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Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness / E. Stora in Cement and concrete research, Vol. 39 N° 9 (Septembre 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 763–772 Titre : Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness Type de document : texte imprimé Auteurs : E. Stora, Auteur ; B. Bary, Auteur ; Q.-C. He, Auteur Année de publication : 2009 Article en page(s) : pp. 763–772 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Chemo–mechanical  degradations;  Leaching;  elastic  moduli;  micromechanics;  cement  paste;  modelling Résumé : The present paper aims at modelling the decalcification process in cement-based materials and its impact on the material stiffness, which represents a serious matter in terms of long-term durability. The resistance of cementitious materials to this chemical alteration is strongly conditioned by their mineral composition and porosity. For this purpose, a multi-scale homogenization approach (Stora et al., Trans. Por. Med. 73, 3, 2008) is implemented in the numerical platform ALLIANCES (P. Montarnal, C. Mügler, J. Colin, M. Descotes, A. Dimier, E. Jacquot, Presentation and use of a reactive transport code in porous media, Phys. Chem. Earth 32, 2007) to estimate from these data the elastic and diffusive properties of cement-based materials. The association of this homogenization model and of the integration platform, which can couple different numerical codes, then allows for evaluating the evolution of the mineral composition and of the diffusive and mechanical properties of a concrete material during chemical deterioration processes. Simulations of pure water leaching of hydrated cement pastes are performed and the consequences of this decalcification on the material's residual elastic behaviour are estimated. The numerical results are confronted with available experimental data and analyzed. The simulations of the non-linear mechanical behaviour of leached cementitious materials taking into account interactions between damage and leaching is not reported here for conciseness but can be found in another document (Stora, Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials. PhD Dissertation, univ. of Paris-Est 2008). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001240 [article] Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness [texte imprimé] / E. Stora, Auteur ; B. Bary, Auteur ; Q.-C. He, Auteur . - 2009 . - pp. 763–772. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 9 (Septembre 2009) . - pp. 763–772 Mots-clés : Chemo–mechanical  degradations;  Leaching;  elastic  moduli;  micromechanics;  cement  paste;  modelling Résumé : The present paper aims at modelling the decalcification process in cement-based materials and its impact on the material stiffness, which represents a serious matter in terms of long-term durability. The resistance of cementitious materials to this chemical alteration is strongly conditioned by their mineral composition and porosity. For this purpose, a multi-scale homogenization approach (Stora et al., Trans. Por. Med. 73, 3, 2008) is implemented in the numerical platform ALLIANCES (P. Montarnal, C. Mügler, J. Colin, M. Descotes, A. Dimier, E. Jacquot, Presentation and use of a reactive transport code in porous media, Phys. Chem. Earth 32, 2007) to estimate from these data the elastic and diffusive properties of cement-based materials. The association of this homogenization model and of the integration platform, which can couple different numerical codes, then allows for evaluating the evolution of the mineral composition and of the diffusive and mechanical properties of a concrete material during chemical deterioration processes. Simulations of pure water leaching of hydrated cement pastes are performed and the consequences of this decalcification on the material's residual elastic behaviour are estimated. The numerical results are confronted with available experimental data and analyzed. The simulations of the non-linear mechanical behaviour of leached cementitious materials taking into account interactions between damage and leaching is not reported here for conciseness but can be found in another document (Stora, Modelling and simulations of the chemo–mechanical behaviour of leached cement-based materials. PhD Dissertation, univ. of Paris-Est 2008). ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609001240

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

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