Damage constitutive model of coal gangue concrete under freeze-thaw cycles

Abstract This paper aims to solve one of the main problems in the application of coal gangue concrete (CGC), that is, whether its mechanical properties can meet the requirements of norms and actual engineering practice in the freeze–thaw environment. In this work, the CGC with coal gangue coarse aggregate replacement rates of 0%, 20%, 40%, and 60% were subjected to freeze–thaw cycle. The frost resistance of CGC was comprehensively analyzed and evaluated from its appearance, relative mass, compressive strength and relative dynamic elastic modulus. Based on the regular pattern of relative dynamic elastic modulus of CGC, the evolution model of freeze–thaw damage of CGC was established to analyze the development of freeze–thaw damage. The CGC specimens after 0, 25, 50, 75, and 100 freeze–thaw cycles were measured by uniaxial compression constitutive test and acoustic emission test. The mechanical properties of CGC under freeze–thaw environment were analyzed through the whole stress–strain curve and the variation of parameters with freeze–thaw cycles. Finally, based on the acoustic emission characteristics of CGC in compression failure process, a load damage evolution model of CGC was established. Combined with the freeze–thaw damage evolution model, the freeze–thaw damage constitutive relationship of CGC was established, which can consider both freeze–thaw damage and load damage. The results suggest that the replacement rate of gangue for the CGC structure that requires frost resistance should be less than 40%; The freeze–thaw damage evolution model of CGC established in this paper can truly and effectively reflect the development of freeze–thaw damage of CGC under freeze–thaw environment; The CGC freeze–thaw damage constitutive model established in this paper can accurately reflect the overall process damage characteristics of CGC under freeze–thaw and load damage. It can provide a theoretical basis for the durability evaluation and life prediction of CGC structure in cold regions.