Enhancing concrete's resistance to sulfate corrosion: Comparative study of silane surface protection and polyvinyl alcohol aggregate encapsulation

The marine environment is rich in ions, with sulfates posing a particularly severe threat to concrete. To enhance the durability of concrete in the ocean, this study enhances concrete's resistance to sulfate attack by coating aggregates with polyvinyl alcohol (PVA) films and comparing the results to those obtained using silane-based hydrophobic agents. Over a 300-day corrosion period, we evaluated damage morphology, crystalline changes, ultrasonic velocity, and compressive strength by SEM, XRD and ultrasonic tester. The findings reveal that PVA-coated aggregates increase the density of the interfacial transition zone, thereby improving the concrete's impermeability and reducing calcium hydroxide consumption. Furthermore, the enhanced bonding between the aggregate and the matrix provided by PVA results in superior resistance to sulfate attack compared to silane treatments. The paper also categorizes sulfate erosion into 4 spatial regions and 6 temporal phases combining macroscopic ultrasonic velocity and microscopic product. This study offers valuable theoretical guidance for improving concrete's sulfate resistance.