Dépouillements

A new look at the measurement of cementitious paste setting by Vicat test / Hassan Sleiman in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 681–686 Titre : A new look at the measurement of cementitious paste setting by Vicat test Type de document : texte imprimé Auteurs : Hassan Sleiman, Auteur ; Arnaud Perrot, Auteur ; Sofiane Amziane, Auteur Année de publication : 2012 Article en page(s) : pp. 681–686 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Setting  time;  Yield  stress;  Cement  paste;  Vicat  test Résumé : The Vicat test is a standard test for measuring the setting times of cement paste and mortar. The physical background of the test is based on the resistance of a paste to dynamic penetration by a rod with a certain weight and shape (shear strain). The information obtained (initial and final set time) is very useful to compare cement setting properties. This study shows that it is possible to obtain more fundamental information about the setting property kinetics with only one modification of the testing procedure. The apparent mass of the static full immersed needle is measured. Due to the deformation of the cement paste at rest, the needle apparent mass varies with time. We show that the variation of the stress mobilized at the plate surface is related to the increase of yield stress during the setting period. The results of these experiments are discussed and compared with the traditional Vicat test for cement paste. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003470 [article] A new look at the measurement of cementitious paste setting by Vicat test [texte imprimé] / Hassan Sleiman, Auteur ; Arnaud Perrot, Auteur ; Sofiane Amziane, Auteur . - 2012 . - pp. 681–686. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 681–686 Mots-clés : Setting  time;  Yield  stress;  Cement  paste;  Vicat  test Résumé : The Vicat test is a standard test for measuring the setting times of cement paste and mortar. The physical background of the test is based on the resistance of a paste to dynamic penetration by a rod with a certain weight and shape (shear strain). The information obtained (initial and final set time) is very useful to compare cement setting properties. This study shows that it is possible to obtain more fundamental information about the setting property kinetics with only one modification of the testing procedure. The apparent mass of the static full immersed needle is measured. Due to the deformation of the cement paste at rest, the needle apparent mass varies with time. We show that the variation of the stress mobilized at the plate surface is related to the increase of yield stress during the setting period. The results of these experiments are discussed and compared with the traditional Vicat test for cement paste. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003470

A novel two-dimensional method to measure surface shrinkage in cementitious materials / T. C. Chen in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 687–698 Titre : A novel two-dimensional method to measure surface shrinkage in cementitious materials Type de document : texte imprimé Auteurs : T. C. Chen, Auteur Année de publication : 2012 Article en page(s) : pp. 687–698 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Shrinkage;  Diffraction  grating;  Moire  interferometry;  Moisture  diffusion Résumé : A novel experimental technique, Cure Reference Method (CRM), was developed for the measurement of surface shrinkage in cementitious materials. The technique combines the replication of diffraction grating on a specimen during the curing process and the use of high-sensitivity moiré interferometry. Once demolded, the specimen was stored in an environmental chamber in order to establish specific curing conditions. Measurements were conducted on a daily basis for the duration of 7 days by recording a set of the consecutive phase shifted fringe patterns using the Portable Engineering Moiré interferometer II (PEMI II). An automated fringe analysis system was developed and used to obtain displacement and strain information in two dimenzsions. Surface shrinkage behavior in both cement paste and mortar specimens was investigated by the use of the technique under controlled temperature and humidity conditions. Furthermore, an experimental control was developed in an effort to remove the effects of drying shrinkage on cementitious specimens at early ages. This was done in an effort to explore the relative contribution of autogenous shrinkage to the overall shrinkage in cementitious materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003457 [article] A novel two-dimensional method to measure surface shrinkage in cementitious materials [texte imprimé] / T. C. Chen, Auteur . - 2012 . - pp. 687–698. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 687–698 Mots-clés : Shrinkage;  Diffraction  grating;  Moire  interferometry;  Moisture  diffusion Résumé : A novel experimental technique, Cure Reference Method (CRM), was developed for the measurement of surface shrinkage in cementitious materials. The technique combines the replication of diffraction grating on a specimen during the curing process and the use of high-sensitivity moiré interferometry. Once demolded, the specimen was stored in an environmental chamber in order to establish specific curing conditions. Measurements were conducted on a daily basis for the duration of 7 days by recording a set of the consecutive phase shifted fringe patterns using the Portable Engineering Moiré interferometer II (PEMI II). An automated fringe analysis system was developed and used to obtain displacement and strain information in two dimenzsions. Surface shrinkage behavior in both cement paste and mortar specimens was investigated by the use of the technique under controlled temperature and humidity conditions. Furthermore, an experimental control was developed in an effort to remove the effects of drying shrinkage on cementitious specimens at early ages. This was done in an effort to explore the relative contribution of autogenous shrinkage to the overall shrinkage in cementitious materials. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003457

Experimental determination of the thermodynamic parameters affecting the adsorption behaviour and dispersion effectiveness of PCE superplasticizers / J. Plank in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 699–709 Titre : Experimental determination of the thermodynamic parameters affecting the adsorption behaviour and dispersion effectiveness of PCE superplasticizers Type de document : texte imprimé Auteurs : J. Plank, Auteur ; B. Sachsenhauser, Auteur ; J. de Reese, Auteur Année de publication : 2012 Article en page(s) : pp. 699–709 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Adsorption  ;  Polycarboxylates;  CaCO3  ;  Thermodynamic  calculations  ;  Workability Résumé : For adsorption of three different allylether-based PCE superplasticizers on CaCO3 surface, the thermodynamic parameters ΔH, ΔS and ΔG were determined experimentally. The GIBBS standard free energy of adsorption ΔG0ads, the standard enthalpy of adsorption ΔH0ads and the standard entropy of adsorption ΔS0ads applying to an unoccupied CaCO3 surface were obtained via a linear regression of ln K (equilibrium constant) versus 1 / T (VAN'T HOFF plot). Additionally, the thermodynamic parameters characteristic for a CaCO3 surface loaded already with polymer (isosteric conditions) were determined using a modified CLAUSIUS–CLAPEYRON equation. For all PCE molecules, negative ΔG values were found, indicating that adsorption of these polymers is energetically favourable and a spontaneous process. Adsorption of PCEs possessing short side chains is mainly instigated by electrostatic attraction and a release of enthalpy. Contrary to this, adsorption of PCEs with long side chains occurs because of a huge gain in entropy. The gain in entropy results from the release of counter ions attached to the carboxylate groups of the polymer backbone and of water molecules and ions adsorbed on the CaCO3 surface. With increased surface loading, however, ΔGisosteric decreases and adsorption ceases when ΔG becomes 0. The presence of Ca2+ ions in the pore solution strongly impacts PCE adsorption, due to complexation of carboxylate groups and a reduced anionic charge amount of the molecule. In the presence of Ca2+, adsorption of allylether-based PCEs is almost exclusively driven by a gain in entropy. Consequently, PCEs should produce a strong entropic effect upon adsorption to be effective cement dispersants. Molecular architecture, anionic charge density and molecular weight as well as the type of anchor groups present in a superplasticizer determine whether enthalpy or entropy is the dominant force for superplasticizer adsorption. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003482 [article] Experimental determination of the thermodynamic parameters affecting the adsorption behaviour and dispersion effectiveness of PCE superplasticizers [texte imprimé] / J. Plank, Auteur ; B. Sachsenhauser, Auteur ; J. de Reese, Auteur . - 2012 . - pp. 699–709. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 699–709 Mots-clés : Adsorption  ;  Polycarboxylates;  CaCO3  ;  Thermodynamic  calculations  ;  Workability Résumé : For adsorption of three different allylether-based PCE superplasticizers on CaCO3 surface, the thermodynamic parameters ΔH, ΔS and ΔG were determined experimentally. The GIBBS standard free energy of adsorption ΔG0ads, the standard enthalpy of adsorption ΔH0ads and the standard entropy of adsorption ΔS0ads applying to an unoccupied CaCO3 surface were obtained via a linear regression of ln K (equilibrium constant) versus 1 / T (VAN'T HOFF plot). Additionally, the thermodynamic parameters characteristic for a CaCO3 surface loaded already with polymer (isosteric conditions) were determined using a modified CLAUSIUS–CLAPEYRON equation. For all PCE molecules, negative ΔG values were found, indicating that adsorption of these polymers is energetically favourable and a spontaneous process. Adsorption of PCEs possessing short side chains is mainly instigated by electrostatic attraction and a release of enthalpy. Contrary to this, adsorption of PCEs with long side chains occurs because of a huge gain in entropy. The gain in entropy results from the release of counter ions attached to the carboxylate groups of the polymer backbone and of water molecules and ions adsorbed on the CaCO3 surface. With increased surface loading, however, ΔGisosteric decreases and adsorption ceases when ΔG becomes 0. The presence of Ca2+ ions in the pore solution strongly impacts PCE adsorption, due to complexation of carboxylate groups and a reduced anionic charge amount of the molecule. In the presence of Ca2+, adsorption of allylether-based PCEs is almost exclusively driven by a gain in entropy. Consequently, PCEs should produce a strong entropic effect upon adsorption to be effective cement dispersants. Molecular architecture, anionic charge density and molecular weight as well as the type of anchor groups present in a superplasticizer determine whether enthalpy or entropy is the dominant force for superplasticizer adsorption. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003482

Method to assess the quality of casein used as superplasticizer in self-levelling compounds / J. Plank in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. Titre : Method to assess the quality of casein used as superplasticizer in self-levelling compounds Type de document : texte imprimé Auteurs : J. Plank, Auteur ; H. Bian, Auteur Année de publication : 2012 Article en page(s) : pp. Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Mortar  ;  Admixture  ;  Workability  ;  Casein;  haracterization Résumé : A fast and accurate method of assessing the quality of casein superplasticizer is presented. The method is based on analysis of the content of α-, β- and κ-casein proteins contained in whole casein by ion exchange fast protein liquid chromatography (FPLC). The chromatographic profiles of six commercial casein samples were determined, revealing that the amount of κ-casein present in the biopolymer is the main assessment criteria for the quality of casein. For high dispersing effectiveness, the content of κ-casein needs to be high. The reason is that at pH ~ 12, a high content of κ-casein results in submicelles possessing smaller size (diameter ~ 10 nm), as was proven by dynamic light scattering measurement (DLS). These smaller submicelles are supposed to adsorb on cement in higher amount than large submicelles. Using this FPLC method, the dispersing performance of any casein sample can be determined very quickly without physical testing of mortar En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000074 [article] Method to assess the quality of casein used as superplasticizer in self-levelling compounds [texte imprimé] / J. Plank, Auteur ; H. Bian, Auteur . - 2012 . - pp. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. Mots-clés : Mortar  ;  Admixture  ;  Workability  ;  Casein;  haracterization Résumé : A fast and accurate method of assessing the quality of casein superplasticizer is presented. The method is based on analysis of the content of α-, β- and κ-casein proteins contained in whole casein by ion exchange fast protein liquid chromatography (FPLC). The chromatographic profiles of six commercial casein samples were determined, revealing that the amount of κ-casein present in the biopolymer is the main assessment criteria for the quality of casein. For high dispersing effectiveness, the content of κ-casein needs to be high. The reason is that at pH ~ 12, a high content of κ-casein results in submicelles possessing smaller size (diameter ~ 10 nm), as was proven by dynamic light scattering measurement (DLS). These smaller submicelles are supposed to adsorb on cement in higher amount than large submicelles. Using this FPLC method, the dispersing performance of any casein sample can be determined very quickly without physical testing of mortar En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000074

Alkali binding in hydrated Portland cement paste / W. Chen in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 716–722 Titre : Alkali binding in hydrated Portland cement paste Type de document : texte imprimé Auteurs : W. Chen, Auteur ; H. J. H. Brouwers, Auteur Année de publication : 2012 Article en page(s) : pp. 716–722 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Alkalis  ;  Hydration  products  ;  Modeling  ;  Pore  solution  ;  Portland  cement Résumé : The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data reported in literatures concerning thirteen different recipes are analyzed and used as references. A three-dimensional computer-based cement hydration model (CEMHYD3D) is used to simulate the hydration of Portland cement pastes. These model predictions are used as inputs for deriving the alkali-binding capacity of the hydration product C–S–H in hydrated Portland cement pastes. It is found that the relation of Na+ between the moles bound in C–S–H and its concentration in the pore solution is linear, while the binding of K+ in C–S–H complies with the Freundlich isotherm. New models are proposed for determining the alkali-binding capacities of C–S–H in hydrated Portland cement paste. An updated method for predicting the alkali concentrations in the pore solution of hydrated Portland cement pastes is developed. It is also used to investigate the effects of various factors (such as the water to cement ratio, clinker composition and alkali types) on the alkali concentrations. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000025 [article] Alkali binding in hydrated Portland cement paste [texte imprimé] / W. Chen, Auteur ; H. J. H. Brouwers, Auteur . - 2012 . - pp. 716–722. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 716–722 Mots-clés : Alkalis  ;  Hydration  products  ;  Modeling  ;  Pore  solution  ;  Portland  cement Résumé : The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data reported in literatures concerning thirteen different recipes are analyzed and used as references. A three-dimensional computer-based cement hydration model (CEMHYD3D) is used to simulate the hydration of Portland cement pastes. These model predictions are used as inputs for deriving the alkali-binding capacity of the hydration product C–S–H in hydrated Portland cement pastes. It is found that the relation of Na+ between the moles bound in C–S–H and its concentration in the pore solution is linear, while the binding of K+ in C–S–H complies with the Freundlich isotherm. New models are proposed for determining the alkali-binding capacities of C–S–H in hydrated Portland cement paste. An updated method for predicting the alkali concentrations in the pore solution of hydrated Portland cement pastes is developed. It is also used to investigate the effects of various factors (such as the water to cement ratio, clinker composition and alkali types) on the alkali concentrations. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000025

Interaction between two anti-graffiti treatments and cement mortar (paste) / P. M. Carmona-Quiroga in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 723–730 Titre : Interaction between two anti-graffiti treatments and cement mortar (paste) Type de document : texte imprimé Auteurs : P. M. Carmona-Quiroga, Auteur Année de publication : 2012 Article en page(s) : pp. 723–730 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Cement  paste  ;  Mortar  ;  Thermal  analysis  ;  29Si  MAS  NMR;Anti-graffiti  coatings Résumé : Much of the twentieth century's built heritage is made of concrete, which is particularly susceptible to graffiti “attacks”. Since the traditional methods used to remove spray paint are not particularly effective on this type of material, the adoption of preventive measures by applying a new type of protective treatments, known as anti-graffiti coatings, may be a good way to tackle the problem. The present study aimed to evaluate the physical properties of a cement mortar coated with two such products and to study the possible molecular interactions between the coatings and the cement paste. Neither product induced chromatic changes on the surface of the material, while both made it water repellent. 29Si MAS NMR analysis detected a lower Q1/Q2 ratio, indicative of a longer chain length, in the C–S–H gel in the cement paste mixed with the anti-graffiti products. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000049 [article] Interaction between two anti-graffiti treatments and cement mortar (paste) [texte imprimé] / P. M. Carmona-Quiroga, Auteur . - 2012 . - pp. 723–730. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 723–730 Mots-clés : Cement  paste  ;  Mortar  ;  Thermal  analysis  ;  29Si  MAS  NMR;Anti-graffiti  coatings Résumé : Much of the twentieth century's built heritage is made of concrete, which is particularly susceptible to graffiti “attacks”. Since the traditional methods used to remove spray paint are not particularly effective on this type of material, the adoption of preventive measures by applying a new type of protective treatments, known as anti-graffiti coatings, may be a good way to tackle the problem. The present study aimed to evaluate the physical properties of a cement mortar coated with two such products and to study the possible molecular interactions between the coatings and the cement paste. Neither product induced chromatic changes on the surface of the material, while both made it water repellent. 29Si MAS NMR analysis detected a lower Q1/Q2 ratio, indicative of a longer chain length, in the C–S–H gel in the cement paste mixed with the anti-graffiti products. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000049

Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement / S.T. Erdoğan in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 731–739 Titre : Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement Type de document : texte imprimé Auteurs : S.T. Erdoğan, Auteur Année de publication : 2012 Article en page(s) : pp. 731–739 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Fineness,  grinding;  Characterization,  particle  size  distribution,  laser  diffraction;  Cement  manufacturers Résumé : Eight different portland cements were imaged on a synchrotron beam line at Brookhaven National Laboratory using X-ray microcomputed tomography at a voxel size of about 1 µm per cubic voxel edge. The particles ranged in size roughly between 10 µm and 100 µm. The shape and size of individual particles were computationally analyzed using spherical harmonic analysis. The particle shape difference between cements was small but significant, as judged by several different quantitative shape measures, including the particle length, width, and thickness distributions. It was found that the average shape of cement particles was closely correlated with the volume fraction of C3S (alite) and C2S (belite) making up the cement powder. It is shown that the non-spherical particle shape of the cements strongly influence laser diffraction results, at least in the sieve size range of 20 µm to 38 µm. Since laser diffraction particle size measurement is being increasingly used by the cement industry, while cement chemistry is always a main factor in cement production, these results could have important implications for how this kind of particle size measurement should be understood and used in the cement industry. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003615 [article] Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement [texte imprimé] / S.T. Erdoğan, Auteur . - 2012 . - pp. 731–739. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 731–739 Mots-clés : Fineness,  grinding;  Characterization,  particle  size  distribution,  laser  diffraction;  Cement  manufacturers Résumé : Eight different portland cements were imaged on a synchrotron beam line at Brookhaven National Laboratory using X-ray microcomputed tomography at a voxel size of about 1 µm per cubic voxel edge. The particles ranged in size roughly between 10 µm and 100 µm. The shape and size of individual particles were computationally analyzed using spherical harmonic analysis. The particle shape difference between cements was small but significant, as judged by several different quantitative shape measures, including the particle length, width, and thickness distributions. It was found that the average shape of cement particles was closely correlated with the volume fraction of C3S (alite) and C2S (belite) making up the cement powder. It is shown that the non-spherical particle shape of the cements strongly influence laser diffraction results, at least in the sieve size range of 20 µm to 38 µm. Since laser diffraction particle size measurement is being increasingly used by the cement industry, while cement chemistry is always a main factor in cement production, these results could have important implications for how this kind of particle size measurement should be understood and used in the cement industry. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003615

Pore size and shape in mortar by thermoporometry / Sun, Juanzhen in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 740–751 Titre : Pore size and shape in mortar by thermoporometry Type de document : texte imprimé Auteurs : Sun, Juanzhen, Auteur ; George W. Scherer, Auteur Année de publication : 2012 Article en page(s) : pp. 740–751 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Mercury  porosimetry  ;  Microstructure  ;  Pore  size  distribution  ;Thermodynamic  calculations  ;  Freezing  and  thawing Résumé : The pore structure of mortar (w/c = 0.55) was examined using thermoporometry (TPM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP). The TPM measurements were calibrated by comparison to NAD and MIP measurements on porous glass; similar comparisons were made on dried and resaturated mortars. For undried mortars, TPM provides the size of pore entries (from the freezing cycle) and interiors (from the melting cycle). In keeping with previous studies, we find that there is an unfrozen layer of water between the ice and the pore wall in porous glass that is about 0.8 nm thick; when lime-saturated water is used, the thickness of that layer increases by about 10%. In mortar, the unfrozen layer is about 1.0–1.2 nm thick, so no freezing occurs in pores with diameters ≤ 4.5 nm, at least down to − 40 °C (where the radius of the crystal/liquid interface is ∼ 1.5 nm). Based on the hysteresis in the freezing and melting curves, the larger mesopores in mortar were found to be rather spheroidal, while the smaller ones were more cylindrical. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003433 [article] Pore size and shape in mortar by thermoporometry [texte imprimé] / Sun, Juanzhen, Auteur ; George W. Scherer, Auteur . - 2012 . - pp. 740–751. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 740–751 Mots-clés : Mercury  porosimetry  ;  Microstructure  ;  Pore  size  distribution  ;Thermodynamic  calculations  ;  Freezing  and  thawing Résumé : The pore structure of mortar (w/c = 0.55) was examined using thermoporometry (TPM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP). The TPM measurements were calibrated by comparison to NAD and MIP measurements on porous glass; similar comparisons were made on dried and resaturated mortars. For undried mortars, TPM provides the size of pore entries (from the freezing cycle) and interiors (from the melting cycle). In keeping with previous studies, we find that there is an unfrozen layer of water between the ice and the pore wall in porous glass that is about 0.8 nm thick; when lime-saturated water is used, the thickness of that layer increases by about 10%. In mortar, the unfrozen layer is about 1.0–1.2 nm thick, so no freezing occurs in pores with diameters ≤ 4.5 nm, at least down to − 40 °C (where the radius of the crystal/liquid interface is ∼ 1.5 nm). Based on the hysteresis in the freezing and melting curves, the larger mesopores in mortar were found to be rather spheroidal, while the smaller ones were more cylindrical. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003433

Linear and non-linear analysis of desorption processes in cement mortar / Halina Garbalińska in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp.752–762 Titre : Linear and non-linear analysis of desorption processes in cement mortar Type de document : texte imprimé Auteurs : Halina Garbalińska, Auteur Année de publication : 2012 Article en page(s) : pp.752–762 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Drying  ;  Humidity  ;  Diffusion  ;  Transport  properties  ;  Mortar Résumé : Based on the gathered experimental data concerning adsorption/desorption processes in cement mortar, it has been stated that the rate of these processes changes in time even if they proceed in stable conditions. In this paper an attempt is made to describe such processes by applying linear and non-linear diffusion theories for comparison. The main aim of these studies is to determine the diffusion coefficient by correlating the theoretically determined desorption isotherms with the experimental ones. The validation of the diffusion coefficient was accomplished through comparison of the theoretical desorption curves with the experimental data for narrow and broad ranges of the air humidity changes. The final conclusion is that the moisture transfer in hygroscopic porous materials for broad ranges of the air humidity changes should be modeled by the non-linear diffusion theory, in which the diffusion coefficient is a function of moisture content. The new material in this paper concerns very long time measurements in desiccators, and evaluation of the diffusion coefficient by an advanced optimization algorithm. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003512 [article] Linear and non-linear analysis of desorption processes in cement mortar [texte imprimé] / Halina Garbalińska, Auteur . - 2012 . - pp.752–762. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp.752–762 Mots-clés : Drying  ;  Humidity  ;  Diffusion  ;  Transport  properties  ;  Mortar Résumé : Based on the gathered experimental data concerning adsorption/desorption processes in cement mortar, it has been stated that the rate of these processes changes in time even if they proceed in stable conditions. In this paper an attempt is made to describe such processes by applying linear and non-linear diffusion theories for comparison. The main aim of these studies is to determine the diffusion coefficient by correlating the theoretically determined desorption isotherms with the experimental ones. The validation of the diffusion coefficient was accomplished through comparison of the theoretical desorption curves with the experimental data for narrow and broad ranges of the air humidity changes. The final conclusion is that the moisture transfer in hygroscopic porous materials for broad ranges of the air humidity changes should be modeled by the non-linear diffusion theory, in which the diffusion coefficient is a function of moisture content. The new material in this paper concerns very long time measurements in desiccators, and evaluation of the diffusion coefficient by an advanced optimization algorithm. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003512

Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate / Thomas Matschei in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. Titre : Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate Type de document : texte imprimé Auteurs : Thomas Matschei, Auteur ; Fredrik P. Glasser, Auteur Année de publication : 2012 Article en page(s) : pp. Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Thermodynamic  Calculations  ;  Durability  ;  CaCO3  ;  Ettringite  ;Monosulfate Résumé : Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH)2 occur between 0 and 40 °C; the changes are affected by added calcite. Hydrogarnet, C3AH6, is destabilised at low carbonate contents and/or low temperatures < 8 °C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 °C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions. The AFt phase is close to its ideal stoichiometry at 25 °C but at low temperatures, < 20 °C, extensive solid solutions occur with CO3-ettringite. A nomenclature scheme is proposed and AFm–AFt phase relations are presented in isothermal sections at 5, 25 and 40 °C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO3 and SO4 for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003421 [article] Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate [texte imprimé] / Thomas Matschei, Auteur ; Fredrik P. Glasser, Auteur . - 2012 . - pp. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. Mots-clés : Thermodynamic  Calculations  ;  Durability  ;  CaCO3  ;  Ettringite  ;Monosulfate Résumé : Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH)2 occur between 0 and 40 °C; the changes are affected by added calcite. Hydrogarnet, C3AH6, is destabilised at low carbonate contents and/or low temperatures < 8 °C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 °C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions. The AFt phase is close to its ideal stoichiometry at 25 °C but at low temperatures, < 20 °C, extensive solid solutions occur with CO3-ettringite. A nomenclature scheme is proposed and AFm–AFt phase relations are presented in isothermal sections at 5, 25 and 40 °C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO3 and SO4 for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003421

Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions / N. Husillos Rodríguez in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 778–786 Titre : Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions Type de document : texte imprimé Auteurs : N. Husillos Rodríguez, Auteur Année de publication : 2012 Article en page(s) : pp. 778–786 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Waste  management  ;  DWTP  sludge;  Cement  ;  Mortar  ;  Calorimetry Résumé : This paper aims to characterize spray-dried DWTP sludge and evaluate its possible use as an addition for the cement industry. It describes the physical, chemical and micro-structural characterization of the sludge as well as the effect of its addition to Portland cements on the hydration, water demand, setting and mechanical strength of standardized mortars. Spray drying DWTP sludge generates a readily handled powdery material whose particle size is similar to those of Portland cement. The atomized sludge contains 12–14% organic matter (mainly fatty acids), while its main mineral constituents are muscovite, quartz, calcite, dolomite and seraphinite (or clinoclor). Its amorphous material content is 35%. The mortars were made with type CEM I Portland cement mixed with 10 to 30% atomized sludge exhibited lower mechanical strength than the control cement and a decline in slump. Setting was also altered in the blended cements with respect to the control. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003445 [article] Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions [texte imprimé] / N. Husillos Rodríguez, Auteur . - 2012 . - pp. 778–786. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 778–786 Mots-clés : Waste  management  ;  DWTP  sludge;  Cement  ;  Mortar  ;  Calorimetry Résumé : This paper aims to characterize spray-dried DWTP sludge and evaluate its possible use as an addition for the cement industry. It describes the physical, chemical and micro-structural characterization of the sludge as well as the effect of its addition to Portland cements on the hydration, water demand, setting and mechanical strength of standardized mortars. Spray drying DWTP sludge generates a readily handled powdery material whose particle size is similar to those of Portland cement. The atomized sludge contains 12–14% organic matter (mainly fatty acids), while its main mineral constituents are muscovite, quartz, calcite, dolomite and seraphinite (or clinoclor). Its amorphous material content is 35%. The mortars were made with type CEM I Portland cement mixed with 10 to 30% atomized sludge exhibited lower mechanical strength than the control cement and a decline in slump. Setting was also altered in the blended cements with respect to the control. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003445

Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals / Jonathan Tailby in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 787–794 Titre : Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals Type de document : texte imprimé Auteurs : Jonathan Tailby, Auteur Année de publication : 2012 Article en page(s) : pp. 787–794 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Composites  ;  Mechanical  properties  ;  Microstructure  ;NMR Résumé : The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C3S, β-C2S, C3A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, 29Si and 27Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C–S–H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC–geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC–geopolymer composite stronger than hydrated OPC paste alone. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003494 [article] Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals [texte imprimé] / Jonathan Tailby, Auteur . - 2012 . - pp. 787–794. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 787–794 Mots-clés : Composites  ;  Mechanical  properties  ;  Microstructure  ;NMR Résumé : The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C3S, β-C2S, C3A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, 29Si and 27Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C–S–H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC–geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC–geopolymer composite stronger than hydrated OPC paste alone. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003494

A new system for crack closure of cementitious materials using shrinkable polymers / Anthony Jefferson in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 795–801 Titre : A new system for crack closure of cementitious materials using shrinkable polymers Type de document : texte imprimé Auteurs : Anthony Jefferson, Auteur Année de publication : 2012 Article en page(s) : pp. 795–801 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Long-term  performance;  Durability;  Shape  Memory  Polymer;Crack–healing Résumé : This paper presents details of an original crack-closure system for cementitious materials using shrinkable polymer tendons. The system involves the incorporation of unbonded pre-oriented polymer tendons in cementitious beams. Crack closure is achieved by thermally activating the shrinkage mechanism of the restrained polymer tendons after the cement-based material has undergone initial curing. The feasibility of the system is demonstrated in a series of small scale experiments on pre-cracked prismatic mortar specimens. The results from these tests show that, upon activation, the polymer tendon completely closes the preformed macro-cracks and imparts a significant stress across the crack faces. The potential of the system to enhance the natural autogenous crack healing process and generally improve the durability of concrete structures is addressed. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000062 [article] A new system for crack closure of cementitious materials using shrinkable polymers [texte imprimé] / Anthony Jefferson, Auteur . - 2012 . - pp. 795–801. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 795–801 Mots-clés : Long-term  performance;  Durability;  Shape  Memory  Polymer;Crack–healing Résumé : This paper presents details of an original crack-closure system for cementitious materials using shrinkable polymer tendons. The system involves the incorporation of unbonded pre-oriented polymer tendons in cementitious beams. Crack closure is achieved by thermally activating the shrinkage mechanism of the restrained polymer tendons after the cement-based material has undergone initial curing. The feasibility of the system is demonstrated in a series of small scale experiments on pre-cracked prismatic mortar specimens. The results from these tests show that, upon activation, the polymer tendon completely closes the preformed macro-cracks and imparts a significant stress across the crack faces. The potential of the system to enhance the natural autogenous crack healing process and generally improve the durability of concrete structures is addressed. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884610000062

Fiber–matrix interaction at early ages of concrete with short fibers / Gonzalo Barluenga in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 802–809 Titre : Fiber–matrix interaction at early ages of concrete with short fibers Type de document : texte imprimé Auteurs : Gonzalo Barluenga, Auteur Année de publication : 2012 Article en page(s) : pp. 802–809 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Short  glass  fiber;  Early  age  shrinkage  ;  Crack  Detection Résumé : The inclusion of small amounts of short fibers has demonstrated to be an effective solution to control cracking due to drying shrinkage of concretes at early ages. The key point of fiber effectiveness is their capacity to sew the crack sides, preventing crack opening, because cracking of concrete matrix induces fiber actuation. In this paper, fiber–matrix interaction is analyzed considering different amounts (from 600 to 1200 g/m3) and lengths (6, 12 and 18 mm) of alkali-resistant (AR) glass fibers and fiber coating effect. The combination of experimental results previously published and analyses with simple FE models allows for better understanding of early age concrete behavior. As concrete mechanical capacity develops with age, while fibers have full properties before being included in concrete matrix, the interphase between matrix and fibers evolves during setting and hardening, and affects cracking control effectiveness, due to stresses induced by fibers into the matrix during concrete hydration. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003469 [article] Fiber–matrix interaction at early ages of concrete with short fibers [texte imprimé] / Gonzalo Barluenga, Auteur . - 2012 . - pp. 802–809. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 802–809 Mots-clés : Short  glass  fiber;  Early  age  shrinkage  ;  Crack  Detection Résumé : The inclusion of small amounts of short fibers has demonstrated to be an effective solution to control cracking due to drying shrinkage of concretes at early ages. The key point of fiber effectiveness is their capacity to sew the crack sides, preventing crack opening, because cracking of concrete matrix induces fiber actuation. In this paper, fiber–matrix interaction is analyzed considering different amounts (from 600 to 1200 g/m3) and lengths (6, 12 and 18 mm) of alkali-resistant (AR) glass fibers and fiber coating effect. The combination of experimental results previously published and analyses with simple FE models allows for better understanding of early age concrete behavior. As concrete mechanical capacity develops with age, while fibers have full properties before being included in concrete matrix, the interphase between matrix and fibers evolves during setting and hardening, and affects cracking control effectiveness, due to stresses induced by fibers into the matrix during concrete hydration. En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609003469

Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete / C. Lee in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 810–819 Titre : Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete Type de document : texte imprimé Auteurs : C. Lee, Auteur ; H. Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 810–819 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Modeling  ;  Concrete  ;  Fiber  Reinforcement  ;  Orientation  Factor Résumé : Considering the probabilistic distributions of fibers in ring-type steel fiber reinforced concrete, the orientation factor and the number of ring-type steel fibers crossing the failure plane were theoretically derived as a function of fiber geometry, specimen dimensions, and fiber volume fraction. A total number of 24 specimens were tested incorporating different fiber types, specimen geometry, and fiber volume fractions of 0.2% and 0.4%: 5 beams and 5 panels containing straight steel fibers; and 6 beams and 8 panels containing ring-type steel fibers. Measurements were made to assess the number of fibers at fractured surfaces of steel fiber reinforced concrete. The developed theoretical expressions reasonably predicted the orientation factor and the number of ring-type steel fibers at failure plane: the average and the standard deviation for the ratios of the test to theory were 1.03 and 0.26, respectively. Theoretical investigations and comparisons were made for the values of orientation factor and the number of fibers at failure plane for straight steel fibers and ring-type steel fibers. En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900341X [article] Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete [texte imprimé] / C. Lee, Auteur ; H. Kim, Auteur . - 2012 . - pp. 810–819. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 810–819 Mots-clés : Modeling  ;  Concrete  ;  Fiber  Reinforcement  ;  Orientation  Factor Résumé : Considering the probabilistic distributions of fibers in ring-type steel fiber reinforced concrete, the orientation factor and the number of ring-type steel fibers crossing the failure plane were theoretically derived as a function of fiber geometry, specimen dimensions, and fiber volume fraction. A total number of 24 specimens were tested incorporating different fiber types, specimen geometry, and fiber volume fractions of 0.2% and 0.4%: 5 beams and 5 panels containing straight steel fibers; and 6 beams and 8 panels containing ring-type steel fibers. Measurements were made to assess the number of fibers at fractured surfaces of steel fiber reinforced concrete. The developed theoretical expressions reasonably predicted the orientation factor and the number of ring-type steel fibers at failure plane: the average and the standard deviation for the ratios of the test to theory were 1.03 and 0.26, respectively. Theoretical investigations and comparisons were made for the values of orientation factor and the number of fibers at failure plane for straight steel fibers and ring-type steel fibers. En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900341X

Exemplaires

Bibliothèque Ecole Nationale Polytechnique d'Alger

Accueil

Se connecter

Météo

Adresse