Study on the freeze-thaw deformation behavior of the brittle porous materials in the elastoplastic regime based on Mohr-Coulomb yield criterion

Freeze-thaw damage of the brittle construction materials has shortened the service life and made threat to the safety of the building structure. The frost heaving pressure induced by water freezing is more than several hundreds of megapascals from the previous poroelastic theory, which has already exceeded the yield strength of the brittle porous materials. Therefore, a novel elastoplastic model has been proposed based on the Mohr-Coulomb (M-C) yield criterion in order to quantify the frost deformation of the saturated brittle porous materials during repeated freeze-thaw cycles. Then, the experimental frost deformation of two widely used building materials, sandstone and cement pastes, are used to validate this model. The results show that the calculated frost strain has a good agreement with the experimental values during the freeze-thaw process. Moreover, the freeze-thaw deformation can be divided into four typical deformation stages, including thermal contraction stage, frost expansion stage, thawing contraction stage and thermal expansion stage. By introducing a plastic parameter eta, the residual plastic strains of this sandstone and cement pastes caused by freeze-thaw action can be well estimated by the present model. This residual plastic strain increases gradually with increasing freeze-thaw cycles, but the growth rate has a decreasing trend due to the production of new empty voids. Finally, the influence of the frost heaving pressure and freeze-thaw hysteresis effect on the freezing process is comprehensively discussed using the present elastoplastic model. This research can provide a better understanding of the freezing process and the frost deformation behavior of the brittle porous materials in the elastoplastic regime under freeze-thaw. (C) 2020 Elsevier Ltd. All rights reserved.