A micromechanics-based model for concrete materials subjected to carbonation
Résumé
In this paper, we present a micromechanics-based elastic–plastic model to describe the mechanical behaviour of concrete composites subjected to carbonation. For this purpose, a three-step nonlinear homogenization procedure is employed. At the microscopic scale, calcite grains generated by the carbonation are embedded in the solid calcium silicate hydrates phase. At the mesoscopic scale, the cement paste is considered as a porous medium. At the macroscopic scale, large aggregates are taken into account. By using the modified secant method, the homogenization procedure leads to a closed-form plastic yield function for the carbonated concrete, taking into account the effects of the volume fraction of calcite grains, the porosity and the aggregates volume fraction. An associated plastic model is then formulated by introducing a specific plastic hardening law. Further, a heuristic non-associated plastic potential is proposed directly at the macroscopic scale in order to capture differences with the associated model for the description of plastic volumetric strain and porosity change. The proposed models are implemented in a standard finite element code and applied to reproduce a series of laboratory tests. Comparisons between numerical results and experimental data are presented to assess the capacity of the model to take into consideration the main features of mechanical behaviour of concrete composites.