Experimental Investigation on Freeze–Thaw Durability of Polyacrylonitrile Fiber-Reinforced Recycled Concrete

As a building material, recycled concrete (RC) has significant advantages in environmental protection and sustainable development. In the cold conditions of northwest China, in order to maintain the toughness and durability of buildings during service, polyacrylonitrile fiber (PANF) is often used as a toughening agent with RC. In this study, mechanical tests and frost durability tests were conducted on polyacrylonitrile fiber-reinforced recycled concrete (PAN-RC). The mixing contents of PANF were 0.7 kg/m³, 0.8 kg/m³, and 0.9 kg/m³, while the substitution rates of recycled coarse aggregate (RCA) were 30%, 40%, and 50%. The experimental results indicate that the incorporation of PANF into recycled concrete significantly improves the mechanical properties and frost resistance durability of the material. From the test results, the freezing resistance of concrete is the best when the replacement amount of RCA is 40% and the amount of PANF is 0.8 kg/m³. Meanwhile, a freeze-thaw damage model for PAN-RC was developed based on experimental research. This model is feasible to predict the freeze-thaw damage degree of fiber-reinforced recycled concrete under various replacement rates of RCA and different dosages of PANF. It is considerable significant for both theoretical understanding and practical engineering applications of RC.