Effect of PVA fibers on durability of nano-SiO2-reinforced cement-based composites subjected to wet-thermal and chloride salt-coupled environment

Marine engineering structures are often faced with complex environmental factors. It is the focus of current research to modify cement-based composites (CBCs) to achieve their high durability in complex environments such as seawater. In this study, the effect of polyvinyl alcohol (PVA) fibers on durability of nano-SiO (NS)-reinforced cement-based composites was investigated by simulating seawater environment and taking PVA fiber content as variable. In addition, based on the probability distribution model, the damage degree of NS and PVA fiber-reinforced cement-based composites (NFRCCs) subjected to wet-thermal and chloride salt-coupled environment (WTCSE) after 300 freeze–thawing cycles (FTCs) was predicted. The test results demonstrated that the NFRCC exhibited the most excellent durability subjected to WTCSE when the content of PVA fibers was 1.2%. Compared with the reference group only doped with NS subjected to WTCSE, its impermeability pressure increased by 150%, the chloride ion electric flux decreased by 31.71%, the compressive strength loss rate decreased by 19.00% after 125 FTC, and the compressive strength corrosion resistance coefficient of chloride salt erosion increased by 9.15% after 25 wetting–drying cycles. The predicted results of the probability distribution model indicated that the damage degree of NFRCC subjected to WTCSE after 300 FTC would not exceed 0.35. The microscopic test analysis showed that the incorporation of PVA fibers reduced the proportion of large pores and the overall porosity of NFRCC subjected to WTCSE. PVA fibers bridged microcracks while adsorbing NS and its hydration products, thus enhancing the adhesion of the substrate. This study provides a reference for the research of high-performance CBC in complex environment.