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Micromechanics-based predictions on the overall stress-strain relations of cement-matrix composites / Tsung-Hui Kuo in Journal of engineering mechanics, Vol. 134 n°12 (Décembre 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 n°12 (Décembre 2008) . - pp.1045–1052. Titre : Micromechanics-based predictions on the overall stress-strain relations of cement-matrix composites Type de document : texte imprimé Auteurs : Tsung-Hui Kuo, Auteur ; Huang Hsing Pan, Auteur ; George J. Weng, Auteur Année de publication : 2009 Article en page(s) : pp.1045–1052. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Mortar  Stress  strain  relation  Micromechanics  Predictions  Cements Résumé : A micromechanics-based model is proposed to determine the nonlinear stress-strain relations of cement-matrix composites at different concentrations of inclusions (aggregates). We first conducted some experiments to uncover the stress-strain behavior of the cement paste with a water-to-cement ratio of 0.45, and those of the mortar with the same cement paste but at three different volume concentrations of aggregates. The behavior of the cement paste is then simulated by Burgers’ rheological model. In the development of the composite model, we extend the linear elastic response to the nonlinear one through the replacement of elastic moduli by the corresponding secant moduli. The nonlinear stress-strain curves of the cement-matrix composite are then determined from those of the cement paste and inclusions. It is shown that the predicted stress-strain curves of the mortar are in close agreement with the experimental curves up to an aggregate volume fraction of 49% or 60wt% . ISSN : 0733-9399 En ligne : Mortar, Stress strain relation, Micromechanics, Predictions, Cements Read More:  [...] [article] Micromechanics-based predictions on the overall stress-strain relations of cement-matrix composites [texte imprimé] / Tsung-Hui Kuo, Auteur ; Huang Hsing Pan, Auteur ; George J. Weng, Auteur . - 2009 . - pp.1045–1052. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°12 (Décembre 2008) . - pp.1045–1052. Mots-clés : Mortar  Stress  strain  relation  Micromechanics  Predictions  Cements Résumé : A micromechanics-based model is proposed to determine the nonlinear stress-strain relations of cement-matrix composites at different concentrations of inclusions (aggregates). We first conducted some experiments to uncover the stress-strain behavior of the cement paste with a water-to-cement ratio of 0.45, and those of the mortar with the same cement paste but at three different volume concentrations of aggregates. The behavior of the cement paste is then simulated by Burgers’ rheological model. In the development of the composite model, we extend the linear elastic response to the nonlinear one through the replacement of elastic moduli by the corresponding secant moduli. The nonlinear stress-strain curves of the cement-matrix composite are then determined from those of the cement paste and inclusions. It is shown that the predicted stress-strain curves of the mortar are in close agreement with the experimental curves up to an aggregate volume fraction of 49% or 60wt% . ISSN : 0733-9399 En ligne : Mortar, Stress strain relation, Micromechanics, Predictions, Cements Read More:  [...]

Study on strain-rate sensitivity of cementitious composites / Huang Hsing Pan in Journal of engineering mechanics, Vol. 136 N° 9 (Septembre 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 9 (Septembre 2010) . - pp. 1076-1082 Titre : Study on strain-rate sensitivity of cementitious composites Type de document : texte imprimé Auteurs : Huang Hsing Pan, Auteur ; George J. Weng, Auteur Article en page(s) : pp. 1076-1082 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Strain  rates  Stress  strain  relations  Cement  Aggregates  Micromechanics  Composite  materials. Résumé : In this study, we conduct a combined experimental and micromechanical investigation into the strain-rate sensitivity of concretes, with a special reference to the effect of aggregate concentration. We first measured the stress-strain relations of Type I portland cement with 0.45 water-to-cement ratio (w/c), and then those of the mortar containing sand aggregates of up to 50% volume concentration, over six orders of magnitude of strain rate, from 5×10−6/s to 1×10−1/s under compression. It was found that, at a given strain rate, the peak stress increases with the aggregate concentration but the peak strain tends to decrease with it. At a given aggregate concentration, the peak stress also increases with strain rate whereas the peak strain generally decreases with it. We then developed an inclusion-matrix type micromechanical model to simulate the behavior of the concrete. In this process the nonlinear viscoelastic behavior of the portland cement was modeled by a modified Burger's model with strain-rate dependent spring and dashpot elements, and the stress-strain relations of the mortar at various aggregate concentrations and strain rates were calculated from a two-phase composite model with a secant-moduli approach. It is shown that the measured data could be sufficiently well predicted by the developed micromechanics composite model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Study on strain-rate sensitivity of cementitious composites [texte imprimé] / Huang Hsing Pan, Auteur ; George J. Weng, Auteur . - pp. 1076-1082. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 9 (Septembre 2010) . - pp. 1076-1082 Mots-clés : Strain  rates  Stress  strain  relations  Cement  Aggregates  Micromechanics  Composite  materials. Résumé : In this study, we conduct a combined experimental and micromechanical investigation into the strain-rate sensitivity of concretes, with a special reference to the effect of aggregate concentration. We first measured the stress-strain relations of Type I portland cement with 0.45 water-to-cement ratio (w/c), and then those of the mortar containing sand aggregates of up to 50% volume concentration, over six orders of magnitude of strain rate, from 5×10−6/s to 1×10−1/s under compression. It was found that, at a given strain rate, the peak stress increases with the aggregate concentration but the peak strain tends to decrease with it. At a given aggregate concentration, the peak stress also increases with strain rate whereas the peak strain generally decreases with it. We then developed an inclusion-matrix type micromechanical model to simulate the behavior of the concrete. In this process the nonlinear viscoelastic behavior of the portland cement was modeled by a modified Burger's model with strain-rate dependent spring and dashpot elements, and the stress-strain relations of the mortar at various aggregate concentrations and strain rates were calculated from a two-phase composite model with a secant-moduli approach. It is shown that the measured data could be sufficiently well predicted by the developed micromechanics composite model. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]