Early crack resistance and interfacial properties of recycled aggregate concrete reinforced with basalt fibre: value-added utilisation of solid construction waste

Cracks that appear during the initial setting and hardening stage of concrete can compromise the durability and service life of structure. The focus of this study was on the crack-resistance properties of recycled aggregate concrete (RAC) doped with basalt fibre (BF) reinforcement to enhance its early-stage crack resistance. By investigating the relationship between recycled fine aggregate (RFA) content and BF volume fraction, intrinsic connections among mechanical properties, drying shrinkage and the crack resistance of RAC were revealed. The results showed that incorporating BF at 0.2% by volume significantly enhanced the RAC's mechanical properties, regulated drying shrinkage and reduced early-stage cracking. The improvement became more pronounced with higher contents of RFAs. For the mix with 100% RFA, the addition of BF at 0.25% by volume reduced the total crack area per unit area of test specimens by 85.4% and decreased the maximum crack width by 60.1%. Combining grey correlation theory with the microhardness distribution at the RFA–mortar interface, the correlation ranking for crack resistance in RAC was found to be drying shrinkage strain > flexural–compressive ratio > tensile–compressive ratio > splitting tensile strength. BF locally reinforces cement paste, leading to a relatively uniform stress distribution. During cracking, BF effectively dissipates energy, mitigating the cracking risk associated with high contents of RFAs.