate Cement Composites-Material Properties: In Vitro and In Vivo Investigations

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2010-01-01

    Full Text Available New polymeric calcium phosphate cement composites (CPCs were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement. In vitro cytotoxicity and in vivo biocompatibility of the two CPCs and hydroxyapatite cement were assessed. The setting time of the cements was 5–15 min. CPC-1 and CPC-2 showed significantly higher compressive and diametral strength values compared to hydroxyapatite cement. CPC-1 and CPC-2 were equivalent to Teflon controls after 1 week. CPC-1, CPC-2, and hydroxyapatite cement elicited a moderate to intense inflammatory reaction at 7 days which decreased over time. CPC-1 and CPC-2 show promise for orthopedic applications.

  1. Effect of Water to Cement Ratio and Age on Portland Composite Cement Mortar Porosity, Strength and Evaporation Rate

    Directory of Open Access Journals (Sweden)

    Enamur R. Latifee

    2016-08-01

    Full Text Available Durability and the compressive strength of concrete are directly related to the porosity. Water to cement ratio is the main parameter behind the nature and amount of pores within the matrix. Porosity is also influenced by the degree of cement hydration and the length of moist-curing. Even after the standard moist curing period, i.e. 28 days the concrete can gain strength and porosity can be reduced under ambient relative humidity and temperature. However, this fact, that is the age effect on porosity reduction of the cement mortar or concrete, kept in air with ambient relative humidity and temperature for long duration could not be found in the literature. Therefore, in this research, different w/c were used with constant amount Portland Composite Cement to find out whether the mortar porosity decreases significantly over time, after 28 days of water curing, while kept in air and if there is any interaction effect between the age of the mortar and different w/c; regarding porosity. It was also intended to find out if water-loss rate variation with different w/c has similar trend as porosity variation with different w/c. It was found that, there is significant decrease in porosity with time for the first six weeks in air and after that it dwindles down gradually, and there is no interaction between age and w/c. Also, after 100 days in air, samples were submerged under water for 24 hours and then kept in air for the evaporation in subsequent days. It has been found that the water evaporation vs. w/c curve, using 11-day evaporation of water from different w/c specimens in ambient condition is almost parallel to porosity vs. w/c curve. Therefore, 11-day evaporation of aged saturated mortar or concrete sample, such as core can also be used as a durability index, which can be used for old structure evaluation.

  2. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash

    Directory of Open Access Journals (Sweden)

    Mengxue Wu

    2017-01-01

    Full Text Available In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the “gel/space ratio” descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD. The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel ( G C to G S C M ratio is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities.

  3. 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.

  4. 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...... the finite-element method. The stiffness of the steel deck reinforced with an overlay depends highly on the composite action. The composite action is closely related to cracking of the overlay and interfacial cracking between the overlay and underlying steel plate (debonding). As an example, a real size...

  5. Composite cements containing natural pozzolan and granulated blast furnace slag

    Directory of Open Access Journals (Sweden)

    Irassar, E. F.

    2006-09-01

    Full Text Available For reasons of market demand and Portland cement production,the manufacture of cements with two or more separately ground additions to produce customized cements is becoming common practice.When pozzolan or slag content in this type of cements is high, however, the initial strength of the resulting product may be adversely impacted. This problem can be minimized by activating one or both of the replacement materials. The present study analyzes the effect of Portland cement additions such as physically activated natural pozzolan(up to 20% and/or granulated blast furnace slag (up to 35% on mortar flexural and compressive strength. The results show that higher strength is attained in ternary than binary cements. Initially (2 and 7 days, the highest compressive strengths are reached by mortars with up to 13% natural pozzolan and 5% slag, whereas at later ages mortars with larger proportions of additions are found to perform best.Debido a las exigencias del mercado y de la producción de cemento Portland, es cada vez más frecuente la elaboración de cementos con dos o más adiciones a partir de la molienda separada de sus constituyentes, dando origen a la formulación de los cementos a medida.Cuando el contenido de adiciones es alto, la utilización de puzolana y escoria en este tipo de cementos presenta la peculiaridad de disminuir la resistencia inicial del cemento resultante. Sin embargo, si algunas o ambas adiciones se activan, este problema puede minimizarse. En este trabajo se analiza la influencia de la incorporación al cemento Portland de puzolana natural (hasta 20% activada físicamente y/o escoria granulada de alto horno (hasta 35% sobre la resistencia a flexión y a compresión de morteros. Los resultados indican que los cementos ternarios presentan un mejor comportamiento resistente que los cementos binarios. Las máximas resistencias a compresión en las primeras edades (2 y 7 díasse alcanzan con hasta 13% de puzolana natural y 5% de

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. Interaction between cements with different composition and superplasticizers

    Directory of Open Access Journals (Sweden)

    Ghorab, H. Y.

    2012-09-01

    Full Text Available The slump behavior of ordinary Portland-, pozzolanic (red brick powder-, sulfate resistant-, and limestone cement pastes caused by ≤ 1% additions of polycondensates and polycarboxylates superplasticizers are monitored for up to 90 minutes. With the plolycondensates, Portland- and pozzolanic cements gain fluidity at higher dosages than sulfate resistant and limestone cements. Limestone cement shows the best slump retention. The aluminate and sulfate phases play a major role in the fluidity. With the polycarboxylates, all cements gain fluidity with dosages of ≤ 0.3%. A polycarboxylate with no resonance of methyl methylene proton in the main chain identified in the NMR spectra creates good slump retention. This is explained by a low mobility of the structure and the predominance of the steric effect. The polycarboxylate shows also strong ether bands relative to the ester groups in the IR spectra and a low polydispersity observed in the elution of few low molecular weight species in the HPLC chromatogram.Se ha estudiado el efecto fluidificante (hasta 90 minutos ejercido por la incorporación de entre 0-1% de aditivos policondensados y policarboxilatos en pastas de cemento Portland, puzolánico, resistente a sulfatos y con adición de caliza. Con la incorporación de los aditivos policondensados, se produjo un incremento de la fluidez de los cementos Portland y puzolánico a mayores dosificaciones que las necesarias en los cementos resistente a sulfatos y con adición de caliza. Éste último presentó la mejor retención de la fluidez. Las fases aluminatos y sulfatos juegan un importante papel en la fluidez inducida. Todos los cementos incrementaron su fluidez con la incorporación de aditivos policarboxilatos a dosificaciones menores del 0,3%. El policarboxilato que no presenta en los espectros de RMN, resonancia asignada al protón de los grupos metil metileno, presenta buena retención de la fluidez. Esto es debido a la baja flexibilidad de

  11. Performance investigation of 1-3 piezoelectric ceramic-cement composite

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Xin, E-mail: chengxin@ujn.edu.cn [University of Jinan, School of Materials Science and Engineering, Jinan 250022 (China); Xu Dongyu, E-mail: xuy_sha@163.com [Shandong University, State Key Lab of Crystal Materials, Jinan 250100 (China); Lu Lingchao; Huang Shifeng [University of Jinan, School of Materials Science and Engineering, Jinan 250022 (China); Jiang Minhua [Shandong University, State Key Lab of Crystal Materials, Jinan 250100 (China)

    2010-05-15

    A 1-3 piezoelectric ceramic-cement composite has been fabricated using sulphoaluminate cement and lead niobium-magnesium zirconate titanate ceramics (P(MN)ZT) as matrix and functional component, respectively. The influences of piezoelectric ceramic volume fraction, aspect ratios of piezoelectric ceramic rods and temperature on the piezoelectric and dielectric properties of the composites were studied. This composite was shown to exhibit an improved electromechanical coupling coefficient with the mechanical quality factor reduced. Furthermore, the acoustic impedance of the composites could also be adjusted to match concrete structures. It has been demonstrated that by adjusting the piezoelectric ceramic volume fraction and shape parameters, the developed composite can be eventually used as sensing element in structural health monitoring.

  12. Strong and tough magnesium wire reinforced phosphate cement composites for load-bearing bone replacement.

    Science.gov (United States)

    Krüger, Reinhard; Seitz, Jan-Marten; Ewald, Andrea; Bach, Friedrich-Wilhelm; Groll, Jürgen

    2013-04-01

    Calcium phosphate cements are brittle biomaterials of low bending strength. One promising approach to improve their mechanical properties is reinforcement with fibers. State of the art degradable reinforced composites contain fibers made of polymers, resorbable glass or whiskers of calcium minerals. We introduce a new class of composite that is reinforced with degradable magnesium alloy wires. Bending strength and ductility of the composites increased with aspect ratio and volume content of the reinforcements up to a maximal bending strength of 139±41MPa. Hybrid reinforcement with metal and polymer fibers (PLA) further improved the qualitative fracture behavior and gave indication of enhanced strength and ductility. Immersion tests of composites in SBF for seven weeks showed high corrosion stability of ZEK100 wires and slow degradation of the magnesium calcium phosphate cement by struvite dissolution. Finally, in vitro tests with the osteoblast-like cell line MG63 demonstrate cytocompatibility of the composite materials.

  13. 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.

  14. 聚甲基酰亚胺泡沫改性水泥基复合吸声材料的制备与吸声性能研究%Study on the preparation of cement base sound absorption composite materials modifidied with polymethacrylimide foam (PMI) and the sound-absorbing performance of the composite material

    Institute of Scientific and Technical Information of China (English)

    彭龙贵; 杨晓凤; 李颖; 杜春宝; 王启强

    2011-01-01

    以普通硅酸盐水泥为基体,聚甲基丙烯酰亚胺(PMI)泡沫为填料制作水泥基吸声复合材料.实验采用半干法工艺成型,主要考察了水灰比、铝粉掺入量和聚甲基丙烯酰亚胺(PMI)掺入量等因素对复合材料材料吸声性能的影响,尤其是对频率f<300 Hz范围内声音的吸声性能的影响.实验中采用驻波管和SEM扫描仪对样品的吸声系数和微观结构进行了测量和分析.结果表明:当水灰比为0.55、铝粉的掺入量为0.04%、聚甲基丙烯酰亚胺(PMI)的掺入量为2.5%时,对频率f<300 Hz范围内的声音的吸声系数的平均值为0.348.%:In this paper,cement-based sound-absorbing composite material is made with ordinary portland cement as matrix and polymethacrylimide foam (PMI) as the filler. Semi-dry forming process is used in experiments, mainly for regulating water-cement ratio.amount of aluminum powder mixing ,polymethacrylimide(PMI) mixing effect on the sound absorption properties .especially of the low frequency sound of /<300 Hz . Standing wave tube and SEM is used in experiments to measure the absorption coefficient of the sample and observe the microstructure of the sample. The results show that when the water cement ration is 0. 55.amount of aluminum powder mixing is 0. 04%.and the amount of polymethacrylimide (PMI) mixing is 2. 5%. The average value of the absorption coefficient on the frequency sound of /<300 Hz is 0. 348.

  15. 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...

  16. Effects of composition and exposure on the solar reflectance of Portland cement concrete

    Energy Technology Data Exchange (ETDEWEB)

    Levinson, Ronnen; Akbari, Hashem

    2001-12-21

    Increasing the solar reflectance (albedo) of a paved surface keeps it cooler in the sun, reducing convection of heat from pavement to air and thereby decreasing the ambient air temperature. Simulations of the influence of pavement albedo on air temperature in Los Angeles predict that increasing the albedo of 1,250 km2 of pavement by 0.25 would save cooling energy worth $15M yr-1, and reduce smog-related medical and lost-work expenses by $76M yr-1. Most sidewalks and a small fraction of roads and parking areas are paved with portland cement concrete, which can be made quite reflective through suitable choice of cement and aggregate. Variations with composition and environmental exposure of the albedos of portland cement concrete pavements were investigated through laboratory fabrication and exposure of 32 mixes of concrete. Twenty-four mixes yielded substandard, ''rough'' concretes due to high, unmet aggregate water demand. The albedos of the remaining eight ''smooth'' concrete mixes ranged from 0.41 to 0.77 (mean 0.59). Simulated weathering, soiling, and abrasion each reduced average concrete albedo (mean decreases 0.06, 0.05, and 0.19, respectively), though some samples became slightly more reflective through weathering or soiling. Simulated rain (wetting) strongly depressed the albedos of concretes (mean decrease 0.23) until their surfaces were dried. Concrete albedo grew as the cement hydration reaction progressed (mean increase 0.08), but stabilized within six weeks of casting. White-cement concretes were on average significantly more reflective than gray-cement concretes. The albedo of the most-reflective white-cement concrete was 0.18 to 0.39 higher than that of the most-reflective gray-cement concrete, depending on state of exposure. Concrete albedo generally correlated with cement albedo and sand albedo, and, after abrasion, with rock albedo. Cement albedo had a disproportionately strong influence on the reflectance

  17. 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.

  18. Novel tricalcium silicate/magnesium phosphate composite bone cement having high compressive strength, in vitro bioactivity and cytocompatibility.

    Science.gov (United States)

    Liu, Wenjuan; Zhai, Dong; Huan, Zhiguang; Wu, Chengtie; Chang, Jiang

    2015-07-01

    Although inorganic bone cements such as calcium phosphate cements have been widely applied in orthopaedic and dental fields because of their self-setting ability, development of high-strength bone cement with bioactivity and biodegradability remains a major challenge. Therefore, the purpose of this study is to prepare a tricalcium silicate/magnesium phosphate (C3S/MPC) composite bone cement, which is intended to combine the excellent bioactivity of C3S with remarkable self-setting properties and mechanical strength of MPC. The self-setting and mechanical properties, in vitro induction of apatite formation and degradation behaviour, and cytocompatibility of the composite cements were investigated. Our results showed that the C3S/MPC composite cement with an optimal composition had compressive strength up to 87 MPa, which was significantly higher than C3S (25 MPa) and MPC (64 MPa). The setting time could be adjusted between 3 min and 29 min with the variation of compositions. The hydraulic reaction products of the C3S/MPC composite cement were composed of calcium silicate hydrate (CSH) derived from the hydration of C3S and gel-like amorphous substance. The C3S/MPC composite cements could induce apatite mineralization on its surface in SBF solution and degraded gradually in Tris-HCl solution. Besides, the composite cements showed good cytocompatibility and stimulatory effect on the proliferation of MC3T3-E1 osteoblast cells. Our results indicated that the C3S/MPC composite bone cement might be a new promising high-strength inorganic bioactive material which may hold the potential for bone repair in load-bearing site.

  19. Effect of Ultrasonic Versus Manual Cementation on the Fracture Strength of Resin Composite Laminates

    NARCIS (Netherlands)

    Ozcan, M.; Mese, A.

    2009-01-01

    This study evaluated the effect of conventional versus ultrasonic cementation techniques on the fracture strength of resin composite laminates. In addition, the failure modes were assessed. Window-type preparations I mm above the cemento-enamel junction were made on intact human maxillary central in

  20. 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.

  1. Phase transformations, microstructure formation and in vitro osteoblast response in calcium silicate/brushite cement composites.

    Science.gov (United States)

    Sopcak, T; Medvecky, L; Giretova, M; Kovalcikova, A; Stulajterova, R; Durisin, J

    2016-08-10

    Self-setting simple calcium silicate/brushite (B) biocements with various Ca/P ratios were prepared by mutual mixing of both monocalcium silicate hydrate (CSH) or β-wollastonite (woll) powders with B and the addition of 2 wt% NaH2PO4 solution as a hardening liquid. The phase composition of the final composites and the texture of the surface calcium phosphate/silica layer were controlled by the starting Ca/P ratio in composites and the pH during setting. It was verified that the presence of continuous bone-like calcium phosphate coating on the surface of the samples was not essential for in vitro osteoblast proliferation. The nanocrystalline calcium deficient hydroxyapatite and amorphous silica were found as the main setting products in composite mixtures with a Ca/P ratio close to the region of the formation of deficient hydroxyapatite-like calcium phosphates. No CSH phase with a lower Ca/Si ratio was identified after transformation. The results confirmed a small effect of the monocalcium silicate addition on the compressive strength (CS) of cements up to 30 wt% (around 20-25 MPa) and a significant rise of the value in 50 woll/B cement (65 MPa). The final setting times of the cement composites varied between 5 and 43 min depending on the P/L ratio and the type of monocalcium silicate phase in the cement mixture. 10CSH/B and 50 woll/B cements with different textures but free of both the needle-like and perpendicularly-oriented hydroxyapatite particles on the surface of the samples had low cytotoxicity.

  2. 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.

  3. Temporary zinc oxide-eugenol cement: eugenol quantity in dentin and bond strength of resin composite.

    Science.gov (United States)

    Koch, Tamara; Peutzfeldt, Anne; Malinovskii, Vladimir; Flury, Simon; Häner, Robert; Lussi, Adrian

    2013-08-01

    Uptake of eugenol from eugenol-containing temporary materials may reduce the adhesion of subsequent resin-based restorations. This study investigated the effect of duration of exposure to zinc oxide-eugenol (ZOE) cement on the quantity of eugenol retained in dentin and on the microtensile bond strength (μTBS) of the resin composite. The ZOE cement (IRM Caps) was applied onto the dentin of human molars (21 per group) for 1, 7, or 28 d. One half of each molar was used to determine the quantity of eugenol (by spectrofluorimetry) and the other half was used for μTBS testing. The ZOE-exposed dentin was treated with either OptiBond FL using phosphoric acid (H₃PO₄) or with Gluma Classic using ethylenediaminetetraacetic acid (EDTA) conditioning. One group without conditioning (for eugenol quantity) and two groups not exposed to ZOE (for eugenol quantity and μTBS testing) served as controls. The quantity of eugenol ranged between 0.33 and 2.9 nmol mg⁻¹ of dentin (median values). No effect of the duration of exposure to ZOE was found. Conditioning with H₃PO₄ or EDTA significantly reduced the quantity of eugenol in dentin. Nevertheless, for OptiBond FL, exposure to ZOE significantly decreased the μTBS, regardless of the duration of exposure. For Gluma Classic, the μTBS decreased after exposure to ZOE for 7 and 28 d. OptiBond FL yielded a significantly higher μTBS than did Gluma Classic. Thus, ZOE should be avoided in cavities later to be restored with resin-based materials.

  4. Effect of Expansive Admixtures on the Shrinkage and Mechanical Properties of High-Performance Fiber-Reinforced Cement Composites

    Directory of Open Access Journals (Sweden)

    Won-Chang Choi

    2013-01-01

    Full Text Available High-performance fiber-reinforced cement composites (HPFRCCs are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J, each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1 and 8% CSA-J (Type 2 considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs.

  5. Obtaining and physical mechanical properties of cement composites with the use of fillers and mixing water from the Chechen Republic fields

    Directory of Open Access Journals (Sweden)

    Erofeev Vladimir Trofimovich

    Full Text Available Improving physical mechanical and operational properties of concretes and other composite materials is one of the most important tasks in construction material science. At the present time various methods are applied for that, which includes the use of additives, composite binders, activated mixing water, etc. Composite construction materials based on cement binders with mineral additives are widelu used, because they possess improved physical mechanical and technological properties. Implementation of additives improve placeability and nonsegregation factors of concrete and mortar mixes, lead to compaction of concrete and mortars structure. The additives substantially lower heat generation of concretes, which is of great importance in concrete casting of large structures. The article presents the results of experimental studies of cement composites filled with powders of rocks and mixable with activated water from the deposits of the Chechen Republic. The soundness of cement compositions with the additives of mountain and river limestone, sandstone and quartz sand was established. The results of experimental studies on establishing the effect of fine and coarse aggregate on strength formation of cement composites activated by water mixing were presented.

  6. Preparation of Super Composite Cement with a Lower Clinker Content and a Larger Amount of Industrial Wastes

    Institute of Scientific and Technical Information of China (English)

    HE Zhen; LIANG Wen-quan; LI Bei-xing; LI Xiang-guo

    2002-01-01

    The effects of the grinding mode,fineness, gypsum kinds and dosage, mix proportions on properties of the composite cements consisting of slag,fly ash, limestone and a lower content clinker were investigated,respectively. The results show that when the proportions among slag, fly ash and limestone are appropriate, the grinding technology and system are reasonable, the optimized gypsums and additives are effective, the 52.5 R grade cement (52.5 R grade cement means a higher strength than 52.5 at early age ) can be prepared by clinker dosage of 50% in weight, the 42.5R or 42.5,32.5 grade composite cement containing 40% and 30% clinker also may be made, respectively. Moreover, the high performance concrete prepared from the above composite cements was studied experimentally.

  7. Performance of the Cement Matrix Composite Material With Rubber Powder

    Institute of Scientific and Technical Information of China (English)

    SONG Shao-min; LIU Juan-hong; ZHANG Xi-qing

    2004-01-01

    The effect of the deferent rubber content substituted for fine aggregate on the mortar performancewas studied. The effects of the rubber coated with the coating materials on the mortar compressive strength, bendingstrength and impact work were discussed. The optimum rubber powder content and the suitable coating materialwere found. Through the electrical probe test- BEI, SEI and calcium ion distribution, and the slight crack and theinterface between the rubber and cement matrix are analyzed. The results show that the rubber powder coated withthe surface treatment materials A, B and C bas the capability of absorbing a large amount of energy under thecompressive and flexural load and the slight cracks of R- C were controlled and restrained.

  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. 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.

  11. Critical surface energy of composite cement containing MDP (10-methacryloyloxydecyl dihydrogen phosphate) and chemical bonding to hydroxyapatite.

    Science.gov (United States)

    Dabsie, Firas; Grégoire, Geneviève; Sharrock, Patrick

    2012-01-01

    Self-adhesive composite cements are increasingly used for cementing inlays/onlays, intraradicular posts, crowns and laminate veneers. Wider clinical acceptance is driven by simpler and faster handling procedures, much like observed for self-etching adhesives. 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) is a bi-functional monomer incorporated as the reactive ingredient in a contemporary self-adhesive cement. We have examined the surface free energy parameters of this cement and studied the mode of action of the cement on dentine substrate by contact angle measurements to determine the critical surface energy of the cement. Retention of the infrared absorption bands characteristic of the acrylate moieties on the surface of hydroxyapatite particles suggests that MDP contributes to the overall bonding to dentine by forming ionic chemical bonds with surface calcium ions in dentine crystalites.

  12. Thio-urethanes improve properties of dual-cured composite cements.

    Science.gov (United States)

    Bacchi, A; Dobson, A; Ferracane, J L; Consani, R; Pfeifer, C S

    2014-12-01

    This study aims at modifying dual-cure composite cements by adding thio-urethane oligomers to improve mechanical properties, especially fracture toughness, and reduce polymerization stress. Thiol-functionalized oligomers were synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene with trimethylol-tris-3-mercaptopropionate, at 1:2 isocyanate:thiol. Oligomer was added at 0, 10 or 20 wt% to BisGMA-UDMA-TEGDMA (5:3:2, with 25 wt% silanated inorganic fillers) or to one commercial composite cement (Relyx Ultimate, 3M Espe). Near-IR was used to measure methacrylate conversion after photoactivation (700 mW/cm(2) × 60s) and after 72 h. Flexural strength and modulus, toughness, and fracture toughness were evaluated in three-point bending. Polymerization stress was measured with the Bioman. The microtensile bond strength of an indirect composite and a glass ceramic to dentin was also evaluated. Results were analyzed with analysis of variance and Tukey's test (α = 0.05). For BisGMA-UDMA-TEGDMA cements, conversion values were not affected by the addition of thio-urethanes. Flexural strength/modulus increased significantly for both oligomer concentrations, with a 3-fold increase in toughness at 20 wt%. Fracture toughness increased over 2-fold for the thio-urethane modified groups. Contraction stress was reduced by 40% to 50% with the addition of thio-urethanes. The addition of thio-urethane to the commercial cement led to similar flexural strength, toughness, and conversion at 72h compared to the control. Flexural modulus decreased for the 20 wt% group, due to the dilution of the overall filler volume, which also led to decreased stress. However, fracture toughness increased by up to 50%. The microtensile bond strength increased for the experimental composite cement with 20 wt% thio-urethane bonding for both an indirect composite and a glass ceramic. Novel dual-cured composite cements containing thio-urethanes showed increased toughness, fracture toughness and

  13. Thio-urethanes Improve Properties of Dual-cured Composite Cements

    Science.gov (United States)

    Bacchi, A.; Dobson, A.; Ferracane, J.L.; Consani, R.; Pfeifer, C.S.

    2014-01-01

    This study aims at modifying dual-cure composite cements by adding thio-urethane oligomers to improve mechanical properties, especially fracture toughness, and reduce polymerization stress. Thiol-functionalized oligomers were synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene with trimethylol-tris-3-mercaptopropionate, at 1:2 isocyanate:thiol. Oligomer was added at 0, 10 or 20 wt% to BisGMA-UDMA-TEGDMA (5:3:2, with 25 wt% silanated inorganic fillers) or to one commercial composite cement (Relyx Ultimate, 3M Espe). Near-IR was used to measure methacrylate conversion after photoactivation (700 mW/cm2 × 60s) and after 72 h. Flexural strength and modulus, toughness, and fracture toughness were evaluated in three-point bending. Polymerization stress was measured with the Bioman. The microtensile bond strength of an indirect composite and a glass ceramic to dentin was also evaluated. Results were analyzed with analysis of variance and Tukey’s test (α = 0.05). For BisGMA-UDMA-TEGDMA cements, conversion values were not affected by the addition of thio-urethanes. Flexural strength/modulus increased significantly for both oligomer concentrations, with a 3-fold increase in toughness at 20 wt%. Fracture toughness increased over 2-fold for the thio-urethane modified groups. Contraction stress was reduced by 40% to 50% with the addition of thio-urethanes. The addition of thio-urethane to the commercial cement led to similar flexural strength, toughness, and conversion at 72h compared to the control. Flexural modulus decreased for the 20 wt% group, due to the dilution of the overall filler volume, which also led to decreased stress. However, fracture toughness increased by up to 50%. The microtensile bond strength increased for the experimental composite cement with 20 wt% thio-urethane bonding for both an indirect composite and a glass ceramic. Novel dual-cured composite cements containing thio-urethanes showed increased toughness, fracture toughness and

  14. Effects of EVA Latex on the Properties of Glass-fiber/ Magnesium-oxychloride Cement Composites

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of Ethylene- Vinyl Acetate copolymer ( EVA ) latex as an additive or a glass fiber sur face modifier on the properties of Glass- Fiber ( GF ) / Magnesium Oxychloride Cement ( MOC ) composites was studied.The mechanical properties, water resistance and aging resistance of the cured GF/ MOC composites were estimated and chemical ingredients analysis and morphological study of the GF/ MOC composites were also performed.It is found that EVA added to the MOC matrix could substantially improve the interfacial adhesion, water resistance and aging resistance of GF / MOC composites.EVA treatment on glass fibers resulted in decreasing initial flexural strength of GF/ MOC composites while enhancing the soft coefficients.In addition, the drying time and dilution of the EVA treatment on glass fibers also had an obvious effect on the properties of GF/ MOC composites.GF / MOC composites.

  15. Adhesion of composite luting cement to Er:YAG-laser-treated dentin.

    Science.gov (United States)

    Carrieri, Teresa C D; de Freitas, Patricia M; Navarro, Ricardo S; Eduardo, Carlos de P; Mori, Matsuyoshi

    2007-09-01

    Although some studies claim to the increase of composite resin adhesion to Er:YAG-laser-treated dentin, there are still no reports on the adhesion of composite resin cements to the irradiated surface. This in vitro study evaluated the tensile bond strength (TBS) of a composite resin cement to dentin treated with the Er:YAG laser. Sixty human dentin samples were divided into four groups (n = 15): G1 (Control)-no treatment; G2-Er:YAG laser 60 mJ, 2 Hz, with water cooling, non-contact (19 J/cm(2)); G3-Er:YAG laser 60 mJ, 10 Hz, 50/10 fiber, contact, without water cooling (40 J/cm(2)); G4-Er:YAG laser 60 mJ, 10 Hz, 50/10 fiber, contact, with water cooling (40 J/cm(2)). After the surface treatment, each sample was submitted to bonding procedures. The analysis of variance (ANOVA) and Tukey tests revealed no statistical significant difference on TBS values for groups G1 (13.73 +/- 3.05 MPa), G2 (12.60 +/- 2.09 MPa) and G4 (11.17 +/- 4.04 MPa). G4 was not statistically different from G3 (8.64 +/- 2.06 MPa). Er:YAG laser irradiation with different settings can constitute an alternative tool to the use of composite resin-luting cements.

  16. Effect of silane activation on shear bond strength of fiber-reinforced composite post to resin cement

    OpenAIRE

    Kim, Hyun-Dong; Lee, Joo-Hee; Ahn, Kang-Min; Kim, Hee-Sun; Cha, Hyun-Suk

    2013-01-01

    PURPOSE Among the surface treatment methods suggested to enhance the adhesion of resin cement to fiber-reinforced composite posts, conflicting results have been obtained with silanization. In this study, the effects of silanization, heat activation after silanization, on the bond strength between fiber-reinforced composite post and resin cement were determined. MATERIALS AND METHODS Six groups (n=7) were established to evaluate two types of fiber post (FRC Postec Plus, D.T. Light Post) and th...

  17. Effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement

    OpenAIRE

    Pyun, Jung-Hoon; Shin, Tae-Bong; Lee, Joo-Hee; Ahn, Kang-Min; Kim, Tae-Hyung; Cha, Hyun-Suk

    2016-01-01

    PURPOSE To evaluate the effects of hydrogen peroxide pretreatment and heat activation of silane on the shear bond strength of fiber-reinforced composite posts to resin cement. MATERIALS AND METHODS The specimens were prepared to evaluate the bond strength of epoxy resin-based fiber posts (D.T. Light-Post) to dual-curing resin cement (RelyX U200). The specimens were divided into four groups (n=18) according to different surface treatments: group 1, no treatment; group 2, silanization; group 3,...

  18. Multifunctional Cement Composites Strain and Damage Sensors Applied on Reinforced Concrete (RC Structural Elements

    Directory of Open Access Journals (Sweden)

    Pedro Garcés

    2013-03-01

    Full Text Available In this research, strain-sensing and damage-sensing functional properties of cement composites have been studied on a conventional reinforced concrete (RC beam. Carbon nanofiber (CNFCC and fiber (CFCC cement composites were used as sensors on a 4 m long RC beam. Different casting conditions (in situ or attached, service location (under tension or compression and electrical contacts (embedded or superficial were compared. Both CNFCC and CFCC were suitable as strain sensors in reversible (elastic sensing condition testing. CNFCC showed higher sensitivities (gage factor up to 191.8, while CFCC only reached gage factors values of 178.9 (tension or 49.5 (compression. Furthermore, damage-sensing tests were run, increasing the applied load progressively up to the RC beam failure. In these conditions, CNFCC sensors were also strain sensitive, but no damage sensing mechanism was detected for the strain levels achieved during the tests. Hence, these cement composites could act as strain sensors, even for severe damaged structures near to their collapse.

  19. [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.

  20. Composition Design for High C3S Cement Clinker and Its Mineral Formation

    Institute of Scientific and Technical Information of China (English)

    HOU Guihua; SHEN Xiaodong; XU Zhongzi

    2007-01-01

    A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO (in mass). Fired at 1 200 ℃,1 350 ℃,1 400℃ and 1 450 ℃ for 30 min, the resultant mineral phases component and mineral morphology were analyzed.The performances of the cement which was made of clinker burned at 1 450 ℃ and fly ash were determined. By means of QXRD, XRD and optical microscopy, it is shown that the clinker burnt at 1 450 ℃ has the larger size crystals and distinct crystal interface, in which the C3S content is 73.37% and the mineral phases is dominantly C3S, following by minor C2S, C3A and tetracalcium aluminoferrite. The results reveal that a new type of high C3S content clinker can completely be made by traditional temperature-time schedule. The performances of the cement produced from this clinker with addtion of 50% fly ash and 5% gupsum were in agreement with the 32.5 strength grade of Portland fly-ash cement. The results also show that the clinker has a significant effect of saving energy and utilizing waste slag.

  1. INVOLUTIVE BASES UNDER COMPOSITION

    Institute of Scientific and Technical Information of China (English)

    Zailiang TANG

    2007-01-01

    In this paper, the behaviors of involutive bases under composition operation are studied.For two kinds of involutive bases, i.e., Pommaret bases, Janet bases, we study their behavior problems under composition. Some further problems are also proposed.

  2. Effects of blended-cement paste chemical composition changes on some strength gains of blended-mortars.

    Science.gov (United States)

    Kirgiz, Mehmet Serkan

    2014-01-01

    Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement.

  3. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Directory of Open Access Journals (Sweden)

    Mehmet Serkan Kirgiz

    2014-01-01

    Full Text Available Effects of chemical compositions changes of blended-cement pastes (BCPCCC on some strength gains of blended cement mortars (BCMSG were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP or 6%, 20%, 21%, and 35% brick powder (BP for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min. Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS and flexural strengths (FS of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2, sodium oxide (Na2O, and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2 at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM in comparison with reference mortars (RM at whole cure days as MP up to 6% or BP up to 35% was blended for cement.

  4. Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

    Science.gov (United States)

    Kirgiz, Mehmet Serkan

    2014-01-01

    Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement. PMID:24587737

  5. 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

  6. Compósitos à base de cimento reforçados com polpa celulósica de bambu. Parte I: Determinação do teor de reforço ótimo Cement-based composite reinforced with bamboo pulp. Part I: Determination of optimum reinforcement percentage

    Directory of Open Access Journals (Sweden)

    Marcos A. S. dos Anjos

    2003-08-01

    Full Text Available Este trabalho apresenta os resultados experimentais de um estudo em que se procurou desenvolver compósitos de matriz cimentícia reforçada com polpa de bambu. Foram usados dois tipos de polpa: refinada e sem refino. Fez-se variar o teor de fibras de 0 a 16% em massa de cimento e se desenvolveu um processo com sucção, moldagem e prensagem para fabricação dos compósitos. As relações constitutivas dos compósitos foram definidas através de ensaio a compressão e tração de corpos-de-prova cilíndricos de 5x10 cm e do ensaio de flexão em três pontos. A partir delas, foi obtida a capacidade de absorção de energia. Determinaram-se, também, algumas propriedades físicas, como absorção, porosidade aparente, densidade seca e úmida dos compósitos. Os resultados mostraram melhor performance dos compósitos com fibras refinadas em relação àquelas com fibras sem refino e também indicaram que o teor ótimo de fibras refinadas se situou em torno de 8%, quando promoveram notáveis melhoramentos das propriedades mecânicas dos compósitos em relação à matriz plena.This work presents the experimental results of a study which intended to develop a composite with cementations matrix reinforced with bamboo pulp. Two types of pulps were used: refined and unrefined pulps. The fibre content varied between 0 and 16% cement (weight basis. After the preparation of fresh composite mix the experimental specimens were prepared applying a specially developed process based on Hastshek method using suction then moulding and pressing. The compression, tension and the flexural behavior and their constitutive relations were established using 5 cm diameter by 10 cm high cylindrical specimens and three point bending tests at respectively. The energy absorbing capacity of the new composites was also established. Physical properties such as water absorption, apparent porosity, dry and humid density were also obtained. The results showed a better performance

  7. Attenuation properties of cement composites: Experimental measurements and Monte Carlo calculations

    Science.gov (United States)

    Florez Meza, Raul Fernando

    Developing new cement based materials with excellent mechanical and attenuation properties is critically important for both medical and nuclear power industries. Concrete continues to be the primary choice material for the shielding of gamma and neutron radiation in facilities such as nuclear reactors, nuclear waste repositories, spent nuclear fuel pools, heavy particle radiotherapy rooms, particles accelerators, among others. The purpose of this research was to manufacture cement pastes modified with magnetite and samarium oxide and evaluate the feasibility of utilizing them for shielding of gamma and neutron radiation. Two different experiments were conducted to accomplish these goals. In the first one, Portland cement pastes modified with different loading of fine magnetite were fabricated and investigated for application in gamma radiation shielding. The experimental results were verified theoretically through XCOM and the Monte Carlo N-Particle (MCNP) transport code. Scanning electron microscopy and x-ray diffraction tests were used to investigate the microstructure of the samples. Mechanical characterization was also perfornmed by compression testing. The results suggest that fine magnetite is a suitable aggregate for increasing the compressive and flexural strength of white Portland cement pastes; however, there is no improvement of the attenuation at intermediate energy (662 keV). For the second experiment, cement pastes with different concentrations of samarium oxide were fabricated and tested for shielding against thermal neutrons. MCNP simulations were used to validate the experimental work. The result shows that samarium oxide increases the effective thermal cross section of Portland cement and has the potential to replace boron bearing compounds currently used in neutron shielding.

  8. 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.

  9. 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.

  10. Influence of Fabric Geometrical Structure on Bonding of the Fabric Reinforced Cement Composites

    Institute of Scientific and Technical Information of China (English)

    YU Qiao-zhen

    2007-01-01

    Influence of fabric geometrical parameters,including the number of filling yams per 10 cm, yarntwist and fiber type, on bonding of the fabric reinforcedcement composites is studied by fabric pull-out test andSEM microstructure analysis. The results show that thebonding strength increase with the increase of the numberof filling yams per 10 cm in the range of this study. Butthe influence of fabric count on the interfacial bonding isdual and there is a critical value. The twist of yarns hasa little effect on the bending strength and interfacialbonding behaves of nylon fabric reinforced cementcomposites. There is an optimum twist range. Withinthis range, the bonding strength increase slowly with theincrease of yarn twist. Beyond this range, it is versus.The bonding strength is strongly affected by the fabriccharacter. The bonding between the nylon fiber fabricand cement is good; that of between glass fiber fabric andcement is moderate and that of between the carbon fiberfabric and cement is poor.

  11. Chemical stability of seven years aged cement-PET composite waste form containing radioactive borate waste simulates

    Science.gov (United States)

    Saleh, H. M.; Tawfik, M. E.; Bayoumi, T. A.

    2011-04-01

    Different samples of radioactive borate waste simulate [originating from pressurized water reactors (PWR)] have been prepared and solidified after mixing with cement-water extended polyester composite (CPC). The polymer-cement composite samples were prepared from recycled poly (ethylene terephthalate) (PET) waste and cement paste (water/cement ratio of 40%). The prepared samples were left to set at room temperature (25 °C ± 5) under humid conditions. After 28 days curing time the obtained specimens were kept in their molds to age for 7 years under ambient conditions. Cement-polymer composite waste form specimens (CPCW) have been subjected to leach tests for both 137Cs and 60Co radionuclides according to the method proposed by the International Atomic Energy Agency (IAEA). Leaching tests were justified under various factors that may exist within the disposal site (e.g. type of leachant, surrounding temperature, leachant behavior, the leachant volume to CPCW surface area…). The obtained data after 260 days of leaching revealed that after 7 years of aging the candidate cement-polymer composite (CPC) containing radioactive borate waste samples are characterized by adequate chemical stability required for the long-term disposal process.

  12. Chemical stability of seven years aged cement-PET composite waste form containing radioactive borate waste simulates

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, H.M., E-mail: hosamsaleh70@yahoo.com [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt); Tawfik, M.E. [Department of Polymers and Pigments, National Research Center, Dokki (Egypt); Bayoumi, T.A. [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt)

    2011-04-15

    Different samples of radioactive borate waste simulate [originating from pressurized water reactors (PWR)] have been prepared and solidified after mixing with cement-water extended polyester composite (CPC). The polymer-cement composite samples were prepared from recycled poly (ethylene terephthalate) (PET) waste and cement paste (water/cement ratio of 40%). The prepared samples were left to set at room temperature (25 deg. C {+-} 5) under humid conditions. After 28 days curing time the obtained specimens were kept in their molds to age for 7 years under ambient conditions. Cement-polymer composite waste form specimens (CPCW) have been subjected to leach tests for both {sup 137}Cs and {sup 60}Co radionuclides according to the method proposed by the International Atomic Energy Agency (IAEA). Leaching tests were justified under various factors that may exist within the disposal site (e.g. type of leachant, surrounding temperature, leachant behavior, the leachant volume to CPCW surface area...). The obtained data after 260 days of leaching revealed that after 7 years of aging the candidate cement-polymer composite (CPC) containing radioactive borate waste samples are characterized by adequate chemical stability required for the long-term disposal process.

  13. 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.

  14. 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.

  15. Effects of etching and adhesive applications on the bond strength between composite resin and glass-ionomer cements

    Directory of Open Access Journals (Sweden)

    Tijen Pamir

    2012-12-01

    Full Text Available OBJECTIVE: This study determined the effects of various surface treatment modalities on the bond strength of composite resins to glass-ionomer cements. MATERIAL AND METHODS: Conventional (KetacTM Molar Quick ApplicapTM or resin-modified (PhotacTM Fil Quick AplicapTM glass-ionomer cements were prepared. Two-step etch-rinse & bond adhesive (AdperTM Single Bond 2 or single-step self-etching adhesive (AdperTM PromptTM L-PopTM was applied to the set cements. In the etch-rinse & bond group, the sample surfaces were pre-treated as follows: (1 no etching, (2 15 s of etching with 35% phosphoric acid, (3 30 s of etching, and (4 60 s of etching. Following the placement of the composite resin (FiltekTM Z250, the bond strength was measured in a universal testing machine and the data obtained were analyzed with the two-way analysis of variance (ANOVA followed by the Tukey's HSD post hoc analysis (p=0.05. Then, the fractured surfaces were examined by scanning electron microscopy. RESULTS: The bond strength of the composite resin to the conventional glass-ionomer cement was significantly lower than that to the resin-modified glass-ionomer cement (p0.05. However, a greater bond strength was obtained with 30 s of phosphoric acid application. CONCLUSIONS: The resin-modified glass-ionomer cement improved the bond strength of the composite resin to the glass-ionomer cement. Both etch-rinse & bond and self-etching adhesives may be used effectively in the lamination of glass-ionomer cements. However, an etching time of at least 30 s appears to be optimal.

  16. 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...

  17. Transmission of composite polymerization contraction force through a flowable composite and a resin-modified glass ionomer cement.

    Science.gov (United States)

    Castañeda-Espinosa, Juan Carlos; Pereira, Rosana Aparecida; Cavalcanti, Ana Paula; Mondelli, Rafael Francisco Lia

    2007-12-01

    The purpose of this study was to evaluate the individual contraction force during polymerization of a composite resin (Z-250), a flowable composite (Filtek Flow, FF) and a resin-modified glass ionomer cement (Vitrebond, VB), and the transmission of Z-250 composite resin polymerization contraction force through different thicknesses of FF and VB. The experiment setup consisted of two identical parallel steel plates connected to a universal testing machine. One was fixed to a transversal base and the other to the equipment's cross head. The evaluated materials were inserted into a 1-mm space between the steel plates or between the inferior steel plate and a previously polymerized layer of an intermediate material (either FF or VB) adhered to the upper steel plate. The composite resin was light-cured with a halogen lamp with light intensity of 500 mW/cm(2) for 60 s. A force/time graph was obtained for each sample for up to 120 s. Seven groups of 10 specimens each were evaluated: G1: Z-250; G2: FF; G3: VB; G4: Z-250 through a 0.5-mm layer of FF; G5: Z-250 through a 1-mm layer of FF; G6: Z-250 through a 0.5-mm of VB; G7: Z-250 through a 1-mm layer of VB. They were averaged and compared using one-way ANOVA and Tukey test at a = 0.05. The obtained contraction forces were: G1: 6.3N + 0.2N; G2: 9.8 + 0.2N; G3: 1.8 + 0.2N; G4: 6.8N + 0.2N; G5: 6.9N + 0.3N; G6: 4.0N + 0.4N and G7: 2.8N + 0.4N. The use of VB as an intermediate layer promoted a significant decrease in polymerization contraction force values of the restorative system, regardless of material thickness. The use of FF as an intermediate layer promoted an increase in polymerization contraction force values with both material thicknesses.

  18. Transmission of composite polymerization contraction force through a flowable composite and a resin-modified glass ionomer cement

    Directory of Open Access Journals (Sweden)

    Juan Carlos Castañeda-Espinosa

    2007-12-01

    Full Text Available The purpose of this study was to evaluate the individual contraction force during polymerization of a composite resin (Z-250, a flowable composite (Filtek Flow, FF and a resin-modified glass ionomer cement (Vitrebond, VB, and the transmission of Z-250 composite resin polymerization contraction force through different thicknesses of FF and VB. The experiment setup consisted of two identical parallel steel plates connected to a universal testing machine. One was fixed to a transversal base and the other to the equipment's cross head. The evaluated materials were inserted into a 1-mm space between the steel plates or between the inferior steel plate and a previously polymerized layer of an intermediate material (either FF or VB adhered to the upper steel plate. The composite resin was light-cured with a halogen lamp with light intensity of 500 mW/cm² for 60 s. A force/time graph was obtained for each sample for up to 120 s. Seven groups of 10 specimens each were evaluated: G1: Z-250; G2: FF; G3: VB; G4: Z-250 through a 0.5-mm layer of FF; G5: Z-250 through a 1-mm layer of FF; G6: Z-250 through a 0.5-mm of VB; G7: Z-250 through a 1-mm layer of VB. They were averaged and compared using one-way ANOVA and Tukey test at a = 0.05. The obtained contraction forces were: G1: 6.3N + 0.2N; G2: 9.8 + 0.2N; G3: 1.8 + 0.2N; G4: 6.8N + 0.2N; G5: 6.9N + 0.3N; G6: 4.0N + 0.4N and G7: 2.8N + 0.4N. The use of VB as an intermediate layer promoted a significant decrease in polymerization contraction force values of the restorative system, regardless of material thickness. The use of FF as an intermediate layer promoted an increase in polymerization contraction force values with both material thicknesses.

  19. 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.

  20. Effects of Stirring and Fluid Perfusion on the In Vitro Degradation of Calcium Phosphate Cement/PLGA Composites.

    Science.gov (United States)

    An, Jie; Leeuwenburgh, Sander C G; Wolke, Joop G C; Jansen, John A

    2015-11-01

    In vitro degradation rates of calcium phosphate bioceramics are investigated using a large variation of soaking protocols that do not all match the dynamic conditions of the perfused physiological environment. Therefore, we studied the effect of stirring and fluid perfusion on the in vitro degradation rate of apatitic calcium phosphate cements (CPC) containing poly(lactic-co-glycolic acid) (PLGA) microspheres. The composites were soaked in phosphate-buffered saline up to 6 weeks under unstirred, stirred, or perfused conditions followed by analysis of mass loss, compression strength, porosity, crystal phase composition, and morphology of the cement composites. The results showed that fluid perfusion reduced the decrease in pH and corresponding degradation rates, while nonperfused soaking conditions (i.e., stirred and unstirred conditions) resulted into more extensive acidification, the rate of which increased with stirring. After 2 weeks, the formation of a secondary brushite phase was observed for cement composites soaked under nonperfused (i.e., stirred and unstirred) conditions, whereas this phase was not detected in cements soaked under perfused conditions. The degradation rate of cement composites decreased in the order unstirred>stirred>perfused, as evidenced by quantification of mass loss, compression strength, and pore morphology. To summarize, we have demonstrated that soaking conditions strongly affected the in vitro degradation process of CPCs. As a consequence, it can be concluded that the experimental design of current in vitro degradation studies does not allow for correlation to (pre-)clinical studies.

  1. Resistance of Phosphogypsum Cement Pozzolanic Compositions against the Influence of Water

    Directory of Open Access Journals (Sweden)

    Sergejus GAIDUČIS

    2011-09-01

    Full Text Available The reprocessing of freshly removed extractive hemihydrate phosphogypsum into hydraulic composite phosphogypsum cement pozzolana (PGCP binder using mechanical activation is analyzed in this work. In order to increase the effectiveness of the dealing with phosphogypsum reprocessing problem and to lower the energy consumption required for the production of binding materials from phosphogypsum, physical mechanical and water resistance properties of the PGCP binder with less amount (10 % of cement (PGCP(10 were analyzed and compared with the properties of conventional PGCP binder, where the amount of cement is 20 % (PGCP(20. The PGCP binder with pozzolana additives of two types - carbonate opoka and microsilica are analysed. Fresh wet hemihydrate phosphogypsum, cement and pozzolana additive were mechanically activated together and from resulting mixture the samples were formed by vibrating. Compressive strength of PGCP(10 samples after 28 days was 26 MPa - 29 MPa, after 4 months - 30 MPa - 32 MPa, PGCP(20 - 32 MPa - 35 MPa and 36 MPa - 42 MPa accordingly. It is found, that hardened PGCP(10 are also quite resistant to short-term (2 days impact of water (softening coefficient was 0.91 - 0.94, however, its resistance to long-term impact of water is significantly less than PGCP(20. PGCP with microsilica is more strength and more resistant to impact of water than PGCP with opoka. Both, PGCP with opoka, as well as the ones with microsilica, are resistant to the formation of ettringite. However, the primary ettringite and high amount of carbonates, found in the PGCP with opoka, stimulates the formation of thaumasite at low positive temperature and humidity.http://dx.doi.org/10.5755/j01.ms.17.3.599

  2. Tensile bond strength of indirect composites luted with three new self-adhesive resin cements to dentin

    Directory of Open Access Journals (Sweden)

    Cafer Türkmen

    2011-08-01

    Full Text Available OBJECTIVE: The aims of this study were to evaluate the tensile bond strengths between indirect composites and dentin of 3 recently developed self-adhesive resin cements and to determine mode of failure by SEM. MATERIAL AND METHODS: Exposed dentin surfaces of 70 mandibular third molars were used. Teeth were randomly divided into 7 groups: Group 1 (control group: direct composite resin restoration (Alert with etch-and-rinse adhesive system (Bond 1 primer/adhesive, Group 2: indirect composite restoration (Estenia luted with a resin cement (Cement-It combined with the same etch-and-rinse adhesive, Group 3: direct composite resin restoration with self-etch adhesive system (Nano-Bond, Group 4: indirect composite restoration luted with the resin cement combined with the same self-etch adhesive, Groups 5-7: indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem, Maxcem, and Embrace WetBond, respectively onto the non-pretreated dentin surfaces. Tensile bond strengths of groups were tested with a universal testing machine at a constant speed of 1 mm/min using a 50 kgf load cell. Results were statistically analyzed by the Student's t-test. The failure modes of all groups were also evaluated. RESULTS: The indirect composite restorations luted with the self-adhesive resin cements (groups 5-7 showed better results compared to the other groups (p0.05. The surfaces of all debonded specimens showed evidence of both adhesive and cohesive failure. CONCLUSION: The new universal self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces.

  3. Tensile bond strength of indirect composites luted with three new self-adhesive resin cements to dentin

    Science.gov (United States)

    TÜRKMEN, Cafer; DURKAN, Meral; CİMİLLİ, Hale; ÖKSÜZ, Mustafa

    2011-01-01

    Objective The aims of this study were to evaluate the tensile bond strengths between indirect composites and dentin of 3 recently developed self-adhesive resin cements and to determine mode of failure by SEM. Material and Methods Exposed dentin surfaces of 70 mandibular third molars were used. Teeth were randomly divided into 7 groups: Group 1 (control group): direct composite resin restoration (Alert) with etch-and-rinse adhesive system (Bond 1 primer/adhesive), Group 2: indirect composite restoration (Estenia) luted with a resin cement (Cement-It) combined with the same etch-and-rinse adhesive, Group 3: direct composite resin restoration with self-etch adhesive system (Nano-Bond), Group 4: indirect composite restoration luted with the resin cement combined with the same self-etch adhesive, Groups 5-7: indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem, Maxcem, and Embrace WetBond, respectively) onto the non-pretreated dentin surfaces. Tensile bond strengths of groups were tested with a universal testing machine at a constant speed of 1 mm/min using a 50 kgf load cell. Results were statistically analyzed by the Student's t-test. The failure modes of all groups were also evaluated. Results The indirect composite restorations luted with the self-adhesive resin cements (groups 5-7) showed better results compared to the other groups (p0.05). The surfaces of all debonded specimens showed evidence of both adhesive and cohesive failure. Conclusion The new universal self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces. PMID:21710095

  4. The effect of temperature and moisture on electrical resistance, strain sensitivity and crack sensitivity of steel fiber reinforced smart cement composite

    Science.gov (United States)

    Teomete, Egemen

    2016-07-01

    Earthquakes, material degradations and other environmental factors necessitate structural health monitoring (SHM). Metal foil strain gages used for SHM have low durability and low sensitivity. These factors motivated researchers to work on cement based strain sensors. In this study, the effects of temperature and moisture on electrical resistance, compressive and tensile strain gage factors (strain sensitivity) and crack sensitivity were determined for steel fiber reinforced cement based composite. A rapid increase of electrical resistance at 200 °C was observed due to damage occurring between cement paste, aggregates and steel fibers. The moisture—electrical resistance relationship was investigated. The specimens taken out of the cure were saturated with water and had a moisture content of 9.49%. The minimum electrical resistance was obtained at 9% moisture at which fiber-fiber and fiber-matrix contact was maximum and the water in micro voids was acting as an electrolyte, conducting electrons. The variation of compressive and tensile strain gage factors (strain sensitivities) and crack sensitivity were investigated by conducting compression, split tensile and notched bending tests with different moisture contents. The highest gage factor for the compression test was obtained at optimal moisture content, at which electrical resistance was minimum. The tensile strain gage factor for split tensile test and crack sensitivity increased by decreasing moisture content. The mechanisms between moisture content, electrical resistance, gage factors and crack sensitivity were elucidated. The relations of moisture content with electrical resistance, gage factors and crack sensitivities have been presented for the first time in this study for steel fiber reinforced cement based composites. The results are important for the development of self sensing cement based smart materials.

  5. 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

  6. 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.

  7. Performance of hybrid cement composite elements under drop-weight impact load

    Directory of Open Access Journals (Sweden)

    Nguyen, V. D.

    2014-05-01

    Full Text Available The performance, under drop-weight impact load, of hybrid cement composite (HCC elements, consisting of a top layer of plain concrete (PC and a bottom layer of fibre reinforced concrete (FRC, in comparison with full-depth FRC and PC was studied. Apart from improving the tensile capacity of PC and saving fibre steel reinforcements of FRC, the results showed that HCC can effectively control the deformations and enhance the impact performance of the structural members as its outcomes were similar to that of a full-depth FRC. The analytical studies using Hughes empirical formulae (HEF and yield line theory (YLT adopted to investigate the practical use of HCC showed that they are applicable for design such HCC elements against impacts.Se estudió el comportamiento, frente a impacto de torre de caída, de elementos híbridos base cemento (HCC, formados por una capa superior de hormigón en masa (PC y una capa inferior de hormigón reforzado con fibras (FRC en comparación con elementos análogos íntegramente fabricados con FRC y PC. Además de proporcionar una mejora en la resistencia frente a flexo-tracción de los PC y un ahorro en refuerzo usando fibras de acero en el caso de los FRC, los resultados mostraron que el HCC puede controlar eficazmente las deformaciones y mejorar el rendimiento frente a impacto de los elementos estructurales ya que sus resultados fueron análogos a la de los FRC. Los estudios analíticos, utilizando HEF e YLT, adoptados para investigar el uso práctico de los HCC mostraron que los mismos son aplicables para el diseño de estos elementos frente a impacto.

  8. 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...

  9. Preparation of Electrolytic Manganese Residue Composite Cementing Material%电解锰渣复合胶凝材料的研制

    Institute of Scientific and Technical Information of China (English)

    王智; 高翠翠; 王庆珍

    2013-01-01

    Electrolytic manganese residue and calcined lime were used to stimulate the activity of the pozzolanic material of fly ash,and electrolytic manganese residue composite cementing material was researched and developed.The influence of electrolytic manganese residue and cement to composite cementing material was studied,and based on this,the optimal mix proportion was concluded.When the mass ratio of electrolytic manganese residue,fly ash,lime and cement was 50 ∶ 30 ∶ 10 ∶ 10,water to binder ratio was 0.55,28 d flexural,compressive strength of electrolytic manganese residue composite cementing material were 2.50 MPa,10.05 MPa.%利用电解锰渣和生石灰激发火山灰质材料粉煤灰的火山灰活性,制备电解锰渣复合胶凝材料.研究了电解锰渣和水泥对复合胶凝材料性能的影响,并在此基础上得出了最佳配合比,当电解锰渣复合胶凝材料中电解锰渣、粉煤灰、生石灰与水泥的质量比为50∶30∶ 10∶10,取水胶质量比为0.55,其28d抗折、抗压强度分别为2.50 MPa、10.05 MPa.

  10. Mechanical Behaviour of Composite Bioactive Bone Cements Consisting of Two Different Types of Surface Treated Hydroxyapatite as Filler

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Bioactive bone cements based on a paste-paste system for orthopaedic applications were developed consisting of hydroxyapatite ( HA ) filler particles in a methacrylate matrix comprising urethane dimethacrylate(UDMA) and triethylene glycol dimethacrylate ( TEGDMA ). To improve the interface between inorganic filler and orgaric matrix the HA particles were subjected to two different surface treatment methods, using polyacrylic acid ( PAA ) and γ- methacryloxy propyl trimethoxy silane (γMPS). The aim of the present study was to determine the influence of surface treatment and the inclusion of multifunctional methacrylates on the mechanical properties,namely 3-point flexural strength (FS) and fracture toughness of the cements and the effect of ageing in simulated body fluid. Comparing the mechanical properties of the two cements, the γMPS-HA cement showed that the fracture toughness of the experimental bone cements were significantly greater (p< 0.001) compared to that of the PMMA cement, whereas PAA-HA containing cement had strength values around 20% lower. Interestingly, PAA was found to be more effective in improving the interface as the PAA treated HA cement ( UTHAPPA ) maintained its strength on immersion in SBF , suggesting that PAA provided a coupling, which was less sensitive to moisture,a similar trend was also observed with the inclusion of the carboxyl containing multifunctional methacrylates.

  11. Consolidation analysis of composite foundation with partially penetrated cement fly-ash gravel (CFG) piles under changing permeable boundary conditions

    Institute of Scientific and Technical Information of China (English)

    邹新军; 赵增明; 徐洞斌

    2015-01-01

    Based on the double-layered foundation theory, the composite ground with partially penetrated cement fly-ash gravel (CFG) piles was regarded as a double-layered foundation including the surface reinforced area and the underlying untreated stratum. Due to the changing permeability property of CFG piles, the whole consolidation process of the composite ground with CFG piles was divided into two stages, i.e., the early stage (permeable CFG pile bodies) and the later stage (impermeable pile bodies). Then, the consolidation equation of the composite foundation with CFG piles was established by using the Terzaghi one-dimensional consolidation theory. Consequently, the unified formula to calculate the excess pore water pressure was derived with the specific solutions for the consolidation degree of composite ground, reinforced area and underlying stratum under instant load obtained respectively. Finally, combined with a numerical example, influencing rules by main factors (including the replacement ratem, the treatment depthh1, the permeability coefficientKs1,Kv2and compression modulusEs1,Es2 of reinforced area and underlying stratum) on the consolidation property of composite ground with CFG piles were discussed in detail. The result shows that the consolidation velocity of underlying stratum is slower than that of the reinforced area. However, the consolidation velocity of underlying stratum is slow at first then fast as a result of the transferring of effective stress to the underlying stratum during the dissipating process of excess pore water pressure.

  12. Influence of the mineralogical composition of cement in the diffusion of chemical species; Influencia de la composicion mineralogica del cemento en la difusion de especies quimicas

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E.

    2015-07-01

    The disposal is the final stage of radioactive waste management. This is essentially placing them in a facility with a reasonable assurance of safety. In this last stage, the ultimate goal is the confinement and isolation of radioactive waste from the human environment for a time period and under conditions such that the release of radionuclides not put in radiation risk to people and the environment. In relation to the storage of radioactive waste of low and medium activity, the final repositories for radioactive waste, based in cement materials are already operating in many countries. The isolation is performed by applying natural or artificial barriers between radioactive waste and man so as to prevent the release of radionuclides to the environment, until they have decreased their toxicity. The cement-based materials are involved in the different stages of the radioactive waste management since they are used for immobilization of waste in the container, container manufacturing and filling the spaces between the containers and vaults container and also as a barrier engineering and construction material in civil engineering. The concrete (cement mix + water + sand + gravel) it is one of the materials used to produce the engineered barrier system and produce containers for radioactive waste. In addition to their mechanical properties (product processing into hydraulic binder after being hydrated), their composition and solubility allow cushion the contact groundwater to ph higher (12.0 - 13.5) during considerable time scales (10{sup 14} - 10{sup 15} years) and it has an active role with the radionuclides confinement present in the radiological inventory of radioactive waste. The study of the microstructures of cement is a constant challenge for specialists working in this area, mainly due to the complex and heterogeneous mineralogical composition. Cement consists of many different phases in order to achieve specific properties such as reactivity properties

  13. 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.

  14. 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.

  15. Base deflection and microleakage of composite restorations.

    Science.gov (United States)

    Paulillo, L A; de Goes, M F; Consani, S

    1994-06-01

    The flexural deflections of human dentin, Herculite XR, Dycal, Vidrion F, zinc phosphate base, and combinations of composite-base were determined. The influence of the flexural deflections in the marginal microleakage was also determined for the composite-base combinations. The flexural deflection test for dentin showed no statistically significant differences between the two floor cavity depths studied. There were significant differences among cements when the thickness of the base was 1 mm whereas no differences occurred at 2 mm. The composite-base combinations did not present statistical differences. There were no statistically significant differences in the microleakage levels among loaded and non-loaded specimens; however, dye penetration was visually greater in loaded samples.

  16. Microstructure of a Planting Material Consisting of Nutrition-Expansive Perlitic-Cement Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ji-ru; LIU Zu-de

    2003-01-01

    An ecotypic revetment material consisting of nutrition-expansive perlitic-cement composites is introduced. This planting material can combine vegetation recovery with slope protection. The XRD, SEM and image analysis techniques were used to study its composition and microstructure. Its strength was measured by an electro-hydraulic servo-controlled testing machine. The results show the unconfined compressive strength is about 393.6 kPa, and the average elastic modulus is about 47.0 MPa. The quartz, felspar, chlorite and calcite are the main non-clay minerals in the planting material. Its particles are mainly spherical,and the range of the equivalent diameter is 1.83 to 15.96 μm. The results also show the planting material contains a large amount of micro non-capillary and capillary pores, and has a microstructure characteristic of honeycomb and coralline. CSH gel produced by hydration of cement increases the strength and water stability of the particles. The anisotropy and slight orientation of the particles increase the void cross-section area,providing an explanation of the high permeability for the planting material.The better porosity of the planting material is apt tokeep moisture and nutriment, provides oxygen for plant root breathing, and aids to exhaust the carbon dioxide by means of exchanging with atmosphere, hence it can facilitate vegetation.

  17. Piezoresistive properties of cement composites reinforced by functionalized carbon nanotubes using photo-assisted Fenton

    Science.gov (United States)

    Jianlin, Luo; Kwok L, Chung; Qiuyi, Li; Shunjian, Chen; Lu, Li; Dongshuai, Hou; Chunwei, Zhang

    2017-03-01

    A combined chemical technique for surface functionalization of carbon nanotubes (CNTs) is presented in this paper. The functionalized CNTs (f-CNTs) were employed to reinforce both the mechanical and electromechanical properties of cementitious composites for the purpose of developing intrinsic self-sensing sensors. With moderate functionalization, the f-CNTs were found to easily disperse in an aqueous system while just aiding with low fraction of dispersants: (a) polyethylene oxide (MPEG), (b) Trition X-100 (Tx-100). Both the FTIR and DSC results show that the oxidation effect of this combined technique were not as strong as those when using conventional strong oxidation methods. As a result, the integrity of electronic structure inside the f-CNT reinforced cement matrixes can be effectively maintained. This paper is aimed at exploring the electrical resistivity and piezoresistive properties of the f-CNT reinforced cement composites (f-CNT-RCCs). Both the monoaxial and cyclic compression tests were undertaken on the specimens with different f-CNT doping levels of 0.1%, 0.2% and 0.3%. Experimental results indicated that excellent piezoresistive properties were achieved at the doping level of 0.3%, wherein high strain sensitivity were recorded as 254.9 and 286.6 for the cases of adding small amounts of surfactants, MPEG and combination of MPEG and Tx100, respectively.

  18. 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.

  19. 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.

  20. 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...

  1. Microstructure and Mechanical Properties of Calcium Phosphate Cement/Gelatine Composite Scaffold with Oriented Pore Structure for Bone Tissue Engineering

    Institute of Scientific and Technical Information of China (English)

    QI Xiaopeng; HE Fupo; YE Jiandong

    2012-01-01

    The macroporous calcium phosphate(CPC) cement with oriented pore structure was prepared by freeze casting.SEM observation showed that the macropores in the porous calcium phosphate cement were interconnected aligned along the ice growth direction.The porosity of the as-prepared porous CPC was measured to be 87.6% by Archimede's principle.XRD patterns of specimens showed that poorly crystallized hydroxyapatite was the main phase present in the hydrated porous calcium phosphate cement.To improve the mechanical properties of the CPC scaffold,the 15% gelatine solution was infiltrated into the pores under vacuum and then the samples were freeze dried to form the CPC/gelatine composite scaffolds.After reinforced with gelatine,the compressive strength of CPC/gelatine composite increased to 5.12 MPa,around fifty times greater than that of the unreinforced macroporous CPC scaffold,which was only 0.1 MPa.And the toughness of the scaffold has been greatly improved via the gelatine reinforcement with a much greater fracture strain.SEM examination of the specimens indicated good bonding between the cement and gelatine.Participating the external load by the deformable gelatine,patching the defects of the CPC pores wall,and crack deflection were supposed to be the reinforcement mechanisms.In conclusion,the calcium phosphate cement/gelatine composite with oriented pore structure prepared in this work might be a potential scaffold for bone tissue engineering.

  2. A novel injectable calcium phosphate cement-bioactive glass composite for bone regeneration.

    Directory of Open Access Journals (Sweden)

    Long Yu

    Full Text Available BACKGROUND: Calcium phosphate cement (CPC can be molded or injected to form a scaffold in situ, which intimately conforms to complex bone defects. Bioactive glass (BG is known for its unique ability to bond to living bone and promote bone growth. However, it was not until recently that literature was available regarding CPC-BG applied as an injectable graft. In this paper, we reported a novel injectable CPC-BG composite with improved properties caused by the incorporation of BG into CPC. MATERIALS AND METHODS: The novel injectable bioactive cement was evaluated to determine its composition, microstructure, setting time, injectability, compressive strength and behavior in a simulated body fluid (SBF. The in vitro cellular responses of osteoblasts and in vivo tissue responses after the implantation of CPC-BG in femoral condyle defects of rabbits were also investigated. RESULTS: CPC-BG possessed a retarded setting time and markedly better injectability and mechanical properties than CPC. Moreover, a new Ca-deficient apatite layer was deposited on the composite surface after immersing immersion in SBF for 7 days. CPC-BG samples showed significantly improved degradability and bioactivity compared to CPC in simulated body fluid (SBF. In addition, the degrees of cell attachment, proliferation and differentiation on CPC-BG were higher than those on CPC. Macroscopic evaluation, histological evaluation, and micro-computed tomography (micro-CT analysis showed that CPC-BG enhanced the efficiency of new bone formation in comparison with CPC. CONCLUSIONS: A novel CPC-BG composite has been synthesized with improved properties exhibiting promising prospects for bone regeneration.

  3. Preparation of Cement Composites with Ordered Microstructures via Doping with Graphene Oxide Nanosheets and an Investigation of Their Strength and Durability

    Directory of Open Access Journals (Sweden)

    Shenghua Lv

    2016-11-01

    Full Text Available The main problem with cement composites is that they have structural defects, including cracks, holes, and a disordered morphology, which significantly affects their strength and durability. Therefore, the construction of cement composites with defect-free structures and high strength and long durability is an important research topic. Here, by controlling the size and chemical groups of graphene oxide nanosheets (GONs used for doping, we were able to control the entire cement matrix to form an ordered microstructure consisting of polyhedron-like crystals and exhibit flower-like patterns. The cracks and holes in the cement matrix just about vanished. The compressive and flexural strengths as well as the parameters for the durability assessment of the corresponding cement composites obviously improved compared with the control samples. Thus, the formation mechanism of the cement matrix with the ordered microstructure is proposed, and a proper explanation is given to regulation action.

  4. Unconfined compressive strength test of composite mineral powder soil-cement%复合矿粉水泥土的无侧限抗压强度试验

    Institute of Scientific and Technical Information of China (English)

    马晓宇; 李平

    2014-01-01

    将工业中生产的废渣制作成的复合矿粉掺加至水泥土中,既增强其性能,同时也可达到利废环保的目的。通过室内无侧限抗压强度试验,运用正交试验方法研究了影响复合矿粉水泥土抗压强度的主要因素及其影响规律。通过极差和方差分析可知,水泥掺量对复合矿粉水泥土的无侧限抗压强度的影响最大,其次是龄期,复合矿粉的影响最小。复合矿粉水泥土的早期强度提高主要是由于水泥的水化,而由矿粉和粉煤灰组成的复合矿粉具有微集料效应和火山灰效应,从而可改善水泥土的强度。%To mix the soil-cement with composite mineral powder made from the slag in industrial production can reinforce the property of the soil-cement,and is also environment-friendly to utilize the waste.Based on the indoor unconfined compressive strength test,we investigated the main factors that influence the compressive strength of composite mineral powder soil-cement. Analysis of range and variance shows that cement content is the major factor affecting the unconfined compressive strength,fol-lowed by age and in the last place,composite mineral powder.The improvement of strength of composite mineral powder soil-ce-ment in the early period is mainly due to hydration of cement,while composite mineral powder which is made of mineral powder and fly ash has micro aggregate effect and pozzolanic effect.In general,the strength of soil-cement could be fairly improved.

  5. 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].

  6. 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.

  7. 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.)

  8. Influence of Nano-SiO2 on the Consistency, Setting Time, Early-Age Strength, and Shrinkage of Composite Cement Pastes

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2016-01-01

    Full Text Available The study outlined the raw materials and mix proportions to prepare composite cement pastes with the addition of silica-based micro- and nanoparticles. The effects of amorphous nano-SiO2 on the early-age properties, including the consistency, setting time, early-age strength, and chemical and autogenous shrinkages, were investigated. Under the condition of the same dosage of superplasticizer used, the consistency of cement paste with nano-SiO2 is higher than that with silica fume. Significant reductions of the initial and final setting times are observed especially for nano-SiO2 addition groups, and the time difference between the initial and final setting times goes up with the increasing proportions of nano-SiO2. The addition of nano-SiO2 is more helpful to the improvement of early-age strengths of the paste with or without fly ash admixed than silica fume additive for the same mass proportion. Both the chemical and autogenous shrinkages of cement paste develop with the increasing amount of micro- or nanolevel silica particles; however, nano-SiO2 plays a more active role than silica fume in inspiring early-age shrinkage. The physical and chemical mechanisms of nano-SiO2 in cement paste are also discussed.

  9. Compósitos à base de cimento reforçado com polpa celulósica de bambu. Parte II: Uso de resíduos cerâmicos na matriz Cement-based composite reinforced with bamboo pulp. Part II: Use of ceramic residues in matrix

    Directory of Open Access Journals (Sweden)

    Marcos A. S. dos Anjos

    2003-08-01

    Full Text Available Este é o segundo dos dois artigos relativos aos resultados experimentais da combinação de matriz cimentícia reforçada com polpa celulósica de bambu. Neste trabalho, são mostrados os resultados da investigação da substituição parcial do cimento por resíduo de fábrica de blocos cerâmicos. O cimento foi substituído em percentagens de 20, 30 e 40% em relação à massa de cimento. Essas combinações foram reforçadas com polpa de bambu refinada. Os procedimentos e programas experimentais foram os mesmos adotados no artigo anterior (Parte 1. Considerando-se os resultados dos ensaios de obtenção das propriedades mecânicas, a substituição de 20% foi a que apresentou melhor performance.This paper is the second part of a series of two articles concerning the experimental results of newly developed composite with cementations matrix reinforced with bamboo pulp. In this part the results of the investigations concerning the partial substitution of Portland cement by grinded residues from a brick factory are presented. The cement was partially replaced in percentages of 20, 30 and 40% by weight. These composites were reinforced with only refined bamboo pulp. The same procedures described in Part I were adopted and used in the experimental program. Considering the results of the mechanical properties it is verified that 20% of cement replacement presented the best results.

  10. 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.

  11. 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...

  12. 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...

  13. Effect of the cross-linking silane concentration in a novel silane system on bonding resin-composite cement

    NARCIS (Netherlands)

    Matinlinna, Jukka; Ozcan, Mutlu; Lassila, Lippo; Kalk, Warner; Vallittu, Pekka

    2008-01-01

    Objective. Four experimental blends of an organo-functional silane monomer with a non-functional cross-linking silane monomer (a novel silane system) were evaluated as adhesion promoters in an experiment in which a resin-composite cement was bonded to silica-coated titanium. Material and Methods. 3-

  14. A novel controlled-release system for antibacterial enzyme lysostaphin delivery using hydroxyapatite/chitosan composite bone cement.

    Directory of Open Access Journals (Sweden)

    Bai Xue

    Full Text Available In this work, a lysostaphin-loaded, control-released, self-setting and injectable porous bone cement with efficient protein delivery was prepared by a novel setting method using hydroxyapatite/chitosan (HA/CS composite scaffold. The cement samples were made through cementitious reactions by mixing solid powder, a mixture of HA/CS composite particles, lysostaphin, Ca(OH2, CaCO3 and NaHCO3, with setting liquid containing citric acid, acetic acid, NaH2PO4, CaCl2 and poloxamer. The setting parameters of the cement samples were determined. The results showed that the final setting time was 96.6±5.2 min and the pH value increased from approximately 6.2 to nearly 10 during the setting process and the porosity was 34% at the end. And the microstructure and composition were detected by scanning electron microscopy (SEM, x-ray diffraction and Fourier transform-infrared spectroscopy. For the release behavior of lysostaphin loaded in the cement sample, the in vitro cement extract experiment indicated that about 94.2±10.9% of the loaded protein was released before day 8 and the in vivo Qdot 625 fluorescence tracking experiment showed that the loaded protein released slower than the free one. Then the biocompatibility of the cement samples was evaluated using the methylthiazol tetrazolium assay, SEM and hematoxylin-eosin staining, which suggested good biocompatibility of cement samples with MC 3T3-E1 cells and subcutaneous tissues of mice. Finally the antibacterial activity assay indicated that the loaded lysostaphin had good release ability and strong antibacterial enzymatic activity against methicillin-resistant Staphylococcus aureus. Collectively, all the results suggested that the lysostaphin-loaded self-setting injectable porous bone cement released the protein in a controlled and effective way and the protein activity was well retained during the setting and releasing process. Thus this bone cement can be potentially applied as a combination of

  15. 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.

  16. 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.

  17. 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.

  18. Development of high performance fiber reinforced cement composites (HPFRCC for application as a transition layer of reinforced beams

    Directory of Open Access Journals (Sweden)

    V. J. Ferrari

    Full Text Available This study presents the development and behavior analysis of high performance fiber reinforced cement composites (HPFRCC. The describedmaterials were specifically developed for application as a transition layer: a repair layer that constitutes the stressed chord of reinforcedconcrete beams strengthened in flexure with carbon fiber reinforced polymers (CFRP. Nineteen different composites were produced by thehybridization process, varying the conventional short steel fiber and steel microfiber (manufactured exclusively for this research contentsto modify the microstructure of the material, thus enhancing the stress transfer process from the cement matrix to the fibers. To analyze theresponse to flexural loading, the composites underwent three point bending tests in notched prism specimens. The response of the materialwas obtained considering strength and tenacity parameters (flexural and fracture. There was evidence of high performance by the composites with a pseudo-hardening behavior.

  19. The influence of natural pozzolana mineralogical composition in the properties of blended cement

    Directory of Open Access Journals (Sweden)

    Gener Rizo, M.

    2002-09-01

    Full Text Available The pozzolana activity is the main property of the active additions but, in order to select them, we have to consider - between other factors- its mineralogical composition with a great influence, not only in the active component, but also in other cement properties. In the present work we have studied 4 different Cuban natural pozzolanes, characterized with the help of X ray diffraction and with thermic and chemical analysis. The pozzolanic activity was also evaluated through a chemical and physicomechanic method. Some cements were prepared with different contents of each one of the pozzolanics, and analysed their physicomechanic and chemical properties. Finally, we found that the pozzolanics mineralogical composition has a great influence in the pozzolanic activity and in the properties of mixed cements. Also we found that it 5 possible to obtain the best resistances in the time and the smaller needs of water when the vitreous phase prevail in the additions.

    La actividad puzolánica es la propiedad fundamental de las adiciones activas, pero para la selección de la misma se debe considerar, entre otros factores, su composición mineralógica, que influye no sólo en los constituyentes activos, sino también en muchas propiedades de los cementos. En el presente trabajo, como material puzolánico se estudiaron 4 puzolanas naturales cubanas, las cuales fueron caracterizadas mediante difracción de Rayos X, análisis térmico y análisis químico; se evaluó, además, la actividad puzolánica mediante un método químico y otro físico-mecánico. Se prepararon cementos con diferentes contenidos de cada una de las puzolanas y se analizaron sus propiedades químicas y físico-mecánicas. Se concluye que la composición mineralógica de las puzolanas influye de forma determinante en la actividad puzolánica y en las propiedades de los cementos mezclados; que los mejores desarrollos de resistencias en el tiempo y los menores requerimientos

  20. 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.

  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. Predicting composition-property relationships for glass ionomer cements: a multifactor central composite approach to material optimization.

    Science.gov (United States)

    Kiri, Lauren; Boyd, Daniel

    2015-06-01

    Adjusting powder-liquid ratio (P/L) and polyacrylic acid concentration (AC) has been documented as a means of tailoring the handling and mechanical properties of glass ionomer cements (GICs). This work implemented a novel approach in which the interactive effects of these two factors on three key GIC properties (working time, setting time, and compressive strength) were investigated using a central composite design of experiments. Using nonlinear regression analysis, formulation-property relationships were derived for each property, which enabled prediction of an optimal formulation (P/L and AC) through application of the desirability approach. A novel aluminum free GIC was investigated, as this material may present the first clinically viable GIC for use in injectable spinal applications, such as vertebroplasty. Ultimately, this study presents the first series of predictive regression models that explain the formulation-dependence of a GIC, and the first statistical method for optimizing both P/L and AC depending on user-defined inputs.

  3. 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%.

  4. Adhesion of indirect MOD resin composite inlays luted with self-adhesive and self-etching resin cements.

    Science.gov (United States)

    Inukai, T; Abe, T; Ito, Y; Pilecki, P; Wilson, R F; Watson, T F; Foxton, R M

    2012-01-01

    This study investigated the effect of loading on the bond strength to dentin and microleakage of MOD indirect composite restorations bonded with self-adhesive and self-etching resin cements with or without acid etching of the proximal enamel margins. Class II MOD cavities were prepared in 48 molar teeth into dentin and divided into three groups of 16 teeth. Impressions were taken and indirect composite inlays fabricated (Estenia C & B). The enamel margins of the proximal boxes of half the specimens were phosphoric acid etched, and the inlays were cemented with one of three cements (Panavia F 2.0, SA Cement, or Rely X Unicem). After luting, eight teeth in each cement group were mechanically loaded at 2.5 cycles/s for 250,000 cycles. Unloaded teeth acted as controls. Teeth were stored in Rhodamine B solution for 24 hours, sectioned buccolingually at the proximal boxes to examine microleakage using confocal microscopy, and further sectioned for μTBS testing of the resin-dentin interface. Analysis of variance was performed to assess the effect of loading and acid etching on microleakage and bond strength. Acid etching had no effect on microleakage. No significant difference in the dentin bond strengths between the three cements existed after loading. Panavia F 2.0 exhibited a significant reduction in bond strength. With regard to microleakage at the proximal boxes, loading had no effect on dye penetration at the cavity floor. However, at the axial walls, loading had a significant deleterious effect on Panavia F 2.0. No difference in microleakage existed between the three cements at both sites before and after loading. In conclusion, the two tested self-adhesive cements exhibited similar bond strengths before and after loading to the self-etching resin cement. Loading reduced dentin bond strengths and increased microleakage at the resin-dentin interface. However, acid etching of the enamel margins had no significant effect on microleakage in the approximal regions of

  5. Probing the hydration of composite cement pastes containing fly ash and silica fume by proton NMR spin-lattice relaxation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Proton NMR spin-lattice relaxation (T1) was used as a prober for observing the hydration process of composite cement pastes blending fly ash and silica fume during the early age.The distribution at initial time,evolution curves and signals intensity of T1 were shown in this paper.Results demonstrate that the T1 distribution curves at initial time exhibit two peaks,which are regarded as two different water phases in the pastes.The evolution curves of T1 are in good agreement with the hydration process of composite pastes and could be roughly divided into four stages:initial period,dormant period,acceleration period and steady period.The hydration mechanism for each stage was discussed.The hydration of the composite cement pastes was retarded by the addition of fly ash and silica fume when compared to that of pure cement.However,the hydration degree of the cement in the blends was promoted.

  6. Composite time-lapse computed tomography and micro finite element simulations: A new imaging approach for characterizing cement flows and mechanical benefits of vertebroplasty.

    Science.gov (United States)

    Stadelmann, Vincent A; Zderic, Ivan; Baur, Annick; Unholz, Cynthia; Eberli, Ursula; Gueorguiev, Boyko

    2016-02-01

    Vertebroplasty has been shown to reinforce weak vertebral bodies and reduce fracture risks, yet cement leakage is a major problem that can cause severe complications. Since cement flow is nearly impossible to control during surgery, small volumes of cement are injected, but then mechanical benefits might be limited. A better understanding of cement flows within bone structure is required to further optimize vertebroplasty and bone augmentation in general. We developed a novel imaging method, composite time-lapse CT, to characterize cement flow during injection. In brief, composite-resolution time-lapse CT exploits the qualities of microCT and clinical CT. The method consists in overlaying low-resolution time-lapse CT scans acquired during injection onto pre-operative high-resolution microCT scans, generating composite-resolution time-lapse CT series of cement flow within bone. In this in vitro study, composite-resolution time-lapse CT was applied to eight intact and five artificially fractured cadaveric vertebrae during vertebroplasty. The time-lapse scans were acquired at one-milliliter cement injection steps until a total of 10 ml cement was injected. The composite-resolution series were then converted into micro finite element models to compute strains distribution under virtual axial loading. Relocation of strain energy density within bone structure was observed throughout the progression of the procedure. Interestingly, the normalized effect of cement injection on the overall stiffness of the vertebrae was similar between intact and fractured specimens, although at different orders of magnitude. In conclusion, composite time-lapse CT can picture cement flows during bone augmentation. The composite images can also be easily converted into finite element models to compute virtual strain distributions under loading at every step of an injection, providing deeper understanding on the biomechanics of vertebroplasty.

  7. Luting of CAD/CAM ceramic inlays: direct composite versus dual-cure luting cement.

    Science.gov (United States)

    Kameyama, Atsushi; Bonroy, Kim; Elsen, Caroline; Lührs, Anne-Katrin; Suyama, Yuji; Peumans, Marleen; Van Meerbeek, Bart; De Munck, Jan

    2015-01-01

    The aim of this study was to investigate bonding effectiveness in direct restorations. A two-step self-etch adhesive and a light-cure resin composite was compared with luting with a conventional dual-cure resin cement and a two-step etch and rinse adhesive. Class-I box-type cavities were prepared. Identical ceramic inlays were designed and fabricated with a computer-aided design/computer-aided manufacturing (CAD/CAM) device. The inlays were seated with Clearfil SE Bond/Clearfil AP-X (Kuraray Medical) or ExciTE F DSC/Variolink II (Ivoclar Vivadent), each by two operators (five teeth per group). The inlays were stored in water for one week at 37°C, whereafter micro-tensile bond strength testing was conducted. The micro-tensile bond strength of the direct composite was significantly higher than that from conventional luting, and was independent of the operator (P<0.0001). Pre-testing failures were only observed with the conventional method. High-power light-curing of a direct composite may be a viable alternative to luting lithium disilicate glass-ceramic CAD/CAM restorations.

  8. Comparison of the resin cement bond strength to an indirect composites treated by Er;YAG laser and sandblast

    Directory of Open Access Journals (Sweden)

    Mansure Mirzaee

    2014-04-01

    Full Text Available   Background and Aims: Indirect composites are designed to overcome the shortcomings of direct composites such as polymerization shrinkage and low degree of conversion. But, good adhesion of resin cements to indirect composites is still difficult. This research was designed to assess the effect of different powers of Er;YAG laser compared with sandblasting. On the micro tensil bond strength of resin cement to indirect composites.   Materials and Methods: Specimens were prepred using dental resin composite (Gradia GC and metallic mold (15×5×5 mm and were cured according to the manufacturer’s instructions. 24 blocks were prepared and randomly divided into 12 groups. G1:no treatment (as control, G 2-6: Er; YAG laser irradiation (2, 3, 4, 5, 6 Watt, G7: sandblast. Two composite blocks were bonded to each other with Panavia F.2. resin cement. The cylindrical sections with dimensions of 1 mm were tested in a microtensile bond strength tester device using 0.5 mm/min speed until fracture points. Data were analyzed using 2-way ANOVA and T-test.   Results: Interaction between lasers irradiation and sandblast treatments were significant (P0.05 whether samples were sandblasted or not. Samples which received 300 mJ of laser showed lower bond strength compared with no laser treatment. Other groups showed no significant difference (P>0.05.   Conclusion: It seems that application of sandblast with proper variables, is a good way to improve bond strength.Laser application had no influence in improving the bond strength between the indirect composite and resin cement.

  9. 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

  10. 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.

  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. 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. Surface hardness properties of resin-modified glass ionomer cements and polyacid-modified composite resins.

    Science.gov (United States)

    Bayindir, Yusuf Ziya; Yildiz, Mehmet

    2004-11-15

    In this study the top and bottom surface hardness of two polyacid-modified composite resins (PMCRs), one resin-modified glass ionomer cement (RMGIC), and one composite resin were evaluated. The affect of water storage on their hardness was also investigated. The study was conducted using four different groups, each having five specimens obtained from fiberglass die molds with a diameter of 5 mm and a height of 2 mm. Measurements were made on the top and bottom surface of each specimen and recorded after 24 hours and again at 60 days. All tested materials showed different hardness values, and the values of top surfaces of the specimens were found to be higher than the bottom surface in all test groups. There was no statistical difference in the Vickers hardness (HV) values when the test specimens were kept in water storage. In conclusion Hytac displayed microhardness values higher than Vitremer and Dyract. We found the order of HV values to be Surfil > Hytac > Dyract > Vitremer, respectively. Vitremer presented the lowest microhardness level and Surfil the highest.

  14. Improve the performance of coated cemented hip stem through the advanced composite materials.

    Science.gov (United States)

    Hedia, H S; Fouda, N

    2015-01-01

    Design of hip joint implant using functionally graded material (FGM) (advanced composite material) has been used before through few researches. It gives great results regarding the stress distribution along the implant and bone interfaces. However, coating of orthopaedic implants has been widely investigated through many researches. The effect of using advanced composite stem material, which mean by functionally graded stem material, in the total hip replacement coated with the most common coated materials has not been studied yet. Therefore, this study investigates the effect of utilizing these two concepts together; FGM and coating, in designing new stem material. It is concluded that the optimal FGM cemented stem is consisting from titanium at the upper stem layers graded to collagen at a lower stem layers. This optimal graded stem coated with hydroxyapatite found to reduce stress shielding by 57% compared to homogenous titanium stem coated with hydroxyapatite. However, the optimal functionally graded stem coated with collagen reduced the stress shielding by 51% compared to homogenous titanium stem coated with collagen.

  15. 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.

  16. Environmental impact assessment of combustible wastes utilization in rotary cement kilns

    OpenAIRE

    2013-01-01

    This study focuses on the environmental impact assessment of the coal combustion and its substitution by alternative fuels from combustible wastes during Portland cement clinker sinterization in rotary cement kiln. Environmental impact assessment was carried out based on the fuels chemical composition and operating parameters of a rotary cement kiln in accordance with EURITS and IMPACT 2002+ methods.

  17. 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

    storage of the hydrogen atom. In such case, neutron tomography does not give information of the pore structure as neutrons will strongly scatter of H and the data have low count and low statistics or low neutron transmission. Hence, as the comparison and the possible tuning technique, neutron tomography measurements are performed on a Deuterium Oxide (D2O) or heavy water samples the same dimensions, cement composition, cement/liquid content and hydration time as the H2O samples. The advantage of using heavy water is that the total neutron cross-section for Deuterium is approximately four times smaller than Hydrogen's and, thus, permits better neutron transmission, i.e. better statistics. D2O does not alter cement properties or its chemical composition; therefore, the samples are almost identical. Comparison of the measurements using water and heavy water samples and the preparation of the measurement cement samples are discussed in this

  18. 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)

  19. 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.

  20. One-pot synthesis of hydroxyapatite–silica nanopowder composite for hardness enhancement of glass ionomer cement (GIC)

    Indian Academy of Sciences (India)

    Ismail A B Rahman; Sam'an Malik Masudi; Norhayati Luddin; Rayees Ahmad Shiekh

    2014-04-01

    Hydroxyapatite–silica nanopowder composite was prepared using one-pot sol–gel technique. The morphology of the powder consists of a mixture of spherical silica particles (∼ 30 nm) embedded within the elongated hydroxyapatite (∼ 103 nm). The synthesized nanoparticles were incorporated into commercial glass ionomer cement (GIC) and Vickers hardness was evaluated. Results shown that the addition of the nanopowder composite gave ∼ 73% increment in the hardness compared to the pure GIC. Higher content of hydroxyapatite–silica nanopowder resulted in dense cement and produced a stronger GIC and the application of this material with improved hardness property might lead to extend the clinical indications, especially in stress bearing areas.

  1. Corrosion control of cement-matrix and aluminum-matrix composites

    Science.gov (United States)

    Hou, Jiangyuan

    Corrosion control of composite materials, particularly aluminum-matrix and cement-matrix composites, was addressed by surface treatment, composite formulation and cathodic protection. Surface treatment methods studied include anodization in the case of aluminum-matrix composites and oxidation treatment (using water) in the case of steel rebar for reinforcing concrete. The effects of reinforcement species (aluminum nitride (AIN) versus silicon carbide (SiC) particles) in the aluminum-matrix composites and of admixtures (carbon fibers, silica fume, latex and methylcellulose) in concrete on the corrosion resistance of composites were addressed. Moreover, the effect of admixtures in concrete and of admixtures in mortar overlay (as anode on concrete) on the efficiency of cathodic protection of steel reinforced concrete was studied. For SiC particle filled aluminum, anodization was performed successfully in an acid electrolyte, as for most aluminum alloys. However, for AlN particle filled aluminum, anodization needs to be performed in an alkaline (0.7 N NaOH) electrolyte instead. The concentration of NaOH in the electrolyte was critical. It was found that both silica fume and latex improved the corrosion resistance of rebar in concrete in both Ca(OH)sb2 and NaCl solutions, mainly because these admixtures decreased the water absorptivity. Silica fume was more effective than latex. Methylcellulose improved the corrosion resistance of rebar in concrete a little in Ca(OH)sb2 solution. Carbon fibers decreased the corrosion resistance of rebar in concrete, but this effect could be made up for by either silica fume or latex, such that silica fume was more effective than latex. Surface treatment in the form of water immersion for two days was found to improve the corrosion resistance of rebar in concrete. This treatment resulted in a thin uniform layer of black iron oxide (containing Fesp{2+}) on the entire rebar surface except on the cross-sectional surface. Prior to the

  2. 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.

  3. 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

  4. 碳纤维水泥基复合材料力电性能及尺寸效应研究进展%RESEARCH ADVANCES ON FORCE-ELECTRICITY PROPERTIES AND SIZE EFFECT OF CARBON FIBER REINFORCED CEMENT BASED COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    刘汉; 童谷生

    2011-01-01

    碳纤维水泥基复合材料(CFRC)是一种新型功能材料,既可作为结构材料又可作为智能材料,与普通混凝土相比,它不仅具有纤维增强所带来的较高的抗拉、抗压、抗折强度与韧性,还具有相对较小的电阻率与力电机敏性等优越性能.本文介绍了碳纤维水泥基复合材料的制备方法、力电性能、应用及其尺寸效应的最新研究进展,展望了其在功能材料方面的研究应用前景.%Carbon fiber reinforced cement based composite is a new kind of functional materials,which can be used as structural material as well as smart material. Compared with normal concrete, it has high tensile, compres sive resistance and flexural strength and toughness, which also has a relatively low resistivity, superior performance of smart and so on. This article introduces the preparation methods, mechanical and electrical performance, application and the latest research advances on its size effect, prospects the development of its research and application on the functional materials.

  5. 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.

  6. Current perspectives of bio-ceramic technology in endodontics: calcium enriched mixture cement - review of its composition, properties and applications.

    Science.gov (United States)

    Utneja, Shivani; Nawal, Ruchika Roongta; Talwar, Sangeeta; Verma, Mahesh

    2015-02-01

    Advancements in bio-ceramic technology has revolutionised endodontic material science by enhancing the treatment outcome for patients. This class of dental materials conciliates excellent biocompatibility with high osseoconductivity that render them ideal for endodontic care. Few recently introduced bio-ceramic materials have shown considerable clinical success over their early generations in terms of good handling characteristics. Calcium enriched mixture (CEM) cement, Endosequence sealer, and root repair materials, Biodentine and BioAggregate are the new classes of bio-ceramic materials. The aim of this literature review is to present investigations regarding properties and applications of CEM cement in endodontics. A review of the existing literature was performed by using electronic and hand searching methods for CEM cement from January 2006 to December 2013. CEM cement has a different chemical composition from that of mineral trioxide aggregate (MTA) but has similar clinical applications. It combines the biocompatibility of MTA with more efficient characteristics, such as significantly shorter setting time, good handling characteristics, no staining of tooth and effective seal against bacterial leakage.

  7. Microstructure and Composition of Hydration Products of Ordinary Portland Cement with Ground Steel-making Slag

    Institute of Scientific and Technical Information of China (English)

    LI Yong-xin; CHEN Yi-min; ZHANG Hong-tao; HE Xing-yang; WEI Jiang-xiong; ZHANG Wen-sheng

    2003-01-01

    The effect of ground steel-making slag on microstructure and composition of hydration products of ordinary Portland cement (OPC) was investigated by mercury intrusion porosimetry ( MIP ), X- ray diffraction (XRD) and differential thermal analysis (DTA). Results show that ground steel-making slag is a kind of high activity mineral additives and it can raise the longer-age strength of OPC mortar. The total porosity and average pore diameter of OPC paste with groand steel-making slag increase with the increase of the amount of ground steelmaking slag replacing OPC at various ages, while after 28 days most pores in OPC paste with ground steel-making slag do not influeace the strength because the diameter of those pores is in the rang of 20 to 50nm. The hydration mechanism of ground steel-making slag is similar to that of OPC but different from that of fly ash and blast furnace slag. The hydration products of ground steel-making slag contain quite a lot of Ca( OH)2 in long age.

  8. 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.

  9. 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.

  10. 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.

  11. 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).

  12. REST based service composition

    DEFF Research Database (Denmark)

    Grönvall, Erik; Ingstrup, Mads; Pløger, Morten

    2011-01-01

    This paper presents an ongoing work developing and testing a Service Composition framework based upon the REST architecture named SECREST. A minimalistic approach have been favored instead of a creating a complete infrastructure. One focus has been on the system's interaction model. Indeed, an aim...

  13. 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

  14. 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.

  15. 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.

  16. Optimization of a novel two-solution poly(methyl methacrylate) bone cement: Effect of composition on material properties and polymerization kinetics

    Science.gov (United States)

    Hasenwinkel, Julie Miller

    A novel two-solution poly(methyl methacrylate) bone cement was developed as an alternative to powder/liquid cements, which are used clinically for the fixation of total joint replacements. This material polymerizes via a free radical mechanism, initiated by the redox reaction of benzoyl peroxide (BPO) and N,N dimethyl-p-toluidine (DMPT). The two-solution concept is advantageous over powder/liquid formulations because it minimizes sources of porosity, produces a homogeneous microstructure, simplifies the mixing and delivery process, and reduces the dependence of material properties on surgical techniques. Experiments were performed to determine the effect of initiation chemistry on the material properties and polymerization kinetics of twelve cement compositions. Select material properties were also evaluated with respect to polymer/monomer ratio and initial polymer molecular weight. The results confirm the hypothesis that initiation chemistry affects material properties via the polymerization kinetics and resulting microstructural properties. The exotherm, setting time, flexural mechanical properties, fracture toughness, fatigue behavior, and residual monomer were evaluated, with respect to initiation chemistry. The flexural strength, modulus, and exotherm were maximized, while the residual monomer was minimized at a BPO:DMPT molar ratio of 1:1. High DMPT concentrations resulted in sub-optimal properties, with short setting times and reduced ductility, fracture toughness, and fatigue strength. Initial polymer molecular weight had no significant effect on the material properties. Polymer conversion and free radical concentration were measured by infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopy. These data were used to calculate the polymerization reaction rates and kinetic rate constants for each composition. Stoichiometric concentrations of BPO and DMPT maximized the radical concentration and conversion. The BPO and DMPT concentrations

  17. 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.

  18. 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.

  19. Influence of different degrees of acetylation in the physical and mechanical properties of particleboards and wood-cement composites

    Directory of Open Access Journals (Sweden)

    Setsuo Iwakiri

    2014-12-01

    Full Text Available Chemical modified wood particles used to particleboards manufacture may, at the same time, improve the dimensional stability and damage the internal bond. The aim of this research was find the optimal point of acetylation for particleboards. Pinus taeda particles with different degrees of acetylation, 8, 15 and 20% of weight percentage gain (WGP, were used in the production of particleboards with urea-formaldehyde resin and wood-cement composites produced by mechanical and vibratory compaction. It was evaluated the water absorption, thickness swelling and internal bind of the particleboards according to the European standards EN 317 and EN 319. Particleboards produced with 15 WPG showed the lowest water absorption and thickness swelling values. However, the use of chemically modified wood had a negative influence in the internal bind of the boards. This phenomenon can be explain due to the similar behavior between resin and water, that way, the high degree acetylation stops the adhesive and adherent bind. In the case of wood-cement composites, the internal bind improves as the acetylation degrees get higher. Nevertheless the inhibition of acetylated wood particles to the cement hydration got higher when the WPG was higher than 8%.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Material Mismatch Effect on the Fracture of a Bone-Composite Cement Interface.

    Science.gov (United States)

    Khandaker, M; Tarantini, S

    2012-12-01

    The interfacial mechanics at the bone-implant interface is a critical issue for implant fixation and the filling of bone defects created by tumors and/or their excision. Our previous study found that micron and nano sizes MgO particles improved the fracture toughness of bone-cement interfaces under tension loading. The strength of bonding of different types of bone with different types of implants may not be the same. The aims of this research were to determine the influences of material mismatch due to bone orientation and a magnesium oxide (MgO) filler material for PMMA bone cement on the mechanical strength between bone and bone cement specimens. This research studied the longitudinal and transverse directions bovine cortical bone as different bone materials and poly Methyl MethAcrylate (PMMA) bone cement with and without MgO additives as different implant materials. The scope of work for this study was: (1) to determine the bending strength and modulus of different bone and bone cement specimens, (2) to determine whether inclusion of MgO particles on PMMA has any influence on these mechanical properties of PMMA, and (3) to determine whether bone orientation and inclusion of MgO particles with PMMA has any influence on the interface strength between bone and PMMA. This study showed that bone orientation has statistically significant effect on the bonding strength between bone and bone cement specimens (P value0.05).

  5. 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.

  6. Study on the effects of white rice husk ash and fibrous materials additions on some properties of fiber-cement composites.

    Science.gov (United States)

    Hamzeh, Yahya; Ziabari, Kamran Pourhooshyar; Torkaman, Javad; Ashori, Alireza; Jafari, Mohammad

    2013-03-15

    This work assesses the effects of white rice husk ash (WRHA) as pozzolanic material, virgin kraft pulp (VKP), old corrugated container (OCC) and fibers derived from fiberboard (FFB) as reinforcing agents on some properties of blended cement composites. In the sample preparation, composites were manufactured using fiber-to-cement ratio of 25:75 by weight and 5% CaCl(2) as accelerator. Type II Portland cement was replaced by WRHA at 0%, 25% and 50% by weight of binder. A water-to-binder ratio of 0.55 was used for all blended cement paste mixes. For parametric study, compressive strength, water absorption and density of the composite samples were evaluated. Results showed that WRHA can be applied as a pozzolanic material to cement and also improved resistance to water absorption. However, increasing the replacement level of WRHA tends to reduce the compressive strength due to the low binding ability. The optimum replacement level of WRHA in mortar was 25% by weight of binder; this replacement percentage resulted in better compressive strengths and water absorption. OCC fiber is shown to be superior to VKF and FFB fibers in increasing the compressive strength, due to its superior strength properties. As expected, the increase of the WRHA content induced the reduction of bulk density of the cement composites. Statistical analysis showed that the interaction of above-mentioned variable parameters was significant on the mechanical and physical properties at 1% confidence level.

  7. 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....

  8. An evaluation of the composition of soil cement bricks with construction and demolition waste - doi: 10.4025/actascitechnol.v33i2.9377

    Directory of Open Access Journals (Sweden)

    Antonio Anderson da Silva Segantini

    2011-04-01

    Full Text Available Sustainable development requires the existence of a production network that includes the reuse of construction waste for new materials. Current analysis investigates an optimal soil-cement composition made up of construction and demolition waste for the manufacture of pressed bricks. Soil-cement bricks were manufactured from construction and demolition wastes (CDW, A-4 classified fine sandy soil and cement CP II Z 32. Laboratory tests, comprising test compaction, optimum water content and maximum dry specific weight, consistency limits, grain size distribution and linear shrinkage, were made to characterize the materials researched. Compressive strength and absorption tests were also undertaken in different combinations of composition. Results showed that the application of CDW improved soil-cement qualities and reduced shrinkage of the material used.

  9. Phase composition, mechanical performance and in vitro biocompatibility of hydraulic setting calcium magnesium phosphate cement.

    Science.gov (United States)

    Klammert, Uwe; Reuther, Tobias; Blank, Melanie; Reske, Isabelle; Barralet, Jake E; Grover, Liam M; Kübler, Alexander C; Gbureck, Uwe

    2010-04-01

    Brushite (CaHPO(4) x 2H(2)O)-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times and low mechanical strengths limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of magnesium-substituted beta-tricalcium phosphate with the general formula Mg(x)Ca((3-x))((PO(4))(2) with 0 cement reactants. The incorporation of magnesium ions increased the setting times of cements from 2 min for a magnesium-free matrix to 8-11 min for Mg(2.25)Ca(0.75)(PO(4))(2) as reactant. At the same time, the compressive strength of set cements was doubled from 19 MPa to more than 40 MPa after 24h wet storage. Magnesium ions were not only retarding the setting reaction to brushite but were also forming newberyite (MgHPO(4) x 3H(2)O) as a second setting product. The biocompatibility of the material was investigated in vitro using the osteoblast-like cell line MC3T3-E1. A considerable increase of cell proliferation and expression of alkaline phosphatase, indicating an osteoblastic differentiation, could be noticed. Scanning electron microscopy analysis revealed an obvious cell growth on the surface of the scaffolds. Analysis of the culture medium showed minor alterations of pH value within the physiological range. The concentrations of free calcium, magnesium and phosphate ions were altered markedly due to the chemical solubility of the scaffolds. We conclude that the calcium magnesium phosphate (newberyite) cements have a promising potential for their use as bone replacement material since they provide a suitable biocompatibility, an extended workability and improved mechanical performance compared with brushite cements.

  10. 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

  11. In situ synchrotron X-ray powder diffraction study of the early hydration of α-tricalcium phosphate/tricalcium silicate composite bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Morejon-Alonso, Loreley; Correa, Jose Raul, E-mail: lmorejon@fq.uh.cu [Departamento de Quimica General, Facultad de Quimica, Universidad de La Habana, UH (Cuba); Motisuke, Mariana [Universidade Federal de Sao Paulo (UNIFESP), Sao Jose dos Campos, SP (Brazil); Carrodeguas, Raul Garcia [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Laboratorio de Avaliacao e Desenvolvimento de Biomateriais do Nordeste; Santos, Luis Alberto dos [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Escola de Engenharia. Departamento de Materiais

    2015-01-15

    Bioactivity, osteogenicity and mechanical properties of α-tricalcium phosphate (α-TCP) based phosphates cements can be improved by adding tricalcium silicate (C{sub 3}S); however, the addition of C{sub 3}S delays the precipitation and growth of calcium deficient hydroxyapatite (CDHA). Thus, the aim of this work was the study of in situ setting reaction of α-TCP/C{sub 3}S composite bone cement under high energy X-ray generated by a synchrotron source within the first 72h. The results showed that the addition of C{sub 3}S induces the precipitation of nanosized CDHA at early times depending on the added content. Calculated crystallite sizes showed that the higher the content of C{sub 3}S, the smaller the crystal size at the beginning of the precipitation. These results are different from those obtained by conventional XRD method, suggesting that the proposed technique is a powerful tool in determining the composition and extent of reaction of CPCs surfaces in real time. (author)

  12. 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.

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    Glaucio Laun Nacif

    2013-04-01

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

  15. 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

  16. 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

  17. 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

  18. 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...

  19. 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...

  20. Evaluation of push-out bond strength of two fiber-reinforced composite posts systems using two luting cements in vitro

    Directory of Open Access Journals (Sweden)

    Ajay Kadam

    2013-01-01

    Full Text Available Introduction: The concept of using a "post" for the restoration of teeth has been practiced to restore the endodontically treated tooth. Metallic posts have been commonly used, but their delirious effects have led to the development of fiber-reinforced materials that have overcome the limitations of metallic posts. The use of glass and quartz fibers was proposed as an alternative to the dark color of carbon fiber posts as far as esthetics was concerned. "Debonding" is the most common failure in fiber-reinforced composite type of posts. This study was aimed to compare the push-out bond strength of a self-adhesive dual-cured luting agent (RelyX U100 with a total etch resin luting agent (Variolink II used to cement two different FRC posts. Materials and Methods: Eighty human maxillary anterior single-rooted teeth were decoronated, endodontically treated, post space prepared and divided into four groups (n = 20; Group I: D.T. light post (RTD and Variolink II (Ivoclare vivadent, Group II: D.T. light post (RTD and RelyX U100 (3M ESPE, Group III: Glassix post (Nordin and Variolink II (Ivoclare vivadent and Group IV: Glassix post (Nordin and RelyX U100 (3M ESPE. Each root was sectioned to get slices of 2 ± 0.05-mm thickness. Push-out tests were performed using a triaxial loading frame. To express bond strength in megapascals (Mpa, load value recorded in Newton (N was divided by the area of the bonded interface. After testing the push-out strengths, the samples were analyzed under a stereomicroscope. Results: The mean values of the push-out bond strength show that Group I and Group III had significantly higher values than Group II and Group IV. The most common mode of failure observed was adhesive between dentin and luting material and between post and luting material. Conclusions: The mean push-out bond strengths were higher for Groups I and III where Variolink II resin cement was used for luting the fiber post, which is based on the total etch

  1. 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.

  2. Methotrexate-loaded glass ionomer cements for drug release in the skeleton: An examination of composition-property relationships.

    Science.gov (United States)

    Kiri, Lauren; Filiaggi, Mark; Boyd, Daniel

    2016-01-01

    Chemotherapeutic-loaded bone cement may be an effective method of drug delivery for the management of cancer-related vertebral fractures that require cement injection for pain relief. Recent advancements in the development of aluminum-free glass ionomer cements (GICs) have rendered this class of biomaterials clinically viable for such applications. To expand the therapeutic benefits of these materials, this study examined, for the first time, their drug delivery potential. Through incrementally loading the GIC with methotrexate (MTX) by up to 10-wt%, composition-property relationships were established, correlating MTX loading with working time and setting time, as well as compressive strength, drug release, and cytotoxic effect over 31 days. The most significant finding of this study was that MTX was readily released from the GIC, while maintaining cytotoxic activity. Release correlated linearly with initial loading and appeared to be diffusion mediated, delivering a total of 1-2% of the incorporated drug. MTX loading in this range exerted minimal effects to handling and strength, indicating the clinical utility of the material was not compromised by MTX loading. The MTX-GIC systems examined herein are promising materials for combined structural delivery applications.

  3. 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

  4. 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.

  5. 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.

  6. Correlation between microstructure, phase composition and mechanical properties of thermo-insulation bonding agents based on waste material

    Directory of Open Access Journals (Sweden)

    Terzić Anja

    2012-01-01

    Full Text Available Building composites - thermo-insulating and/or high-temperature resistant bonding agents in which fly ash, as potentially environmentally harmful waste material, is combined with ordinary and refractory cement is new option for reapplication of this waste material. In this study, investigated bonding agents were based on two types of fly ashes from coal combustion process and cements - ordinary Portland cement and highaluminate cement. Change of mineral phase composition of the composites with increasing temperature was analyzed by means of XRD method. Microstructural changes within investigated composites were investigated by means of scanning electron microscopy (SEM. Macro-performance - mechanical properties of the investigated bonding agents was finally correlated with its microstructure. The investigated bonding agents showed excellent compressive strength, while SEM and XRD analysis indicated its valuable refractory and thermo-insulation properties. [Projekat Ministarstva nauke Republike Srbije, br. 172057 i br. 45008

  7. 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.

  8. Effect of chemical vapor infiltration treatment on the wave-absorbing performance of carbon fiber/cement composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology.A thinner layer ofpyrocarbon was deposited on the fiber surface.The dispersion of carbon fibers in a cement matrix and the mechanical properties of carbon fiber/cement composites were investigated by scanning electron microscopy (SEM) and other tests.The reflectivity of electromagnetic waves by the composites was measured in the frequency range of 8.0-18 GHz for different carbon fiber contents of 0.2wt%,0.4wt%,0.6wt% ,and 1.0wt%.The results show that the reflectivity tends to increase with the increase of fiber content above 0.4wt%.The minimum reflectivity is -19.3 dB and the composites exhibit wave-absorbing performances.After pyrocarbon is deposited on the fiber,all the reflectivity data are far greater.They are all above -10 dB and display mainly wave-reflecting performances.

  9. 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.

  10. 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.

  11. Characterisation of Al corrosion and its impact on the mechanical performance of composite cement wasteforms by the acoustic emission technique

    Science.gov (United States)

    Spasova, L. M.; Ojovan, M. I.

    2008-04-01

    In this study acoustic emission (AE) non-destructive method was used to evaluate the mechanical performance of cementitious wasteforms with encapsulated Al waste. AE waves generated as a result of Al corrosion in small-size blast furnace slag/ordinary Portland cement wasteforms were recorded and analysed. The basic principles of the conventional parameter-based AE approach and signal-based analysis were combined to establish a relationship between recorded AE signals and different interactions between the Al and the encapsulating cement matrix. The AE technique was shown as a potential and valuable tool for a new area of application related to monitoring and inspection of the mechanical stability of cementitious wasteforms with encapsulated metallic wastes such as Al.

  12. Biocompatibility and degradation of poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composites

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2005-01-01

    Injectable calcium phosphate (Ca-P) cement materials exhibit favorable osteocompatible behavior but are resorbed slowly because of a lack of a bone ingrowth-enabling macroporosity. In this study, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (average size 66 +/- 25 microm) were incorporated

  13. 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.

  14. 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}).

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Effect of surface treatments of laboratory-fabricated composites on the microtensile bond strength to a luting resin cement.

    Science.gov (United States)

    Soares, Carlos José; Giannini, Marcelo; Oliveira, Marcelo Tavares de; Paulillo, Luis Alexandre Maffei Sartini; Martins, Luis Roberto Marcondes

    2004-03-01

    The purpose of this study was to evaluate the influence of different surface treatments on composite resin on the microtensile bond strength to a luting resin cement. Two laboratory composites for indirect restorations, Solidex and Targis, and a conventional composite, Filtek Z250, were tested. Forty-eight composite resin blocks (5.0 x 5.0 x 5.0mm) were incrementally manufactured, which were randomly divided into six groups, according to the surface treatments: 1- control, 600-grit SiC paper (C); 2- silane priming (SI); 3- sandblasting with 50 mm Al2O3 for 10s (SA); 4- etching with 10% hydrofluoric acid for 60 s (HF); 5- HF + SI; 6 - SA + SI. Composite blocks submitted to similar surface treatments were bonded together with the resin adhesive Single Bond and Rely X luting composite. A 500-g load was applied for 5 minutes and the samples were light-cured for 40s. The bonded blocks were serially sectioned into 3 slabs with 0.9mm of thickness perpendicularly to the bonded interface (n = 12). Slabs were trimmed to a dumbbell shape and tested in tension at 0.5mm/min. For all composites tested, the application of a silane primer after sandblasting provided the highest bond strength means.

  1. Influence of chemical composition of civil construction waste in the cement paste; Influencia da composicao quimica dos residuos da construcao civil a pasta de cimento

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, G.A.; Andrade, A.C.D.; Souza, J.M.M.; Evangelista, A.C.J.; Almeida, V.C., E-mail: valeria@eq.ufrj.b [Universidade Federal do Rio de Janeiro (EQ/UFRJ), RJ (Brazil). Escola de Quimica

    2009-07-01

    The construction and demolition waste when disposed inappropriately might cause serious public health problems. Its reutilization focusing on the development of new products using simple production techniques, assuring a new product life cycle and not damaging the environment is inserted in sustainable concept. The aim of this work was identifying the characteristics of types of waste generated in a residential reform (glassy ceramic and fill dirt leftovers) verifying separately its influence on cement pastes mechanical behavior. Cement pastes + wastes were prepared in 25% and 50% proportions with an approximately 0,35 water/cement relation and, glue time determination, water absorption, resistance to compression and X-ray fluorescence assays were taken. The results indicate that the chemical composition of the waste causes changes in the behavior of cement pastes, reflecting on their resistance to compression. (author)

  2. 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

  3. Resistance to fracture of endodontically treated premolars restored with glass ionomer cement or acid etch composite resin: An in vitro study

    Directory of Open Access Journals (Sweden)

    B Ranga

    2010-01-01

    Full Text Available Aim: Due to the weakness of endodontically treated posterior teeth requires more strengthened restoration to withstand occlusal forces. The purpose of the present study was to determine and compare the resistance to fracture of endodontically treated maxillary 1 st premolars restored with different materials in mesio-occluso-distal (MOD cavity preparations. Materials and Methods: MOD cavity preparations in 80 endodontically treated maxillary 1 st premolars were restored using four different methods. Fiber rings were filled with stone plaster and the teeth were placed into the plaster up to the level of cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instrom T.T. machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. Result: The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. Conclusion: The resistance to the fracture of the teeth was the same when they were stored with glass ionomer cement as a base over which composite resin was placed. When the entire cavities were filled with glass ionomer cement, the resistance to fracture of the teeth decreased significantly compared with the acid etch resin technique.

  4. 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

  5. Study on an Improved Phosphate Cement Binder for the Development of Fiber-Reinforced Inorganic Polymer Composites

    Directory of Open Access Journals (Sweden)

    Zhu Ding

    2014-11-01

    Full Text Available Magnesium phosphate cement (MPC has been proven to be a very good repair material for deteriorated concrete structures. It has excellent adhesion performance, leading to high bonding strength with old concrete substrates. This paper presents an experimental study into the properties of MPC binder as the matrix of carbon fiber sheets to form fiber-reinforced inorganic polymer (FRIP composites. The physical and mechanical performance of the fresh mixed and the hardened MPC paste, the bond strength of carbon fiber sheets in the MPC matrix, the tensile strength of the carbon FRIP composites and the microstructure of the MPC matrix and fiber-reinforced MPC composites were investigated. The test results showed that the improved MPC binder is well suited for developing FRIP composites, which can be a promising alternative to externally-bonded fiber-reinforced polymer (FRP composites for the strengthening of concrete structures. Through the present study, an in-depth understanding of the behavior of fiber-reinforced inorganic MPC composites has been achieved.

  6. Cement-based composites: Strain rate effects on fracture

    Energy Technology Data Exchange (ETDEWEB)

    Mindess, S.; Shah, S.P.

    1986-01-01

    This book contains over 20 selections. Some of the titles are: Continuum damage mechanics studies on the dynamic fracture of concrete; Dynamic compressive strength of cementitious materials; Rate-sensitivity of mode I and mode II fracture concrete; and An impact damage model of concrete.

  7. 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.

  8. 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.

  9. 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.

  10. Effect of various Portland cement paste compositions on early-age strain

    Science.gov (United States)

    Guzzetta, Alana G.

    Early-age strain in paste, mortar, and concrete mixtures was investigated using a new method where the specimen shape was a cone frustum. Strain of the specimen from both the horizontal and vertical directions was captured by height change measurement. The volumetric strain was then calculated as a function of the height change and was plotted versus time. A correlation was found between the slopes of the volumetric strain curve resulting from this test method and the initial setting time of the tested material. An initial evaluation of the repeatability of this innovative test method was conducted. The early-age strain effects of aggregate volume, shrinkage reducing admixture, water-cementitious ratio (w/cm), and partial cement replacement with supplementary cementitious materials were tested and individually compared. From these comparisons, it was observed that ambient temperature, bleed water development, and rheological properties had a significant impact on the volumetric strain results. Data showed increased strain as aggregate volume was reduced and as the w/cm was changed from 0.25 up to 0.50. The addition of shrinkage reducing admixture generally caused an increase in the 36-hour volumetric strain value. In most of the mixtures, cement replacement with 20% fly ash or 10% metakaolin reduced the measured volumetric strain when the w/cm was 0.30. Replacement of cement with 10% silica fume caused an insignificant change in volumetric strain results.

  11. Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

    Science.gov (United States)

    Baronins, J.; Setina, J.; Sahmenko, G.; Lagzdina, S.; Shishkin, A.

    2015-11-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

  12. 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.

  13. Improvement of in vitro physicochemical properties and osteogenic activity of calcium sulfate cement for bone repair by dicalcium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chun-Cheng [School of Dentistry, Chung Shan Medical University, Taichung City 402, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung City 402, Taiwan (China); Wang, Chien-Wen [Department of Biomedical Engineering, National Cheng Kung University, Tainan City 701, Taiwan (China); Hsueh, Nai-Shuo [Institute of Oral Science, Chung Shan Medical University, Taichung City 402, Taiwan (China); Ding, Shinn-Jyh, E-mail: sjding@csmu.edu.tw [School of Dentistry, Chung Shan Medical University, Taichung City 402, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung City 402, Taiwan (China); Institute of Oral Science, Chung Shan Medical University, Taichung City 402, Taiwan (China)

    2014-02-05

    Highlights: • Dicalcium silicate can improve osteogenic activity of calcium sulfate cement. • The higher the calcium sulfate content, the shorter the setting time in the composite cement. • The results were useful for designing calcium-based cement with optimal properties. -- Abstract: An ideal bone graft substitute should have the same speed of degradation as formation of new bone tissue. To improve the properties of calcium sulfate hemihydrate (CSH) featured for its rapid resorption, a low degradation material of dicalcium silicate (DCS) was added to the CSH cement. This study examined the effect of DCS (20, 40, 60 and 80 wt%) on the in vitro physicochemical properties and osteogenic activities of the calcium-based composite cements. The diametral tensile strength, porosity and weight loss of the composite cements were evaluated before and after soaking in a simulated body fluid (SBF). The osteogenic activities, such as proliferation, differentiation and mineralization, of human mesenchymal stem cells (hMSCs) seeded on cement surfaces were also examined. As a result, the greater the DCS amount, the higher the setting time was in the cement. Before soaking in SBF, the diametral tensile strength of the composite cements was decreased due to the introduction of DCS. On 180-day soaking, the composite cements containing 20, 40, 60 and 80 wt% DCS lost 80%, 69%, 61% and 44% in strength, respectively. Regarding in vitro bioactivity, the DCS-rich cements were covered with clusters of apatite spherulites after soaking for 7 days, while there was no formation of apatite spherulites on the CSH-rich cement surfaces. The presence of DCS could reduce the degradation of the CSH cements, as evidenced in the results of weight loss and porosity. More importantly, DCS may promote effectively the cell proliferation, proliferation and mineralization. The combination of osteogenesis of DCS and degradation of CSH made the calcium-based composite cements an attractive choice for

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.)

  19. 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.

  20. 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.

  1. Fracture frequency and longevity of fractured resin composite, polyacid-modified resin composite, and resin-modified glass ionomer cement class IV restorations: an up to 14 years of follow-up

    DEFF Research Database (Denmark)

    van Dijken, Jan W V; Pallesen, Ulla

    2010-01-01

    The aim of this study was to evaluate the fracture frequency and longevity of fractured class IV resin composite (RC), polyacid-modified resin composite (compomer; PMRC), and resin-modified glass ionomer cement (RMGIC) restorations in a longitudinal long-term follow-up. Eighty-five class IV RC (43...

  2. 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.

  3. A novel injectable, cohesive and toughened Si-HPMC (silanized-hydroxypropyl methylcellulose) composite calcium phosphate cement for bone substitution.

    Science.gov (United States)

    Liu, Weizhen; Zhang, Jingtao; Rethore, Gildas; Khairoun, Khalid; Pilet, Paul; Tancret, Franck; Bouler, Jean-Michel; Weiss, Pierre

    2014-07-01

    This study reports on the incorporation of the self-setting polysaccharide derivative hydrogel (silanized-hydroxypropyl methylcellulose, Si-HPMC) into the formulation of calcium phosphate cements (CPCs) to develop a novel injectable material for bone substitution. The effects of Si-HPMC on the handling properties (injectability, cohesion and setting time) and mechanical properties (Young's modulus, fracture toughness, flexural and compressive strength) of CPCs were systematically studied. It was found that Si-HPMC could endow composite CPC pastes with an appealing rheological behavior at the early stage of setting, promoting its application in open bone cavities. Moreover, Si-HPMC gave the composite CPC good injectability and cohesion, and reduced the setting time. Si-HPMC increased the porosity of CPCs after hardening, especially the macroporosity as a result of entrapped air bubbles; however, it improved, rather than compromised, the mechanical properties of composite CPCs, which demonstrates a strong toughening and strengthening effect. In view of the above, the Si-HPMC composite CPC may be particularly promising as bone substitute material for clinic application.

  4. Streptococcus mutans-induced secondary caries adjacent to glass ionomer cement, composite resin and amalgam restorations in vitro.

    Science.gov (United States)

    Gama-Teixeira, Adriana; Simionato, Maria Regina Lorenzeti; Elian, Silvia Nagib; Sobral, Maria Angela Pita; Luz, Maria Aparecida Alves de Cerqueira

    2007-01-01

    The aim of this study was to define, in vitro, the potential to inhibit secondary caries of restorative materials currently used in dental practice. Standard cavities were prepared on the buccal and lingual surfaces of fifty extracted human third molars. The teeth were randomly divided into five groups, each one restored with one of the following materials: glass ionomer cement (GIC); amalgam; light-cured composite resin; ion-releasing composite; and light-cured, fluoride-containing composite resin. The teeth were thermocycled, sterilized with gamma irradiation, exposed to a cariogenic challenge using a bacterial system using Streptococcus mutans, and then prepared for microscopic observation. The following parameters were measured in each lesion formed: extension, depth, and caries inhibition area. The outer lesions developed showed an intact surface layer and had a rectangular shape. Wall lesions were not observed inside the cavities. After Analysis of Variance and Component of Variance Models Analysis, it was observed that the GIC group had the smallest lesions and the greatest number of caries inhibition areas. The lesions developed around Amalgam and Ariston pHc restorations had an intermediate size and the largest lesions were observed around Z-100 and Heliomolar restorations. It may be concluded that the restorative materials GIC, amalgam and ion-releasing composites may reduce secondary caries formation.

  5. 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...

  6. 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

  7. 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.

  8. Mechanical Characterization of High-Performance Steel-Fiber Reinforced Cement Composites with Self-Healing Effect

    Directory of Open Access Journals (Sweden)

    Dong Joo Kim

    2014-01-01

    Full Text Available The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of micro-cracks, strongly affected by the type of fiber and sand, clearly produced the effects on the self-healing behavior. The use of fine silica sand in HPSFRCs with high strength deformed steel fibers successfully led to rapid healing owing to very fine cracks with width less than 20 µm. The use of very fine silica sand instead of normal sand produced 17%–19% higher tensile strength and 51%–58% smaller width of micro-cracks.

  9. 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

  10. Durabilidade de compósito biomassa vegetal-cimento modificado por polímero Durability of cellulose-cement composites modified by polymer

    Directory of Open Access Journals (Sweden)

    Lia L. Pimentel

    2006-08-01

    Full Text Available A durabilidade de compósito biomassa vegetal-cimento é um dos fatores mais importantes para a colocação desse material no mercado consumidor. A utilização de polímeros em concreto e argamassa, com o objetivo de melhorar sua durabilidade, é cada vez mais freqüente. Este estudo visou à caracterização de propriedades físicas e mecânicas de compósito biomassa vegetal-cimento modificado com polímeros e a análise da durabilidade desse compósito. Foi testado um polímero de base acrílica em compósitos produzidos com resíduo de Pinus caribaea. Foram realizados ensaios de envelhecimento acelerado, por meio de ciclos de molhamento e secagem, por imersão em água quente e ensaio de envelhecimento natural. As propriedades físicas do compósito avaliadas foram a massa específica aparente e a absorção total de água por imersão. As propriedades mecânicas foram determinadas por meio de ensaios de resistência à tração na flexão, analisando-se a tensão e a energia de ruptura. Os corpos-de-prova foram extraídos de placas executadas por simples prensagem. Ensaios de microscopia eletrônica de varredura foram utilizados para observar o estado da fibra e da matriz após os processos de envelhecimento. O uso de polímero melhorou o desempenho mecânico do compósito nas primeiras idades e também promoveu significativa redução da capacidade de absorção de água, demonstrando que o uso desse material pode vir a melhorar a durabilidade desses compósitos, uma vez que reduziu sensivelmente sua capacidade de absorção.The durability of the cellulose-cement composites is a decisive factor to introduce such material in the market. Polymers have been used in concrete and mortar production to increase its durability. The goal of this work was the physical and mechanical characterization of cellulose-cement composites modified by a polymer and the subsequent durability evaluation. The work also evaluated the dispersion of acrylic

  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. 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.

  13. Prediction of chloride ingress and binding in cement paste

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Nielsen, Erik Pram; Herforth, Duncan

    2007-01-01

    This paper summarizes recent work on an analytical model for predicting the ingress rate of chlorides in cement-based materials. An integral part of this is a thermodynamic model for predicting the phase equilibria in hydrated Portland cement. The model’s ability to predict chloride binding...... in Portland cement pastes at any content of chloride, alkalis, sulfates and carbonate was verified experimentally and found to be equally valid when applied to other data in the literature. The thermodynamic model for predicting the phase equilibria in hydrated Portland cement was introduced into an existing...... Finite Difference Model for the ingress of chlorides into concrete which takes into account its multi-component nature. The “composite theory” was then used to predict the diffusivity of each ion based on the phase assemblage present in the hydrated Portland cement paste. Agreement was found between...

  14. 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.

  15. Translucent quartz-fiber post luted in vivo with self-curing composite cement: case report and microscopic examination at a two-year clinical follow-up.

    Science.gov (United States)

    Dallari, Adriano; Rovatti, Laura; Dallari, Beatrice; Mason, Pier Nicola; Suh, Byoung In

    2006-06-01

    A maxillary central incisor with mild periodontitis and extensive loss of coronal tooth structure was endodontically treated and restored with a translucent quartz-fiber post and a composite core. Treatment was completed with the cementation of full-ceramic crowns on teeth 11 and 21. Informed consent was obtained from the patient. Due to the extent of the periodontal disease, tooth 11 was extracted two years later. With the patient's consent, the tooth was used for research. The tooth was sectioned at 11 levels perpendicularly to the long axis and investigated by means of optical microscopy and scanning electron microscope (SEM). The visual examination showed perfect adhesion between the various interfaces (restoration-dentin-post) at both the coronal and root levels. The adhesion between the post and dentin appeared to be free of gaps, and even where the composite cement showed a nonhomogeneous thickness, voids were not apparent. The tooth under examination allowed the authors to check the effectiveness of the adhesion and the integrity of the hybrid layer after exposure to the oral cavity for two years. The results of this investigation show that there were no gaps between the adhesive resin and dentin and no hydrolysis of the adhesive bond. This case suggests that it is possible to obtain good results in the short term from the cementation of quartz-fiber posts with composite resin cements.

  16. Zirconium diboride-based composites

    Energy Technology Data Exchange (ETDEWEB)

    Monteverde, F.; Dalle Fabbriche, D.; Bellosi, A. [CNR-IRTEC, Faenza (Italy). Research Inst. for Ceramics Technology

    2002-07-01

    Two zirconium diboride-based composites were produced and characterised. The starting compositions (wt%) were: 55ZrB{sub 2} + 41TiB{sub 2} + 4Ni and 83ZrB{sub 2} + 13B{sub 4}C + 4Ni. Microstructure, mechanical and physical properties of the hot pressed composites were studied. In both the cases, the nickel introduced as sintering aid promoted the densification during sintering. (orig.)

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Tissue response to experimental dental cements prepared from a modified powder glass composition.

    Science.gov (United States)

    Boaventura, Juliana Maria Capelozza; Bertolini, Marcio José; Padovani, Gislaine Cristina; de Oliveira, Maria Rita Brancini; Zaghete, Maria Aparecida; de Oliveira Júnior, Osmir Batista; de Andrade, Marcelo Ferrarezi

    2012-01-01

    The present work seeks to evaluate the biocompatibility of experimental glass ionomer cements (GIC) prepared from niobium-calcium fluoro-alumino-silicate glass powder and two commercial GICs. The GICs were implanted into the subcutaneous connective tissue of sixty rats. The rats were sacrificed during four varying time periods: 7, 15, 30, and 60 days and histopathological examinations were then performed. The Kruskal-Wallis test was performed to evaluate any significant differences between the materials. Additionally, multiple comparisons of the mean rank were also carried out using the Dunn test (p<0.05). No significant differences were observed that one GIC was superior to the other. The tissue response for all of the GICs tested was similar in all the periods examined.

  2. Advances in glass-ionomer cements

    OpenAIRE

    Davidson, Carel Leon

    2006-01-01

    This article describes the properties, advances and shortcomings of glass-ionomer cement as a restorative material. The adhesion of glass-ionomer to tooth structure is less technique sensitive than composite resins and its quality increases with time. Therefore glass-ionomer might turn out to the more reliable restorative material in minimal invasive dentistry based on adhesive techniques.

  3. Advances in glass-ionomer cements.

    Science.gov (United States)

    Davidson, Carel Leon

    2006-01-01

    This article describes the properties, advances and shortcomings of glass-ionomer cement as a restorative material. The adhesion of glass-ionomer to tooth structure is less technique sensitive than composite resins and its quality increases with time. Therefore glass-ionomer might turn out to the more reliable restorative material in minimal invasive dentistry based on adhesive techniques.

  4. 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

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. Design procedures for Strain Hardening Cement Composites (SHCC) and measurement of their shear properties by mechanical and 2-D Digital Image Correlation (DIC) method

    Science.gov (United States)

    Aswani, Karan

    The main objective of this study is to investigate the behaviour and applications of strain hardening cement composites (SHCC). Application of SHCC for use in slabs of common configurations was studied and design procedures are prepared by employing yield line theory and integrating it with simplified tri-linear model developed in Arizona State University by Dr. Barzin Mobasher and Dr. Chote Soranakom. Intrinsic material property of moment-curvature response for SHCC was used to derive the relationship between applied load and deflection in a two-step process involving the limit state analysis and kinematically admissible displacements. For application of SHCC in structures such as shear walls, tensile and shear properties are necessary for design. Lot of research has already been done to study the tensile properties and therefore shear property study was undertaken to prepare a design guide. Shear response of textile reinforced concrete was investigated based on picture frame shear test method. The effects of orientation, volume of cement paste per layer, planar cross-section and volume fraction of textiles were investigated. Pultrusion was used for the production of textile reinforced concrete. It is an automated set-up with low equipment cost which provides uniform production and smooth final surface of the TRC. A 3-D optical non-contacting deformation measurement technique of digital image correlation (DIC) was used to conduct the image analysis on the shear samples by means of tracking the displacement field through comparison between the reference image and deformed images. DIC successfully obtained full-field strain distribution, displacement and strain versus time responses, demonstrated the bonding mechanism from perspective of strain field, and gave a relation between shear angle and shear strain.

  10. Self-sensing and thermal energy experimental characterization of multifunctional cement-matrix composites with carbon nano-inclusions

    Science.gov (United States)

    D'Alessandro, A.; Pisello, A. L.; Sambuco, Sara; Ubertini, F.; Asdrubali, F.; Materazzi, A. L.; Cotana, F.

    2016-04-01

    The recent progress of Nanotechnology allowed the development of new smart materials in several fields of engineering. In particular, innovative construction materials with multifunctional enhanced properties can be produced. The paper presents an experimental characterization on cement-matrix pastes doped with Carbon Nanotubes, Carbon Nano-fibers, Carbon Black and Graphene Nano-platelets. Both electro-mechanical and thermo-physical investigations have been carried out. The conductive nano-inclusions provide the cementitious matrix with piezo-resistive properties allowing the detection of external strain and stress changes. Thereby, traditional building materials, such as concrete and cementitious materials in general, would be capable of self-monitoring the state of deformation they are subject to, giving rise to diffuse sensing systems of structural integrity. Besides supplying self-sensing abilities, carbon nano-fillers may change mechanical, physical and thermal properties of cementitious composites. The experimental tests of the research have been mainly concentrated on the thermal conductivity and the optical properties of the different nano-modified materials, in order to make a critical comparison between them. The aim of the work is the characterization of an innovative multifunctional composite capable of combining self-monitoring properties with proper mechanical and thermal-energy efficiency characteristics. The potential applications of these nano-modified materials cover a wide range of possibilities, such as structural elements, floors, geothermal piles, radiant systems and more.

  11. The influence of fatigue loading on the quality of the cement layer and retention strength of carbon fiber post-resin composite core restorations.

    Science.gov (United States)

    Bolhuis, Peter; de Gee, Anton; Feilzer, Albert

    2005-01-01

    Clinical studies have shown that endodontically treated teeth restored with short posts or deficient ferrules show a high failure risk. This study. evaluated the influence of fatigue loading on the quality of the cement layer between prefabricated quartz coated carbon fiber posts with restricted length and the root canal wall in maxillary pre-molars. Two adhesive resin composite cements, chemical-cured Panavia 21 (Group 1) and dual-cured RelyX-ARC (Group 2), and one resin-modified glass-ionomer cement, chemical-cured RelyX (Group 3), delta were selected for this study. Post- and-core restorations were made on single-rooted human maxillary premolars from which the coronal sections were removed at the level of the proximal cemento-enamel junction (CEJ). Following endodontic treatment, a post-and-core restoration with 6-mm post length was prepared for each tooth. The posts were directly cemented into the root canal and, after applying an adhesive (Clearfil Photo Bond), they were built up with a core build-up composite (Clearfil Photo Core). For each group (n=8), half of the specimens were exposed to fatigue loading (10(6) load cycles) almost perpendicular to the axial axis (85 degrees), while the other half were used as the control. Three parallel, transverse root sections, 1.5-mm thick, were cut from each specimen at the apical, medial and coronal location. These sections were examined by Scanning Electron Microscopy (SEM) to evaluate the integrity of the cement layer, while the retention strength of the cemented post sections was determined with the push-out test. The multivariate results of MANOVA showed that the condition main effect (fatigue or control) was not significant (p=0.059); the two other main effects, type of cement and section location, were significant (p=0.001 and p=0.008). For both the push-out strength and SEM evaluation of the cement layer integrity, the results significantly improved from RelyX to RelyX-ARC to Panavia 21 and also from apical to

  12. 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

  13. 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.

  14. EFFECT OF MgO ON THE COMPOSITION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT IN THE PRESENCE OF Na2O AND K2O

    Directory of Open Access Journals (Sweden)

    Jie Zhang

    2015-06-01

    Full Text Available The purpose of this study is to explore the effect of MgO (1 - 9 wt. % on the composition and properties of belite-barium calcium sulphoaluminate cement with additions of Na2O and K2O. The results show that 1 - 5 wt. % content of MgO can stabilize crystal types of M3-C3S, R-C3S and β-C2S. Moreover, MgO can promote the formation of C3S and C4AF, but has little effect on the formation of C2.75B1.25A3$ and C3A. The C3A/C4AF ratio is reduced by 22 % at 5 wt. % MgO, which indicates that appropriate MgO can decrease the liquid viscosity. In the presence of Na2O and K2O, the highest limit of incorporated amount of MgO is about 3 wt. %, which is higher than that in Portland cement clinker of 2 wt. %. Besides, MgO favors the formation of small C3S crystals in size of 4 - 20 μm. MgO enhances the hydration rate and mechanical property of cement at an optimal dosage (1 - 5 wt. %, beyond which an adverse effect could be resulted. At a MgO dosage of 5 wt. %, the compressive strengths of the cement at 1, 3, 7 and 28 days are 15.8, 39.3, 68.6 and 97.3 MPa, which increases by 116 %, 17 %, 10 % and 6 % respectively compared to the cement without MgO dopant. This study could lead to the effective use of magnesia-rich limestone in industrial production of belite-barium calcium sulphoaluminate cement.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Bonding of Cf/SiC composite to Invar alloy using an active cement, Ag-Cu eutectic and Cu interlayer

    Science.gov (United States)

    Lei, Zhao; Xiaohong, Li; Jinbao, Hou; Qiang, Sun; Fuli, Zhang

    2012-10-01

    The interfacial microstructures and mechanical properties of the joints formed by active cement added brazing in vacuum of Cf/SiC composite to Invar alloy, using Ag-Cu eutectic alloy and pure copper foil as braze alloy and interlayer respectively, were investigated. CuTi, Cu4Ti3, Fe2Ti and the reaction layer of TiC and Si were the predominant components at the joint interface. The maximum shear strength of the joint was 77 MPa for brazing at 850 °C for 15 min. The results show that active cement added brazing in vacuum using Ag-Cu eutectic alloy and Cu interlayer can be used successfully for joining Cf/SiC composites to Invar alloy.

  2. 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.

  3. rhBMP-2 release from injectable poly(DL-lactic-co-glycolic acid)/calcium-phosphate cement composites.

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2003-01-01

    BACKGROUND: In bone tissue engineering, poly(DL-lactic-co-glycolic acid) (PLGA) microparticles are frequently used as a delivery vehicle for bioactive molecules. Calcium phosphate cement is an injectable, osteoconductive, and degradable bone cement that sets in situ. The objective of this study was

  4. 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

  5. Assessment of Tensile Bond Strength of Fiber-Reinforced Composite Resin to Enamel Using Two Types of Resin Cements and Three Surface Treatment Methods

    Directory of Open Access Journals (Sweden)

    Tahereh Ghaffari

    2015-10-01

    Full Text Available Background: Resin-bonded bridgework with a metal framework is one of the most conservative ways to replace a tooth with intact abutments. Visibility of metal substructure and debonding are the complications of these bridgeworks. Today, with the introduction of fiber-reinforced composite resins, it is possible to overcome these complications. The aim of this study was to evaluate the bond strength of fiber-reinforced composite resin materials (FRC to enamel. Methods: Seventy-two labial cross-sections were prepared from intact extracted teeth. Seventy-two rectangular samples of cured Vectris were prepared and their thickness was increased by adding Targis. The samples were divided into 3 groups for three different surface treatments: sandblasting, etching with 9% hydrofluoric acid, and roughening with a round tapered diamond bur. Each group was then divided into two subgroups for bonding to etched enamel by Enforce and Variolink II resin cements. Instron universal testing machine was used to apply a tensile force. The fracture force was recorded and the mode of failure was identified under a reflective microscope. Results: There were no significant differences in bond strength between the three surface treatment groups (P=0.53. The mean bond strength of Variolink II cement was greater than that of Enforce (P=0.04. There was no relationship between the failure modes (cohesive and adhesive and the two cement types. There was some association between surface treatment and failure mode. There were adhesive failures in sandblasted and diamond-roughened groups and the cohesive failure was dominant in the etched group. Conclusion: It is recommended that restorations made of fiber-reinforced composite resin be cemented with VariolinkII and surface-treated by hydrofluoric acid. Keywords: Tensile bond strength; surface treatment methods; fiber-reinforced composite resin

  6. Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

    Directory of Open Access Journals (Sweden)

    Lee Yen-Chen

    2011-02-01

    Full Text Available Abstract Background Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined. Method The Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine. Results The results revealed the following 1 Regardless of the screw outer geometry (conical or cylindrical, solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws. 2 For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling, no significant difference in pullout strength was found between conical and cylindrical screws (p >0.05. 3 Cement infiltration into the open cell of

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Preparation of calcium sulphoaluminate cement using fertiliser plant wastes.

    Science.gov (United States)

    Singh, Maneesh; Kapur, P C; Pradip

    2008-08-30

    Phosphochalks from fertiliser plants contain significant amount of calcium sulphate along with P(2)O(5) and fluorine. The presence of these impurities makes them unsuitable for most applications and, hence its availability in millions of tons. We demonstrate that it is possible to prepare calcium sulphoaluminate-aluminoferrite based special cements having strength values comparable to ordinary Portland cement (OPC) using these waste chalks. Such cements are insensitive to the presence of impurities in the raw mixture, clinker at low temperatures (1,230 degrees C) and the clinkers produced are soft and friable. An empirical technique has been developed to predict the phase composition of the clinkers given the chemical composition of the starting raw mixture. The proposed low temperature clinkering route appears to be a promising method for converting waste phosphochalks into construction grade cements.

  12. 改善复合发泡水泥板性能的研究%Improve the performance of composite foam cement panels

    Institute of Scientific and Technical Information of China (English)

    徐建军; 刘宏亮; 钱中秋; 丁常正

    2013-01-01

    为改善复合发泡水泥板性能,克服其易粉化、强度低和吸水高的缺陷,从提高复合发泡水泥板的强度、降低其吸水率进行实验研究.结果表明,掺加憎水剂、苯丙乳液和降低水料比,能大幅度降低复合发泡水泥板的吸水率,提高其强度和表面硬度,克服了复合发泡水泥板易粉化、强度低和吸水高的缺陷.%In order to improve the performance of composite foam cement panels and overcome the defect of easy powder, low strength and high water absorption, experimental research was conducted from the aspect of improving strength and reducing water absorption of composite foam cement panels. Experimental results show that adding hydrophobic agent, styrene-acrylic emulsion and reducing the ratio of water can significantly reduce water absorption and improve its strength and surface hardness of the composite foam cement panels,and overcome the defect of easy powder, low strength and high water absorption.

  13. Micromechanical Models of Mechanical Response of High Performance Fibre Reinforced Cement Composites

    DEFF Research Database (Denmark)

    Li, V. C.; Mihashi, H.; Alwan, J.;

    1996-01-01

    generation of FRC with high performance and economical viability, is in sight. However, utilization of micromechanical models for a more comprehensive set of important HPFRCC properties awaits further investigations into fundamental mechanisms governing composite properties, as well as intergrative efforts......The state-of-the-art in micromechanical modeling of the mechanical response of HPFRCC is reviewed. Much advances in modeling has been made over the last decade to the point that certain properties of composites can be carefully designed using the models as analytic tools. As a result, a new...

  14. 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.

  15. 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)

  16. 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.

  17. Influence of fly ash and its mean particle size on certain engineering properties of cement composite mortars

    Energy Technology Data Exchange (ETDEWEB)

    Gengying Li; Xiaozhong Wu [Shantou University, Shantou (China). Department of Civil Engineering

    2005-06-01

    An experimental investigation on the effects of incorporating large volumes of fly ash on the early engineering properties and long-term strength of masonry mortars is reported. The effect of fly ash and its mean particle size (PD) on the variation of workability and strength has been studied. It was found that fly ash and its mean particle size play a very significant role on the strength of masonry mortars. It has been observed that the early-term strength, except the mortars incorporating coarse fly ash (CFA), was slightly influenced by the replacement with fly ash. The long-term strength (both the bond strength and the compressive strength) will significantly increase, especially for the bond strength of mortars incorporating coarse fly ash. It was also found that the bond strength significantly increased as the mean particle size of fly ash decreases after 28 days curing. However, the 7-day strength was little influenced by fly ash particle size. The fluidity of composite mortar enhanced due to replace cement and lime with fly ash, and the mean PD of fly ash significantly influenced the workability.

  18. The effect of different surfactants/plastisizers on the electrical behavior of CNT nano-modified cement mortars

    Science.gov (United States)

    Dalla, P. T.; Alafogianni, P.; Tragazikis, I. K.; Exarchos, D. A.; Dassios, K.; Barkoula, N.-M.; Matikas, T. E.

    2015-03-01

    Cement-based materials have in general low electrical conductivity. Electrical conductivity is the measure of the ability of the material to resist the passage of electrical current. The addition of a conductive admixture such as Multi-Walled Carbon Nanotubes (MWCNTs) in a cement-based material increases the conductivity of the structure. This research aims to characterize nano-modified cement mortars with MWCNT reinforcements. Such nano-composites would possess smartness and multi-functionality. Multifunctional properties include electrical, thermal and piezo-electric characteristics. One of these properties, the electrical conductivity, was measured using a custom made apparatus that allows application of known D.C. voltage on the nano-composite. In this study, the influence of different surfactants/plasticizers on CNT nano-modified cement mortar specimens with various concentrations of CNTs (0.2% wt. cement CNTs - 0.8% wt. cement CNTs) on the electrical conductivity is assessed.

  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. Recommended method for measurement of absorbency of superabsorbent polymers in cement-based materials

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro

    2015-01-01

    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......The application of superabsorbent polymers in concrete technology is now becoming a reality in several places in the world. Independently of the specific technical application involving any of the hydrogels, the design of cement-based materials requires that the knowledge on the absorbency......—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...

  1. 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.

  2. 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...

  3. 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.

  4. 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...

  5. The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

    Institute of Scientific and Technical Information of China (English)

    Jing MAO; Yan LIU; Bin ZHOU; Liyun YAO

    2008-01-01

    In this study, calcium phosphate cements (CPC) were prepared by mixing cement powders of tetracalcium phosphate (TTCP) with a cement liquid of phosphate acid saline solution. Tetracycline (TTC)-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry (FT-IR) no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

  6. Effects of air abrasion with alumina or glass beads on surface characteristics of CAD/CAM composite materials and the bond strength of resin cements

    Directory of Open Access Journals (Sweden)

    ARAO Nobuaki

    2015-12-01

    Full Text Available ABSTRACT Objective The study aimed to evaluate effects of air abrasion with alumina or glass beads on bond strengths of resin cements to CAD/CAM composite materials. Material and Methods CAD/CAM composite block materials [Cerasmart (CS and Block HC (BHC] were pretreated as follows: (a no treatment (None, (b application of a ceramic primer (CP, (c alumina-blasting at 0.2 MPa (AB, (d AB followed by CP (AB+CP, and (e glass-beads blasting at 0.4 MPa (GBB followed by CP (GBB+CP. The composite specimens were bonded to resin composite disks using resin cements [G-CEM Cerasmart (GCCS and ResiCem (RC]. The bond strengths after 24 h (TC 0 and after thermal cycling (TC 10,000 at 4–60°C were measured by shear tests. Three-way ANOVA and the Tukey compromise post hoc tests were used to analyze statistically significant differences between groups (α=0.05. Results For both CAD/CAM composite materials, the None group exhibited a significant decrease in bond strength after TC 10,000 (p0.05. The AB+CP group showed a significantly higher bond strength after TC 10,000 than did the AB group for RC (p<0.05, but not for GCCS. The GBB+CP group showed the highest bond strength for both thermal cyclings (p<0.05. Conclusions Air abrasion with glass beads was more effective in increasing bond durability between the resin cements and CAD/CAM composite materials than was using an alumina powder and a CP.

  7. Mechanical and fracture behavior of calcium phosphate cements

    Science.gov (United States)

    Jew, Victoria Chou

    compared to in water. Based on observed trends, mechanisms of stress corrosion cracking are considered. Strengthening methods using proteins as second phase additions to HA cement were also investigated. Critical flexure strength of these composites increases to a limited extent, primarily due to bridging of the fracture surfaces by organic phases. Despite the increase for critical values, stress corrosion crack growth of cement-albumin composites remains similar to unreinforced cement. This discrepancy between critical and subcritical behavior is discussed.

  8. PHYSICO-MECHANICAL CHARACTERIZATION OF A COMPOSITE FROM SUGAR CANE STRAW PARTICLES AND ALTERNATIVE CEMENTS

    Directory of Open Access Journals (Sweden)

    ANTONIO LUDOVICO BERALDO

    2013-01-01

    Full Text Available Actualmente, el bagazo de caña de azúcar es empleado como combustible alternativo. Mientras tanto, otros residuos como partículas obtenidas de la paja (SCSP, generados en la cosecha mecanizada, pueden presentar interés para varias aplicaciones, como en la producción de combustible o como árido no convencional para la producción de compuestos cementicios, en este caso remplazando parcialmente los áridos. En esta investigación, se evaluó el comportamiento de composites de SCSP (remplazando 33% de arena, en volumen combinado con cuatro tipos de matrices inorgánicas, una basada en cemento portland (OPC y otras tres matrices alternativas basadas en la sustitución de OPC por puzolanas, tales como la ceniza volante molida (GFA y el residuo de catalizador de petróleo (FCC: (A:100%OPC; B:50%OPC+50%GFA; C:50%OPC+40%GFA+10%FCC y D:50%OPC+30%GFA+20%FCC. El desempeño de los composites fue evaluado diariamente por ensayos no destructivos (END por ultrasonido y, después de los 28 días de curado, por ensayos de flexión y compresión. Los resultados indicaron la influencia de la edad del compuesto en la velocidad del pulso ultrasónico (VPU, observándose su estabilización alrededor de los 28 días; y también la influencia del tipo de matriz sobre el desempeño mecánico del composite. La resistencia a flexión y a compresión de los composites de la matriz A fueron superiores a los de las matrices alternativas. De entre ellas, la matriz D mostró superioridad en relación a las matrices B y C. De una forma general, el remplazo de 33% de arena por SCSP disminuyó acentuadamente el desempeño mecánico del composite: resistencia a flexión (del 9% al 24% y a compresión (del 38% al 53%. Para las tres matrices con puzolana, el descenso en el desempeño mecánico fue significativamente menor.

  9. 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....

  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. 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

  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. Protein-based composite materials

    Directory of Open Access Journals (Sweden)

    Xiao Hu

    2012-05-01

    Full Text Available Protein-based composite biomaterials have been actively pursued as they can encompass a range of physical properties to accommodate a broader spectrum of functional requirements, such as elasticity to support diverse tissues. By optimizing molecular interfaces between structural proteins, useful composite materials can be fabricated as films, gels, particles, and fibers, as well as for electrical and optical devices. Such systems provide analogies to more traditional synthetic polymers yet with expanded utility due to the material's tunability, mechanical properties, degradability, biocompatibility, and functionalization, such as for drug delivery, biosensors, and tissue regeneration.

  14. Effect of loading weight on bond durability of composite-type resin cement under cyclic impact test (part 2). Loading with light weight of 100-120 g.

    Science.gov (United States)

    Ohsawa, Masahiro; Fujiwara, Mamoru; Hayashi, Yoshihiko

    2009-03-01

    The bond durability of composite-type resin cement was evaluated by means of cyclic impact tests using three different loads. In terms of experimental setup, a casting alloy, 12% Au-Pd-Ag, was used as the adherend and bonded to a cast block using a composite-type cement (Bistite II). A shear load--using plungers of three different weights at 100, 110, and 120 g--was dropped from a 3-mm height onto a small piece of the casting alloy until debonding. The cycle numbers that caused debonding were 1756 +/- 680 x 10(4) times for 100 g, 1403 +/- 515 x 10(4) times for 110 g, and 420 +/- 200 x 10(4) times for 120 g, respectively. Therefore, the group loaded with 120 g showed a significantly lower value as compared to the other two groups. On the fracture mode of the cement, it was a bulk fracture regardless of the loading weight employed in this study--the same result obtained in a previous study where heavier weights were employed.

  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. 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...

  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. 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.

  19. The role of glass composition in the behaviour of glass acetic acid and glass lactic acid cements.

    Science.gov (United States)

    Shahid, Saroash; Billington, R W; Pearson, G J

    2008-02-01

    Cements have recently been described, made from glass ionomer glass reacted with acetic and lactic acid instead of polymeric carboxylic acid. From their behaviour a theory relating to a possible secondary setting mechanism of glass ionomer has been adduced. However, only one glass (G338) was used throughout. In this study a much simpler glass ionomer glass (MP4) was compared with G338. This produced very different results. With acetic acid G338 formed cement which became resistant to water over a period of hours, as previously reported, MP4 formed cement which was never stable to water. With lactic acid G338 behaved similarly to G338 with acetic acid, again as reported, but MP4 produced a cement which was completely resistant to water at early exposure and unusually became slightly less resistant if exposure was delayed for 6 h or more. These findings indicate that the theories relating to secondary setting in glass ionomer maturation may need revision.

  20. The interaction of pH, pore solution composition and solid phase composition of carbonated blast furnace slag cement paste activated with aqueous sodium monofluorophosphate

    NARCIS (Netherlands)

    Kempl, J.; Copuroglu, O.

    2015-01-01

    Blast Furnace Slag (BFS) is a waste product of industrial steel production and a common additive in the cement industry in Northern European countries. However, cementitious materials made from slag-rich cement, particularly CEM III /B, are very susceptible to carbonation. Recent investigations have

  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. Cement from magnesium substituted hydroxyapatite.

    Science.gov (United States)

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  3. Microwave assisted preparation of magnesium phosphate cement (MPC) for orthopedic applications: A novel solution to the exothermicity problem

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: Huan.Zhou@rockets.utoledo.edu [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH 43606 (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH 43606 (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH 43606 (United States); Division of Dentistry, The University of Toledo, Toledo, OH 43606 (United States)

    2013-10-15

    There are two interesting features of this paper. First, we report herein a novel microwave assisted technique to prepare phosphate based orthopedic cements, which do not generate any exothermicity during setting. The exothermic reactions during the setting of phosphate cements can cause tissue damage during the administration of injectable compositions and hence a solution to the problem is sought via microwave processing. This solution through microwave exposure is based on a phenomenon that microwave irradiation can remove all water molecules from the alkaline earth phosphate cement paste to temporarily stop the setting reaction while preserving the active precursor phase in the formulation. The setting reaction can be initiated a second time by adding aqueous medium, but without any exothermicity. Second, a special emphasis is placed on using this technique to synthesize magnesium phosphate cements for orthopedic applications with their enhanced mechanical properties and possible uses as drug and protein delivery vehicles. The as-synthesized cements were evaluated for the occurrences of exothermic reactions, setting times, presence of Mg-phosphate phases, compressive strength levels, microstructural features before and after soaking in (simulated body fluid) SBF, and in vitro cytocompatibility responses. The major results show that exposure to microwaves solves the exothermicity problem, while simultaneously improving the mechanical performance of hardened cements and reducing the setting times. As expected, the cements are also found to be cytocompatible. Finally, it is observed that this process can be applied to calcium phosphate cements system (CPCs) as well. Based on the results, this microwave exposure provides a novel technique for the processing of injectable phosphate bone cement compositions. - Highlights: • A microwave assisted system for bone cement manufacturing • A solution to exothermicity problem of acid–base reaction based bone cement

  4. Dual-setting brushite-silica gel cements.

    Science.gov (United States)

    Geffers, Martha; Barralet, Jake E; Groll, Jürgen; Gbureck, Uwe

    2015-01-01

    The current study describes a dual-mechanism-setting cement that combines a brushite-forming cement paste with a second inorganic silica-based precursor. Materials were obtained by pre-hydrolyzing tetraethyl orthosilicate (TEOS) under acidic conditions following the addition of a calcium phosphate cement (CPC) powder mixed of β-tricalcium phosphate and monocalcium phosphate. Cement setting occurred by a dissolution-precipitation process, while changes in pH during setting simultaneously initiated the condensation reaction of the hydrolyzed TEOS. This resulted in an interpenetrating phase composite material in which the macropores of the CPC were infiltrated by the microporous silica gel, leading to a higher density and a compressive strength ∼5-10 times higher than the CPC reference. This also altered the release of vancomycin as a model drug, whereby in contrast to the quantitative release from the CPC reference, 25% of the immobilized drug remained in the composite matrix. By varying the TEOS content in the composite, the cement phase composition could be controlled to form either brushite, anhydrous monetite or a biphasic mixture of both. The composites with the highest silicate content showed a cell proliferation similar to a hydroxyapatite reference with a significantly higher activity per cell. Surprisingly, the biological response did not seem to be attributed to the released silicate ions, but to the release of phosphate and the adsorption of magnesium ions from the cell culture medium.

  5. Biphasic products of dicalcium phosphate-rich cement with injectability and nondispersibility

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Chia-Ling [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, Feng Chia University, Taichung, 407, Taiwan (China); Dental Medical Devices and Materials Research Center, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Hung, Chun-Cheng; Wang, Jen-Chyan [Dental Medical Devices and Materials Research Center, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng, E-mail: wencchen@fcu.edu.tw [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, Feng Chia University, Taichung, 407, Taiwan (China)

    2014-06-01

    In this study, a calcium phosphate cement was developed using tetracalcium phosphate and surface-modified dicalcium phosphate anhydrous (DCPA). This developed injectable bone graft substitute can be molded to the shape of the bone cavity and set in situ through the piping system that has an adequate mechanical strength, non-dispersibility, and biocompatibility. The materials were based on the modified DCPA compositions of calcium phosphate cement (CPC), where the phase ratio of the surface-modified DCPA is higher than that of the conventional CPC for forming dicalcium phosphate (DCP)-rich cement. The composition and morphology of several calcium phosphate cement specimens during setting were analyzed via X-ray diffractometry and transmission electron microscopy coupled with an energy dispersive spectroscopy system. The compressive strength of DCP-rich CPCs was greater than 30 MPa after 24 h of immersion in vitro. The reaction of the CPCs produced steady final biphasic products of DCPs with apatite. The composites of calcium phosphate cements derived from tetracalcium phosphate mixed with surface-modified DCPA exhibited excellent mechanical properties, injectability, and interlocking forces between particles, and they also featured nondispersive behavior when immersed in a physiological solution. - Highlights: • Bone cement precursor with nanocrystals is characterized. • DCP-rich CPCs with nanocrystals exhibited biphasic product phases. • Nanocrystals in cement significantly affected the interlocking ability. • Nanocrystals in cement exhibited higher strength and anti-dispersion. • DCP-rich CPCs increase the potential of bioresorption after reaction.

  6. Shear bond strength evaluation of resin composite bonded to three different liners: TheraCal LC, Biodentine, and resin-modified glass ionomer cement using universal adhesive: An in vitro study

    OpenAIRE

    Deepa, Velagala L; Bhargavi Dhamaraju; Indira Priyadharsini Bollu; Tandri S Balaji

    2016-01-01

    Aims: To compare and evaluate the bonding ability of resin composite (RC) to three different liners: TheraCal LC TM (TLC), a novel resin-modified (RM) calcium silicate cement, Biodentine TM (BD), and resin-modified glass ionomer cement (RMGIC) using an universal silane-containing adhesive and characterizing their failure modes. Materials and Methods: Thirty extracted intact human molars with occlusal cavity (6-mm diameter and 2-mm height) were mounted in acrylic blocks and divided into th...

  7. 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.

  8. 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.

  9. 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.

  10. Photocurable bioactive bone cement based on hydroxyethyl methacrylate-poly(acrylic/maleic) acid resin and mesoporous sol gel-derived bioactive glass.

    Science.gov (United States)

    Hesaraki, S

    2016-06-01

    This paper reports on strong and bioactive bone cement based on ternary bioactive SiO2-CaO-P2O5 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.

  11. 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

  12. 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.

  13. 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.

  14. Chemical composition, effective atomic number and electron density study of trommel sieve waste (TSW), Portland cement, lime, pointing and their admixtures with TSW in different proportions.

    Science.gov (United States)

    Kurudirek, Murat; Aygun, Murat; Erzeneoğlu, Salih Zeki

    2010-06-01

    The trommel sieve waste (TSW) which forms during the boron ore production is considered to be a promising building material with its use as an admixture with Portland cement and is considered to be an alternative radiation shielding material, also. Thus, having knowledge on the chemical composition and radiation interaction properties of TSW as compared to other building materials is of importance. In the present study, chemical compositions of the materials used have been determined using a wavelength dispersive X-ray fluorescence spectrometer (WDXRFS). Also, TSW, some commonly used building materials (Portland cement, lime and pointing) and their admixtures with TSW have been investigated in terms of total mass attenuation coefficients (mu/rho), photon interaction cross sections (sigma(t)), effective atomic numbers (Z(eff)) and effective electron densities (N(e)) by using X-rays at 22.1, 25keV and gamma-rays at 88keV photon energies. Possible conclusions were drawn with respect to the variations in photon energy and chemical composition.

  15. 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.

  16. 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.

  17. 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.

  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. 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.

  20. Kinetics of strength gain of biocidal cements

    Directory of Open Access Journals (Sweden)

    Rodin Aleksandr Ivanovich

    Full Text Available Biocorrosion becomes the determinative durability factor of buildings and constructions. Damages of construction materials caused by bacteria, filamentous fungi, actinomycetes constitute a serious danger to the constructions of a building or a structure and to the health of people. Biodeteriorations are typical both in old and new constructions. A great quantity of destruction factors of industrial and residential buildings under the influence of microorganisms was established in practice. Providing products and constructions based on concretes fungicidal and bactericidal properties is an important direction of modern construction material science. The most efficient way to solve this task is creation of biocidal cements. The article presents the results of experimental studies of kinetic dependences of strength gain by biocidal cements by physico-mechanical and physico-chemical analysis methods. The identical velocity character of initial hydration of the developed compositions of biocidal cements is set, as well as a more calm behavior of hardening processes at later terms. It has been established that the compositions of biocidal cements modified by sodium sulfate and sodium fluoride possess the greatest strength.

  1. 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).

  2. 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.

  3. 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.

  4. Silicon-based nanoenergetic composites

    Energy Technology Data Exchange (ETDEWEB)

    Asay, Blaine [Los Alamos National Laboratory; Son, Steven [PURDUE UNIV; Mason, Aaron [PURDUE UNIV; Yarrington, Cole [PURDUE UNIV; Cho, K Y [PURDUE UNIV; Gesner, J [PSU; Yetter, R A [PSU

    2009-01-01

    Fundamental combustion properties of silicon-based nano-energetic composites was studied by performing equilibrium calculations, 'flame tests', and instrumented burn-tube tests. That the nominal maximum flame temperature and for many Si-oxidizer systems is about 3000 K, with exceptions. Some of these exceptions are Si-metal oxides with temperatures ranging from 2282 to 2978 K. Theoretical maximum gas production of the Si composites ranged from 350-6500 cm{sup 3}/g of reactant with NH{sub 4}ClO{sub 4} - Si producing the most gas at 6500 cm{sup 3}/g and Fe{sub 2}O{sub 3} producing the least. Of the composites tested NH{sub 4}ClO{sub 4} - Si showed the fastest burning rates with the fastest at 2.1 km/s. The Si metal oxide burning rates where on the order of 0.03-75 mls the slowest of which was nFe{sub 2}O{sub 3} - Si.

  5. Antibacterial potential of contemporary dental luting cements.

    Science.gov (United States)

    Daugela, Povilas; Oziunas, Rimantas; Zekonis, Gediminas

    2008-01-01

    The aims of this investigation were to evaluate the antibacterial activities of different types of dental luting cements and to compare antibacterial action during and after setting. Agar diffusion testing was used to evaluate the antibacterial properties of seven types of dental luting cements (glass ionomer cements (GICs), resin modified GICs, resin composite, zinc oxide eugenol, zinc oxide non-eugenol, zinc phosphate, zinc polycarboxylate cements) on Streptococcus mutans bacteria. Instantly mixed zinc phosphate cements showed the strongest antibacterial activity in contrast to the non-eugenol, eugenol and resin cements that did not show any antibacterial effects. Non-hardened glass ionomer, resin modified and zinc polycarboxylate cements exhibited moderate antibacterial action. Hardened cements showed weaker antibacterial activities, than those ones applied right after mixing.

  6. 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.

  7. 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.

  8. 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...

  9. Influence of ferrite phase in alite-calcium sulfoaluminate cements

    Science.gov (United States)

    Duvallet, Tristana Yvonne Francoise

    Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition

  10. Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

    Directory of Open Access Journals (Sweden)

    Babafemi A.J.

    2012-01-01

    Full Text Available This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method was adopted. The results show that the compressive strength of the VA-blended cement laterized concrete increased with the increase in curing age but decreased as the VA and laterite (LAT contents increased. The optimum replacement level was 20%LAT/20%VA. At this level the compressive strength increased with curing age at a decreasing rate beyond 28 days. The target compressive strength of 25N/mm2 was achieved for this mixture at 90 days of curing. VA content and curing age was noted to have significant effect (α ≤ 0.5 on the compressive strength of the VA-blended cement laterized concrete.

  11. Porous poly(DL-lactic-co-glycolic acid)/calcium phosphate cement composite for reconstruction of bone defects.

    NARCIS (Netherlands)

    Ruhe, P.Q.; Hedberg, E.L.; Padron, N.T.; Spauwen, P.H.M.; Jansen, J.A.; Mikos, A.G.

    2006-01-01

    Calcium phosphate (Ca-P) cements are injectable, self-setting ceramic pastes generally known for their favorable bone response. Ingrowth of bone and subsequent degradation rates can be enhanced by the inclusion of macropores. Initial porosity can be induced by CO(2) foaming during setting of the cem

  12. Development of multi-walled carbon nanotubes reinforced monetite bionanocomposite cements for orthopedic applications

    Energy Technology Data Exchange (ETDEWEB)

    Boroujeni, Nariman Mansoori [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Zhou, Huan, E-mail: Huan.Zhou@Rockets.utoledo.edu [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F. [Department of Mechanical, Industrial and Manufacturing Engineering, 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)

    2013-10-15

    In this study, we present results of our research on biodegradable monetite (DCPA, CaHPO{sub 4}) cement with surface-modified multi-walled carbon nanotubes (mMWCNTs) as potential bone defect repair material. The cement pastes showed desirable handling properties and possessed a suitable setting time for use in surgical setting. The incorporation of mMWCNTs shortened the setting time of DCPA and increased the compressive strength of DCPA cement from 11.09 ± 1.85 MPa to 21.56 ± 2.47 MPa. The cytocompatibility of the materials was investigated in vitro using the preosteoblast cell line MC3T3-E1. An increase of cell numbers was observed on both DCPA and DCPA-mMWCNTs. Scanning electron microscopy (SEM) results also revealed an obvious cell growth on the surface of the cements. Based on these results, DCPA-mMWCNTs composite cements can be considered as potential bone defect repair materials. - Highlights: • A monetite bone cement for orthopedic applications is reported. • Incorporation of MWCNTs into monetite bone cement is discussed. • Surface functionalized MWCNTs can improve the mechanical strength of monetite cement. • MWCNTs have no impacts on the cytocompatibility of monetite cements.

  13. 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".

  14. Magnetoelectric Composite Based Microwave Attenuator

    Science.gov (United States)

    Tatarenko, A. S.; Srinivasan, G.

    2005-03-01

    Ferrite-ferroelectric composites are magnetoelectric (ME) due to their response to elastic and electromagnetic force fields. The ME composites are characterized by tensor permittivity, permeability and ME susceptibility. The unique combination of magnetic, electrical, and ME interactions, therefore, opens up the possibility of electric field tunable ferromagnetic resonance (FMR) based devices [1]. Here we discuss an ME attenuator operating at 9.3 GHz based on FMR in a layered sample consisting of lead magnesium niobate-lead titanate bonded to yttrium iron garnet (YIG) film on a gadolinium gallium garnet substrate. Electrical tuning is realized with the application of a control voltage due to ME effect; the shift is 0-15 Oe as E is increased from 0 to 3 kV/cm. If the attenuator is operated at FMR, the corresponding insertion loss will range from 25 dB to 2 dB. 1. S. Shastry and G. Srinivasan, M.I. Bichurin, V.M. Petrov, A.S. Tatarenko. Phys. Rev. B, 70 064416 (2004). - supported by grants the grants from the National Science Foundation (DMR-0302254), from Russian Ministry of Education (Å02-3.4-278) and from Universities of Russia Foundation (UNR 01.01.026).

  15. Physicochemical changes of cements by ground water corrosion in radioactive waste storage; Evolucion fisicoquimica de los cementos por corrosion de aguas subterraneas en un almacen de desechos radioactivos

    Energy Technology Data Exchange (ETDEWEB)

    Contreras R, A.; Badillo A, V. E.; Robles P, E. F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Nava E, N. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)], e-mail: aida.contreras@inin.gob.mx

    2009-10-15

    Knowing that the behavior of cementations materials based on known hydraulic cement binder is determined essentially by the physical and chemical transformation of cement paste (water + cement) that is, the present study is essentially about the cement paste evolution in contact with aqueous solutions since one of principal risks in systems security are the ground and surface waters, which contribute to alteration of various barriers and represent the main route of radionuclides transport. In this research, cements were hydrated with different relations cement-aqueous solution to different times. The pastes were analyzed by different solid observation techniques XRD and Moessbauer with the purpose of identify phases that form when are in contact with aqueous solutions of similar composition to ground water. The results show a definitive influence of chemical nature of aqueous solution as it encourages the formation of new phases like hydrated calcium silicates, which are the main phases responsible of radionuclides retention in a radioactive waste storage. (Author)

  16. 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.

  17. 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.

  18. 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