Micromechanics Model to Describe Strain Behavior of Concrete in Freezing Process

Abstract

On the basis of micromechanics consideration of frost damage, a theoretical model to describe the freeze-induced strain behavior of porous materials such as concrete is presented. The model is derived from the thermodynamic equilibrium condition. Fundamental equations are derived on the microscopic level where temperature-induced phase transitions and the resulting mass transfer within the pore structure are taken into consideration. The local deformation obtained from the microscopic considerations around pores is then averaged to evaluate the nominal strain on a macroscopic level. Components of the macroscopic deformation in the presented model are the thermal strain, the expansion due to the internal pressure caused by the phase transition, the smeared cracking strain due to accumulation of microcracks, and the shrinkage due to the mass transfer caused by the microice-lens mechanism. Experimental studies are carried out with mortar specimens of three different mix proportions. The theoretical prediction is then compared with the experimental results and a good agreement is obtained.