PVA fiber-reinforced seawater sea-sand concrete under seawater freeze thaw cycles: Constitutive model and enhancement mechanism

Seawater sea-sand concrete (SSC), recognized for its cost-effectiveness and environmental benefits, has attracted growing attention in recent years. Previous studies have indicated that normal-strength SSC undergoes severe surface salt scaling and internal damage under seawater freezethaw cycles (FTCs). Against this backdrop, the present study investigates the effectiveness of polyvinyl alcohol (PVA) fibers in improving the seawater freezethaw resistance of normal-strength SSC through a series of physical, mechanical, and microstructural tests. Results demonstrate that the addition of PVA fibers alleviates the degradation in axial compressive strength and modulus of elasticity of SSC subjected to seawater FTCs. This enhancement is ascribed to the capacity of fibers to bear crystallization pressure from growing ice crystals, thereby inhibiting the expansion of capillary pore sizes from 5 to 550 nm to 550–5000 nm. Moreover, fiber incorporation markedly reduced surface salt scaling, which can be attributed to their ability to resist the glue-spall stress imposed on the surface cement paste by cracking sea ice. Based on these results, a PVA fiber content of 0.12 vol% is recommended for optimizing the seawater freeze–thaw resistance of normal-strength SSC. Constitutive models are further developed to support structural design and numerical simulation.