Dépouillements

Synthesis of belite cement clinker of high hydraulic reactivity / Larbi Kacimi in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 559–565 Titre : Synthesis of belite cement clinker of high hydraulic reactivity Type de document : texte imprimé Auteurs : Larbi Kacimi, Auteur ; Angélique Simon-Masseron, Auteur ; Souria Salem, Auteur Année de publication : 2009 Article en page(s) : pp. 559–565 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Belite;  Clinker;  Reactivity;  Mineralizer;  Clinkerization Résumé : This study is concerned with the increase of the cooling rate of belite clinker, by using the water quenching for the chemical stabilization of reactive belite, which improves the hydraulic properties of this clinker. The addition of adequate mineralizers, as NaF and Fe2O3, contributes to the improvement of the clinker properties obtained at low burning temperature. X-ray fluorescence spectroscopy, X-ray diffraction analysis and optical microscopy were used to determine the chemical and mineralogical compositions of this clinker. The samples were analyzed by means of a scanning electronic microscope connected with an energy-dispersive X-ray spectrometer to detect the composition of the belite phase and its morphology. Physical and mechanical properties of this clinker cement were determined. The results show that the belite clinker obtained at 1150 °C, with lime saturation factor 0.67, is characterized by a great hydraulic reactivity, similar to that of the ordinary alite clinker. The addition of 2% of NaF and the water quenching improved the chemical, mineralogical and structural properties, while improving the cement hydraulic properties. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000891 [article] Synthesis of belite cement clinker of high hydraulic reactivity [texte imprimé] / Larbi Kacimi, Auteur ; Angélique Simon-Masseron, Auteur ; Souria Salem, Auteur . - 2009 . - pp. 559–565. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 559–565 Mots-clés : Belite;  Clinker;  Reactivity;  Mineralizer;  Clinkerization Résumé : This study is concerned with the increase of the cooling rate of belite clinker, by using the water quenching for the chemical stabilization of reactive belite, which improves the hydraulic properties of this clinker. The addition of adequate mineralizers, as NaF and Fe2O3, contributes to the improvement of the clinker properties obtained at low burning temperature. X-ray fluorescence spectroscopy, X-ray diffraction analysis and optical microscopy were used to determine the chemical and mineralogical compositions of this clinker. The samples were analyzed by means of a scanning electronic microscope connected with an energy-dispersive X-ray spectrometer to detect the composition of the belite phase and its morphology. Physical and mechanical properties of this clinker cement were determined. The results show that the belite clinker obtained at 1150 °C, with lime saturation factor 0.67, is characterized by a great hydraulic reactivity, similar to that of the ordinary alite clinker. The addition of 2% of NaF and the water quenching improved the chemical, mineralogical and structural properties, while improving the cement hydraulic properties. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000891

Fuel mixture approach for solution combustion synthesis of Ca3Al2O6 powders / Robert Ianoş in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 566–572 Titre : Fuel mixture approach for solution combustion synthesis of Ca3Al2O6 powders Type de document : texte imprimé Auteurs : Robert Ianoş, Auteur ; Ioan Lazău, Auteur ; Cornelia Păcurariu, Auteur Année de publication : 2009 Article en page(s) : pp. 566–572 Note générale : Génie Civil Langues : Anglais (eng) Résumé : Single-phase 3CaO·Al2O3 powders were prepared via solution combustion synthesis using a fuel mixture of urea and β-alanine. The concept of using this fuel mixture comes from the individual reactivity of calcium nitrate and aluminum nitrate with respect to urea and β-alanine. It was proved that urea is the optimum fuel for Al(NO3)3 whereas β-alanine is the most suitable fuel for Ca(NO3)2. X-ray diffraction and thermal analysis investigations revealed that heating at 300 °C the precursor mixture containing the desired metal nitrates, urea and β-alanine triggers a vigorous combustion reaction, which yields single-phase nanocrystalline 3CaO·Al2O3 powder (33.3 nm). In this case additional annealing was no longer required. The use of a single fuel failed to ensure the formation of 3CaO·Al2O3 directly from the combustion reaction. After annealing at 900 °C for 1 h, the powders obtained by using a single fuel (urea or β-alanine) developed a phase composition comprising of 3CaO·Al2O3, 12CaO·7Al2O3 and CaO. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000775 [article] Fuel mixture approach for solution combustion synthesis of Ca3Al2O6 powders [texte imprimé] / Robert Ianoş, Auteur ; Ioan Lazău, Auteur ; Cornelia Păcurariu, Auteur . - 2009 . - pp. 566–572. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 566–572 Résumé : Single-phase 3CaO·Al2O3 powders were prepared via solution combustion synthesis using a fuel mixture of urea and β-alanine. The concept of using this fuel mixture comes from the individual reactivity of calcium nitrate and aluminum nitrate with respect to urea and β-alanine. It was proved that urea is the optimum fuel for Al(NO3)3 whereas β-alanine is the most suitable fuel for Ca(NO3)2. X-ray diffraction and thermal analysis investigations revealed that heating at 300 °C the precursor mixture containing the desired metal nitrates, urea and β-alanine triggers a vigorous combustion reaction, which yields single-phase nanocrystalline 3CaO·Al2O3 powder (33.3 nm). In this case additional annealing was no longer required. The use of a single fuel failed to ensure the formation of 3CaO·Al2O3 directly from the combustion reaction. After annealing at 900 °C for 1 h, the powders obtained by using a single fuel (urea or β-alanine) developed a phase composition comprising of 3CaO·Al2O3, 12CaO·7Al2O3 and CaO. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000775

Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars / P. Ballester in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 573–579 Titre : Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars Type de document : texte imprimé Auteurs : P. Ballester, Auteur ; A. Hidalgo, Auteur ; I. Mármol, Auteur Année de publication : 2009 Article en page(s) : pp. 573–579 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Mortar;  Cement;  Curing;  Temperature Résumé : The effect of temperature on fresh mortar and cement paste was evaluated by simulating the curing conditions of external buildings plastering applied under extremely hot weather. The specimens were heated at controlled temperatures in the 40−80 °C range by exposure to IR radiation over short periods. The effect of soaking for a short time was also examined. The results of compressive strength tests, scanning electron microscopy, infrared spectroscopy and mercury porosimetry helped to characterize the mechanical and physico-chemical properties of the studied sample. Early age behaviour (28 days) in neat cement was barely affected by the temperature. By contrast, exposure to high temperatures caused significant microstructural changes in the mortar. However, successive soaking over short periods was found to reactivate the mechanism of curing and restore the expected mechanical properties. Based on the results, application of cement based mortar at high temperatures is effective when followed by a short, specific soaking process. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900088X [article] Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars [texte imprimé] / P. Ballester, Auteur ; A. Hidalgo, Auteur ; I. Mármol, Auteur . - 2009 . - pp. 573–579. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 573–579 Mots-clés : Mortar;  Cement;  Curing;  Temperature Résumé : The effect of temperature on fresh mortar and cement paste was evaluated by simulating the curing conditions of external buildings plastering applied under extremely hot weather. The specimens were heated at controlled temperatures in the 40−80 °C range by exposure to IR radiation over short periods. The effect of soaking for a short time was also examined. The results of compressive strength tests, scanning electron microscopy, infrared spectroscopy and mercury porosimetry helped to characterize the mechanical and physico-chemical properties of the studied sample. Early age behaviour (28 days) in neat cement was barely affected by the temperature. By contrast, exposure to high temperatures caused significant microstructural changes in the mortar. However, successive soaking over short periods was found to reactivate the mechanism of curing and restore the expected mechanical properties. Based on the results, application of cement based mortar at high temperatures is effective when followed by a short, specific soaking process. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900088X

Mechanism of stabilization of Na-montmorillonite clay with cement kiln dust / Sulapha Peethamparan in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 580–589 Titre : Mechanism of stabilization of Na-montmorillonite clay with cement kiln dust Type de document : texte imprimé Auteurs : Sulapha Peethamparan, Auteur ; Jan Olek, Auteur ; Sidney Diamond, Auteur Année de publication : 2009 Article en page(s) : pp. 580–589 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement  kiln  dust  Montmorillonite  clay;  Stabilization;  Mechanism;  Microstructure Résumé : A study of the physicochemical interaction of a high free lime (CaO) content cement kiln dust (CKD) with expansive Na-montmorillonite clay is presented. Moist compacted specimens of the CKD-treated clay, the clay alone, the CKD alone, and (for comparison) the clay treated with 7% CaO were each cured for periods up to 90 days and examined by XRD, TGA, and SEM techniques. The results for the CKD-treated clay indicated that calcium hydroxide, derived from the CaO present in the CKD, was extensively adsorbed on the surfaces of the clay flakes, but apparently only limited pozzolanic reaction occurred. Gypsum was rapidly produced from sulfate-bearing components in the CKD, and subsequently ettringite was produced as well, some of the latter apparently incorporating aluminum derived from the clay. Much of the clay was left unreacted, but the morphology of the clay particle assemblage was significantly modified in response to the CKD treatment. Similar morphological changes were also induced by the CaO treatment, suggesting that similar underlying mechanisms were also active here. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000738 [article] Mechanism of stabilization of Na-montmorillonite clay with cement kiln dust [texte imprimé] / Sulapha Peethamparan, Auteur ; Jan Olek, Auteur ; Sidney Diamond, Auteur . - 2009 . - pp. 580–589. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 580–589 Mots-clés : Cement  kiln  dust  Montmorillonite  clay;  Stabilization;  Mechanism;  Microstructure Résumé : A study of the physicochemical interaction of a high free lime (CaO) content cement kiln dust (CKD) with expansive Na-montmorillonite clay is presented. Moist compacted specimens of the CKD-treated clay, the clay alone, the CKD alone, and (for comparison) the clay treated with 7% CaO were each cured for periods up to 90 days and examined by XRD, TGA, and SEM techniques. The results for the CKD-treated clay indicated that calcium hydroxide, derived from the CaO present in the CKD, was extensively adsorbed on the surfaces of the clay flakes, but apparently only limited pozzolanic reaction occurred. Gypsum was rapidly produced from sulfate-bearing components in the CKD, and subsequently ettringite was produced as well, some of the latter apparently incorporating aluminum derived from the clay. Much of the clay was left unreacted, but the morphology of the clay particle assemblage was significantly modified in response to the CKD treatment. Similar morphological changes were also induced by the CaO treatment, suggesting that similar underlying mechanisms were also active here. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000738

Determination of the energy consumption during the production of various concrete recipes / B. Daumann in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 590–599 Titre : Determination of the energy consumption during the production of various concrete recipes Type de document : texte imprimé Auteurs : B. Daumann, Auteur Année de publication : 2009 Article en page(s) : pp. 590–599 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Powder  mixing;  Concrete  mixing;  Image  analysis;  Energy  consumption;  Application  of  energy Résumé : This article presents a report of the mixing of concrete on the laboratory scale in a single-shaft and twin-shaft mixer. For both mixers we selected five concrete recipes that cover a broad spectrum of concrete mixing techniques. The concrete recipes differ from each other amongst other things by virtue of the aggregate-sized distribution curves, water–cement ratio, flow properties, compressive strength and mixing times. The specifically volume-related application of energy – which is necessary for the homogenization of the particular recipe in the mixer – is an essential influencing variable. The comparison of the specifically volume-related application of energy is possible only if the concrete recipes possess the same homogeneity. The time curve of the homogeneity plotted against the necessary mixing time indicates the mixing efficiency, which in turn is determined by an imaging measurement process. Comprehensive mixing experiments show that the resulting application of energy, measured via the current composition, does not provide sufficient information in order to define the actual homogeneity in the mixture. A method was developed for the purpose of comparing concrete mixtures based on various recipes with the same homogeneity in relation to the specifically volume-related application of energy. The particular application of energy can be determined via the required mixing time and the power output process in terms of time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000878 [article] Determination of the energy consumption during the production of various concrete recipes [texte imprimé] / B. Daumann, Auteur . - 2009 . - pp. 590–599. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 590–599 Mots-clés : Powder  mixing;  Concrete  mixing;  Image  analysis;  Energy  consumption;  Application  of  energy Résumé : This article presents a report of the mixing of concrete on the laboratory scale in a single-shaft and twin-shaft mixer. For both mixers we selected five concrete recipes that cover a broad spectrum of concrete mixing techniques. The concrete recipes differ from each other amongst other things by virtue of the aggregate-sized distribution curves, water–cement ratio, flow properties, compressive strength and mixing times. The specifically volume-related application of energy – which is necessary for the homogenization of the particular recipe in the mixer – is an essential influencing variable. The comparison of the specifically volume-related application of energy is possible only if the concrete recipes possess the same homogeneity. The time curve of the homogeneity plotted against the necessary mixing time indicates the mixing efficiency, which in turn is determined by an imaging measurement process. Comprehensive mixing experiments show that the resulting application of energy, measured via the current composition, does not provide sufficient information in order to define the actual homogeneity in the mixture. A method was developed for the purpose of comparing concrete mixtures based on various recipes with the same homogeneity in relation to the specifically volume-related application of energy. The particular application of energy can be determined via the required mixing time and the power output process in terms of time. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000878

Study of mineralogy and leaching behavior of stabilized/solidified sludge using differential acid neutralization analysis: Part I: Experimental study / O. Peyronnard in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 600–609 Titre : Study of mineralogy and leaching behavior of stabilized/solidified sludge using differential acid neutralization analysis: Part I: Experimental study Type de document : texte imprimé Auteurs : O. Peyronnard, Auteur ; M. Benzaazoua, Auteur ; Blanc, André, Auteur Année de publication : 2009 Article en page(s) : pp. 600–609 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Waste  management;  Characterization;  Stability;  Fly  ash;  Portland  cement Résumé : In this work, differential acid neutralization analysis, chemical analysis of selected leachates and mineralogical study (XRD and SEM-EDS) are combined to investigate the relationship between mineralogy and leaching behavior of hydroxide sludge doped in Zn and Cr stabilized/solidified by hydraulic binders. The leaching behavior of stabilized hydroxide sludge is controlled by the dissolution of portlandite (pH ~ 12) followed by the dissolution of AFt/AFm and hydrogarnets (pH between 12 and 10) and finally the dissolution of ettringite and of the siliceous matrix of C–S–H (pH < 10). The zinc behavior is independent of the main components and is controlled by the dissolution of calcium hydroxizincate and its reprecipitation as hydroxyde or its adsorption on C–S–H. Chromium release is linked to the sulfate one due to a substitution in AFt/AFm phases. The proposed combination of tests is highly pertinent to establish the links between mineralogy and leaching behavior. Nevertheless, the hypotheses formulated are insufficient to implement a behavioral model to describe the leaching behavior. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000751 [article] Study of mineralogy and leaching behavior of stabilized/solidified sludge using differential acid neutralization analysis: Part I: Experimental study [texte imprimé] / O. Peyronnard, Auteur ; M. Benzaazoua, Auteur ; Blanc, André, Auteur . - 2009 . - pp. 600–609. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 600–609 Mots-clés : Waste  management;  Characterization;  Stability;  Fly  ash;  Portland  cement Résumé : In this work, differential acid neutralization analysis, chemical analysis of selected leachates and mineralogical study (XRD and SEM-EDS) are combined to investigate the relationship between mineralogy and leaching behavior of hydroxide sludge doped in Zn and Cr stabilized/solidified by hydraulic binders. The leaching behavior of stabilized hydroxide sludge is controlled by the dissolution of portlandite (pH ~ 12) followed by the dissolution of AFt/AFm and hydrogarnets (pH between 12 and 10) and finally the dissolution of ettringite and of the siliceous matrix of C–S–H (pH < 10). The zinc behavior is independent of the main components and is controlled by the dissolution of calcium hydroxizincate and its reprecipitation as hydroxyde or its adsorption on C–S–H. Chromium release is linked to the sulfate one due to a substitution in AFt/AFm phases. The proposed combination of tests is highly pertinent to establish the links between mineralogy and leaching behavior. Nevertheless, the hypotheses formulated are insufficient to implement a behavioral model to describe the leaching behavior. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000751

Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis / Mauricio Lopez in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 610–619 Titre : Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis Type de document : texte imprimé Auteurs : Mauricio Lopez, Auteur ; Lawrence F. Kahn, Auteur ; Kimberly E. Kurtis, Auteur Année de publication : 2009 Article en page(s) : pp. 610–619 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Aggregate;  Cement  paste;  Creep;  Interfacial  transition  zone;  Shrinkage Résumé : Image analysis and strain mapping were used to examine the nature of elastic, creep and shrinkage strains in high performance lightweight concrete (HPLC). The strain maps showed non-uniform deformations related to microstructural features. Both average strain and non-uniformity increased with time under testing. Paste-rich regions exhibited higher creep plus shrinkage than the lightweight aggregate (LWA) particles examined herein; it is suggested that LWA could have a role in reducing deformations of the paste. Compared to normal weight high performance concrete (HPC), the paste and LWA in the HPLC exhibited more gradual spatial differences in elastic deformations, creep and shrinkage. It is proposed that this difference results from the lower stiffness of the LWA compared to granite used in the HPC. The results indicate that improvement in elastic property matching between the lightweight aggregate and high performance paste reduces stress concentrations at the aggregate/paste interface and contributes to reductions in deformations of HPLC compared to HPC. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000763 [article] Characterization of elastic and time-dependent deformations in high performance lightweight concrete by image analysis [texte imprimé] / Mauricio Lopez, Auteur ; Lawrence F. Kahn, Auteur ; Kimberly E. Kurtis, Auteur . - 2009 . - pp. 610–619. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 610–619 Mots-clés : Aggregate;  Cement  paste;  Creep;  Interfacial  transition  zone;  Shrinkage Résumé : Image analysis and strain mapping were used to examine the nature of elastic, creep and shrinkage strains in high performance lightweight concrete (HPLC). The strain maps showed non-uniform deformations related to microstructural features. Both average strain and non-uniformity increased with time under testing. Paste-rich regions exhibited higher creep plus shrinkage than the lightweight aggregate (LWA) particles examined herein; it is suggested that LWA could have a role in reducing deformations of the paste. Compared to normal weight high performance concrete (HPC), the paste and LWA in the HPLC exhibited more gradual spatial differences in elastic deformations, creep and shrinkage. It is proposed that this difference results from the lower stiffness of the LWA compared to granite used in the HPC. The results indicate that improvement in elastic property matching between the lightweight aggregate and high performance paste reduces stress concentrations at the aggregate/paste interface and contributes to reductions in deformations of HPLC compared to HPC. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000763

Fracture mechanical behavior of concrete and the condition of its fracture surface / Viktor Mechtcherine in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 620–628 Titre : Fracture mechanical behavior of concrete and the condition of its fracture surface Type de document : texte imprimé Auteurs : Viktor Mechtcherine, Auteur Année de publication : 2009 Article en page(s) : pp. 620–628 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Concrete;  Heterogeneity;  Fracture  mechanics;Stress–crack  pening  relations;  Fracture  surfaces;  Fractal  geometry Résumé : In this research project, a series of uniaxial, deformation controlled tensile tests were performed in order to study the fracture mechanical behavior of concrete. The parameters under investigation were the strength of concrete, curing conditions, concrete temperature and loading rate. The fracture surfaces of the tested specimens were investigated in detail and their condition was quantified using the fractal geometry. The evaluation of the experimental results and the results of the fractological investigation displayed correlations between the shape of the stress–crack opening relation of concrete and the values of the roughness as well as the fractal dimension of its fracture surface for all parameters under investigation. Relationships were drawn between the individual material as well as test parameters and the degree of concrete heterogeneity, which proved to be decisive for the formation and propagation of cracks in concrete. It was concluded that the roughness of the fracture surfaces might be considered as a representative replica of the crack system correlating directly with the concrete heterogeneity. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000726 [article] Fracture mechanical behavior of concrete and the condition of its fracture surface [texte imprimé] / Viktor Mechtcherine, Auteur . - 2009 . - pp. 620–628. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 620–628 Mots-clés : Concrete;  Heterogeneity;  Fracture  mechanics;Stress–crack  pening  relations;  Fracture  surfaces;  Fractal  geometry Résumé : In this research project, a series of uniaxial, deformation controlled tensile tests were performed in order to study the fracture mechanical behavior of concrete. The parameters under investigation were the strength of concrete, curing conditions, concrete temperature and loading rate. The fracture surfaces of the tested specimens were investigated in detail and their condition was quantified using the fractal geometry. The evaluation of the experimental results and the results of the fractological investigation displayed correlations between the shape of the stress–crack opening relation of concrete and the values of the roughness as well as the fractal dimension of its fracture surface for all parameters under investigation. Relationships were drawn between the individual material as well as test parameters and the degree of concrete heterogeneity, which proved to be decisive for the formation and propagation of cracks in concrete. It was concluded that the roughness of the fracture surfaces might be considered as a representative replica of the crack system correlating directly with the concrete heterogeneity. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000726

Synthesis of copolymers of methoxy polyethylene glycol acrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid: Its characterization and application as superplasticizer in concrete / Arzu Büyükyağcı in Cement and concrete research, Vol. 39 N° 7 (Juillet 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 629–635 Titre : Synthesis of copolymers of methoxy polyethylene glycol acrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid: Its characterization and application as superplasticizer in concrete Type de document : texte imprimé Auteurs : Arzu Büyükyağcı, Auteur ; Gözde Tuzcu, Auteur ; Leyla Aras, Auteur Année de publication : 2009 Article en page(s) : pp. 629–635 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Water-soluble  copolymers;  Concrete;  Superplasticizer;  Fluidity;  Grafting Résumé : Water-soluble copolymers of methoxy polyethylene glycol acrylate (mPEGA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radicalic polymerization and evaluated as slump-retaining dispersant for cement particles. The slump-retaining effect of the synthesized copolymers was studied in terms of reaction pH, composition, and molecular weight of mPEG side chains. mPEG grafted copolymers (mPEGA-co-AMPS) were characterized by FTIR, 1H NMR. In this study, dilute solution viscometry measurements were performed to compare the molecular weight effect on fluidity of the copolymers and mechanical properties of the mortar samples prepared by the copolymers were investigated to determine the flexural strength and compressive strengths. It was observed that the reaction pH had a noticeable effect on the molecular weight of the PEG-grafted samples thus causing a significant effect on fluidity. mPEGA-co-AMPS synthesized at a pH of 6 has given the highest fluidity result. Copolymers with mPEG side chains with a molecular weight of 1100 gave higher fluidity and viscosity average molecular weight values than the copolymers with mPEG 2000 side chains. Furthermore, for all the samples tested in this research, increase in molecular weight caused an increase in fluidity, however, a decrease in mechanical properties due to the different air contents of these copolymers. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000714 [article] Synthesis of copolymers of methoxy polyethylene glycol acrylate and 2-acrylamido-2-methyl-1-propanesulfonic acid: Its characterization and application as superplasticizer in concrete [texte imprimé] / Arzu Büyükyağcı, Auteur ; Gözde Tuzcu, Auteur ; Leyla Aras, Auteur . - 2009 . - pp. 629–635. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 7 (Juillet 2009) . - pp. 629–635 Mots-clés : Water-soluble  copolymers;  Concrete;  Superplasticizer;  Fluidity;  Grafting Résumé : Water-soluble copolymers of methoxy polyethylene glycol acrylate (mPEGA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radicalic polymerization and evaluated as slump-retaining dispersant for cement particles. The slump-retaining effect of the synthesized copolymers was studied in terms of reaction pH, composition, and molecular weight of mPEG side chains. mPEG grafted copolymers (mPEGA-co-AMPS) were characterized by FTIR, 1H NMR. In this study, dilute solution viscometry measurements were performed to compare the molecular weight effect on fluidity of the copolymers and mechanical properties of the mortar samples prepared by the copolymers were investigated to determine the flexural strength and compressive strengths. It was observed that the reaction pH had a noticeable effect on the molecular weight of the PEG-grafted samples thus causing a significant effect on fluidity. mPEGA-co-AMPS synthesized at a pH of 6 has given the highest fluidity result. Copolymers with mPEG side chains with a molecular weight of 1100 gave higher fluidity and viscosity average molecular weight values than the copolymers with mPEG 2000 side chains. Furthermore, for all the samples tested in this research, increase in molecular weight caused an increase in fluidity, however, a decrease in mechanical properties due to the different air contents of these copolymers. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000714

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