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A contribution to the poro-mechanics of heat-treated mortars under confinement: experiments and micro-mechanical modelling

type de publication      communication internationale avec actes publiés
date de publication 09-06-2009
auteur(s) Chen Xiaoting; Davy Catherine A.; Skoczylas Frédéric; Shao Jian-Fu
  
conférence 4th International Biot's Conference on Poromechanics
     dates de 08-06-2009 à 10-06-2009
     lieu Columbia University, New York, USA
     nom des actes Proceedings of the 4th International Biot's Conference on Poromechanics, Eds. H. I. Ling, A. Smyth, R. Betti, DEStech Publications Inc., Pennsylvania USA
  
pages 858 – 863
  Sous presse
ISBN / ISSN 978-1-60595-006-8
résumé This work investigates the effect of heating upon the poro-mechanical behavior of cement-based materials. A typical normalized mortar, with a (w/c) ratio of 0.5 is studied. It is preliminary subjected to a heating/cooling cycle (of up to 400°C). Firstly, we identify experimentally the poro-elastic properties of these mortars under hydrostatic loading. Results show that under drained conditions, plastic straining increases with heat-treatment temperature T. Similarly, drained bulk modulus Kb decreases significantly with T. Both results are related to various degradation phenomena occurring under heating. These are mainly micro-crack creation, increase of connected porosity and coarsening of pore size. On the opposite, it is also observed that, at given heat-treatment temperature, Kb increases with confining pressure. This is related to micro-crack closure and partial pore network collapse. Variations of solid matrix bulk modulus Ks and Biot’s coefficient b are also investigated with heating temperature. Most remarkably, for heat treatment temperatures above 200°C, Ks decreases with confinement, which is interpreted as a consequence of micro-crack closure and occluded porosity increase. Secondly, a micro-mechanical model based on the dilute scheme is formulated, which relates material bulk compressibility (1/Kb) to crack density and aspect ratio. The distribution of micro-crack aspect ratio is analyzed. The variation of bulk modulus Kb with confining pressure is then determined and compared to experimental data.
mots clés poro-elasticity, thermal treatment, Biot's coefficient, micro-mechanics
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