Experimental and Numerical Study on Ultra-High Performance Concrete Repair of Uniformly Corroded Reinforced Concrete Pipes

This study investigates the deterioration of corroded reinforced concrete pipes and their restoration using ultra-high performance concrete (UHPC), utilizing Three-Edge Bearing Tests and 3D finite element analysis under uniform corrosion-induced wall thinning. Unrepaired pipes exhibit elastic behavior, crack propagation, and yield stages, with failure driven by concrete cracking and rebar yielding. UHPC repair mitigates load drop during crack propagation, extends the yield phase, and enhances plastic deformation capacity. Pipe load-bearing capacity is negatively correlated with corrosion thickness and positively correlated with repair thickness (R2 > 0.979) and repair compensation ratio. Interfacial performance analysis indicates natural bond degradation under sustained loading, transitioning the pipe to a unitized structure. Embedding steel nails significantly improves interfacial bond strength, increasing failure bearing capacity by 2.91 and 3.56 times compared to natural and PE film interfaces, respectively. Numerical simulations reveal that interface shear strength is five times more influential on bearing capacity decay than interface fracture energy, underscoring its critical role in durability design. An optimization strategy is proposed: reinforce stress-concentrated areas with nails to enhance shear strength and prioritize monitoring interfacial slip to ensure service safety.