The inherent defects of recycled coarse aggregate (RCA) lead to poor frost resistance in recycled aggregate concrete (RAC), limiting its application in cold coastal regions. Waste polypropylene fibre (WPF), utilized as a reinforcement material, can improve the frost resistance of RAC. This study systematically analyzes the influence of WPF on the frost resistance of RAC and establishes a life prediction model. The results indicate that the damage to concrete in a saline freeze–thaw environment is significantly greater than that in a freshwater environment. WPF mitigates the development of freeze–thaw damage in RAC effectively by bridging microcracks and segmenting interconnected pores, thereby optimizing the pore structure and enhancing the matrix compactness. After 125 freeze–thaw cycles, the attenuation amplitude of the relative dynamic elastic modulus (RDEM) for RAC incorporated with WPF decreased by 9.69% and 5.77% in freshwater and saline environments, respectively, while the compressive strength increased by 20.65% and 18.57%. Concurrently, the negative mass growth rate of RAC in freshwater decreased by 20.62%, and the mass loss in the salt solution decreased by 5.84%. Furthermore, life predictions based on both RDEM and the compressive strength loss rate demonstrate that WPF extends the service life of RAC. Notably, the RDEM-based prediction yields a longer life but corresponds to a larger strength loss, whereas the prediction based on the compressive strength loss rate, although slightly shorter, corresponds to a more stable residual strength.
Yang et al. (Thu,) studied this question.