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691 : Matériaux de construction. Pièces et parties composantes
Ouvrages de la bibliothèque en indexation 691
Affiner la rechercheEarly-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)
[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 Early C3A hydration in the presence of different kinds of calcium sulfate / S. Pourcheta in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009)
[article]
in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 989–996
Titre : Early C3A hydration in the presence of different kinds of calcium sulfate Type de document : texte imprimé Auteurs : S. Pourcheta, Auteur ; L. Regnaud, Auteur ; J.P. Perez, Auteur Année de publication : 2010 Article en page(s) : pp. 989–996 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Hydration ; Ca3Al2O6 ; Ettringite ; Kinetics Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A–CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A–gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also leads to an increase of the ettringite formation rate during at least the five first hours under experimental conditions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001793 [article] Early C3A hydration in the presence of different kinds of calcium sulfate [texte imprimé] / S. Pourcheta, Auteur ; L. Regnaud, Auteur ; J.P. Perez, Auteur . - 2010 . - pp. 989–996.
Génie Civil
Langues : Anglais (eng)
in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 989–996
Mots-clés : Hydration ; Ca3Al2O6 ; Ettringite ; Kinetics Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A–CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A–gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also leads to an increase of the ettringite formation rate during at least the five first hours under experimental conditions. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001793 Early hydration of clinker–slag–metakaolin combination in steam curing conditions, relation with mechanical properties / F. Cassagnabèrea in Cement and concrete research, Vol. 39 N° 12 (Décembre 2009)
[article]
in Cement and concrete research > Vol. 39 N° 12 (Décembre 2009) . - pp. 1164-1173
Titre : Early hydration of clinker–slag–metakaolin combination in steam curing conditions, relation with mechanical properties Type de document : texte imprimé Auteurs : F. Cassagnabèrea, Auteur ; M. Mouret, Auteur ; G. Escadeillas, Auteur Année de publication : 2010 Article en page(s) : pp. 1164-1173 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement/slag/MK binder ; Steam curing ; Early age; Hydration product Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : High strength can be obtained at early ages for precast concrete elements by the use of CEMI 52.5R cement (OPC) and thermal treatment (steam curing). To compensate for the announced withdrawal of CEM I cements because of high CO2 emissions during their production and the ecotax that this will imply, one attractive alternative is the use of composed cements resulting from the combination of clinker with mineral admixtures. In steam curing conditions, previous studies have shown an increase in the compressive strength at one day of age for mortars incorporating an OPC/blast furnace slag (GGBS)/metakaolin (MK) combination, in comparison with mortars incorporating OPC only. The present study investigates the connection between the compressive strength, at one day of age, of steam cured mortars made with various binders and the hydration of these binders. The progress of the hydration was characterised by means of XRD, thermal and microprobe analyses. The results indicate that the increase in compressive strength when MK is incorporated (OPC/MK or OPC/MK/GGBS) can be explained by an increase in the amount of C-S-H, C-A-H, C-A-S-H phases, a decrease in the amount of CH and a change in the chemical nature of the matrix (decrease in C/S ratio). The decrease in compressive strength of OPC/slag-based material can be explained by a reduction in the amount of hydrated phases (particularly C-S-H) and compactness.
These are promising results for precast concrete manufacturers who are concerned about preserving the environment.DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001859 [article] Early hydration of clinker–slag–metakaolin combination in steam curing conditions, relation with mechanical properties [texte imprimé] / F. Cassagnabèrea, Auteur ; M. Mouret, Auteur ; G. Escadeillas, Auteur . - 2010 . - pp. 1164-1173.
Génie Civil
Langues : Anglais (eng)
in Cement and concrete research > Vol. 39 N° 12 (Décembre 2009) . - pp. 1164-1173
Mots-clés : Cement/slag/MK binder ; Steam curing ; Early age; Hydration product Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : High strength can be obtained at early ages for precast concrete elements by the use of CEMI 52.5R cement (OPC) and thermal treatment (steam curing). To compensate for the announced withdrawal of CEM I cements because of high CO2 emissions during their production and the ecotax that this will imply, one attractive alternative is the use of composed cements resulting from the combination of clinker with mineral admixtures. In steam curing conditions, previous studies have shown an increase in the compressive strength at one day of age for mortars incorporating an OPC/blast furnace slag (GGBS)/metakaolin (MK) combination, in comparison with mortars incorporating OPC only. The present study investigates the connection between the compressive strength, at one day of age, of steam cured mortars made with various binders and the hydration of these binders. The progress of the hydration was characterised by means of XRD, thermal and microprobe analyses. The results indicate that the increase in compressive strength when MK is incorporated (OPC/MK or OPC/MK/GGBS) can be explained by an increase in the amount of C-S-H, C-A-H, C-A-S-H phases, a decrease in the amount of CH and a change in the chemical nature of the matrix (decrease in C/S ratio). The decrease in compressive strength of OPC/slag-based material can be explained by a reduction in the amount of hydrated phases (particularly C-S-H) and compactness.
These are promising results for precast concrete manufacturers who are concerned about preserving the environment.DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001859 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)
[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 Effect of air voids on salt scaling and internal freezing / Zhenhua Sun in Cement and concrete research, Vol. 40 N° 2 (02 ex.) (Fevrier 2010)
[article]
in Cement and concrete research > Vol. 40 N° 2 (02 ex.) (Fevrier 2010) . - pp. 260-270
Titre : Effect of air voids on salt scaling and internal freezing Type de document : texte imprimé Auteurs : Zhenhua Sun, Auteur ; George W. Scherer, Auteur Année de publication : 2010 Article en page(s) : pp. 260-270 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Pore size distribution Freezing and Thawing Thermal analysis Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : By combining calorimetric measurements with dilatometry, it has been possible to calculate the contributions of thermal expansion, pore pressure, and crystallization pressure of ice to the strain observed in a mortar during freezing/thawing cycles. Air-entrained mortars contract upon freezing, while non-air-entrained mortars expand. The expansion of the latter is attributed primarily to hydraulic pressure, owing to the rapid growth of ice, which nucleates at low temperatures in laboratory samples. Poromechanical calculations account quantitatively for the contraction of samples with air entrainment, assuming that ice crystals form in the air voids. As originally proposed by Powers and Helmuth, those crystals create suction in the pore liquid that offsets the crystallization pressure of ice in the mesopores of the paste, resulting in a net contraction. Ice in the matrix also contributes significantly to the increase in the thermal expansion coefficient of the mortar.
The magnitude of the contraction in air-entrained mortar is shown to account for a reduction of salt scaling damage. According to the glue-spall theory, the damage results from cracking of the ice on the surface of concrete, when the thermal expansion mismatch stress exceeds the strength of the ice. The contraction of the mortar caused by air entrainment offsets the thermal expansion mismatch sufficiently to prevent cracking.
Based on observations of the nucleation temperature of ice in laboratory samples of various sizes, it is estimated that there is one site capable of nucleating ice at − 1 °C in a cube of mortar roughly 34 cm on an edge (or, one per square meter in a slab 3 cm thick). This suggests that ice nucleates in the field at high temperatures, compared to what is typically seen in the laboratory, and propagates slowly through the pores as the temperature drops. This mode of growth may lead to fatigue damage over many cycles, owing to local stresses from crystallization pressure, where the contribution of hydraulic pressure is insignificant.
DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWG-4XJW020-3&_user=6 [...] [article] Effect of air voids on salt scaling and internal freezing [texte imprimé] / Zhenhua Sun, Auteur ; George W. Scherer, Auteur . - 2010 . - pp. 260-270.
Génie Civil
Langues : Anglais (eng)
in Cement and concrete research > Vol. 40 N° 2 (02 ex.) (Fevrier 2010) . - pp. 260-270
Mots-clés : Pore size distribution Freezing and Thawing Thermal analysis Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : By combining calorimetric measurements with dilatometry, it has been possible to calculate the contributions of thermal expansion, pore pressure, and crystallization pressure of ice to the strain observed in a mortar during freezing/thawing cycles. Air-entrained mortars contract upon freezing, while non-air-entrained mortars expand. The expansion of the latter is attributed primarily to hydraulic pressure, owing to the rapid growth of ice, which nucleates at low temperatures in laboratory samples. Poromechanical calculations account quantitatively for the contraction of samples with air entrainment, assuming that ice crystals form in the air voids. As originally proposed by Powers and Helmuth, those crystals create suction in the pore liquid that offsets the crystallization pressure of ice in the mesopores of the paste, resulting in a net contraction. Ice in the matrix also contributes significantly to the increase in the thermal expansion coefficient of the mortar.
The magnitude of the contraction in air-entrained mortar is shown to account for a reduction of salt scaling damage. According to the glue-spall theory, the damage results from cracking of the ice on the surface of concrete, when the thermal expansion mismatch stress exceeds the strength of the ice. The contraction of the mortar caused by air entrainment offsets the thermal expansion mismatch sufficiently to prevent cracking.
Based on observations of the nucleation temperature of ice in laboratory samples of various sizes, it is estimated that there is one site capable of nucleating ice at − 1 °C in a cube of mortar roughly 34 cm on an edge (or, one per square meter in a slab 3 cm thick). This suggests that ice nucleates in the field at high temperatures, compared to what is typically seen in the laboratory, and propagates slowly through the pores as the temperature drops. This mode of growth may lead to fatigue damage over many cycles, owing to local stresses from crystallization pressure, where the contribution of hydraulic pressure is insignificant.
DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWG-4XJW020-3&_user=6 [...] Effect of carbonation on the hydro-mechanical properties of Portland cements / A. Fabbria in Cement and concrete research, Vol. 39 N° 12 (Décembre 2009)
PermalinkEffect of elevated temperatures on geopolymer paste, mortar and concrete / Daniel L. Y. Kong in Cement and concrete research, Vol. 40 N° 2 (02 ex.) (Fevrier 2010)
PermalinkEffect of fibre morphology on flocculation of fibre–cement suspensions / G.H.D. Tonoli in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009)
PermalinkEffect of limestone filler content and superplasticizer dosage on rheological parameters of highly flowable mortar under light pressure conditions / Jean-Yves Petit in Cement and concrete research, Vol. 40 N° 2 (02 ex.) (Fevrier 2010)
PermalinkEffect of moisture content of concrete on water uptake / P. Rucker-Gramm in Cement and concrete research, Vol. 40 N° 1 (Janvier 2010)
PermalinkEffect on fresh C-S-H gels of the simultaneous addition of alkali and aluminium / I. García Lodeiro in Cement and concrete research, Vol. 40 N° 1 (Janvier 2010)
PermalinkEffects of fibre type and matrix structure on the mechanical performance of self-compacting micro-concrete composites / Burak Felekoğlu in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009)
PermalinkElectrical resistance tomography imaging of concrete / Kimmo Karhunen in Cement and concrete research, Vol. 40 N° 1 (Janvier 2010)
PermalinkEstimating time and temperature dependent yield stress of cement paste using oscillatory rheology and genetic algorithms / M. Nehdi in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009)
PermalinkExperimental evidence of a moisture clog effect in cement-based materials under temperature / Xiao-Ting Chen in Cement and concrete research, Vol. 39 N° 12 (Décembre 2009)
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