Dépouillements

The density of cement phases / M. Balonis in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 733–739 Titre : The density of cement phases Type de document : texte imprimé Auteurs : M. Balonis, Auteur ; F.P. Glasser, Auteur Année de publication : 2009 Article en page(s) : pp. 733–739 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Density;  X-ray  diffraction;  Cement;  Crystal  structure;  Characterization Résumé : The densities of principal crystalline phases occurring in Portland cement are critically assessed and tabulated, in some cases with addition of new data. A reliable and self-consistent density set for crystalline phases was obtained by calculating densities from crystallographic data and unit cell contents. Independent laboratory work was undertaken to synthesize major AFm and AFt cement phases, determine their unit cell parameters and compare the results with those recorded in the literature. Parameters were refined from powder diffraction patterns using CELREF 2 software. A density value is presented for each phase, showing literature sources, in some cases describing limitations on the data, and the weighting attached to numerical values where an averaging process was used for accepted data. A brief discussion is made of the consequences of the packing of water to density changes in AFm and AFt structures. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001343 [article] The density of cement phases [texte imprimé] / M. Balonis, Auteur ; F.P. Glasser, Auteur . - 2009 . - pp. 733–739. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 733–739 Mots-clés : Density;  X-ray  diffraction;  Cement;  Crystal  structure;  Characterization Résumé : The densities of principal crystalline phases occurring in Portland cement are critically assessed and tabulated, in some cases with addition of new data. A reliable and self-consistent density set for crystalline phases was obtained by calculating densities from crystallographic data and unit cell contents. Independent laboratory work was undertaken to synthesize major AFm and AFt cement phases, determine their unit cell parameters and compare the results with those recorded in the literature. Parameters were refined from powder diffraction patterns using CELREF 2 software. A density value is presented for each phase, showing literature sources, in some cases describing limitations on the data, and the weighting attached to numerical values where an averaging process was used for accepted data. A brief discussion is made of the consequences of the packing of water to density changes in AFm and AFt structures. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001343

Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry / Céline Cau Dit Coumes in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 740–747 Titre : Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry Type de document : texte imprimé Auteurs : Céline Cau Dit Coumes, Auteur ; Simone Courtois, Auteur ; Sandrine Peysson, Auteur Année de publication : 2009 Article en page(s) : pp. 740–747 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Radioactive  waste;  Waste  management;  Mixture-proportioning;  Portland  cement;  Sulfoaluminate Résumé : Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL− 1. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement–waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 °C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CS̄̄A) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CS̄̄A cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001380 [article] Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry [texte imprimé] / Céline Cau Dit Coumes, Auteur ; Simone Courtois, Auteur ; Sandrine Peysson, Auteur . - 2009 . - pp. 740–747. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 740–747 Mots-clés : Radioactive  waste;  Waste  management;  Mixture-proportioning;  Portland  cement;  Sulfoaluminate Résumé : Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL− 1. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement–waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 °C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CS̄̄A) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CS̄̄A cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001380

Rheological behavior of mortars under different squeezing rates / Fábio A. Cardoso in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 748–753 Titre : Rheological behavior of mortars under different squeezing rates Type de document : texte imprimé Auteurs : Fábio A. Cardoso, Auteur ; M. John Vanderley, Auteur ; Rafael G. Pileggi, Auteur Année de publication : 2009 Article en page(s) : pp. 748–753 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Rheology  Mortar  Squeeze  flow Résumé : In the present work the squeeze flow technique was used to evaluate the rheological behavior of cement-based mortars containing macroscopic aggregates up to 1.2 mm. Compositions with different water and air contents were tested at three squeezing rates (0.01, 0.1 and 1 mm/s) 15 and 60 min after mixing. The mortars prepared with low (13 wt.%) and usual water content (15 wt.%) presented opposite behaviors as a function of elapsed time and squeezing speed. The first lost its cohesion with time and required higher loads when squeezed faster, while the latter became stiffer with time and was more difficult to be squeezed slowly as a result of phase segregation. Due to the increase of air content, the effects of this compressible phase became more significant and a more complex behavior was observed. Rheological properties such as elongational viscosity and yield stress were also determined. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900129X [article] Rheological behavior of mortars under different squeezing rates [texte imprimé] / Fábio A. Cardoso, Auteur ; M. John Vanderley, Auteur ; Rafael G. Pileggi, Auteur . - 2009 . - pp. 748–753. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 748–753 Mots-clés : Rheology  Mortar  Squeeze  flow Résumé : In the present work the squeeze flow technique was used to evaluate the rheological behavior of cement-based mortars containing macroscopic aggregates up to 1.2 mm. Compositions with different water and air contents were tested at three squeezing rates (0.01, 0.1 and 1 mm/s) 15 and 60 min after mixing. The mortars prepared with low (13 wt.%) and usual water content (15 wt.%) presented opposite behaviors as a function of elapsed time and squeezing speed. The first lost its cohesion with time and required higher loads when squeezed faster, while the latter became stiffer with time and was more difficult to be squeezed slowly as a result of phase segregation. Due to the increase of air content, the effects of this compressible phase became more significant and a more complex behavior was observed. Rheological properties such as elongational viscosity and yield stress were also determined. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900129X

A multiscale model for modulus of elasticity of concrete at high temperatures / Jaesung Lee in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 754–762 Titre : A multiscale model for modulus of elasticity of concrete at high temperatures Type de document : texte imprimé Auteurs : Jaesung Lee, Auteur ; Xi, Yunping, Auteur ; Kaspar Willam, Auteur Année de publication : 2009 Article en page(s) : pp. 754–762 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Composite  mechanics;  Modulus  of  elasticity;  High  temperature;  Concrete Résumé : In this paper, the thermal degradation of modulus of elasticity of concrete is modeled by composite mechanics at three scales of observation: (a) at the level of concrete, (b) at the level of mortar, and (c) the cement paste level. At the latter, the change of volume fractions of the constituents are evaluated based on phase transformations which take place in different temperature ranges. Stoichiometric models are used to determine the volume changes of the constituents. At the mortar and concrete levels, the temperature dependence of fine and coarse aggregates is considered based on available test data. The multiscale chemo-mechanical model can be used to predict the temperature dependence and thermal degradation of the elastic concrete modulus. The model predictions are compared with test data in the literature as well as in-house test data. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001227 [article] A multiscale model for modulus of elasticity of concrete at high temperatures [texte imprimé] / Jaesung Lee, Auteur ; Xi, Yunping, Auteur ; Kaspar Willam, Auteur . - 2009 . - pp. 754–762. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 754–762 Mots-clés : Composite  mechanics;  Modulus  of  elasticity;  High  temperature;  Concrete Résumé : In this paper, the thermal degradation of modulus of elasticity of concrete is modeled by composite mechanics at three scales of observation: (a) at the level of concrete, (b) at the level of mortar, and (c) the cement paste level. At the latter, the change of volume fractions of the constituents are evaluated based on phase transformations which take place in different temperature ranges. Stoichiometric models are used to determine the volume changes of the constituents. At the mortar and concrete levels, the temperature dependence of fine and coarse aggregates is considered based on available test data. The multiscale chemo-mechanical model can be used to predict the temperature dependence and thermal degradation of the elastic concrete modulus. The model predictions are compared with test data in the literature as well as in-house test data. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001227

Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness / E. Stora in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 763–772 Titre : Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness Type de document : texte imprimé Auteurs : E. Stora, Auteur ; B. Bary, Auteur ; Q.-C. He, Auteur Année de publication : 2009 Article en page(s) : pp. 763–772 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Chemo–mechanical  degradations;  Leaching;  elastic  moduli;  micromechanics;  cement  paste;  modelling Résumé : The present paper aims at modelling the decalcification process in cement-based materials and its impact on the material stiffness, which represents a serious matter in terms of long-term durability. The resistance of cementitious materials to this chemical alteration is strongly conditioned by their mineral composition and porosity. For this purpose, a multi-scale homogenization approach (Stora et al., Trans. Por. Med. 73, 3, 2008) is implemented in the numerical platform ALLIANCES (P. Montarnal, C. Mügler, J. Colin, M. Descotes, A. Dimier, E. Jacquot, Presentation and use of a reactive transport code in porous media, Phys. Chem. Earth 32, 2007) to estimate from these data the elastic and diffusive properties of cement-based materials. The association of this homogenization model and of the integration platform, which can couple different numerical codes, then allows for evaluating the evolution of the mineral composition and of the diffusive and mechanical properties of a concrete material during chemical deterioration processes. Simulations of pure water leaching of hydrated cement pastes are performed and the consequences of this decalcification on the material's residual elastic behaviour are estimated. The numerical results are confronted with available experimental data and analyzed. The simulations of the non-linear mechanical behaviour of leached cementitious materials taking into account interactions between damage and leaching is not reported here for conciseness but can be found in another document (Stora, Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials. PhD Dissertation, univ. of Paris-Est 2008). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001240 [article] Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness [texte imprimé] / E. Stora, Auteur ; B. Bary, Auteur ; Q.-C. He, Auteur . - 2009 . - pp. 763–772. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 763–772 Mots-clés : Chemo–mechanical  degradations;  Leaching;  elastic  moduli;  micromechanics;  cement  paste;  modelling Résumé : The present paper aims at modelling the decalcification process in cement-based materials and its impact on the material stiffness, which represents a serious matter in terms of long-term durability. The resistance of cementitious materials to this chemical alteration is strongly conditioned by their mineral composition and porosity. For this purpose, a multi-scale homogenization approach (Stora et al., Trans. Por. Med. 73, 3, 2008) is implemented in the numerical platform ALLIANCES (P. Montarnal, C. Mügler, J. Colin, M. Descotes, A. Dimier, E. Jacquot, Presentation and use of a reactive transport code in porous media, Phys. Chem. Earth 32, 2007) to estimate from these data the elastic and diffusive properties of cement-based materials. The association of this homogenization model and of the integration platform, which can couple different numerical codes, then allows for evaluating the evolution of the mineral composition and of the diffusive and mechanical properties of a concrete material during chemical deterioration processes. Simulations of pure water leaching of hydrated cement pastes are performed and the consequences of this decalcification on the material's residual elastic behaviour are estimated. The numerical results are confronted with available experimental data and analyzed. The simulations of the non-linear mechanical behaviour of leached cementitious materials taking into account interactions between damage and leaching is not reported here for conciseness but can be found in another document (Stora, Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials. PhD Dissertation, univ. of Paris-Est 2008). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001240

Comparison of two processes for treating rice husk ash for use in high performance concrete / Andres Salas in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 773–778 Titre : Comparison of two processes for treating rice husk ash for use in high performance concrete Type de document : texte imprimé Auteurs : Andres Salas, Auteur ; Silvio Delvasto, Auteur Année de publication : 2009 Article en page(s) : pp. 773–778 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Durability;  Mechanical  properties;  Pozzolan;  Silica  fume;  High  performance  concrete Résumé : Rice husk ashes (RHA) have been used as pozzolanic admixtures for high performance concrete (HPC). This study reports on a chemical treatment before burning that improves the effectiveness of the RHA. The resulting ash (ChRHA) was compared to ash produced by conventional incineration (TRHA). The digestive chemical treatment before burning produced an RHA with properties comparable to silica fume. The ChRHA was highly amorphous, white in color, presented higher specific surface area and exhibited greater pozzolanic activity. The fresh and hardened properties of HPC made with different percentages of these RHAs were compared. The hardened concrete testing included the determination of the modulus of elasticity and the compressive and flexural properties. It was shown that ChRHA and TRHA were effective supplementary cementing materials, although concrete mixes required higher dosages of superplasticizer compared to the control concrete mix. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001094 [article] Comparison of two processes for treating rice husk ash for use in high performance concrete [texte imprimé] / Andres Salas, Auteur ; Silvio Delvasto, Auteur . - 2009 . - pp. 773–778. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 773–778 Mots-clés : Durability;  Mechanical  properties;  Pozzolan;  Silica  fume;  High  performance  concrete Résumé : Rice husk ashes (RHA) have been used as pozzolanic admixtures for high performance concrete (HPC). This study reports on a chemical treatment before burning that improves the effectiveness of the RHA. The resulting ash (ChRHA) was compared to ash produced by conventional incineration (TRHA). The digestive chemical treatment before burning produced an RHA with properties comparable to silica fume. The ChRHA was highly amorphous, white in color, presented higher specific surface area and exhibited greater pozzolanic activity. The fresh and hardened properties of HPC made with different percentages of these RHAs were compared. The hardened concrete testing included the determination of the modulus of elasticity and the compressive and flexural properties. It was shown that ChRHA and TRHA were effective supplementary cementing materials, although concrete mixes required higher dosages of superplasticizer compared to the control concrete mix. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001094

Charactéristing the time-dependant behaviour on the single fibre level of SHCC / William P. Boshoff in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 779–786 Titre : Charactéristing the time-dependant behaviour on the single fibre level of SHCC : Part 1: mechanism of fibre pull-out creep Type de document : texte imprimé Auteurs : William P. Boshoff, Auteur ; Viktor Mechtcherine, Auteur ; Van Zijl, Gideon P. A., Auteur Année de publication : 2009 Article en page(s) : pp. 779–786 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Creep;  Fibre  reinforcement;  Tensile  properties;  Shrinkage;  Fibre  pull-out Résumé : SHCC (Strain Hardening Cement-based Composite) has been designed and optimised to overcome the main weaknesses of ordinary concrete, which is its brittleness. SHCC shows a high tensile ductility and can resist the full load at a tensile strain of more than 4%. An in depth investigation into the time-dependant behaviour is still lacking for SHCC. This paper is the first part of a two paper series about the time-dependant behaviour on the single fibre level. In this paper, the tensile creep behaviour of SHCC is studied to distinguish mechanisms of creep. Tensile creep and shrinkage test results are reported for dumbbell type SHCC specimens. The specimens are pre-cracked to simulate in-service conditions, with subsequent sustained load at various levels, here chosen as 30%, 50%, 70% and 80% of the ultimate resistance. To distinguish the sources of significant creep deformation under these sustained loads, single fibre pull-out tests are performed under sustained load. It is shown that the time-dependent fibre pull-out is a significant source of time-dependent deformation, along with the formation of new cracks in SHCC under sustained load. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001379 [article] Charactéristing the time-dependant behaviour on the single fibre level of SHCC : Part 1: mechanism of fibre pull-out creep [texte imprimé] / William P. Boshoff, Auteur ; Viktor Mechtcherine, Auteur ; Van Zijl, Gideon P. A., Auteur . - 2009 . - pp. 779–786. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 779–786 Mots-clés : Creep;  Fibre  reinforcement;  Tensile  properties;  Shrinkage;  Fibre  pull-out Résumé : SHCC (Strain Hardening Cement-based Composite) has been designed and optimised to overcome the main weaknesses of ordinary concrete, which is its brittleness. SHCC shows a high tensile ductility and can resist the full load at a tensile strain of more than 4%. An in depth investigation into the time-dependant behaviour is still lacking for SHCC. This paper is the first part of a two paper series about the time-dependant behaviour on the single fibre level. In this paper, the tensile creep behaviour of SHCC is studied to distinguish mechanisms of creep. Tensile creep and shrinkage test results are reported for dumbbell type SHCC specimens. The specimens are pre-cracked to simulate in-service conditions, with subsequent sustained load at various levels, here chosen as 30%, 50%, 70% and 80% of the ultimate resistance. To distinguish the sources of significant creep deformation under these sustained loads, single fibre pull-out tests are performed under sustained load. It is shown that the time-dependent fibre pull-out is a significant source of time-dependent deformation, along with the formation of new cracks in SHCC under sustained load. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001379

Characterising the time-dependant behaviour on the single fibre level of SHCC: Part 2: The rate effects on fibre pull-out tests / William P. Boshoff in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 787–797 Titre : Characterising the time-dependant behaviour on the single fibre level of SHCC: Part 2: The rate effects on fibre pull-out tests Type de document : texte imprimé Auteurs : William P. Boshoff, Auteur ; Viktor Mechtcherine, Auteur ; Van Zijl, Gideon P. A., Auteur Année de publication : 2009 Article en page(s) : pp. 787–797 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fibre  reinforcement;  Pull-out  strength;  Tensile  properties;  Rate  effects;  SHCC Résumé : This paper is the second part of a two paper series about the time-dependant behaviour of Strain Hardening Cement-based Composite (SHCC) on the single fibre level. Having dealt with mechanisms of creep in SHCC in the first part, this paper reports single fibre pull-out tests that were done to investigate the effect of the pull-out rate on the mechanical response of the interface between the fibre and the matrix. It was found that not only the pull-out resistance increased with an increase of the pull-out rate but the probability of fibre rupture during pull-out as well. Another important finding was that the interfacial shear resistance and slip-hardening coefficient are not only dependant on the pull-out rate, but also the embedment length. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001355 [article] Characterising the time-dependant behaviour on the single fibre level of SHCC: Part 2: The rate effects on fibre pull-out tests [texte imprimé] / William P. Boshoff, Auteur ; Viktor Mechtcherine, Auteur ; Van Zijl, Gideon P. A., Auteur . - 2009 . - pp. 787–797. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 787–797 Mots-clés : Fibre  reinforcement;  Pull-out  strength;  Tensile  properties;  Rate  effects;  SHCC Résumé : This paper is the second part of a two paper series about the time-dependant behaviour of Strain Hardening Cement-based Composite (SHCC) on the single fibre level. Having dealt with mechanisms of creep in SHCC in the first part, this paper reports single fibre pull-out tests that were done to investigate the effect of the pull-out rate on the mechanical response of the interface between the fibre and the matrix. It was found that not only the pull-out resistance increased with an increase of the pull-out rate but the probability of fibre rupture during pull-out as well. Another important finding was that the interfacial shear resistance and slip-hardening coefficient are not only dependant on the pull-out rate, but also the embedment length. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001355

Effect of pig slurry on two cement mortars: Changes in strength, porosity and crystalline phases / E. Sánchez in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 798–804 Titre : Effect of pig slurry on two cement mortars: Changes in strength, porosity and crystalline phases Type de document : texte imprimé Auteurs : E. Sánchez, Auteur ; A. Moraguesb, Auteur ; A. Guerrero, Auteur Année de publication : 2009 Article en page(s) : pp. 798–804 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mortar;  Flexural  and  compressive  strength;  Pig  slurry;  Mercury  porosimetry Résumé : The present article addresses the variations observed in porosity and flexural and compressive strength in two types of cement mortar when submerged in pig slurry. The tests were conducted in a 100 m3 experimental lagoon. The mortars were exposed to three types of environments for 36 months: two submerged in the test lagoon, at two different depths, and one outside it. Bending and compression measurements were taken after 3, 12, 24, 36 and 48 months. In addition, 3, 24, 36 and 48 month specimens were tested for total porosity and pore-size distribution. Changes in the mineralogical characteristics of the mortars after 24, 36 and 48 months were also recorded. The strength studies showed that the load capacity attained by the two cements was similar after 48 months, the use of more expensive 42.5 sulphate-resistant cement is not justified. The XRD results showed no evidence in any of the cements of precipitation originating in the ions in the aggressive medium. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001367 [article] Effect of pig slurry on two cement mortars: Changes in strength, porosity and crystalline phases [texte imprimé] / E. Sánchez, Auteur ; A. Moraguesb, Auteur ; A. Guerrero, Auteur . - 2009 . - pp. 798–804. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 798–804 Mots-clés : Mortar;  Flexural  and  compressive  strength;  Pig  slurry;  Mercury  porosimetry Résumé : The present article addresses the variations observed in porosity and flexural and compressive strength in two types of cement mortar when submerged in pig slurry. The tests were conducted in a 100 m3 experimental lagoon. The mortars were exposed to three types of environments for 36 months: two submerged in the test lagoon, at two different depths, and one outside it. Bending and compression measurements were taken after 3, 12, 24, 36 and 48 months. In addition, 3, 24, 36 and 48 month specimens were tested for total porosity and pore-size distribution. Changes in the mineralogical characteristics of the mortars after 24, 36 and 48 months were also recorded. The strength studies showed that the load capacity attained by the two cements was similar after 48 months, the use of more expensive 42.5 sulphate-resistant cement is not justified. The XRD results showed no evidence in any of the cements of precipitation originating in the ions in the aggressive medium. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001367

Assessing the influence of ITZ on the steady-state chloride diffusivity of concrete using a numerical model / Jian-jun Zheng in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp.805–813 Titre : Assessing the influence of ITZ on the steady-state chloride diffusivity of concrete using a numerical model Type de document : texte imprimé Auteurs : Jian-jun Zheng, Auteur ; Hong S. Wong, Auteur ; Nick R. Buenfeld, Auteur Année de publication : 2009 Article en page(s) : pp.805–813 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Interfacial  transition  zone;  Transport  properties;  Microstructure;  Modeling;  Transfer  matrix  method Résumé : In this study, the influence of the aggregate-cement paste interfacial transition zone (ITZ) on the steady-state chloride diffusivity of mortars and concretes was examined using a semi-empirical, three-phase composite sphere model. Mortars and concretes were modelled as three-phase composites consisting of the aggregate, bulk cement paste and an inhomogeneous ITZ. The latter was divided into a series of homogenous concentric shell elements of equal thickness. The initial porosity and cement gradients at the ITZ were first estimated from the overall water/cement ratio (w0/c). The evolution of the porosity, solid hydration products and remnants of unreacted cement were then calculated from the hydration degree and local water/cement ratio (w/c) using Powers' empirical model. Based on the Laplacian equation, an element transfer matrix was derived analytically to predict the steady-state chloride diffusivity. The model was calibrated using the available experimental data and then applied to perform a sensitivity analysis to evaluate the effects of aggregate content, water/cement ratio, curing period, ITZ width, maximum aggregate size and aggregate gradation on diffusivity. Some of these variables are impractical to quantify by laboratory experimentation. Implications of the findings with regard to the role of ITZ on mass transport properties are discussed. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001306 [article] Assessing the influence of ITZ on the steady-state chloride diffusivity of concrete using a numerical model [texte imprimé] / Jian-jun Zheng, Auteur ; Hong S. Wong, Auteur ; Nick R. Buenfeld, Auteur . - 2009 . - pp.805–813. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp.805–813 Mots-clés : Interfacial  transition  zone;  Transport  properties;  Microstructure;  Modeling;  Transfer  matrix  method Résumé : In this study, the influence of the aggregate-cement paste interfacial transition zone (ITZ) on the steady-state chloride diffusivity of mortars and concretes was examined using a semi-empirical, three-phase composite sphere model. Mortars and concretes were modelled as three-phase composites consisting of the aggregate, bulk cement paste and an inhomogeneous ITZ. The latter was divided into a series of homogenous concentric shell elements of equal thickness. The initial porosity and cement gradients at the ITZ were first estimated from the overall water/cement ratio (w0/c). The evolution of the porosity, solid hydration products and remnants of unreacted cement were then calculated from the hydration degree and local water/cement ratio (w/c) using Powers' empirical model. Based on the Laplacian equation, an element transfer matrix was derived analytically to predict the steady-state chloride diffusivity. The model was calibrated using the available experimental data and then applied to perform a sensitivity analysis to evaluate the effects of aggregate content, water/cement ratio, curing period, ITZ width, maximum aggregate size and aggregate gradation on diffusivity. Some of these variables are impractical to quantify by laboratory experimentation. Implications of the findings with regard to the role of ITZ on mass transport properties are discussed. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001306

Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure / Ha-Won Song in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 814–824 Titre : Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure Type de document : texte imprimé Auteurs : Ha-Won Song, Auteur ; Seung-Jun Kwon, Auteur Année de publication : 2009 Article en page(s) : pp. 814–824 Note générale : Génie Civil Langues : Anglais (eng) Résumé : Chloride attack is one of the major causes of deterioration of reinforced concrete structures. In order to evaluate the chloride behavior in concrete, a reasonable prediction for the diffusion coefficient of chloride ion, which governs mechanism of chloride diffusion inside concrete, is basically required. However, it is difficult to obtain chloride diffusion coefficients from experiments due to time and cost limitations. In this study, a numerical technique for chloride diffusion in high performance concrete (HPC) using a neural network algorithm is proposed. In order to collect comparative data on diffusion coefficients in concrete with various mineral admixtures such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF), a series of electrically driven chloride penetration tests was performed. Seven material components in various mix designs and duration time are selected as neurons in a back-propagation algorithm, and associated learning of the neural network is carried out. An evaluation technique for chloride behavior in HPC using the obtained diffusion coefficients from the neural network algorithm is developed based on, so-called, Multi-Component Hydration Heat Model (MCHHM) and Micro Pore Structure Formation Model (MPSFM). The applicability of the developed technique is verified by comparing the analytical simulation results and the experimental results obtained in this study. Furthermore, this proposed technique using the neural network algorithm and micro modeling is applied to available experimental data for verification of its applicability. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001288 [article] Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure [texte imprimé] / Ha-Won Song, Auteur ; Seung-Jun Kwon, Auteur . - 2009 . - pp. 814–824. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 814–824 Résumé : Chloride attack is one of the major causes of deterioration of reinforced concrete structures. In order to evaluate the chloride behavior in concrete, a reasonable prediction for the diffusion coefficient of chloride ion, which governs mechanism of chloride diffusion inside concrete, is basically required. However, it is difficult to obtain chloride diffusion coefficients from experiments due to time and cost limitations. In this study, a numerical technique for chloride diffusion in high performance concrete (HPC) using a neural network algorithm is proposed. In order to collect comparative data on diffusion coefficients in concrete with various mineral admixtures such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF), a series of electrically driven chloride penetration tests was performed. Seven material components in various mix designs and duration time are selected as neurons in a back-propagation algorithm, and associated learning of the neural network is carried out. An evaluation technique for chloride behavior in HPC using the obtained diffusion coefficients from the neural network algorithm is developed based on, so-called, Multi-Component Hydration Heat Model (MCHHM) and Micro Pore Structure Formation Model (MPSFM). The applicability of the developed technique is verified by comparing the analytical simulation results and the experimental results obtained in this study. Furthermore, this proposed technique using the neural network algorithm and micro modeling is applied to available experimental data for verification of its applicability. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001288

Real-time evolution of electrical resistance in cracking concrete / C. Boulay in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 825–831 Titre : Real-time evolution of electrical resistance in cracking concrete Type de document : texte imprimé Auteurs : C. Boulay, Auteur ; S. Dal Pont, Auteur Année de publication : 2009 Article en page(s) : pp. 825–831 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Splitting  test;  Concrete  electrical  resistance;  Traversing  crack;  Conductance-cracked  concrete  real-time  relation Résumé : The aim of this paper is to present a real-time relation between the evolution of the electrical resistance and the crack width opening in a saturated concrete sample. The splitting (Brazilian) test has been enhanced and adapted so that the monitoring of a single crack opening and the electrical resistance of the specimen are possible. The experimental results showed that the electrical resistance is constant before the peak (when no crack is observed) and decreases only when the peak of load is reached and when a crack is initiated. No threshold value and no delay between the crack opening and the resistance evolution have been observed, even in the case of a breathing crack. The evolution of the electrical conductance has then been modeled by taking into account the (simplified) morphology of the crack and assuming a constant value for the electrolyte conductivity. The model and the experimental conductance through a traversing crack have proved to be in good agreement. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001318 [article] Real-time evolution of electrical resistance in cracking concrete [texte imprimé] / C. Boulay, Auteur ; S. Dal Pont, Auteur . - 2009 . - pp. 825–831. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 825–831 Mots-clés : Splitting  test;  Concrete  electrical  resistance;  Traversing  crack;  Conductance-cracked  concrete  real-time  relation Résumé : The aim of this paper is to present a real-time relation between the evolution of the electrical resistance and the crack width opening in a saturated concrete sample. The splitting (Brazilian) test has been enhanced and adapted so that the monitoring of a single crack opening and the electrical resistance of the specimen are possible. The experimental results showed that the electrical resistance is constant before the peak (when no crack is observed) and decreases only when the peak of load is reached and when a crack is initiated. No threshold value and no delay between the crack opening and the resistance evolution have been observed, even in the case of a breathing crack. The evolution of the electrical conductance has then been modeled by taking into account the (simplified) morphology of the crack and assuming a constant value for the electrolyte conductivity. The model and the experimental conductance through a traversing crack have proved to be in good agreement. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001318

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