Performance regulation mechanism and environmental impact of low-carbon repair materials under synergistic effect of hollow silica microspheres and domestic PVA fibers

Bridge expansion joints and bridge deck pavement layers are prone to shrinkage-induced cracking, delamination, and poor durability, and often require frequent maintenance under traffic loading. This study aims to develop high-strength, low-shrinkage low-cost, and low-carbon composite materials for bridge repair and reinforcement. Twelve sets of repair materials with different proportions were designed and prepared, with a focus on evaluating the fluidity, mechanical properties, drying shrinkage, mass loss, production cost, energy consumption, and carbon emissions of the repair materials. The study systematically investigated the influence mechanism of hollow silica microspheres (HSM) and domestic polyvinyl alcohol (PVA) fibers on the performance of repair materials. The test results showed that with an appropriate amount of HSM added, the material becomes more compact internally. Incorporating 20% HSM can significantly improve the performance of the repair material, with flexural strength increased by 14.04%, compressive strength increased by 31.96%, and tensile strength increased by 35.56%. After incorporating multi-scale PVA fibers, the mechanical properties of the repair material are significantly improved. When 12 mm and 3 mm PVA fibers were combined, the 28 d tensile strength can reach 7.42 MPa, the flexural strength was 11.3 MPa, and the compressive strength was 44 MPa. Compared with ECC of the same strength, its production costs, energy consumption, and carbon emissions are significantly reduced, showing good economic and environmental benefits. The research results confirm that by optimizing the content of HSM and the mixing ratio of domestic PVA fibers, a balance between mechanical properties, environmental sustainability, and engineering costs of repair materials can be achieved, providing effective material support for bridge repair and reinforcement projects.