Permeable Concrete Using Recycled Glass Aggregate Study on Freeze–Thaw Resistance at Different Moisture Contents

As a novel composite material, recycled aggregate permeable concrete effectively promotes the reuse of waste materials and serves as a key component in sponge city construction. In practical engineering applications, this material is rarely in a fully saturated state. To better simulate real-world service conditions, this study employed waste glass as recycled coarse aggregate to fabricate permeable concrete. Orthogonal experiments were conducted to optimize the mixture proportions and, based on the optimal mix design, the freeze–thaw resistance was evaluated under varying moisture content levels. The results show that recycled permeable concrete achieves the best freeze–thaw resistance when the water–cement ratio is 0.30, sand content is 6%, glass replacement rate is 25%, and the water-reducing admixture dosage is 0.2%. The glass aggregate replacement rate significantly influenced compressive strength, flexural strength, and impact resistance: as the replacement rate increased from 0% to 75%, compressive strength decreased by 33.32%, flexural strength declined by 41.39%, and the impact loss rate rose by 10.41%. Moreover, when moisture content increased from 0% to 100%, after 50 freeze–thaw cycles, the specimen mass loss rate increased by 1.22%, and the relative dynamic elastic modulus decreased by 5.43%. However, the relative compressive strength and relative flexural strength increased by 11.24% and 9.15%, respectively, indicating that the material still satisfies the essential performance requirements for permeable concrete. In conclusion, this study on the freeze–thaw resistance of recycled permeable concrete under different moisture conditions expands its application potential and provides a solid theoretical foundation and practical reference for the freeze-resistant design of new permeable pavement systems.