Dépouillements

Synthesis of pure Portland cement phases / A. Wesselsky in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 973-980 Titre : Synthesis of pure Portland cement phases Type de document : texte imprimé Auteurs : A. Wesselsky, Auteur ; O.M. Jensen, Auteur Année de publication : 2010 Article en page(s) : pp. 973-980 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Portland  cement  ;Cement  manufacture  ;Ca3SiO5  ;Ca2SiO4  ;Ca3Al2O6 Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Pure clinker phases are often used to test cement hydration behavior in simplified experimental conditions. These phases are in general structurally identical to, but chemically much simpler than their heavily substituted counterparts found in technical clinkers. The synthesis of the pure phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the process of solid state synthesis are described including practical advice on equipment and techniques. In addition, mix compositions that have been successfully used are given. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001744 [article] Synthesis of pure Portland cement phases [texte imprimé] / A. Wesselsky, Auteur ; O.M. Jensen, Auteur . - 2010 . - pp. 973-980. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 973-980 Mots-clés : Portland  cement  ;Cement  manufacture  ;Ca3SiO5  ;Ca2SiO4  ;Ca3Al2O6 Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : Pure clinker phases are often used to test cement hydration behavior in simplified experimental conditions. These phases are in general structurally identical to, but chemically much simpler than their heavily substituted counterparts found in technical clinkers. The synthesis of the pure phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the process of solid state synthesis are described including practical advice on equipment and techniques. In addition, mix compositions that have been successfully used are given. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001744

Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides / A. K. Chatterjee in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 981-988 Titre : Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides Type de document : texte imprimé Auteurs : A. K. Chatterjee, Auteur Année de publication : 2010 Article en page(s) : pp. 981-988 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : BaO;Calcium  aluminate  cement;  Refractory  cement;  Strontium  compounds Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the family of aluminous cements the potential of strontium aluminate, the strontium–barium aluminate and the barium aluminate cements have been sporadically and incoherently studied over several decades in various parts of the world and more particularly in the East European countries without much wide-spread commercial success. Attempts had also been made to extend the exploratory studies to the (Ca, Sr, Ba)O–Al2O3–ZrO2–HfO2 system to synthesize super-refractory binders. In fact, the above compositions, prima facie, seem to have the potential of arriving at cementitious formulations that, apart from being super-refractory, may as well be highly resistant to seawater, X-rays and gamma radiation. Looking at these potentials, quite a few experimental studies have been carried out under the guidance and supervision of the present author. The present paper is an endeavour to collate the data on some of these systems both from the published literature as well as from the author's findings. The prime motive has been to review and re-assess the prospects of manufacturing a range of new aluminous binders with superior properties. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002002 [article] Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides [texte imprimé] / A. K. Chatterjee, Auteur . - 2010 . - pp. 981-988. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 981-988 Mots-clés : BaO;Calcium  aluminate  cement;  Refractory  cement;  Strontium  compounds Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the family of aluminous cements the potential of strontium aluminate, the strontium–barium aluminate and the barium aluminate cements have been sporadically and incoherently studied over several decades in various parts of the world and more particularly in the East European countries without much wide-spread commercial success. Attempts had also been made to extend the exploratory studies to the (Ca, Sr, Ba)O–Al2O3–ZrO2–HfO2 system to synthesize super-refractory binders. In fact, the above compositions, prima facie, seem to have the potential of arriving at cementitious formulations that, apart from being super-refractory, may as well be highly resistant to seawater, X-rays and gamma radiation. Looking at these potentials, quite a few experimental studies have been carried out under the guidance and supervision of the present author. The present paper is an endeavour to collate the data on some of these systems both from the published literature as well as from the author's findings. The prime motive has been to review and re-assess the prospects of manufacturing a range of new aluminous binders with superior properties. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609002002

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) 

Public ISBD [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

Flow conditions of fresh mortar and concrete in different pipes / Stefan Jacobsen in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 997–1006 Titre : Flow conditions of fresh mortar and concrete in different pipes Type de document : texte imprimé Auteurs : Stefan Jacobsen, Auteur ; Lars Haugan, Auteur ; Tor Arne Hammer, Auteur Année de publication : 2010 Article en page(s) : pp. 997–1006 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fresh  concrete;  Workability;  Rheology;  Pumping Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The variation in fresh concrete flow rate over the pipe cross section was investigated on differently coloured and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl). First, uncoloured (gray) concrete was poured through the pipe and the pipe blocked. Similar but coloured (black) concrete was then poured into the pipe filled with gray concrete, flowing after the gray concrete for a while before being blocked and hardened. The advance of the colouring along the pipe wall (showing boundary flow rate) was observed on the moulded concrete surface appearing after removing the pipe from the hardened concrete. The shapes of the interfaces between uncoloured and coloured concrete (showing variation of flow rate over the pipe cross section) were observed on sawn surfaces of concrete half cylinders cut along the length axes of the concrete-filled pipe. Flow profiles over the pipe cross section were clearly seen with maximum flow rates near the centre of the pipe and low flow rate at the pipe wall (typically rubber pipe with reference concrete without silica fume and/or stabilizers). More plug-shaped profiles, with long slip layers and less variation of flow rate over the cross section, were also seen (typically in smooth acrylic pipes). Flow rate, amount of concrete sticking to the wall after flow and SEM-images of pipe surface roughness were observed, illustrating the problem of testing full scale pumping. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.bledco.com/business/Rouiba/education/Enseignement-universitaire/ECOLE [...] [article] Flow conditions of fresh mortar and concrete in different pipes [texte imprimé] / Stefan Jacobsen, Auteur ; Lars Haugan, Auteur ; Tor Arne Hammer, Auteur . - 2010 . - pp. 997–1006. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 997–1006 Mots-clés : Fresh  concrete;  Workability;  Rheology;  Pumping Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The variation in fresh concrete flow rate over the pipe cross section was investigated on differently coloured and highly flowable concrete mixes flowing through pipes of different materials (rubber, steel, acryl). First, uncoloured (gray) concrete was poured through the pipe and the pipe blocked. Similar but coloured (black) concrete was then poured into the pipe filled with gray concrete, flowing after the gray concrete for a while before being blocked and hardened. The advance of the colouring along the pipe wall (showing boundary flow rate) was observed on the moulded concrete surface appearing after removing the pipe from the hardened concrete. The shapes of the interfaces between uncoloured and coloured concrete (showing variation of flow rate over the pipe cross section) were observed on sawn surfaces of concrete half cylinders cut along the length axes of the concrete-filled pipe. Flow profiles over the pipe cross section were clearly seen with maximum flow rates near the centre of the pipe and low flow rate at the pipe wall (typically rubber pipe with reference concrete without silica fume and/or stabilizers). More plug-shaped profiles, with long slip layers and less variation of flow rate over the cross section, were also seen (typically in smooth acrylic pipes). Flow rate, amount of concrete sticking to the wall after flow and SEM-images of pipe surface roughness were observed, illustrating the problem of testing full scale pumping. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.bledco.com/business/Rouiba/education/Enseignement-universitaire/ECOLE [...]

Estimating 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) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1007–1016 Titre : Estimating time and temperature dependent yield stress of cement paste using oscillatory rheology and genetic algorithms Type de document : texte imprimé Auteurs : M. Nehdi, Auteur ; S. Al Martini, Auteur Année de publication : 2010 Article en page(s) : pp. 1007–1016 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement  paste;  Rheology;  Modeling;  Genetic  algorithm;  Temperature;  Mixing  time;  Superplasticizer;  Yield  stress Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : A controlled shear stress–shear rate rheometer was used to determine the viscoelastic behavior of cement paste incorporating various superplasticizers and subjected to prolonged mixing at high temperature. At a low applied shear stress range, the oscillatory shear strain/stress curve of cement paste was characteristic of a linear elastic solid; while the higher stress range was characteristic of a viscous liquid exhibiting a linear strain increase with increasing applied shear stress. The transition from solid-like to liquid-like behavior occurred over a very narrow stress increment. This transition stress corresponded to the yield stress parameter estimated from conventional flow curves using the Bingham model. The yield stress from oscillatory shear stress tests was estimated using the intersection between the viscous part of the oscillatory shear strain/stress curve and the oscillatory shear stress axis. In this study, equations describing the variation of shear strain versus shear stress beyond the solid–fluid transition for cement pastes incorporating various superplasticizers at different ambient temperatures and mixing times were developed using genetic algorithms (GA). The yield stress of cement pastes was subsequently predicted using the developed equations by calculating the stress corresponding to zero strain. A sensitivity analysis was performed to evaluate the effects of the mixing time, ambient temperature, and superplasticizer dosage on the calculated yield stress. It is shown that the computed yield stress values compare well with corresponding experimental data measured using oscillatory rheology. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001719 [article] Estimating time and temperature dependent yield stress of cement paste using oscillatory rheology and genetic algorithms [texte imprimé] / M. Nehdi, Auteur ; S. Al Martini, Auteur . - 2010 . - pp. 1007–1016. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1007–1016 Mots-clés : Cement  paste;  Rheology;  Modeling;  Genetic  algorithm;  Temperature;  Mixing  time;  Superplasticizer;  Yield  stress Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : A controlled shear stress–shear rate rheometer was used to determine the viscoelastic behavior of cement paste incorporating various superplasticizers and subjected to prolonged mixing at high temperature. At a low applied shear stress range, the oscillatory shear strain/stress curve of cement paste was characteristic of a linear elastic solid; while the higher stress range was characteristic of a viscous liquid exhibiting a linear strain increase with increasing applied shear stress. The transition from solid-like to liquid-like behavior occurred over a very narrow stress increment. This transition stress corresponded to the yield stress parameter estimated from conventional flow curves using the Bingham model. The yield stress from oscillatory shear stress tests was estimated using the intersection between the viscous part of the oscillatory shear strain/stress curve and the oscillatory shear stress axis. In this study, equations describing the variation of shear strain versus shear stress beyond the solid–fluid transition for cement pastes incorporating various superplasticizers at different ambient temperatures and mixing times were developed using genetic algorithms (GA). The yield stress of cement pastes was subsequently predicted using the developed equations by calculating the stress corresponding to zero strain. A sensitivity analysis was performed to evaluate the effects of the mixing time, ambient temperature, and superplasticizer dosage on the calculated yield stress. It is shown that the computed yield stress values compare well with corresponding experimental data measured using oscillatory rheology. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001719

Effect of fibre morphology on flocculation of fibre–cement suspensions / G.H.D. Tonoli in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1017–1022 Titre : Effect of fibre morphology on flocculation of fibre–cement suspensions Type de document : texte imprimé Auteurs : G.H.D. Tonoli, Auteur ; E. Fuente, Auteur ; C. Monte, Auteur Année de publication : 2010 Article en page(s) : pp. 1017–1022 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : ispersion  ;  Physical  properties  ;Fibre  reinforcement  ;Composite  ;  FBRM Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The objective of the present research was to evaluate the effect of fibre morphology (e.g., length, width, fibrillation, broken ends, content of fines and number of fibres per gram) on flocculation and drainage properties of fibre–cement suspensions and on physical properties of the fibre–cement composites. Mechanical refining was used to change the morphological properties of Eucalyptus and Pinus pulps. Results show that the mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles (with dimensions between 1 and 20 µm) as a consequence of the increased fibrillation and content of fines, which increased the capacity of the fibres to capture the mineral particles. High levels of refining were necessary for Pinus pulp to obtain cement retention values similar to those obtained by unrefined Eucalyptus pulp. This is due to the higher number of fibres per gram in Eucalyptus pulp than in Pinus pulp. Pulp refining improved the packing of the particles and, although decreased the drainage rate, it contributed to a less porous structure, which improved the microstructure of the composite. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001707 [article] Effect of fibre morphology on flocculation of fibre–cement suspensions [texte imprimé] / G.H.D. Tonoli, Auteur ; E. Fuente, Auteur ; C. Monte, Auteur . - 2010 . - pp. 1017–1022. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1017–1022 Mots-clés : ispersion  ;  Physical  properties  ;Fibre  reinforcement  ;Composite  ;  FBRM Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The objective of the present research was to evaluate the effect of fibre morphology (e.g., length, width, fibrillation, broken ends, content of fines and number of fibres per gram) on flocculation and drainage properties of fibre–cement suspensions and on physical properties of the fibre–cement composites. Mechanical refining was used to change the morphological properties of Eucalyptus and Pinus pulps. Results show that the mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles (with dimensions between 1 and 20 µm) as a consequence of the increased fibrillation and content of fines, which increased the capacity of the fibres to capture the mineral particles. High levels of refining were necessary for Pinus pulp to obtain cement retention values similar to those obtained by unrefined Eucalyptus pulp. This is due to the higher number of fibres per gram in Eucalyptus pulp than in Pinus pulp. Pulp refining improved the packing of the particles and, although decreased the drainage rate, it contributed to a less porous structure, which improved the microstructure of the composite. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001707

Effects 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) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1023–1032 Titre : Effects of fibre type and matrix structure on the mechanical performance of self-compacting micro-concrete composites Type de document : texte imprimé Auteurs : Burak Felekoğlu, Auteur ; Kamile Tosun, Auteur ; Bülent Baradan, Auteur Année de publication : 2010 Article en page(s) : pp. 1023–1032 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Micro-concrete;  Fiber  Reinforcement  ;  Fracture  Toughness  ;Fly  Ash  ;  SEM Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The compatibility of matrix and fibre properties is one of the key parameters in the successful design of fibre reinforced cementitious composites. In order to achieve the desired performance, the properties of each constituent of composite should be properly configured. The aim of this study was to investigate the performance of two polymer based micro-fibres (polypropylene and polyvinyl alcohol) in different matrices (high strength and comparatively low strength with fly ash incorporation) which were designed to contain considerably high amounts of fibres (1% by volume) while maintaining their self-compactability. The fresh state thixotropic behaviour of fibre reinforced matrices was minimised by proper adjustment of water/cementitious material ratio and admixture dosage. The mechanical properties (first crack strength and displacement, flexural strength and relative toughness) of prismatic composite samples were compared by three point flexural loading test. The typical behaviours of selected composites and collapse mechanisms of PP and PVA fibres in these matrices were characterised by microstructural studies. It was concluded that, a high strength matrix with a high strength fibre give the best performance from the view point of flexural strength and toughness performance. However, incorporation of fly ash did not cause a significant reduction in composite performance possibly due to its enhancing effect on matrix–fibre interface adhesion. The possibilities and suggestions to further improve the performance of the composites were also discussed. DEWEY : 620.13 ISSN : 0009-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001677 [article] Effects of fibre type and matrix structure on the mechanical performance of self-compacting micro-concrete composites [texte imprimé] / Burak Felekoğlu, Auteur ; Kamile Tosun, Auteur ; Bülent Baradan, Auteur . - 2010 . - pp. 1023–1032. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1023–1032 Mots-clés : Micro-concrete;  Fiber  Reinforcement  ;  Fracture  Toughness  ;Fly  Ash  ;  SEM Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The compatibility of matrix and fibre properties is one of the key parameters in the successful design of fibre reinforced cementitious composites. In order to achieve the desired performance, the properties of each constituent of composite should be properly configured. The aim of this study was to investigate the performance of two polymer based micro-fibres (polypropylene and polyvinyl alcohol) in different matrices (high strength and comparatively low strength with fly ash incorporation) which were designed to contain considerably high amounts of fibres (1% by volume) while maintaining their self-compactability. The fresh state thixotropic behaviour of fibre reinforced matrices was minimised by proper adjustment of water/cementitious material ratio and admixture dosage. The mechanical properties (first crack strength and displacement, flexural strength and relative toughness) of prismatic composite samples were compared by three point flexural loading test. The typical behaviours of selected composites and collapse mechanisms of PP and PVA fibres in these matrices were characterised by microstructural studies. It was concluded that, a high strength matrix with a high strength fibre give the best performance from the view point of flexural strength and toughness performance. However, incorporation of fly ash did not cause a significant reduction in composite performance possibly due to its enhancing effect on matrix–fibre interface adhesion. The possibilities and suggestions to further improve the performance of the composites were also discussed. DEWEY : 620.13 ISSN : 0009-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001677

Durability properties of micro-cracked ECC containing high volumes fly ash / Mustafa Şahmaran in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1033–1043 Titre : Durability properties of micro-cracked ECC containing high volumes fly ash Type de document : texte imprimé Auteurs : Mustafa Şahmaran, Auteur ; Victor C. Li, Auteur Année de publication : 2010 Article en page(s) : pp. 1033–1043 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Microcracking  ;  Durability  ;  Fly  ash  ;  Self-healing Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper presents the durability of Engineered Cementitious Composites (ECC) that contain high percentages of Class-F fly ash (FA). ECC is a newly developed high performance fiber reinforced cementitious composite with substantial benefit in both high ductility in excess of 3% under uniaxial tensile loading and improved durability due to intrinsically tight crack width. Composites containing two different contents of FA as a replacement of cement (55 and 70% by weight of total cementitious material) are examined after 28 days of curing. Accelerated aging (exposure to continuous sodium hydroxide at 38 °C and sodium chloride solutions at room temperature) and tests of transport properties (salt ponding, rapid chloride permeability and sorptivity tests) are used to study the effect of FA on the durability of the ECC. After accelerated aging, direct tensile tests are performed to evaluate the effect of deterioration on the tensile strength, tensile strain capacity and crack width of ECCs. In addition to virgin specimens, the durability performances of mechanically loaded specimens are also tested. Test results show that both mechanically pre-loaded and virgin (without pre-loading) ECC mixtures with high volumes of FA remain durable in terms of mechanical performances after accelerated aging period, and show a tensile strain capacity of more than 2%. In terms of transport properties, micro-cracks induced by mechanical pre-loading increase the chloride transport and the sorptivity values of ECC. Moreover, increasing FA content is shown to have a negative effect especially on the transport properties of ECC tested in this study. However, the risk of water transport by capillary suction and chloride transport by diffusion in ECC, cracked or uncracked, is found to be comparable with that in normal sound concrete. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001690 [article] Durability properties of micro-cracked ECC containing high volumes fly ash [texte imprimé] / Mustafa Şahmaran, Auteur ; Victor C. Li, Auteur . - 2010 . - pp. 1033–1043. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1033–1043 Mots-clés : Microcracking  ;  Durability  ;  Fly  ash  ;  Self-healing Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper presents the durability of Engineered Cementitious Composites (ECC) that contain high percentages of Class-F fly ash (FA). ECC is a newly developed high performance fiber reinforced cementitious composite with substantial benefit in both high ductility in excess of 3% under uniaxial tensile loading and improved durability due to intrinsically tight crack width. Composites containing two different contents of FA as a replacement of cement (55 and 70% by weight of total cementitious material) are examined after 28 days of curing. Accelerated aging (exposure to continuous sodium hydroxide at 38 °C and sodium chloride solutions at room temperature) and tests of transport properties (salt ponding, rapid chloride permeability and sorptivity tests) are used to study the effect of FA on the durability of the ECC. After accelerated aging, direct tensile tests are performed to evaluate the effect of deterioration on the tensile strength, tensile strain capacity and crack width of ECCs. In addition to virgin specimens, the durability performances of mechanically loaded specimens are also tested. Test results show that both mechanically pre-loaded and virgin (without pre-loading) ECC mixtures with high volumes of FA remain durable in terms of mechanical performances after accelerated aging period, and show a tensile strain capacity of more than 2%. In terms of transport properties, micro-cracks induced by mechanical pre-loading increase the chloride transport and the sorptivity values of ECC. Moreover, increasing FA content is shown to have a negative effect especially on the transport properties of ECC tested in this study. However, the risk of water transport by capillary suction and chloride transport by diffusion in ECC, cracked or uncracked, is found to be comparable with that in normal sound concrete. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001690

Dynamic behaviour and visco-elastic damage model of ultra-high performance cementitious composite / Jianzhong Lai in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1044–1051 Titre : Dynamic behaviour and visco-elastic damage model of ultra-high performance cementitious composite Type de document : texte imprimé Auteurs : Jianzhong Lai, Auteur ; Wei Sun, Auteur Année de publication : 2010 Article en page(s) : pp. 1044–1051 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Cement  composite;  Mechanical  properties;  Fiber  reinforcement;  Modeling Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The dynamic behaviour of ultra-high performance cementitious composite (UHPCC) with compressive strength of 200 MPa with different steel fiber volume fractions was studied under impact using the split Hopkinson pressure bar. Three aspects of the testing: a gimbal device, wave shaping and direct strain measurement, were used to increase experimental accuracy. Results indicate that UHPCC has obvious strain rate effects. The peak stress, peak strain, elastic modulus and the area under the stress–strain curve increase with increasing strain rate. When the strain rate exceeds a threshold value, specimens with and without fibers begin to fracture. At high strain rate the unreinforced specimens fracture into small parts while fiber reinforced ones only have fine cracks on the edges. A visco-elastic damage model of UHPCC is proposed based on a nonlinear visco-elastic model (the ZWT model) and the material damage measured by the ultrasonic wave velocity method. DEWEY : 620.13 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001720 [article] Dynamic behaviour and visco-elastic damage model of ultra-high performance cementitious composite [texte imprimé] / Jianzhong Lai, Auteur ; Wei Sun, Auteur . - 2010 . - pp. 1044–1051. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1044–1051 Mots-clés : Cement  composite;  Mechanical  properties;  Fiber  reinforcement;  Modeling Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The dynamic behaviour of ultra-high performance cementitious composite (UHPCC) with compressive strength of 200 MPa with different steel fiber volume fractions was studied under impact using the split Hopkinson pressure bar. Three aspects of the testing: a gimbal device, wave shaping and direct strain measurement, were used to increase experimental accuracy. Results indicate that UHPCC has obvious strain rate effects. The peak stress, peak strain, elastic modulus and the area under the stress–strain curve increase with increasing strain rate. When the strain rate exceeds a threshold value, specimens with and without fibers begin to fracture. At high strain rate the unreinforced specimens fracture into small parts while fiber reinforced ones only have fine cracks on the edges. A visco-elastic damage model of UHPCC is proposed based on a nonlinear visco-elastic model (the ZWT model) and the material damage measured by the ultrasonic wave velocity method. DEWEY : 620.13 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001720

Experimental investigation of the effect of temperature on the first desorption isotherm of concrete / Stéphane Poyet in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1052–1059 Titre : Experimental investigation of the effect of temperature on the first desorption isotherm of concrete Type de document : texte imprimé Auteurs : Stéphane Poyet, Auteur Année de publication : 2010 Article en page(s) : pp. 1052–1059 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Temperature;  Surface  area;  Adsorption;  Durability;  Concrete;  Radioactive  waste;  Waste  management Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the framework of the radioactive waste management in France, interim storage concrete structures should be submitted to temperatures up to 80 °C and subsequent desiccation. The impact of temperature on the sorption properties of concretes has been poorly studied and results are scarce. An experimental campaign was thus carried out to characterize the first desorption isotherms of a modern concrete at 30 °C and 80 °C. The results show a significant influence of the temperature increase that will have to be accounted for the durability assessment of the long-term interim storage concrete structures. Investigating the causes of these modifications, it appeared that desorption induced by temperature might be the principal mechanism rather than microstructure alteration and water properties evolution. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001495 [article] Experimental investigation of the effect of temperature on the first desorption isotherm of concrete [texte imprimé] / Stéphane Poyet, Auteur . - 2010 . - pp. 1052–1059. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1052–1059 Mots-clés : Temperature;  Surface  area;  Adsorption;  Durability;  Concrete;  Radioactive  waste;  Waste  management Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the framework of the radioactive waste management in France, interim storage concrete structures should be submitted to temperatures up to 80 °C and subsequent desiccation. The impact of temperature on the sorption properties of concretes has been poorly studied and results are scarce. An experimental campaign was thus carried out to characterize the first desorption isotherms of a modern concrete at 30 °C and 80 °C. The results show a significant influence of the temperature increase that will have to be accounted for the durability assessment of the long-term interim storage concrete structures. Investigating the causes of these modifications, it appeared that desorption induced by temperature might be the principal mechanism rather than microstructure alteration and water properties evolution. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001495

Temperature dependence of the sorption isotherms of cement-based materials: Heat of sorption and Clausius–Clapeyron formula / Stéphane Poyet in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1060–1067 Titre : Temperature dependence of the sorption isotherms of cement-based materials: Heat of sorption and Clausius–Clapeyron formula Type de document : texte imprimé Auteurs : Stéphane Poyet, Auteur ; Sébastien Charles, Auteur Année de publication : 2010 Article en page(s) : pp. 1060–1067 Note générale : Génie Civil Langues : Anglais (eng) Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the field of radioactive waste management the concrete structures are expected to undergo significant heating due to the waste thermal power and significant drying (in the French design, the temperature is not expected to exceed 80 °C). The durability assessment of such structures thus requires the knowledge of the evolution of the water vapour sorption properties versus temperature. The latter can be easily estimated using the Clausius–Clapeyron (CC) equation: the approach presented hereafter requires the knowledge of the isosteric heat of adsorption and one desorption isotherm (at ambient or any other temperature). Moreover, it is shown that using the CC equation and the desorption isotherms at two different temperatures, it is possible to estimate accurately the desorption isotherm at any other temperature. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001768 [article] Temperature dependence of the sorption isotherms of cement-based materials: Heat of sorption and Clausius–Clapeyron formula [texte imprimé] / Stéphane Poyet, Auteur ; Sébastien Charles, Auteur . - 2010 . - pp. 1060–1067. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1060–1067 Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : In the field of radioactive waste management the concrete structures are expected to undergo significant heating due to the waste thermal power and significant drying (in the French design, the temperature is not expected to exceed 80 °C). The durability assessment of such structures thus requires the knowledge of the evolution of the water vapour sorption properties versus temperature. The latter can be easily estimated using the Clausius–Clapeyron (CC) equation: the approach presented hereafter requires the knowledge of the isosteric heat of adsorption and one desorption isotherm (at ambient or any other temperature). Moreover, it is shown that using the CC equation and the desorption isotherms at two different temperatures, it is possible to estimate accurately the desorption isotherm at any other temperature. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001768

Reinforcement corrosion initiation and activation times in concrete structures exposed to severe marine environments / R.E. Melchers in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1068–1076 Titre : Reinforcement corrosion initiation and activation times in concrete structures exposed to severe marine environments Type de document : texte imprimé Auteurs : R.E. Melchers, Auteur ; C. Q. Li, Auteur Année de publication : 2010 Article en page(s) : pp. 1068–1076 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Corrosion;  Long-term  performance;  Chloride;  Reinforcement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The corrosion of steel reinforcement bars in reinforced concrete structures exposed to severe marine environments usually is attributed to the aggressive nature of chloride ions. In some cases in practice corrosion has been observed to commence already within a few years of exposure even with considerable concrete cover to the reinforcement and apparently high quality concretes. However, there are a number of other cases in practice for which corrosion initiation took much longer, even in cases with quite modest concrete cover and modest concrete quality. Many of these structures show satisfactory long-term structural performance, despite having high levels of localized chloride concentrations at the reinforcement. This disparity was noted already more than 50 years ago, but appears still not fully explained. This paper presents a systematic overview of cases reported in the engineering and corrosion literature and considers possible reasons for these differences. Consistent with observations by others, the data show that concretes made from blast furnace cements have better corrosion durability properties. The data also strongly suggest that concretes made with limestone or non-reactive dolomite aggregates or sufficiently high levels of other forms of calcium carbonates have favourable reinforcement corrosion properties. Both corrosion initiation and the onset of significant damage are delayed. Some possible reasons for this are explored briefly. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900163X [article] Reinforcement corrosion initiation and activation times in concrete structures exposed to severe marine environments [texte imprimé] / R.E. Melchers, Auteur ; C. Q. Li, Auteur . - 2010 . - pp. 1068–1076. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1068–1076 Mots-clés : Corrosion;  Long-term  performance;  Chloride;  Reinforcement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : The corrosion of steel reinforcement bars in reinforced concrete structures exposed to severe marine environments usually is attributed to the aggressive nature of chloride ions. In some cases in practice corrosion has been observed to commence already within a few years of exposure even with considerable concrete cover to the reinforcement and apparently high quality concretes. However, there are a number of other cases in practice for which corrosion initiation took much longer, even in cases with quite modest concrete cover and modest concrete quality. Many of these structures show satisfactory long-term structural performance, despite having high levels of localized chloride concentrations at the reinforcement. This disparity was noted already more than 50 years ago, but appears still not fully explained. This paper presents a systematic overview of cases reported in the engineering and corrosion literature and considers possible reasons for these differences. Consistent with observations by others, the data show that concretes made from blast furnace cements have better corrosion durability properties. The data also strongly suggest that concretes made with limestone or non-reactive dolomite aggregates or sufficiently high levels of other forms of calcium carbonates have favourable reinforcement corrosion properties. Both corrosion initiation and the onset of significant damage are delayed. Some possible reasons for this are explored briefly. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900163X

The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment / Ruijin Zhang in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1077–1086 Titre : The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment Type de document : texte imprimé Auteurs : Ruijin Zhang, Auteur ; Arnaud Castel, Auteur ; Raoul François, Auteur Année de publication : 2010 Article en page(s) : pp. 1077–1086 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Crack  Detection  ;Corrosion  ;Long-Term  Performance  ;  Bond  Strength  ;  Reinforcement Résumé : This paper deals with two corroded reinforcement concrete beams, which have been stored under sustained load in a chloride environment for 14 and 23 years respectively. The evolution of corrosion pattern of reinforcement and its influence on serviceability are studied. In chloride-induced corrosion process, corrosion cracking affects significantly the corrosion pattern. During the corrosion cracking initiation period, only local pitting corrosion occurs. At early stage of cracking propagation, localized pitting corrosion is still predominant as cracks widths are very small and cracks are not interconnected, but a general corrosion slowly develops as the cracks widen. At late cracking stage, interconnected cracking with wide width develops along large parts of the beam leading to a general corrosion pattern. Macrocells and microcells concepts are used for the interpretation of the results. Mechanical experiments and corrosion simulation tests are performed to clarify the influence of this corrosion pattern evolution on the serviceability of the beams (deflection increase). Experimental results show that, when the corrosion is localized (early cracking stage), the steel–concrete bond loss is the main factor affecting the beams serviceability. The local cross-section loss resulting from pitting attack does not significantly influence the deflection of the beam. When corrosion is generalized (late cracking stage), as the steel–concrete bond is already lost, the generalized steel cross-section reduction becomes the main factor affecting the beams serviceability. But, at this stage, the deflection increase is slower due to the low general corrosion rate. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001860 [article] The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment [texte imprimé] / Ruijin Zhang, Auteur ; Arnaud Castel, Auteur ; Raoul François, Auteur . - 2010 . - pp. 1077–1086. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1077–1086 Mots-clés : Crack  Detection  ;Corrosion  ;Long-Term  Performance  ;  Bond  Strength  ;  Reinforcement Résumé : This paper deals with two corroded reinforcement concrete beams, which have been stored under sustained load in a chloride environment for 14 and 23 years respectively. The evolution of corrosion pattern of reinforcement and its influence on serviceability are studied. In chloride-induced corrosion process, corrosion cracking affects significantly the corrosion pattern. During the corrosion cracking initiation period, only local pitting corrosion occurs. At early stage of cracking propagation, localized pitting corrosion is still predominant as cracks widths are very small and cracks are not interconnected, but a general corrosion slowly develops as the cracks widen. At late cracking stage, interconnected cracking with wide width develops along large parts of the beam leading to a general corrosion pattern. Macrocells and microcells concepts are used for the interpretation of the results. Mechanical experiments and corrosion simulation tests are performed to clarify the influence of this corrosion pattern evolution on the serviceability of the beams (deflection increase). Experimental results show that, when the corrosion is localized (early cracking stage), the steel–concrete bond loss is the main factor affecting the beams serviceability. The local cross-section loss resulting from pitting attack does not significantly influence the deflection of the beam. When corrosion is generalized (late cracking stage), as the steel–concrete bond is already lost, the generalized steel cross-section reduction becomes the main factor affecting the beams serviceability. But, at this stage, the deflection increase is slower due to the low general corrosion rate. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001860

The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment / Ruijin Zhang in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1077–1086 Titre : The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment Type de document : texte imprimé Auteurs : Ruijin Zhang, Auteur ; Arnaud Castel, Auteur ; Raoul François, Auteur Année de publication : 2010 Article en page(s) : pp. 1077–1086 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Crack  Detection  ;  Corrosion  ;  Long-Term  Performance  ;  Bond  Strength  ;  Reinforcement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper deals with two corroded reinforcement concrete beams, which have been stored under sustained load in a chloride environment for 14 and 23 years respectively. The evolution of corrosion pattern of reinforcement and its influence on serviceability are studied. In chloride-induced corrosion process, corrosion cracking affects significantly the corrosion pattern. During the corrosion cracking initiation period, only local pitting corrosion occurs. At early stage of cracking propagation, localized pitting corrosion is still predominant as cracks widths are very small and cracks are not interconnected, but a general corrosion slowly develops as the cracks widen. At late cracking stage, interconnected cracking with wide width develops along large parts of the beam leading to a general corrosion pattern. Macrocells and microcells concepts are used for the interpretation of the results. Mechanical experiments and corrosion simulation tests are performed to clarify the influence of this corrosion pattern evolution on the serviceability of the beams (deflection increase). Experimental results show that, when the corrosion is localized (early cracking stage), the steel–concrete bond loss is the main factor affecting the beams serviceability. The local cross-section loss resulting from pitting attack does not significantly influence the deflection of the beam. When corrosion is generalized (late cracking stage), as the steel–concrete bond is already lost, the generalized steel cross-section reduction becomes the main factor affecting the beams serviceability. But, at this stage, the deflection increase is slower due to the low general corrosion rate. REFERENCE : 0008-8846 DEWEY : 620.13 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001860 [article] The corrosion pattern of reinforcement and its influence on serviceability of reinforced concrete members in chloride environment [texte imprimé] / Ruijin Zhang, Auteur ; Arnaud Castel, Auteur ; Raoul François, Auteur . - 2010 . - pp. 1077–1086. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1077–1086 Mots-clés : Crack  Detection  ;  Corrosion  ;  Long-Term  Performance  ;  Bond  Strength  ;  Reinforcement Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This paper deals with two corroded reinforcement concrete beams, which have been stored under sustained load in a chloride environment for 14 and 23 years respectively. The evolution of corrosion pattern of reinforcement and its influence on serviceability are studied. In chloride-induced corrosion process, corrosion cracking affects significantly the corrosion pattern. During the corrosion cracking initiation period, only local pitting corrosion occurs. At early stage of cracking propagation, localized pitting corrosion is still predominant as cracks widths are very small and cracks are not interconnected, but a general corrosion slowly develops as the cracks widen. At late cracking stage, interconnected cracking with wide width develops along large parts of the beam leading to a general corrosion pattern. Macrocells and microcells concepts are used for the interpretation of the results. Mechanical experiments and corrosion simulation tests are performed to clarify the influence of this corrosion pattern evolution on the serviceability of the beams (deflection increase). Experimental results show that, when the corrosion is localized (early cracking stage), the steel–concrete bond loss is the main factor affecting the beams serviceability. The local cross-section loss resulting from pitting attack does not significantly influence the deflection of the beam. When corrosion is generalized (late cracking stage), as the steel–concrete bond is already lost, the generalized steel cross-section reduction becomes the main factor affecting the beams serviceability. But, at this stage, the deflection increase is slower due to the low general corrosion rate. REFERENCE : 0008-8846 DEWEY : 620.13 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001860

Mechanical and fracture properties of cement-based bi-materials after thermal cycling / Antonios Kanellopoulos in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1087–1094 Titre : Mechanical and fracture properties of cement-based bi-materials after thermal cycling Type de document : texte imprimé Auteurs : Antonios Kanellopoulos, Auteur ; Farhat A. Farhat, Auteur ; Demetrios Nicolaides, Auteur Année de publication : 2010 Article en page(s) : pp. 1087–1094 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : High-performance  concrete  ;  Bi-materials  ;  Fracture  properties  ;  Thermal  treatment  ;  Mechanical  properties Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This study investigates the effect of thermal cycles on the fracture properties of the cement-based bi-materials. Sixty eight cubes were exposed to a varied number of 24-hour thermal cycles ranging from 0 to 90 and subsequently were tested in a wedge splitting configuration. The mechanical and fracture properties of normal strength and high strength concretes are substantially improved after 30 thermal cycles, but less so after 90 thermal cycles both in isolation and when bonded to an ultra high-performance fibre-reinforced cement-based composite. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001689 [article] Mechanical and fracture properties of cement-based bi-materials after thermal cycling [texte imprimé] / Antonios Kanellopoulos, Auteur ; Farhat A. Farhat, Auteur ; Demetrios Nicolaides, Auteur . - 2010 . - pp. 1087–1094. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1087–1094 Mots-clés : High-performance  concrete  ;  Bi-materials  ;  Fracture  properties  ;  Thermal  treatment  ;  Mechanical  properties Index. décimale : 691 Matériaux de construction. Pièces et parties composantes Résumé : This study investigates the effect of thermal cycles on the fracture properties of the cement-based bi-materials. Sixty eight cubes were exposed to a varied number of 24-hour thermal cycles ranging from 0 to 90 and subsequently were tested in a wedge splitting configuration. The mechanical and fracture properties of normal strength and high strength concretes are substantially improved after 30 thermal cycles, but less so after 90 thermal cycles both in isolation and when bonded to an ultra high-performance fibre-reinforced cement-based composite. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001689

Effect of water-repellent admixtures on the behaviour of aerial lime-based mortars / A. Izaguirre in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1095–1104 Titre : Effect of water-repellent admixtures on the behaviour of aerial lime-based mortars Type de document : texte imprimé Auteurs : A. Izaguirre, Auteur ; J. Lanas, Auteur ; J. I. Álvarez, Auteur Année de publication : 2010 Article en page(s) : pp. 1095–1104 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Admixture;  Durability;  Freezing  and  thawing;  Mechanical  properties;  Lime  mortar Résumé : Two different anionic surfactants, sodium oleate and calcium stearate, commercialized as water repellents for cement-based mortars, were added to lime-based mortars in order to check whether they were improved by these admixtures. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time, hardened state properties such as density, water absorption through capillarity, water vapour permeability, long-term compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing–thawing cycles. A clear improvement in lime-based mortars was achieved when sodium oleate was added: strong capillarity reduction and excellent durability in the face of freezing–thawing processes, without any compressive strength drop. The mechanism for this improvement was related to air void formation due to the air-entraining ability of these surfactants. Insolubility of calcium stearate turned out to be responsible for fewer air bubbles – as SEM examination revealed – and showed lower effectiveness. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001835 [article] Effect of water-repellent admixtures on the behaviour of aerial lime-based mortars [texte imprimé] / A. Izaguirre, Auteur ; J. Lanas, Auteur ; J. I. Álvarez, Auteur . - 2010 . - pp. 1095–1104. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1095–1104 Mots-clés : Admixture;  Durability;  Freezing  and  thawing;  Mechanical  properties;  Lime  mortar Résumé : Two different anionic surfactants, sodium oleate and calcium stearate, commercialized as water repellents for cement-based mortars, were added to lime-based mortars in order to check whether they were improved by these admixtures. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time, hardened state properties such as density, water absorption through capillarity, water vapour permeability, long-term compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing–thawing cycles. A clear improvement in lime-based mortars was achieved when sodium oleate was added: strong capillarity reduction and excellent durability in the face of freezing–thawing processes, without any compressive strength drop. The mechanism for this improvement was related to air void formation due to the air-entraining ability of these surfactants. Insolubility of calcium stearate turned out to be responsible for fewer air bubbles – as SEM examination revealed – and showed lower effectiveness. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001835

Cement content determination through selective stain in hardened concrete / Lucía Linares in Cement and concrete research, Vol. 39 N° 11 (Novembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1105–1109 Titre : Cement content determination through selective stain in hardened concrete Type de document : texte imprimé Auteurs : Lucía Linares, Auteur ; López Atalaya, Auteur ; Servando Chinchón, Auteur Année de publication : 2010 Article en page(s) : pp. 1105–1109 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Concrete;  Cement  paste;  Image  analysis;  Coloured  compounds Résumé : A cement quantification method has been developed in Ø 15 × 30 cm concrete specimens applying selective stain. A tannic acid–tartaric acid solution was used to stain the cement paste. This paper explains the procedure to determine the quantity of cement in the samples: the reagents utilised for the stain, preparation, cutting and stain of the specimens, the capture and treatment of images of the stained samples, and the preparation of the calibration curves. Next, we assess the accuracy of this method and include the resolution of a practical case in which a comparison is drawn between the values obtained through the application of this method and those obtained using a ‘reference’ method. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001781 [article] Cement content determination through selective stain in hardened concrete [texte imprimé] / Lucía Linares, Auteur ; López Atalaya, Auteur ; Servando Chinchón, Auteur . - 2010 . - pp. 1105–1109. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 11 (Novembre 2009) . - pp. 1105–1109 Mots-clés : Concrete;  Cement  paste;  Image  analysis;  Coloured  compounds Résumé : A cement quantification method has been developed in Ø 15 × 30 cm concrete specimens applying selective stain. A tannic acid–tartaric acid solution was used to stain the cement paste. This paper explains the procedure to determine the quantity of cement in the samples: the reagents utilised for the stain, preparation, cutting and stain of the specimens, the capture and treatment of images of the stained samples, and the preparation of the calibration curves. Next, we assess the accuracy of this method and include the resolution of a practical case in which a comparison is drawn between the values obtained through the application of this method and those obtained using a ‘reference’ method. DEWEY : 620.13 ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001781

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