Structural Rehabilitation of Corrosion-Thinned Reinforced Concrete Pipes: Experimental Investigation of HP-ECC Lining Systems for Pipe Restoration

Aging urban drainage systems face significant corrosion challenges, necessitating advanced trenchless rehabilitation. This study investigates the restoration of corrosion-thinned reinforced concrete pipes using high-performance engineered cementitious composites (HP-ECC) via cementitious lining. Through experimental modeling and a controlled-variable approach, we evaluated the effects of corrosion severity, repair layer thickness, and interface treatment on load-bearing capacity. Key findings include the following: (1) corrosion-induced wall thinning compromises RC pipe integrity, with deeper corrosion intensifying material degradation and structural deformation, reducing load-bearing capacity due to impaired strain compatibility; and (2) HP-ECC enhances cracking and ultimate load capacities, achieving 7-day flexural and compressive strengths of 75.9% of 28-day values, with ductile microcrack propagation improving durability. Load-bearing capacity correlates linearly with repair layer thickness. (3) PE film adhesion reduces load-bearing capacity compared to naturally bonded interfaces, increasing delamination risks due to weakened bonding; and (4) interfacial nail insertion strengthens the composite structure, yielding up to 2.92 times higher load-bearing capacity, enabling thinner repair layers without compromising hydraulic efficiency. These findings support bond-enhancing techniques, such as nail insertion, for optimizing the rehabilitation of corroded RC pipes, ensuring robust and durable urban infrastructure restoration. Future work will quantify irregular corrosion effects and develop thickness design methods for localized defects.