Enhancing chloride resistance of freeze–thaw affected concrete through innovative nanomaterial–polymer hybrid cementitious coating

Abstract The deterioration of concrete structures in cold marine environments presents a significant durability challenge, particularly due to the synergistic effects of chloride attack and freeze–thaw cycles. However, this problem has not been solved satisfactorily. This study explores an innovative strategy for improving concrete durability via the development of a nano- and polymer-modified cementitious coating system. The research team formulated a composite coating by incorporating precisely controlled concentrations (0.5–1.5 wt%) of nano-SiO 2 or nano-CaCO 3 with waterborne polyacrylate emulsion. Comprehensive experimental investigations were conducted on coated concrete specimens, including mass loss analysis, relative dynamic modulus of elasticity evaluation and Coulomb electric flux test during freeze–thaw cycles, and long-term salt solution immersion. The results demonstrate that the coating system exhibits a dual protective mechanism, effectively mitigating freeze–thaw induced damage while significantly enhancing the chloride resistance of concrete before and after freeze–thaw cycles. Microstructural analysis reveals that the synergistic combination of nanomaterials and polymer optimizes the pore structure of the coating, reducing total porosity and decreasing harmful and more harmful pore volume. Among the tested coating formulations, the 1.0 wt% nano-SiO 2 composite demonstrates superior performance, showing 68% improvement in chloride resistance and 2.27 times in ultimate freeze–thaw cycles compared to uncoated concrete.