Dépouillements

Phase development in conventional and active belite cement pastes by Rietveld analysis and chemical constraints / Antonio J.M. Cuberos in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 833–842 Titre : Phase development in conventional and active belite cement pastes by Rietveld analysis and chemical constraints Type de document : texte imprimé Auteurs : Antonio J.M. Cuberos, Auteur ; Ángeles G. De la Torre, Auteur ; M. Carmen Martín-Sedeño, Auteur Année de publication : 2009 Article en page(s) : pp. 833–842 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Alkali  activated  cement;  Hydration  products;  X-ray  diffraction;Quantitative  phase  analysis Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : High belite cements may be an alternative to reduce CO2 emissions. Although CO2 emissions may be depleted up to 10%, unfortunately, the hydration reactivity of belite phases is slow which leads to low mechanical strengths at early ages. In order to enhance their hydraulic reactivity, the activation of these cements by doping with alkaline oxides has been proposed. Here, we have synthesised a laboratory belite clinker without activation (47 wt.% of β-C2S and 19 wt.% of αH′-C2S) and two alkaline oxide activated clinkers (one with 13 wt.% of β-C2S, 24 wt.% of αH′-C2S and 19 wt.% of α-C2S; and the second with 12 wt.% of β-C2S, 42 wt.% of αH′-C2S and 5 wt.% of α-C2S). We have also developed a methodology to analyse quantitatively the phase evolution of cement pastes and we have applied it to these high belite cements. Rietveld quantitative phase analysis of synchrotron X-ray powder diffraction data, together with chemical constraints, is used to determine the phase development up to 1 year of hydration in the belite cement pastes. β-C2S almost does not react during the first 3 months, meanwhile αH′-C2S reacts on average more than 50% in the same period. Moreover, the degree of reaction of α-C2S is slightly larger (on average about 70% after three months) than that of αH′-C2S. Full phase analyses are reported and discussed including the time evolution of amorphous phases and free water. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001446 [article] Phase development in conventional and active belite cement pastes by Rietveld analysis and chemical constraints [texte imprimé] / Antonio J.M. Cuberos, Auteur ; Ángeles G. De la Torre, Auteur ; M. Carmen Martín-Sedeño, Auteur . - 2009 . - pp. 833–842. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 833–842 Mots-clés : Alkali  activated  cement;  Hydration  products;  X-ray  diffraction;Quantitative  phase  analysis Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : High belite cements may be an alternative to reduce CO2 emissions. Although CO2 emissions may be depleted up to 10%, unfortunately, the hydration reactivity of belite phases is slow which leads to low mechanical strengths at early ages. In order to enhance their hydraulic reactivity, the activation of these cements by doping with alkaline oxides has been proposed. Here, we have synthesised a laboratory belite clinker without activation (47 wt.% of β-C2S and 19 wt.% of αH′-C2S) and two alkaline oxide activated clinkers (one with 13 wt.% of β-C2S, 24 wt.% of αH′-C2S and 19 wt.% of α-C2S; and the second with 12 wt.% of β-C2S, 42 wt.% of αH′-C2S and 5 wt.% of α-C2S). We have also developed a methodology to analyse quantitatively the phase evolution of cement pastes and we have applied it to these high belite cements. Rietveld quantitative phase analysis of synchrotron X-ray powder diffraction data, together with chemical constraints, is used to determine the phase development up to 1 year of hydration in the belite cement pastes. β-C2S almost does not react during the first 3 months, meanwhile αH′-C2S reacts on average more than 50% in the same period. Moreover, the degree of reaction of α-C2S is slightly larger (on average about 70% after three months) than that of αH′-C2S. Full phase analyses are reported and discussed including the time evolution of amorphous phases and free water. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001446

Effect of activation conditions of a kaolinite based waste on rheology of blended cement pastes / P. F. G. Banfill in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 843–848 Titre : Effect of activation conditions of a kaolinite based waste on rheology of blended cement pastes Type de document : texte imprimé Auteurs : P. F. G. Banfill, Auteur ; O. Rodríguez, Auteur ; M.I. Sánchez de Rojas, Auteur Année de publication : 2009 Article en page(s) : pp. 843–848 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Rheology;  Thermal  treatment;  Cement  paste;  Waste  paper  sludge Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper reports the influence of calcining temperature on the rheology of blended cement pastes with 10 and 20% of thermally activated paper sludge as pozzolan at water/binder ratio of 0.5 and 0.4. The kaolinite based waste was activated at different activation temperatures (700–800 °C) and retention times of 2 and 5 h. The yield stress of the blended pastes increased when the activation intensity increased as a result of the increased calcite and free lime content. Due to the stiffness of the blended pastes, a superplasticiser (sodium lignosulfonate) was used in order to reduce the yield stress. The best results could be obtained using the lower calcining temperature (700 °C and 2 h). DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001409 [article] Effect of activation conditions of a kaolinite based waste on rheology of blended cement pastes [texte imprimé] / P. F. G. Banfill, Auteur ; O. Rodríguez, Auteur ; M.I. Sánchez de Rojas, Auteur . - 2009 . - pp. 843–848. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 843–848 Mots-clés : Rheology;  Thermal  treatment;  Cement  paste;  Waste  paper  sludge Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper reports the influence of calcining temperature on the rheology of blended cement pastes with 10 and 20% of thermally activated paper sludge as pozzolan at water/binder ratio of 0.5 and 0.4. The kaolinite based waste was activated at different activation temperatures (700–800 °C) and retention times of 2 and 5 h. The yield stress of the blended pastes increased when the activation intensity increased as a result of the increased calcite and free lime content. Due to the stiffness of the blended pastes, a superplasticiser (sodium lignosulfonate) was used in order to reduce the yield stress. The best results could be obtained using the lower calcining temperature (700 °C and 2 h). DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001409

Studying nucleation and growth kinetics of alite hydration using μic / Shashank Bishnoi in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 849–860 Titre : Studying nucleation and growth kinetics of alite hydration using μic Type de document : texte imprimé Auteurs : Shashank Bishnoi, Auteur ; Scrivener, Karen, Auteur Année de publication : 2009 Article en page(s) : pp. 849–860 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Alite;  Hydration;  Kinetics;  Modelling;  Microstructure;  Calcium–silicate–hydrate  (C–S–H) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper investigates the applicability of nucleation and growth mechanisms to the hydration of alite. Various possible mechanisms of nucleation and growth were simulated using the recently-developed microstructural modelling platform μic. Comparison with the Avrami equation and the boundary nucleation model demonstrate the limitations of these equations. Experimental measurements of the rates of hydration of alite powders with different particle size distributions were then simulated with a boundary nucleation and growth model in μic. The results show that while the nucleation and growth of C–S–H having bulk densities in the currently accepted range can explain the acceleration during the first few hours of hydration, it cannot explain the later deceleration. It was also found that the resistance to flow of ions offered by the layer of hydrates forming over the surface of the alite particles (diffusion control) cannot explain the deceleration. The deceleration could be reproduced when C–S–H was assumed to be loosely packed in the beginning with its density of packing increasing with hydration. It is proposed that during the early hours of hydration a loosely-packed C–S–H fills a large fraction of the microstructure and the further development of its microstructure occurs due to an increase in its packing. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001641 [article] Studying nucleation and growth kinetics of alite hydration using μic [texte imprimé] / Shashank Bishnoi, Auteur ; Scrivener, Karen, Auteur . - 2009 . - pp. 849–860. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 849–860 Mots-clés : Alite;  Hydration;  Kinetics;  Modelling;  Microstructure;  Calcium–silicate–hydrate  (C–S–H) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper investigates the applicability of nucleation and growth mechanisms to the hydration of alite. Various possible mechanisms of nucleation and growth were simulated using the recently-developed microstructural modelling platform μic. Comparison with the Avrami equation and the boundary nucleation model demonstrate the limitations of these equations. Experimental measurements of the rates of hydration of alite powders with different particle size distributions were then simulated with a boundary nucleation and growth model in μic. The results show that while the nucleation and growth of C–S–H having bulk densities in the currently accepted range can explain the acceleration during the first few hours of hydration, it cannot explain the later deceleration. It was also found that the resistance to flow of ions offered by the layer of hydrates forming over the surface of the alite particles (diffusion control) cannot explain the deceleration. The deceleration could be reproduced when C–S–H was assumed to be loosely packed in the beginning with its density of packing increasing with hydration. It is proposed that during the early hours of hydration a loosely-packed C–S–H fills a large fraction of the microstructure and the further development of its microstructure occurs due to an increase in its packing. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001641

Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation / Pietro Lura in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 861–867 Titre : Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation Type de document : texte imprimé Auteurs : Pietro Lura, Auteur ; Jon Couch, Auteur ; Ole Mejlhede Jensen, Auteur Année de publication : 2009 Article en page(s) : pp. 861–867 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fresh  concrete;  Setting;  Acoustic  emission;  Cavitation;  Shrinkage Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In this study, the acoustic emission activity of cement pastes was investigated during the first day of hydration. Deaired, fresh cement pastes were cast in sealed sample holders designed to minimize friction and restraint. The majority of acoustic emission events occurred in lower water to cement ratio pastes, while cement pastes with higher water to cement ratios showed significantly less acoustic activity. These acoustic events occurred around the time of setting. A layer of water on the surface of the cement pastes substantially reduced acoustic emission activity at the time of setting. According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs in a cement paste, often referred to as time-zero. Knowledge of time-zero is fundamental for determining when mechanical properties develop and in calculations of residual stresses. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001422 [article] Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation [texte imprimé] / Pietro Lura, Auteur ; Jon Couch, Auteur ; Ole Mejlhede Jensen, Auteur . - 2009 . - pp. 861–867. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 861–867 Mots-clés : Fresh  concrete;  Setting;  Acoustic  emission;  Cavitation;  Shrinkage Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In this study, the acoustic emission activity of cement pastes was investigated during the first day of hydration. Deaired, fresh cement pastes were cast in sealed sample holders designed to minimize friction and restraint. The majority of acoustic emission events occurred in lower water to cement ratio pastes, while cement pastes with higher water to cement ratios showed significantly less acoustic activity. These acoustic events occurred around the time of setting. A layer of water on the surface of the cement pastes substantially reduced acoustic emission activity at the time of setting. According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs in a cement paste, often referred to as time-zero. Knowledge of time-zero is fundamental for determining when mechanical properties develop and in calculations of residual stresses. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001422

Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting / Nicolas Robeyst in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 868–875 Titre : Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting Type de document : texte imprimé Auteurs : Nicolas Robeyst, Auteur ; Christian U. Grosse, Auteur ; Nele de Belie, Auteur Année de publication : 2009 Article en page(s) : pp. 868–875 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Ultrasonic;  Fresh  concrete  (A);  Granulated  blast-furnace  slag  (D);  Fly  ash  (D);  Admixture  (D) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Research on ultrasonic methods to monitor the setting of concrete has mainly focussed on the wave velocity as a useful quantity. To investigate the application of also the wave energy as a parameter, an experimental program was set up to apply the ultrasonic wave transmission technique on several mortar samples containing air entrainer, blast-furnace slag or fly ash causing clearly different setting behaviour. The increase of the relative energy E/Eref during setting is generally retarded if ordinary Portland cement is replaced by blast-furnace slag or fly ash. The mixtures with cement of a lower strength class or with large air content were difficult to test with the energy measurements since they were more sensitive to poor sensor contact due to shrinkage. For the other samples, the thresholds E/Eref = 0.02 and 0.13 are proposed to easily determine respectively initial and final setting based on the ultrasonic energy measurements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001471 [article] Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting [texte imprimé] / Nicolas Robeyst, Auteur ; Christian U. Grosse, Auteur ; Nele de Belie, Auteur . - 2009 . - pp. 868–875. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 868–875 Mots-clés : Ultrasonic;  Fresh  concrete  (A);  Granulated  blast-furnace  slag  (D);  Fly  ash  (D);  Admixture  (D) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Research on ultrasonic methods to monitor the setting of concrete has mainly focussed on the wave velocity as a useful quantity. To investigate the application of also the wave energy as a parameter, an experimental program was set up to apply the ultrasonic wave transmission technique on several mortar samples containing air entrainer, blast-furnace slag or fly ash causing clearly different setting behaviour. The increase of the relative energy E/Eref during setting is generally retarded if ordinary Portland cement is replaced by blast-furnace slag or fly ash. The mixtures with cement of a lower strength class or with large air content were difficult to test with the energy measurements since they were more sensitive to poor sensor contact due to shrinkage. For the other samples, the thresholds E/Eref = 0.02 and 0.13 are proposed to easily determine respectively initial and final setting based on the ultrasonic energy measurements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001471

Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting / Nicolas Robeyst in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 868–875 Titre : Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting Type de document : texte imprimé Auteurs : Nicolas Robeyst, Auteur ; Christian U. Grosse, Auteur ; Nele de Belie, Auteur Année de publication : 2009 Article en page(s) : pp. 868–875 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Ultrasonic;  Fresh  concrete  (A);  Granulated  blast-furnace  slag  (D);  Fly  ash  (D);  Admixture  (D) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Research on ultrasonic methods to monitor the setting of concrete has mainly focussed on the wave velocity as a useful quantity. To investigate the application of also the wave energy as a parameter, an experimental program was set up to apply the ultrasonic wave transmission technique on several mortar samples containing air entrainer, blast-furnace slag or fly ash causing clearly different setting behaviour. The increase of the relative energy E/Eref during setting is generally retarded if ordinary Portland cement is replaced by blast-furnace slag or fly ash. The mixtures with cement of a lower strength class or with large air content were difficult to test with the energy measurements since they were more sensitive to poor sensor contact due to shrinkage. For the other samples, the thresholds E/Eref = 0.02 and 0.13 are proposed to easily determine respectively initial and final setting based on the ultrasonic energy measurements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001471 [article] Measuring the change in ultrasonic p-wave energy transmitted in fresh mortar with additives to monitor the setting [texte imprimé] / Nicolas Robeyst, Auteur ; Christian U. Grosse, Auteur ; Nele de Belie, Auteur . - 2009 . - pp. 868–875. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 868–875 Mots-clés : Ultrasonic;  Fresh  concrete  (A);  Granulated  blast-furnace  slag  (D);  Fly  ash  (D);  Admixture  (D) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Research on ultrasonic methods to monitor the setting of concrete has mainly focussed on the wave velocity as a useful quantity. To investigate the application of also the wave energy as a parameter, an experimental program was set up to apply the ultrasonic wave transmission technique on several mortar samples containing air entrainer, blast-furnace slag or fly ash causing clearly different setting behaviour. The increase of the relative energy E/Eref during setting is generally retarded if ordinary Portland cement is replaced by blast-furnace slag or fly ash. The mixtures with cement of a lower strength class or with large air content were difficult to test with the energy measurements since they were more sensitive to poor sensor contact due to shrinkage. For the other samples, the thresholds E/Eref = 0.02 and 0.13 are proposed to easily determine respectively initial and final setting based on the ultrasonic energy measurements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001471

Comparison between two ultrasonic methods in their ability to monitor the setting process of cement pastes / Gregor Trtnik in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 876–882 Titre : Comparison between two ultrasonic methods in their ability to monitor the setting process of cement pastes Type de document : texte imprimé Auteurs : Gregor Trtnik, Auteur ; Marko Ivan Valič, Auteur ; Franci Kavčič, Auteur Année de publication : 2009 Article en page(s) : pp. 876–882 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement  paste;  Hydration;  Ultrasonic  wave  transmission  method;  Ultrasonic  wave  reflection  method;  Setting Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper presents the comparison between ultrasonic wave transmission (USWT) method and ultrasonic wave reflection (USWR) method in their ability to monitor the setting process of cement pastes. The velocity of ultrasonic longitudinal waves and shear wave reflection coefficient were measured simultaneously on cement pastes with different hydration kinetics. Even though both methods are able to reliably monitor the hydration process and formation of structure of an arbitrary cement paste, they monitor the setting process in different ways. The relationship between the velocity of longitudinal waves and shear wave reflection coefficient can be simplified into three characteristic phases and the end of the first phase can be used to define the beginning of the setting process of cement paste. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001537 [article] Comparison between two ultrasonic methods in their ability to monitor the setting process of cement pastes [texte imprimé] / Gregor Trtnik, Auteur ; Marko Ivan Valič, Auteur ; Franci Kavčič, Auteur . - 2009 . - pp. 876–882. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 876–882 Mots-clés : Cement  paste;  Hydration;  Ultrasonic  wave  transmission  method;  Ultrasonic  wave  reflection  method;  Setting Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper presents the comparison between ultrasonic wave transmission (USWT) method and ultrasonic wave reflection (USWR) method in their ability to monitor the setting process of cement pastes. The velocity of ultrasonic longitudinal waves and shear wave reflection coefficient were measured simultaneously on cement pastes with different hydration kinetics. Even though both methods are able to reliably monitor the hydration process and formation of structure of an arbitrary cement paste, they monitor the setting process in different ways. The relationship between the velocity of longitudinal waves and shear wave reflection coefficient can be simplified into three characteristic phases and the end of the first phase can be used to define the beginning of the setting process of cement paste. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001537

Water absorption in internally cured mortar made with water-filled lightweight aggregate / Ryan Henkensiefken in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 883–892 Titre : Water absorption in internally cured mortar made with water-filled lightweight aggregate Type de document : texte imprimé Auteurs : Ryan Henkensiefken, Auteur ; Javier Castro, Auteur ; Dale Bentz, Auteur Année de publication : 2009 Article en page(s) : pp. 883–892 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Interfacial  transition  zone;  Internal  curing;  Lightweight  aggregate;  Sorptivity Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The increased propensity for shrinkage cracking in low water-to-cement ratio (w/c) concrete has inspired the development of new technologies that can reduce the risk of early-age cracking. One of these is internal curing. Internal curing uses saturated lightweight aggregate to supply ‘curing water’ to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development; however, relatively little detailed information exists about the effects of internal curing on fluid transport properties such as water absorption or diffusivity. This study examines the absorption of water into mortar specimens made with saturated lightweight aggregates (SLWA). These results indicate that the inclusion of SLWA can reduce the water absorption of mortar specimens. This observation was reinforced with electrical conductivity measurements that exhibited similar reductions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001392 [article] Water absorption in internally cured mortar made with water-filled lightweight aggregate [texte imprimé] / Ryan Henkensiefken, Auteur ; Javier Castro, Auteur ; Dale Bentz, Auteur . - 2009 . - pp. 883–892. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 883–892 Mots-clés : Interfacial  transition  zone;  Internal  curing;  Lightweight  aggregate;  Sorptivity Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The increased propensity for shrinkage cracking in low water-to-cement ratio (w/c) concrete has inspired the development of new technologies that can reduce the risk of early-age cracking. One of these is internal curing. Internal curing uses saturated lightweight aggregate to supply ‘curing water’ to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development; however, relatively little detailed information exists about the effects of internal curing on fluid transport properties such as water absorption or diffusivity. This study examines the absorption of water into mortar specimens made with saturated lightweight aggregates (SLWA). These results indicate that the inclusion of SLWA can reduce the water absorption of mortar specimens. This observation was reinforced with electrical conductivity measurements that exhibited similar reductions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001392

Internal curing of engineered cementitious composites for prevention of early age autogenous shrinkage cracking / Mustafa Şahmaran in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 893–901 Titre : Internal curing of engineered cementitious composites for prevention of early age autogenous shrinkage cracking Type de document : texte imprimé Auteurs : Mustafa Şahmaran, Auteur ; Mohamed Lachemi, Auteur Année de publication : 2009 Article en page(s) : pp. 893–901 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Autogenous  shrinkage;  Drying  shrinkage;  Engineered  cementitious  composites  (ECC);  Internal  curing;  Uniaxial  tensile  test;  Flexural  test Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This investigation was carried out to study the effects of using a replacement percentage of saturated lightweight fine aggregate (LWA) as an internal curing agent on the shrinkage and mechanical behavior of Engineered Cementitious Composites (ECC). ECC is a micromechanically-based, designed high-performance, fiber-reinforced cementitious composite with high ductility and improved durability due to tight crack width. Standard ECC mixtures are typically produced with micro-silica sand (200 µm maximum aggregate size). Two replacement levels of silica sand with saturated LWA (fraction 0.59–4.76 mm) were adopted: the investigation used 10 and 20% by weight of total silica sand content, respectively. For each LWA replacement level, two different ECC mixtures with a fly ash-to-Portland cement ratio (FA/PC) of 1.2 and 2.2 were cast. In a control test series, two types of standard ECC mixtures with only silica sand were also studied. To investigate the effect of replacing a portion of the silica sand with saturated LWA on the mechanical properties of ECC, the study compared the results of uniaxial tensile, flexure and compressive strength tests, crack development, autogenous shrinkage and drying shrinkage. The test results showed that the autogenous shrinkage strains of the control ECCs with a low water-to-cementitious material ratio (W/CM) (0.27) and high volume FA developed rapidly, even at early ages. The results also showed that up to a 20% replacement of normal-weight silica sand with saturated LWA was very effective in reducing the autogenous shrinkage and drying shrinkage of ECC. On the other hand, the partial replacement of silica sand with saturated LWA with a nominal maximum aggregate size of 4.76 mm is shown to have a negative effect, especially on the ductility and strength properties of ECC. The test results also confirm that the autogenous shrinkage and drying shrinkage of ECC significantly decreases with increasing FA content. Moreover, increasing FA content is shown to have a positive effect on the ductility of ECC. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001665 [article] Internal curing of engineered cementitious composites for prevention of early age autogenous shrinkage cracking [texte imprimé] / Mustafa Şahmaran, Auteur ; Mohamed Lachemi, Auteur . - 2009 . - pp. 893–901. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 893–901 Mots-clés : Autogenous  shrinkage;  Drying  shrinkage;  Engineered  cementitious  composites  (ECC);  Internal  curing;  Uniaxial  tensile  test;  Flexural  test Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This investigation was carried out to study the effects of using a replacement percentage of saturated lightweight fine aggregate (LWA) as an internal curing agent on the shrinkage and mechanical behavior of Engineered Cementitious Composites (ECC). ECC is a micromechanically-based, designed high-performance, fiber-reinforced cementitious composite with high ductility and improved durability due to tight crack width. Standard ECC mixtures are typically produced with micro-silica sand (200 µm maximum aggregate size). Two replacement levels of silica sand with saturated LWA (fraction 0.59–4.76 mm) were adopted: the investigation used 10 and 20% by weight of total silica sand content, respectively. For each LWA replacement level, two different ECC mixtures with a fly ash-to-Portland cement ratio (FA/PC) of 1.2 and 2.2 were cast. In a control test series, two types of standard ECC mixtures with only silica sand were also studied. To investigate the effect of replacing a portion of the silica sand with saturated LWA on the mechanical properties of ECC, the study compared the results of uniaxial tensile, flexure and compressive strength tests, crack development, autogenous shrinkage and drying shrinkage. The test results showed that the autogenous shrinkage strains of the control ECCs with a low water-to-cementitious material ratio (W/CM) (0.27) and high volume FA developed rapidly, even at early ages. The results also showed that up to a 20% replacement of normal-weight silica sand with saturated LWA was very effective in reducing the autogenous shrinkage and drying shrinkage of ECC. On the other hand, the partial replacement of silica sand with saturated LWA with a nominal maximum aggregate size of 4.76 mm is shown to have a negative effect, especially on the ductility and strength properties of ECC. The test results also confirm that the autogenous shrinkage and drying shrinkage of ECC significantly decreases with increasing FA content. Moreover, increasing FA content is shown to have a positive effect on the ductility of ECC. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001665

Numerical and analytical effective elastic properties of degraded cement pastes / B. Bary in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 902–912 Titre : Numerical and analytical effective elastic properties of degraded cement pastes Type de document : texte imprimé Auteurs : B. Bary, Auteur ; M. Ben Haha, Auteur ; E. Adam, Auteur Année de publication : 2009 Article en page(s) : pp. 902–912 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Elastic  moduli;  Numerical  simulations;  Cement  paste;  Homogenization;  Degradation Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Cement pastes are heterogeneous materials composed of hydrates, anhydrous products and pores of various shapes. They are generally characterized by a high particle concentration and phase contrasts, in particular in the case of degraded materials which exhibit important porosity. This paper compares the performance of several classical effective medium approximation schemes (Mori–Tanaka, Zheng-Du, self-consistent) through their ability to estimate the mechanical parameters of cement paste samples obtained numerically. For this purpose, finite element simulations are performed on 3D structures to compute for each sample accurate values of these mechanical properties. For these simulations, the cement paste is considered as a matrix of C–S–H in which are embedded inclusions of anhydrous, hydration products, and pores. In order to evaluate the importance of the particle shape, two types of samples are generated, one with only spherical inclusions and the other containing both spherical and prismatic particles. Simulations with three perpendicular loading directions and both uniform and mixed boundary conditions are performed in order to verify that the dispersion in the computed elastic moduli is low, or equivalently that the generated structures are close to representative volume elements (RVEs). It is shown that the considered effective medium approximation schemes, except the self-consistent one, provide relatively good estimations of the overall mechanical parameters when compared to simulation results, including when both particle volume fraction and phase contrast are high. The analytical methods taking into account the particle shapes also give estimates close to the corresponding numerical simulations, the latter confirming the influence of the particle form. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001434 [article] Numerical and analytical effective elastic properties of degraded cement pastes [texte imprimé] / B. Bary, Auteur ; M. Ben Haha, Auteur ; E. Adam, Auteur . - 2009 . - pp. 902–912. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 902–912 Mots-clés : Elastic  moduli;  Numerical  simulations;  Cement  paste;  Homogenization;  Degradation Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Cement pastes are heterogeneous materials composed of hydrates, anhydrous products and pores of various shapes. They are generally characterized by a high particle concentration and phase contrasts, in particular in the case of degraded materials which exhibit important porosity. This paper compares the performance of several classical effective medium approximation schemes (Mori–Tanaka, Zheng-Du, self-consistent) through their ability to estimate the mechanical parameters of cement paste samples obtained numerically. For this purpose, finite element simulations are performed on 3D structures to compute for each sample accurate values of these mechanical properties. For these simulations, the cement paste is considered as a matrix of C–S–H in which are embedded inclusions of anhydrous, hydration products, and pores. In order to evaluate the importance of the particle shape, two types of samples are generated, one with only spherical inclusions and the other containing both spherical and prismatic particles. Simulations with three perpendicular loading directions and both uniform and mixed boundary conditions are performed in order to verify that the dispersion in the computed elastic moduli is low, or equivalently that the generated structures are close to representative volume elements (RVEs). It is shown that the considered effective medium approximation schemes, except the self-consistent one, provide relatively good estimations of the overall mechanical parameters when compared to simulation results, including when both particle volume fraction and phase contrast are high. The analytical methods taking into account the particle shapes also give estimates close to the corresponding numerical simulations, the latter confirming the influence of the particle form. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001434

Oxygen diffusion through hydrophobic cement-based materials / F. Tittarelli in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 924–928 Titre : Oxygen diffusion through hydrophobic cement-based materials Type de document : texte imprimé Auteurs : F. Tittarelli, Auteur Année de publication : 2009 Article en page(s) : pp. 924–928 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : cement  (D);  Diffusion  (C);  Hydrophobic  admixture Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The oxygen diffusion coefficient through hydrophobic cement-based materials fully immersed in water was determined by potentiostatic measurements on concrete and by the use of a diffusion cell on cement pastes and mortars. The obtained results show that very high oxygen diffusion occurs through cement paste, mortar and concrete made with hydrophobic admixture as opposed to negligible diffusion through the reference cement matrix without admixture. Moreover, the oxygen diffusion coefficients measured through hydrophobic cement matrices immersed in water were comparable with those reported in literature for unsaturated cement materials in air. These experimental results appear to confirm that oxygen dissolved in water directly diffuses as a gaseous phase through the empty pores of a hydrophobic cement matrix. This could explain the severe corrosion of steel reinforcement embedded in cracked hydrophobic concrete immersed in an aqueous chloride solution observed in a previous work. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001513 [article] Oxygen diffusion through hydrophobic cement-based materials [texte imprimé] / F. Tittarelli, Auteur . - 2009 . - pp. 924–928. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 924–928 Mots-clés : cement  (D);  Diffusion  (C);  Hydrophobic  admixture Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The oxygen diffusion coefficient through hydrophobic cement-based materials fully immersed in water was determined by potentiostatic measurements on concrete and by the use of a diffusion cell on cement pastes and mortars. The obtained results show that very high oxygen diffusion occurs through cement paste, mortar and concrete made with hydrophobic admixture as opposed to negligible diffusion through the reference cement matrix without admixture. Moreover, the oxygen diffusion coefficients measured through hydrophobic cement matrices immersed in water were comparable with those reported in literature for unsaturated cement materials in air. These experimental results appear to confirm that oxygen dissolved in water directly diffuses as a gaseous phase through the empty pores of a hydrophobic cement matrix. This could explain the severe corrosion of steel reinforcement embedded in cracked hydrophobic concrete immersed in an aqueous chloride solution observed in a previous work. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001513

Processing of electron microprobe data from the analysis of altered cementitious materials / A. Bertron in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 929–935 Titre : Processing of electron microprobe data from the analysis of altered cementitious materials Type de document : texte imprimé Auteurs : A. Bertron, Auteur ; G. Escadeillas, Auteur ; P. de Parseval, Auteur Année de publication : 2009 Article en page(s) : pp. 929–935 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement  paste;  Degradation;  Electron  microprobe Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The purpose of this paper is to present a method for processing electron microprobe data coming from the analysis of degraded cementitious materials. The application domain is that of cement matrices exposed to attack by aggressive media inducing the leaching of one or more chemical elements from the cement paste — typically attacked by neutral or acid aqueous environments. As raw data obtained from electron probe microanalysis (EPMA) come in the form of relative quantities of elements, the aim of the processing is to obtain the absolute variation of the specimen's chemical composition in the degraded zone and consequently to allow a better understanding of the degradation mechanisms by the aggressive environment under consideration. This method was designed for degraded specimens in which the porosity was not filled with resin before the EPMA. The method uses the titanium content of the cement matrix as a control, this element being stable during attack by neutral or acidic media. The method is described in detail using the example of the attack of cement pastes by a mix of several organic acids (notably acetic acid) at pH 4. The use of EPMA for sound and altered cement pastes is also validated. The application domain of the correction method is discussed. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001410 [article] Processing of electron microprobe data from the analysis of altered cementitious materials [texte imprimé] / A. Bertron, Auteur ; G. Escadeillas, Auteur ; P. de Parseval, Auteur . - 2009 . - pp. 929–935. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 929–935 Mots-clés : Cement  paste;  Degradation;  Electron  microprobe Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The purpose of this paper is to present a method for processing electron microprobe data coming from the analysis of degraded cementitious materials. The application domain is that of cement matrices exposed to attack by aggressive media inducing the leaching of one or more chemical elements from the cement paste — typically attacked by neutral or acid aqueous environments. As raw data obtained from electron probe microanalysis (EPMA) come in the form of relative quantities of elements, the aim of the processing is to obtain the absolute variation of the specimen's chemical composition in the degraded zone and consequently to allow a better understanding of the degradation mechanisms by the aggressive environment under consideration. This method was designed for degraded specimens in which the porosity was not filled with resin before the EPMA. The method uses the titanium content of the cement matrix as a control, this element being stable during attack by neutral or acidic media. The method is described in detail using the example of the attack of cement pastes by a mix of several organic acids (notably acetic acid) at pH 4. The use of EPMA for sound and altered cement pastes is also validated. The application domain of the correction method is discussed. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001410

Quantitative determination of anhydrite III from dehydrated gypsum by XRD / Sebastian Seufert in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 936–941 Titre : Quantitative determination of anhydrite III from dehydrated gypsum by XRD Type de document : texte imprimé Auteurs : Sebastian Seufert, Auteur ; C. Hesse, Auteur ; F. Goetz-Neunhoeffer, Auteur Année de publication : 2009 Article en page(s) : pp. 936–941 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Portland  cement;  Hydration;  X-ray  diffraction  characterization;Calcium  sulfate Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Technical OPC contains mixed sulfate carriers in varying amounts. Gypsum and anhydrite are added to the clinker during the milling process where the gypsum dehydrates partially to bassanite and anhydrite. Due to different hydration kinetics of these phases, it is crucial to be able to characterize the composition of sulfate in a cement system to reach an optimal and reproducible cement hydration. In the current paper different calcium sulfate compositions are investigated by XRD methods in order to identify phase content. Special focus is put on the discrimination of the hemihydrate (bassanite) and anhydrite III as well as on transformation processes of anhydrite III through ambient humidity. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001483 [article] Quantitative determination of anhydrite III from dehydrated gypsum by XRD [texte imprimé] / Sebastian Seufert, Auteur ; C. Hesse, Auteur ; F. Goetz-Neunhoeffer, Auteur . - 2009 . - pp. 936–941. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 936–941 Mots-clés : Portland  cement;  Hydration;  X-ray  diffraction  characterization;Calcium  sulfate Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Technical OPC contains mixed sulfate carriers in varying amounts. Gypsum and anhydrite are added to the clinker during the milling process where the gypsum dehydrates partially to bassanite and anhydrite. Due to different hydration kinetics of these phases, it is crucial to be able to characterize the composition of sulfate in a cement system to reach an optimal and reproducible cement hydration. In the current paper different calcium sulfate compositions are investigated by XRD methods in order to identify phase content. Special focus is put on the discrimination of the hemihydrate (bassanite) and anhydrite III as well as on transformation processes of anhydrite III through ambient humidity. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001483

An investigation into the strength development of Wastepaper Sludge Ash blended with Ground Granulated Blastfurnace Slag / E. Mozaffari in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. Titre : An investigation into the strength development of Wastepaper Sludge Ash blended with Ground Granulated Blastfurnace Slag Type de document : texte imprimé Auteurs : E. Mozaffari, Auteur ; J.M. Kinuthia, Auteur ; J. Bai Wild, Auteur Année de publication : 2009 Article en page(s) : pp. Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Wastepaper  Sludge  Ash;  lag;  Lime;  Setting;  Strength Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Wastepaper Sludge Ash (WSA) contains reactive components such as free lime (CaO), and less reactive and inert mineral species. When water is added to WSA some constituents hydrate faster than others, lime being the fastest giving high alkalinity to the solution. If the WSA is combined with Ground Granulated Blastfurnace Slag (GGBS) then the latter, activated by the raised pH, produces new minerals which will contribute further to the strength development of the paste. The kinetics of the hydration reactions and the possible ways of making lime a more effective contributor in activating other phases in the WSA–GGBS system are discussed. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001525 [article] An investigation into the strength development of Wastepaper Sludge Ash blended with Ground Granulated Blastfurnace Slag [texte imprimé] / E. Mozaffari, Auteur ; J.M. Kinuthia, Auteur ; J. Bai Wild, Auteur . - 2009 . - pp. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. Mots-clés : Wastepaper  Sludge  Ash;  lag;  Lime;  Setting;  Strength Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Wastepaper Sludge Ash (WSA) contains reactive components such as free lime (CaO), and less reactive and inert mineral species. When water is added to WSA some constituents hydrate faster than others, lime being the fastest giving high alkalinity to the solution. If the WSA is combined with Ground Granulated Blastfurnace Slag (GGBS) then the latter, activated by the raised pH, produces new minerals which will contribute further to the strength development of the paste. The kinetics of the hydration reactions and the possible ways of making lime a more effective contributor in activating other phases in the WSA–GGBS system are discussed. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001525

Porosity and specific surface area of Roman cement pastes / Renata Tišlova in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 950–956 Titre : Porosity and specific surface area of Roman cement pastes Type de document : texte imprimé Auteurs : Renata Tišlova, Auteur ; Antonina Kozłowska, Auteur ; Roman Kozłowski, Auteur Année de publication : 2009 Article en page(s) : pp. 950–956 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mercury  porosimetry;  Pore  size  distribution;Surface  area;Cement  paste;  Roman  cement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Mercury porosimetry, water vapour and nitrogen adsorption were used to follow the hydration of Roman cements — belite cements calcined at low temperature. Generally, unimodal distribution of pore sizes was observed, with the threshold pore width decreasing considerably with increasing curing time. An open porous structure with the threshold pore diameter between 0.2 and 0.8 μm and the specific surface area not exceeding 20 m2/g was produced at early ages when quick growth of the C–A–H phases is observed. The surface area reached up to 120 m2/g and the threshold pore width shifted to around 0.02 μm when the subsequent formation of C–S–H gel filled the larger pores. Both mercury porosimetry and water vapour adsorption were found to be capable of following the progress of hydration of the Roman cements with high reliability at least for a comparative evaluation of historic Roman cement mortars and repair materials used in restoration projects. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001501 [article] Porosity and specific surface area of Roman cement pastes [texte imprimé] / Renata Tišlova, Auteur ; Antonina Kozłowska, Auteur ; Roman Kozłowski, Auteur . - 2009 . - pp. 950–956. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 950–956 Mots-clés : Mercury  porosimetry;  Pore  size  distribution;Surface  area;Cement  paste;  Roman  cement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Mercury porosimetry, water vapour and nitrogen adsorption were used to follow the hydration of Roman cements — belite cements calcined at low temperature. Generally, unimodal distribution of pore sizes was observed, with the threshold pore width decreasing considerably with increasing curing time. An open porous structure with the threshold pore diameter between 0.2 and 0.8 μm and the specific surface area not exceeding 20 m2/g was produced at early ages when quick growth of the C–A–H phases is observed. The surface area reached up to 120 m2/g and the threshold pore width shifted to around 0.02 μm when the subsequent formation of C–S–H gel filled the larger pores. Both mercury porosimetry and water vapour adsorption were found to be capable of following the progress of hydration of the Roman cements with high reliability at least for a comparative evaluation of historic Roman cement mortars and repair materials used in restoration projects. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001501

Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples / H.S. Wong in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 957–965 Titre : Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples Type de document : texte imprimé Auteurs : H.S. Wong, Auteur ; N. R. Buenfeld, Auteur Année de publication : 2009 Article en page(s) : pp. 957–965 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Backscattered  electron  imaging  ;  Image  analysis  ;  Microstructure  ;  SEM  ;  w/c  ratio Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25–0.50) and curing ages (3–90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900146X [article] Determining the water–cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples [texte imprimé] / H.S. Wong, Auteur ; N. R. Buenfeld, Auteur . - 2009 . - pp. 957–965. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 957–965 Mots-clés : Backscattered  electron  imaging  ;  Image  analysis  ;  Microstructure  ;  SEM  ;  w/c  ratio Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25–0.50) and curing ages (3–90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900146X

Fracture of concrete structure using simplified meshless method / Y. Dong in Cement and concrete research, Vol. 39 N° 10 (Octobre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 966–972 Titre : Fracture of concrete structure using simplified meshless method Type de document : texte imprimé Auteurs : Y. Dong, Auteur ; S. Fang, Auteur ; Y. Zhang, Auteur Année de publication : 2009 Article en page(s) : pp. 966–972 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Computational  mechanics;  Crack;  racture;  Meshless;  EFG;  Material  failure;  Concrete;  Enrichment;  Partition  of  unity Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Numerical analysis of fracture in concrete is studied with a simplified meshless method. In this meshless method, the crack is represented by a set of disconnected cohesive crack segments that are required to pass through meshless nodes. The crack method therefore falls in the category of discrete crack methods. However, in contrast to most other methods where the crack is represented as continuous line/surface, no representation of the crack surface is needed. Hence, there is no need to track the crack path. Branching cracks and coalescing cracks are a natural outcome of the analysis and no specific algorithms need to be incorporated to model such complicated events. Besides the simplicity of the method, the accuracy is maintained. This is demonstrated through several examples. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001458 [article] Fracture of concrete structure using simplified meshless method [texte imprimé] / Y. Dong, Auteur ; S. Fang, Auteur ; Y. Zhang, Auteur . - 2009 . - pp. 966–972. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 10 (Octobre 2009) . - pp. 966–972 Mots-clés : Computational  mechanics;  Crack;  racture;  Meshless;  EFG;  Material  failure;  Concrete;  Enrichment;  Partition  of  unity Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Numerical analysis of fracture in concrete is studied with a simplified meshless method. In this meshless method, the crack is represented by a set of disconnected cohesive crack segments that are required to pass through meshless nodes. The crack method therefore falls in the category of discrete crack methods. However, in contrast to most other methods where the crack is represented as continuous line/surface, no representation of the crack surface is needed. Hence, there is no need to track the crack path. Branching cracks and coalescing cracks are a natural outcome of the analysis and no specific algorithms need to be incorporated to model such complicated events. Besides the simplicity of the method, the accuracy is maintained. This is demonstrated through several examples. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001458

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