Pore characteristics of recycled aggregate concrete and its relationship with durability under complex environmental factors

Abstract

The influences and mechanisms of single and coupled effect of carbonation, dry-wet cycles and freeze–thaw cycles on the durability of three types of recycled aggregate concrete were studied. The compressive strength, chloride ion migration coefficient and micro pore parameters of recycled aggregate concrete were tested. The results showed that carbonation and dry-wet cycles can improve the pore tortuosity and reduce the connectivity of pores, while freeze–thaw cycles, coupling of carbonation and freeze–thaw cycles, and coupling of carbonation, dry-wet cycles and freeze–thaw cycles can significantly reduce the pore tortuosity and deteriorate the pore structure. The key reason for durability failure of recycled aggregate concrete in a complex environment is the increase of large pore volume fraction. When more factors are coupled, the increase in the pore volume fraction is greater. Based on the pore tortuosity and large pore volume fraction, an integrated pore index was proposed, and a prediction model of compressive strength and chloride ion migration coefficient of recycled aggregate concrete under complex environmental factors was established, which provided the basis to evaluate and maintain the durability of recycled aggregate concrete.