Effect of environmental thermal fatigue on concrete performance based on mesostructural and microstructural analyses

Abstract

Abstract An environmental thermal fatigue (ETF) test method was proposed here. Porosimetry and quantitative microcrack analysis was used to evaluate the effect of mesostructural changes in the cement matrix and interfacial transition zone (ITZ) on the mechanical performance of concrete under ETF. The morphology, thermal behavior, and chemically bound water content were further used to study the mechanisms behind the mesostructural changes. A mesomechanical model based on the porosity and microcracks was proposed based on the relationship between the mesostructural parameters and mechanical performance. Damage caused by environmental thermal fatigue stresses and strengthening due to rehydration reactions occurred simultaneously. The mechanical performance first increased and then decreased with increasing ETF cycles due to rehydration reactions strengthening the cement matrix, followed by an increase in Ca(OH)2 content that degraded the strength due to deterioration of the ITZ structure. The pore structure first refined and then coarsened. Microcracks were mainly located in the ITZ and were enhanced with increasing ETF cycles, where this enhancement was more obvious in the late of ETF.