Dépouillements

Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete / José Mora-Ruacho in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 141–146 Titre : Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete Type de document : texte imprimé Auteurs : José Mora-Ruacho, Auteur ; Gettu, Ravindra, Auteur ; Antonio Aguado, Auteur Année de publication : 2009 Article en page(s) : pp. 141–146 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Drying;  Fresh  concrete;  Durability;  Shrinkage;  Admixtures Résumé : Fresh concrete exposed to high evaporation rates is prone to plastic shrinkage cracking, especially in structures with large surface area/volume ratios. The present work shows that the reduction of the surface tension of the mixing water is an effective way for decreasing such cracking. In this study, conventional and high strength concretes with superplasticizers and shrinkage reducing admixtures (SRAs) were exposed to drying in the plastic state. Continuous monitoring of the surface displacement facilitated the identification of the different stages of plastic shrinkage cracking. Measurements of capillary pressure, settlement, internal temperature and evaporation rate were also made. The results show the effectiveness of SRAs in reducing plastic shrinkage cracking, even in high strength concrete. This is attributed to the reduction in the evaporation rate, delay of the peak capillary pressure due to the development of menisci in the pores and lower settlement. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000052 [article] Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete [texte imprimé] / José Mora-Ruacho, Auteur ; Gettu, Ravindra, Auteur ; Antonio Aguado, Auteur . - 2009 . - pp. 141–146. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 141–146 Mots-clés : Drying;  Fresh  concrete;  Durability;  Shrinkage;  Admixtures Résumé : Fresh concrete exposed to high evaporation rates is prone to plastic shrinkage cracking, especially in structures with large surface area/volume ratios. The present work shows that the reduction of the surface tension of the mixing water is an effective way for decreasing such cracking. In this study, conventional and high strength concretes with superplasticizers and shrinkage reducing admixtures (SRAs) were exposed to drying in the plastic state. Continuous monitoring of the surface displacement facilitated the identification of the different stages of plastic shrinkage cracking. Measurements of capillary pressure, settlement, internal temperature and evaporation rate were also made. The results show the effectiveness of SRAs in reducing plastic shrinkage cracking, even in high strength concrete. This is attributed to the reduction in the evaporation rate, delay of the peak capillary pressure due to the development of menisci in the pores and lower settlement. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000052

Effect of alkalis on fresh C–S–H gels. FTIR analysis / I. García Lodeiro in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 147–153 Titre : Effect of alkalis on fresh C–S–H gels. FTIR analysis Type de document : texte imprimé Auteurs : I. García Lodeiro, Auteur ; D.E. Macphee, Auteur ; A. Palomo, Auteur Année de publication : 2009 Article en page(s) : pp. 147–153 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Calcium–Silicate–Hydrate  (C–S–H);  Spectroscopy;  Alkalis Résumé : The present study addresses the effect of different concentrations of Na2O on the structure of a composition of fresh C–S–H gels. The gels were synthesized from laboratory reagents, using calcium nitrate as the source of calcium and a sodium silicate solution for the silicon. A 10-M solution of NaOH was used to maintain a pH of over 13 throughout. The synthesized gels were exposed to different amounts of 8-M NaOH to determine their chemical stability and subsequently characterized with Fourier transform IR spectroscopy. The results showed that the addition of different concentrations of sodium leads to C–S–H gel modification even in the very short term. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000039 [article] Effect of alkalis on fresh C–S–H gels. FTIR analysis [texte imprimé] / I. García Lodeiro, Auteur ; D.E. Macphee, Auteur ; A. Palomo, Auteur . - 2009 . - pp. 147–153. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 147–153 Mots-clés : Calcium–Silicate–Hydrate  (C–S–H);  Spectroscopy;  Alkalis Résumé : The present study addresses the effect of different concentrations of Na2O on the structure of a composition of fresh C–S–H gels. The gels were synthesized from laboratory reagents, using calcium nitrate as the source of calcium and a sodium silicate solution for the silicon. A 10-M solution of NaOH was used to maintain a pH of over 13 throughout. The synthesized gels were exposed to different amounts of 8-M NaOH to determine their chemical stability and subsequently characterized with Fourier transform IR spectroscopy. The results showed that the addition of different concentrations of sodium leads to C–S–H gel modification even in the very short term. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000039

Simulation of the thermal stress in mass concrete using a thermal stress measuring device / Muhammad Nasir Amin in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp.154–164 Titre : Simulation of the thermal stress in mass concrete using a thermal stress measuring device Type de document : texte imprimé Auteurs : Muhammad Nasir Amin, Auteur ; Jeong-Jae Kim, Auteur Année de publication : 2009 Article en page(s) : pp.154–164 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mass  concrete;  Thermal  stress;  Thermal  stress  device;Degree  of  restraint;  Numerical  simulation;  Thermal  expansion  coefficient;  Finite  element  code  DIANA Résumé : An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002378 [article] Simulation of the thermal stress in mass concrete using a thermal stress measuring device [texte imprimé] / Muhammad Nasir Amin, Auteur ; Jeong-Jae Kim, Auteur . - 2009 . - pp.154–164. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp.154–164 Mots-clés : Mass  concrete;  Thermal  stress;  Thermal  stress  device;Degree  of  restraint;  Numerical  simulation;  Thermal  expansion  coefficient;  Finite  element  code  DIANA Résumé : An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002378

Coupled effect of time and temperature on variations of plastic viscosity of highly flowable mortar / Jean-Yves Petit in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 165–170 Titre : Coupled effect of time and temperature on variations of plastic viscosity of highly flowable mortar Type de document : texte imprimé Auteurs : Jean-Yves Petit, Auteur ; Kamal H. Khayat, Auteur ; Eric Wirquin, Auteur Année de publication : 2009 Article en page(s) : pp. 165–170 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Temperature  ;  Fresh  concrete  ;  High-range  water  reducers  ;  Rheology  ;  Plastic  viscosity Résumé : Self-consolidating concrete (SCC) is being increasingly used as construction material for its workability. However, the rheological properties of such concrete, which is made with significant concentration of high-range water-reducing admixture (HRWRA), depend in most cases on the casting temperature of the material. The study presented herein aimed at evaluating the coupled influence of time and temperature on the variations of plastic viscosity (µ) of micro mortar made with polymelamine (PMS), polynaphtalene (PNS) and polycarboxylate (PCP) polymer. In total, seven micro mortar mixtures proportioned with various binder compositions and water-to-binder ratios of 0.42 and 0.53 were prepared at 10 to 33 °C. Test results show that the plastic viscosity varies linearly with the coupled effect of time and temperature for mixtures made with PNS or PMS HRWRA. However, for mixtures made with PCP-HRWRA, both temperature and mixture proportioning have influence on the variation of viscosity with time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002366 [article] Coupled effect of time and temperature on variations of plastic viscosity of highly flowable mortar [texte imprimé] / Jean-Yves Petit, Auteur ; Kamal H. Khayat, Auteur ; Eric Wirquin, Auteur . - 2009 . - pp. 165–170. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 165–170 Mots-clés : Temperature  ;  Fresh  concrete  ;  High-range  water  reducers  ;  Rheology  ;  Plastic  viscosity Résumé : Self-consolidating concrete (SCC) is being increasingly used as construction material for its workability. However, the rheological properties of such concrete, which is made with significant concentration of high-range water-reducing admixture (HRWRA), depend in most cases on the casting temperature of the material. The study presented herein aimed at evaluating the coupled influence of time and temperature on the variations of plastic viscosity (µ) of micro mortar made with polymelamine (PMS), polynaphtalene (PNS) and polycarboxylate (PCP) polymer. In total, seven micro mortar mixtures proportioned with various binder compositions and water-to-binder ratios of 0.42 and 0.53 were prepared at 10 to 33 °C. Test results show that the plastic viscosity varies linearly with the coupled effect of time and temperature for mixtures made with PNS or PMS HRWRA. However, for mixtures made with PCP-HRWRA, both temperature and mixture proportioning have influence on the variation of viscosity with time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002366

Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer: Part II. Influence of mineral additions and chemical admixtures on the shear thickening flow behaviour / G. Heirman in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 171–181 Titre : Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer: Part II. Influence of mineral additions and chemical admixtures on the shear thickening flow behaviour Type de document : texte imprimé Auteurs : G. Heirman, Auteur ; R. Hendrickx, Auteur ; L. Vandewalle, Auteur Année de publication : 2009 Article en page(s) : pp. 171–181 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fresh  concrete  ;  Rheology  ;  Admixture  ;  Filler  ;  Shear  thickening Résumé : The influence of mineral additions and chemical admixtures on the shear thickening flow behaviour of powder type self-compacting concrete (SCC) is studied by means of a wide-gap concentric cylinder rheometer. The Couette inverse problem is treated by means of the integration method in order to derive the flow curve τ(γ̇) from the torque measurements. According to the experimental results, the shear thickening effect is found to be strongly influenced by the addition of the chemical admixture (a polycarboxylate ether based superplasticizer), whereas mineral additions were found to modify the intensity of shear thickening. The limestone, quartzite and fly ash addition used in this research project, respectively increase, unalter and decrease the shear thickening intensity. The powder volume and the available amount of free water proved to have a major impact on the viscosity of the powder type SCC mixes. Increasing the powder volume or decreasing the amount of free water results in an increased viscosity of the SCC mix. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002354 [article] Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer: Part II. Influence of mineral additions and chemical admixtures on the shear thickening flow behaviour [texte imprimé] / G. Heirman, Auteur ; R. Hendrickx, Auteur ; L. Vandewalle, Auteur . - 2009 . - pp. 171–181. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 171–181 Mots-clés : Fresh  concrete  ;  Rheology  ;  Admixture  ;  Filler  ;  Shear  thickening Résumé : The influence of mineral additions and chemical admixtures on the shear thickening flow behaviour of powder type self-compacting concrete (SCC) is studied by means of a wide-gap concentric cylinder rheometer. The Couette inverse problem is treated by means of the integration method in order to derive the flow curve τ(γ̇) from the torque measurements. According to the experimental results, the shear thickening effect is found to be strongly influenced by the addition of the chemical admixture (a polycarboxylate ether based superplasticizer), whereas mineral additions were found to modify the intensity of shear thickening. The limestone, quartzite and fly ash addition used in this research project, respectively increase, unalter and decrease the shear thickening intensity. The powder volume and the available amount of free water proved to have a major impact on the viscosity of the powder type SCC mixes. Increasing the powder volume or decreasing the amount of free water results in an increased viscosity of the SCC mix. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002354

Concrete mixing kinetics by means of power measurement / B. Cazacliu in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 182–194 Titre : Concrete mixing kinetics by means of power measurement Type de document : texte imprimé Auteurs : B. Cazacliu, Auteur ; N. Roquet, Auteur Année de publication : 2009 Article en page(s) : pp. 182–194 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Dispersion  ;  Microstructure  ;  Rheology  ;  Mixing Résumé : This paper introduces a new model for concrete mixing kinetics. The model defines five successive stages through which the mixture characteristics change. It is also shown that the time-variation of the mixer power consumption is a relevant tool to identify the transient stages of the mixture during mixing. In particular, it detects the instant when maximum cohesive paste occurs and identifies the fluidity time. The fluidity time is the instant when mixture turns to fresh concrete. In that sense, this transition time can be seen as an indicator of mixing difficulty for a given mixer. The influence of the mix-design and that of the liquid loading sequence on the mixing behavior are investigated; three sets of experiments are used for the assessment of the model. It is shown that one key parameter is the rheology of the mixture at the fluidity time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002238 [article] Concrete mixing kinetics by means of power measurement [texte imprimé] / B. Cazacliu, Auteur ; N. Roquet, Auteur . - 2009 . - pp. 182–194. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 182–194 Mots-clés : Dispersion  ;  Microstructure  ;  Rheology  ;  Mixing Résumé : This paper introduces a new model for concrete mixing kinetics. The model defines five successive stages through which the mixture characteristics change. It is also shown that the time-variation of the mixer power consumption is a relevant tool to identify the transient stages of the mixture during mixing. In particular, it detects the instant when maximum cohesive paste occurs and identifies the fluidity time. The fluidity time is the instant when mixture turns to fresh concrete. In that sense, this transition time can be seen as an indicator of mixing difficulty for a given mixer. The influence of the mix-design and that of the liquid loading sequence on the mixing behavior are investigated; three sets of experiments are used for the assessment of the model. It is shown that one key parameter is the rheology of the mixture at the fluidity time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002238

Effect of heat-treatment and hydrostatic loading upon the poro-elastic properties of a mortar / Xiao-Ting Chen in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 195–205 Titre : Effect of heat-treatment and hydrostatic loading upon the poro-elastic properties of a mortar Type de document : texte imprimé Auteurs : Xiao-Ting Chen, Auteur ; C.A. Davya, Auteur ; F. Skoczylas, Auteur Année de publication : 2009 Article en page(s) : pp. 195–205 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mortar;  Poro-elasticity;  Thermal  treatment;  Hydrostatic  stress;Micro-cracking Résumé : This contribution aims at identifying experimentally the poro-elastic properties of a cement-based material under different levels of confining pressure, and after a heat-treatment up to 400 °C. The model material used is a normalized mortar, with a (W/C) ratio of 0.5. After a given heating/cooling cycle, drained bulk modulus Kb, solid matrix bulk modulus Ks and Biot's coefficient b are measured at different confining pressure levels (with a maximum of 25 MPa). Results show that under drained conditions, mortar stress–strain relationship evolves with increasing heat-treatment temperature from linear elastic with brittle failure (up to 105 °C heat treatment) to plastic and ductile (from 200 °C and above). Plastification testifies of material degradation under gradual confining pressure. At the microstructure scale, this is attributed to thermal damage after heat treatment above 105 °C, which consists mainly in various micro-cracking. This leads to easier failure of solid skeleton bridges (or trabecules), and to pore network collapse. Concomitantly to this, at given confining pressure Pc, secant drained bulk modulus Kb decreases monotonously, for heat-treatment temperatures above 105 °C. On the opposite, at given heat-treatment temperature above 105 °C, secant drained bulk modulus Kb increases when confining pressure is increased. This testifies of a solid matrix rigidification in the elastic domain, and it is attributed to increased skeleton compactness linked with pore network collapse. This is directly attributable to heat treatment followed by confinement. At given confining pressure Pc, matrix bulk modulus Ks and Biot's coefficient b increase with heat-treatment temperature above 105 °C. The increase in b means that mortar becomes less and less cohesive and more and more of a granular nature. Moreover, Biot's coefficient b and solid matrix bulk modulus Ks are independent of confining pressure Pc for intact mortar, whereas they decrease for heat-treated mortars when Pc increases. From literature analysis alone, it was quite unexpected that after heat treatment, Ks should vary under confinement. This is interpreted as the closure, under confining pressure, of micro-void connections and of micro-cracks created by heat-treatment. Therefore, increasing confinement induces more and more occluded pores in the solid matrix, whereby Ks diminishes. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002202 [article] Effect of heat-treatment and hydrostatic loading upon the poro-elastic properties of a mortar [texte imprimé] / Xiao-Ting Chen, Auteur ; C.A. Davya, Auteur ; F. Skoczylas, Auteur . - 2009 . - pp. 195–205. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 195–205 Mots-clés : Mortar;  Poro-elasticity;  Thermal  treatment;  Hydrostatic  stress;Micro-cracking Résumé : This contribution aims at identifying experimentally the poro-elastic properties of a cement-based material under different levels of confining pressure, and after a heat-treatment up to 400 °C. The model material used is a normalized mortar, with a (W/C) ratio of 0.5. After a given heating/cooling cycle, drained bulk modulus Kb, solid matrix bulk modulus Ks and Biot's coefficient b are measured at different confining pressure levels (with a maximum of 25 MPa). Results show that under drained conditions, mortar stress–strain relationship evolves with increasing heat-treatment temperature from linear elastic with brittle failure (up to 105 °C heat treatment) to plastic and ductile (from 200 °C and above). Plastification testifies of material degradation under gradual confining pressure. At the microstructure scale, this is attributed to thermal damage after heat treatment above 105 °C, which consists mainly in various micro-cracking. This leads to easier failure of solid skeleton bridges (or trabecules), and to pore network collapse. Concomitantly to this, at given confining pressure Pc, secant drained bulk modulus Kb decreases monotonously, for heat-treatment temperatures above 105 °C. On the opposite, at given heat-treatment temperature above 105 °C, secant drained bulk modulus Kb increases when confining pressure is increased. This testifies of a solid matrix rigidification in the elastic domain, and it is attributed to increased skeleton compactness linked with pore network collapse. This is directly attributable to heat treatment followed by confinement. At given confining pressure Pc, matrix bulk modulus Ks and Biot's coefficient b increase with heat-treatment temperature above 105 °C. The increase in b means that mortar becomes less and less cohesive and more and more of a granular nature. Moreover, Biot's coefficient b and solid matrix bulk modulus Ks are independent of confining pressure Pc for intact mortar, whereas they decrease for heat-treated mortars when Pc increases. From literature analysis alone, it was quite unexpected that after heat treatment, Ks should vary under confinement. This is interpreted as the closure, under confining pressure, of micro-void connections and of micro-cracks created by heat-treatment. Therefore, increasing confinement induces more and more occluded pores in the solid matrix, whereby Ks diminishes. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002202

Durability of self-consolidating concrete to sulfate attack under combined cyclic environments and flexural loading / M. T. Bassuoni in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 206–226 Titre : Durability of self-consolidating concrete to sulfate attack under combined cyclic environments and flexural loading Type de document : texte imprimé Auteurs : M. T. Bassuoni, Auteur ; M.L. Nehdi, Auteur Année de publication : 2009 Article en page(s) : pp. 206–226 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Performance  tests;  Self-consolidating  concrete;  C-sulfate  attack;  E-composite  cements;  Air-entrainment;  E-hybrid  fibre  reinforcement Résumé : Classical sulfate immersion tests for concrete have often given different behaviour from that observed in real field exposure. Such tests do not consider other parameters existing in service that can affect the mechanisms and kinetics of sulfate attack. On the other hand, the current shift towards performance-based standards and specifications for concrete requires the development of performance tests that better correlate to field conditions. Such holistic tests can effectively evaluate the service life of normal and emerging types of concrete. With the growing use of self-consolidating concrete (SCC) in various infrastructure applications, it has become necessary to establish reliable data on its durability. In the present study, the durability of a wide range of SCC mixture designs to sulfate attack is assessed when other concomitant damage mechanisms (cyclic environmental conditions and flexural loading) are considered. Based on the tested mixture design variables (type of binders, air-entrainment, sand-to-total aggregates mass ratio, and hybrid fibre reinforcement), potential performance risks (in terms of physico-mechanical parameters) under such a combined exposure were identified. Those risks were not tangible under a full-immersion test method. Thermal, mineralogical and microscopy analyses revealed the coexistence of complex deterioration processes in SCC under the combined exposure, which is fundamentally different from the occurrence of a single damage mechanism (sulfate attack). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002196 [article] Durability of self-consolidating concrete to sulfate attack under combined cyclic environments and flexural loading [texte imprimé] / M. T. Bassuoni, Auteur ; M.L. Nehdi, Auteur . - 2009 . - pp. 206–226. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 206–226 Mots-clés : Performance  tests;  Self-consolidating  concrete;  C-sulfate  attack;  E-composite  cements;  Air-entrainment;  E-hybrid  fibre  reinforcement Résumé : Classical sulfate immersion tests for concrete have often given different behaviour from that observed in real field exposure. Such tests do not consider other parameters existing in service that can affect the mechanisms and kinetics of sulfate attack. On the other hand, the current shift towards performance-based standards and specifications for concrete requires the development of performance tests that better correlate to field conditions. Such holistic tests can effectively evaluate the service life of normal and emerging types of concrete. With the growing use of self-consolidating concrete (SCC) in various infrastructure applications, it has become necessary to establish reliable data on its durability. In the present study, the durability of a wide range of SCC mixture designs to sulfate attack is assessed when other concomitant damage mechanisms (cyclic environmental conditions and flexural loading) are considered. Based on the tested mixture design variables (type of binders, air-entrainment, sand-to-total aggregates mass ratio, and hybrid fibre reinforcement), potential performance risks (in terms of physico-mechanical parameters) under such a combined exposure were identified. Those risks were not tangible under a full-immersion test method. Thermal, mineralogical and microscopy analyses revealed the coexistence of complex deterioration processes in SCC under the combined exposure, which is fundamentally different from the occurrence of a single damage mechanism (sulfate attack). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002196

Passing ability of fresh concrete: A probabilistic approach / N. Roussel in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 227–232 Titre : Passing ability of fresh concrete: A probabilistic approach Type de document : texte imprimé Auteurs : N. Roussel, Auteur ; T.L.H. Nguyen, Auteur ; O. Yazoghli, Auteur Année de publication : 2009 Article en page(s) : pp. 227–232 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Rheology;  Casting;  Aggregates;  Blocking Résumé : In the present paper, it is first reminded that the probability of granular blocking of a suspension crossing a flow contraction increases with the number of particles crossing the obstacles, their volume fraction and the ratio between the diameter of the particles and the contraction gap. It is moreover reminded that this phenomenon can be described using a simple dimensionless geometric parameter as this phenomenon only slightly depends on the rheology of the suspending fluid. An adaptation of this dimensionless parameter to the specific case of concrete is proposed and compared to experimental results. Finally, an application to the prediction of the passing ability of Ordinary Rheology Concrete (ORC) and Self Compacting Concrete (SCC) is proposed and compared to the European technical recommendations. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002184 [article] Passing ability of fresh concrete: A probabilistic approach [texte imprimé] / N. Roussel, Auteur ; T.L.H. Nguyen, Auteur ; O. Yazoghli, Auteur . - 2009 . - pp. 227–232. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 227–232 Mots-clés : Rheology;  Casting;  Aggregates;  Blocking Résumé : In the present paper, it is first reminded that the probability of granular blocking of a suspension crossing a flow contraction increases with the number of particles crossing the obstacles, their volume fraction and the ratio between the diameter of the particles and the contraction gap. It is moreover reminded that this phenomenon can be described using a simple dimensionless geometric parameter as this phenomenon only slightly depends on the rheology of the suspending fluid. An adaptation of this dimensionless parameter to the specific case of concrete is proposed and compared to experimental results. Finally, an application to the prediction of the passing ability of Ordinary Rheology Concrete (ORC) and Self Compacting Concrete (SCC) is proposed and compared to the European technical recommendations. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002184

Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity / G. Mertens in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 233–240 Titre : Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity Type de document : texte imprimé Auteurs : G. Mertens, Auteur ; R. Snellings, Auteur ; K. Van Balen, Auteur Année de publication : 2009 Article en page(s) : pp. 233–240 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Kinetics;  Characterization;  Ca(OH)2;  Pozzolan;  Zeolites Résumé : The pozzolanic reaction between portlandite and different types of nearly pure natural zeolites was studied. Analcime, phillipsite, chabazite, erionite, mordenite and clinoptilolite-rich tuffs were mixed with portlandite and water (1:1:2 by weight), and the progress of the pozzolanic reaction was quantitatively determined by thermogravimetrical analyses from 3 to 180 days. A thorough characterization of the raw materials was performed by quantitative XRD, XRF, SEM-EDX, BET specific surface area measurements, grain-size analyses, FTIR and Cation Exchange Capacity measurements. The difference in reactivity of the samples containing zeolites with varying Si/Al ratios, as well as between clinoptilolite-rich samples exchanged with different cations or ground to different grain sizes was assessed. The results indicate that the external surface area only influences the short-term reactivity, whereas the cation content has an effect on both the long- and short-term reactivity. The early reactivity of the unexchanged samples can be explained by these two parameters, but their long-term reactivity is mainly related to the Si/Al ratio of the zeolites. Samples with zeolites rich in Si react faster then their Al-rich counterparts. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002172 [article] Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity [texte imprimé] / G. Mertens, Auteur ; R. Snellings, Auteur ; K. Van Balen, Auteur . - 2009 . - pp. 233–240. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 233–240 Mots-clés : Kinetics;  Characterization;  Ca(OH)2;  Pozzolan;  Zeolites Résumé : The pozzolanic reaction between portlandite and different types of nearly pure natural zeolites was studied. Analcime, phillipsite, chabazite, erionite, mordenite and clinoptilolite-rich tuffs were mixed with portlandite and water (1:1:2 by weight), and the progress of the pozzolanic reaction was quantitatively determined by thermogravimetrical analyses from 3 to 180 days. A thorough characterization of the raw materials was performed by quantitative XRD, XRF, SEM-EDX, BET specific surface area measurements, grain-size analyses, FTIR and Cation Exchange Capacity measurements. The difference in reactivity of the samples containing zeolites with varying Si/Al ratios, as well as between clinoptilolite-rich samples exchanged with different cations or ground to different grain sizes was assessed. The results indicate that the external surface area only influences the short-term reactivity, whereas the cation content has an effect on both the long- and short-term reactivity. The early reactivity of the unexchanged samples can be explained by these two parameters, but their long-term reactivity is mainly related to the Si/Al ratio of the zeolites. Samples with zeolites rich in Si react faster then their Al-rich counterparts. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002172

Sulfate attack on cementitious materials containing limestone filler — A review / E.F. Irassar in Cement and concrete research, Vol. 39 N° 3 (Mars 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 241–254 Titre : Sulfate attack on cementitious materials containing limestone filler — A review Type de document : texte imprimé Auteurs : E.F. Irassar, Auteur Année de publication : 2009 Article en page(s) : pp. 241–254 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Degradation;  Sulfate  attack;  CaCO3;  Limestone;  Filler;  Thaumasite Résumé : This review summarizes the results of sulfate performance in laboratory and field tests where limestone is used as a constituent of cement (PLC) or as a sand replacement where it is particularly beneficial to the properties of self compacting concretes (SCC). Laboratory studies on paste, mortar or concrete specimens exposed to Na2SO4 and MgSO4 solutions in a wide range of concentrations at different temperatures as well as mixtures with different compositions, cement compositions and limestone proportions are considered in a conceptual analysis as for the resistance to external sulfate attack and, especially, thaumasite sulfate attack. A detailed analysis of environmental aggressiveness (concentration, temperature and pH), mixture composition and cement composition used in each study are presented for PLC and SCC. Reported field studies are also shown, only a few cases have used limestone filler in their composition. A conceptual graphical analysis is then proposed to relate the degree of surface deterioration and mineralogical composition of attacked surface to the main variables of external sulfate attack: water/cementitious material ratio, limestone content and C3A content of the cement. Observation of graphical analysis clearly shows that deterioration by ESA is mainly governed by effective w/c ratio and C3A content of the cement. Surface damage is controlled when low effective w/c ratio and low C3A are used. In MgSO4 solution, low temperatures increase the degree of deterioration. Thaumasite is the last attack stage in the different sulfate environments. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002123 [article] Sulfate attack on cementitious materials containing limestone filler — A review [texte imprimé] / E.F. Irassar, Auteur . - 2009 . - pp. 241–254. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 3 (Mars 2009) . - pp. 241–254 Mots-clés : Degradation;  Sulfate  attack;  CaCO3;  Limestone;  Filler;  Thaumasite Résumé : This review summarizes the results of sulfate performance in laboratory and field tests where limestone is used as a constituent of cement (PLC) or as a sand replacement where it is particularly beneficial to the properties of self compacting concretes (SCC). Laboratory studies on paste, mortar or concrete specimens exposed to Na2SO4 and MgSO4 solutions in a wide range of concentrations at different temperatures as well as mixtures with different compositions, cement compositions and limestone proportions are considered in a conceptual analysis as for the resistance to external sulfate attack and, especially, thaumasite sulfate attack. A detailed analysis of environmental aggressiveness (concentration, temperature and pH), mixture composition and cement composition used in each study are presented for PLC and SCC. Reported field studies are also shown, only a few cases have used limestone filler in their composition. A conceptual graphical analysis is then proposed to relate the degree of surface deterioration and mineralogical composition of attacked surface to the main variables of external sulfate attack: water/cementitious material ratio, limestone content and C3A content of the cement. Observation of graphical analysis clearly shows that deterioration by ESA is mainly governed by effective w/c ratio and C3A content of the cement. Surface damage is controlled when low effective w/c ratio and low C3A are used. In MgSO4 solution, low temperatures increase the degree of deterioration. Thaumasite is the last attack stage in the different sulfate environments. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884608002123

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