Study on the Frost Resistance of Concrete Modified with Waste Rubber and Fiber Synergy

Frost resistance is a key indicator of concrete durability in cold environments. To enhance performance, this study incorporated polymers and fibers to improve the frost resistance of concrete specimens. Firstly, the water–binder ratio and fly ash content were optimized. Then, waste rubber particles (WRs) and carbon fibers (CFs) were added to the concrete, and tests such as dry density, compressive strength, and resistivity under freeze–thaw cycles were conducted to explore the optimal proportion for improving the freeze–thaw durability of the concrete. Finally, the frost resistance performance of the concrete specimens is evaluated based on these parameters. Results showed that, compared to traditional concrete, specimens with 5% WRs and 0.3% CFs exhibited significantly higher compressive and flexural strengths. Scanning electron microscopy and resistivity tests show that the synergistic effect of WRs and CFs mainly enhances the freeze–thaw durability of concrete by optimizing its pore structure. Notably, adding 0.3% CFs increased compressive strength by 16%. These findings indicate that when adding WRs and fibers to concrete, the synergistic effect of the two significantly enhances the frost resistance and durability of the concrete. This not only enables the recycling of waste but also provides an effective strategy for producing durable and frost-resistant concrete in extremely cold environments.