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Hamlin M. Jennings - One of the best experts on this subject based on the ideXlab platform.
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density and water content of nanoscale solid c s h formed in alkali activated slag aas paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
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Density and water content of nanoscale solid C–S–H formed in alkali-activated slag (AAS) paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
Jeffrey J. Thomas - One of the best experts on this subject based on the ideXlab platform.
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An Apparatus for Dissecting Volumetric Changes in Hydrating Cement Paste
Mechanics and Physics of Creep Shrinkage and Durability of Concrete, 2013Co-Authors: Muhannad Abuhaikal, Jeffrey J. Thomas, S. Musso, Franz J. UlmAbstract:An apparatus has been designed to study the volumetric changes under controlled curing conditions. The apparatus is capable of measuring the Chemical Shrinkage as well as the macroscopic volumetric changes of sealed and saturated specimens under controlled pressure and temperature. Specifically, when measuring separately the macroscopic deformation (bulk Shrinkage) and the water absorption of a saturated specimen, we find that the sum of the bulk deformations and water absorption adds up to the Chemical Shrinkage. Furthermore, while we observe pore pressure drops in the hydrating cement paste even in the presence of an infinite supply of pressurized water (i.e. Chemical Shrinkage test conditions), bulk Shrinkage occurs even in the absence of negative liquid pressure and at (almost) zero effective stress. That is, at (very) early ages, other driving forces than capillary forces are at work to cause bulk Shrinkage.
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density and water content of nanoscale solid c s h formed in alkali activated slag aas paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
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Density and water content of nanoscale solid C–S–H formed in alkali-activated slag (AAS) paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
Andrew J. Allen - One of the best experts on this subject based on the ideXlab platform.
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density and water content of nanoscale solid c s h formed in alkali activated slag aas paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
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Density and water content of nanoscale solid C–S–H formed in alkali-activated slag (AAS) paste and implications for Chemical Shrinkage
Cement and Concrete Research, 2012Co-Authors: Jeffrey J. Thomas, Andrew J. Allen, Hamlin M. JenningsAbstract:Abstract Alkali-activated slag (AAS) paste was analyzed using small-angle neutron scattering (SANS). The scattering response indicates that the microstructure consists of a uniform matrix of hydration product with a high surface area studded with unhydrated cores of slag particles. In contrast with portland cement paste, no surface fractal scattering regime was detected, and elevated temperature curing (at 60 °C) had no detectable effect on the microstructure at any length scale studied. The specific surface area of the AAS pastes is about 25% higher than that of a portland cement paste cured under the same conditions. The composition and mass density of the nanoscale solid C–S–H phase formed in the AAS paste was determined using a previously developed neutron scattering method, in conjunction with a hydration model. The result ((CaO)0.99–SiO2–(Al2O3)0.06–(H2O)0.97, d = (2.73 ± 0.02) g/cm3) is significantly lower in calcium and in water as compared to portland cement or pure tricalcium silicate paste. These values were used to calculate the Chemical Shrinkage that would result from complete hydration of the AAS paste. The result, (12.2 ± 1.5) cm3 of volumetric Shrinkage per 100 g of unhydrated cement, is about twice the amount of Chemical Shrinkage exhibited by normal cement pastes.
Pierre Mounanga - One of the best experts on this subject based on the ideXlab platform.
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Contribution to the modeling of hydration and Chemical Shrinkage of slag-blended cement at early age
Construction and Building Materials, 2013Co-Authors: Tarek Merzouki, Marwen Bouasker, Nour El Houda Khalifa, Pierre MounangaAbstract:Abstract This paper presents a contribution to the modeling of the Chemical Shrinkage of the slag-blended cement paste (binder) at early age. Assuming that the Chemical Shrinkage is a direct result of hydration, the hydration modeling of slag-blended cement was studied by considering the interaction between the hydrations of blast furnace slag (BFS) and ordinary Portland cement. The reaction of BFS in the presence of calcium hydroxide CH (Portlandite) produced from the hydration of the cement was investigated. The kinetic hydration of cement was developed, and the volume phases in the cementitious material during the hydration process were calculated. The Chemical Shrinkage, which is the negative volume balance between the reactants and the products formed, is then calculated. In parallel with this numerical modeling, an experimental study was conducted to investigate the effect of slag’s addition (0%, 30%, 50% and 80%) on the heat of hydration and Chemical Shrinkage at early age (maturation up to 7 days). The proposed hydration model incorporates the effect of following variables; the Chemical composition of the binder, the fineness, the water to binder ratio ( w / b ), the curing time and the temperature.
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Chemical Shrinkage of cement pastes and mortars at very early age : Effect of limestone filler and granular inclusions
Cement and Concrete Composites, 2008Co-Authors: Marwen Bouasker, Pierre Mounanga, Ph Turcry, Ahmed Loukili, Abdelhafid KhelidjAbstract:This article presents a study on the influence of limestone filler and granular inclusions on the Chemical Shrinkage of cementitious matrices at very early age (⩽24 h). Measurements of Chemical Shrinkage and hydration degree are carried out on cement pastes and mortars. During this study, two cement types (CEM 1 and CEM 2), two water-to-cement ratios (W/C = 0.30 and 0.40) and three substitution rates of cement by limestone filler (LF/C = 0; 0.25 and 0.67) are used. The effects of aggregate shape (glass beads and natural sand), aggregate-to-cement mass ratio (A/C = 0.5 and 1) and particle size distribution (D = 1 and 2 mm) on the Chemical Shrinkage and the hydration rate are quantified. The results obtained show that limestone filler causes an acceleration of both Le Chatelier’s contraction and hydration process since the very first hours of hydration. In addition, the Chemical Shrinkage amplitude is not significantly influenced by the presence of aggregates. Finally, the presence of limestone filler and granular inclusions does not cause significant modification of the quasi-linear relation observed at early age between the Chemical Shrinkage and the hydration degree of the cementitious matrices.
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Predicting Ca(OH)2 content and Chemical Shrinkage of hydrating cement pastes using analytical approach
Cement and Concrete Research, 2004Co-Authors: Pierre Mounanga, Ahmed Loukili, Abdelhafid Khelidj, Véronique Baroghel-bounyAbstract:A semiempirical model is proposed to predict the evolution of Chemical Shrinkage and Ca(OH)(2) content of cement paste at early age of hydration. The model is based on Chemical equations and cement compound hydration rates. Chemical Shrinkage and Ca(OH)(2) amount are computed using the stoichiometric results of the hydration reactions considered in the model and the density of hydration products and reactants. The model validation is conducted by comparison between computed and experimental results achieved on ordinary cement pastes with different water-to-cement (w/c) ratios (0.25, 0.30, 0.35 and 0.40) cured at 10, 20, 30, 40 and 50 degreesC, respectively. Hydration degree and Ca(OH)(2) content are determined using the thermogravimetric analysis (TGA) and Chemical Shrinkage evolution using a gravimetric method. The comparison reveals a good consistency between modelled and experimental data at early age of hydration.
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Predicting Ca(OH)2 content and Chemical Shrinkage of hydrating cement pastes using analytical approach
Cement and Concrete Research, 2004Co-Authors: Pierre Mounanga, Ahmed Loukili, Abdelhafid Khelidj, Véronique Baroghel-bounyAbstract:A semiempirical model is proposed to predict the evolution of Chemical Shrinkage and Ca(OH)2 content of cement paste at early age of hydration. The model is based on Chemical equations and cement compound hydration rates. Chemical Shrinkage and Ca(OH)2 amount are computed using the stoichiometric results of the hydration reactions considered in the model and the density of hydration products and reactants. The model validation is conducted by comparison between computed and experimental results achieved on ordinary cement pastes with different water-to-cement (w/c) ratios (0.25, 0.30, 0.35 and 0.40) cured at 10, 20, 30, 40 and 50 °C, respectively. Hydration degree and Ca(OH)2 content are determined using the thermogravimetric analysis (TGA) and Chemical Shrinkage evolution using a gravimetric method. The comparison reveals a good consistency between modelled and experimental data at early age of hydration.
Robert Darbe - One of the best experts on this subject based on the ideXlab platform.
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An innovative test apparatus for oil well cement: In-situ measurement of Chemical Shrinkage and tensile strength
Construction and Building Materials, 2015Co-Authors: Xueyu Pang, Christian Meyer, Gary P. Funkhouser, Robert DarbeAbstract:Abstract An innovative apparatus has been developed in this study to cure and test oil well cement specimens under simulated down-hole conditions with high temperature and high pressure. The test apparatus can be used to monitor cement Chemical Shrinkage in real time and measure fluid pressure tensile strength under in-situ conditions, i.e. without changing the temperature or releasing the pressure of the specimen. This paper describes the basic principles of this newly developed test method and detailed configuration of the test apparatus. A series of tests were performed on different classes of oil well cement to evaluate the functionality of the test device. Specimens in groups of four were cured at temperatures ranging from 24 to 60 °C and pressures ranging from 0.69 to 13.1 MPa.
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A comparison study of Portland cement hydration kinetics as measured by Chemical Shrinkage and isothermal calorimetry
Cement and Concrete Composites, 2013Co-Authors: Xueyu Pang, Christian Meyer, Dale P Bentz, Gary P. Funkhouser, Robert DarbeAbstract:Abstract Two different methods of evaluating cement hydration kinetics, namely Chemical Shrinkage and isothermal calorimetry tests, are used to investigate the early stage hydration of different classes of oilwell cement at various temperatures. For a given cement paste, the hydration kinetics curves measured by the two methods are proportional to each other at the same curing temperature. The ratio of heat of hydration to Chemical Shrinkage for different cements used in this study ranges from 7500 J/mL to 8000 J/mL at 25 °C and increases almost linearly with increasing curing temperature at a rate that varies only slightly with cement composition (approximately 58 J/mL per °C). A previously proposed scale factor model for simulating the effect of curing temperature and pressure on cement hydration kinetics is further validated in this study for its temperature aspect. The model is shown to be particularly helpful in correcting for slight temperature errors in the experiments.