Evolution of mechanical properties of recycled rubber aggregate alkali‐activated slag concrete subjected to freeze–thaw cycling

Abstract To investigate the evolution of mechanical properties of recycled rubber aggregate alkali‐activated slag concrete (RA‐AASC) under freeze–thaw cycles, cube compressive strength tests, splitting tensile strength tests, and SEM examination were conducted by considering the number of freeze–thaw cycles, coarse rubber aggregate (CRR), and fine rubber aggregate (FRR) as variables. The results indicate that both the cube compressive strength and splitting tensile strength of RA‐AASC decrease at an accelerated rate with increasing freeze–thaw cycles, and the tensile performance is more sensitive to freeze–thaw damage. A 50% replacement ratio of FRR can inhibit strength loss within a certain number of freeze–thaw cycles, whereas an excessive replacement ratio accelerates deterioration. CRR has a significantly greater adverse effect on the mechanical properties of RA‐AASC than FRR, and the combined incorporation of CRR and FRR offsets the beneficial effect on freeze–thaw damage resistance. Microscopic analysis shows that fine rubber particles can fill pores and buffer frost‐heaving stress, while CRR weakens the aggregate skeleton and intensifies interfacial debonding, which are the main microscopic mechanisms responsible for the differences in mechanical performance.