Durability of prestressed high-strength concrete (PHC) piles in landfill leachate: Corrosion behavior, microstructural evolution, and structural integrity assessment

This study investigates the corrosion behavior of prestressed high-strength concrete (PHC) piles in the aggressive environment of landfill leachate, with a focus on mechanisms and durability implications. Through accelerated corrosion tests simulating 50 years of service, the research reveals a critical overlooked factor in traditional durability analyses: the uneven layered microstructure of PHC piles induced by centrifugal force during manufacturing. Chloride ion concentration in concrete progressively increased to 0.065–0.072 % post-corrosion, accompanied by a corrosion potential drop to −341 mV. Despite minor surface rusting of reinforcement, the tensile strength of prestressed steel bars decreased by only 2 %, while concrete retained compressive strengths of 79.0–80.1 MPa-still meeting design specifications. Advanced analyses (XRD, SEM, MIP, X-CT) identified ettringite formation and a distinct pore gradient between inner and outer concrete layers, a direct result of centrifugal casting. The outer layer exhibited lower porosity (3.59–3.70 %) compared to inner regions (4.86–5.90 %), enhancing resistance to ion ingress. Finite element analysis confirmed that PHC piles maintained structural stability under design loads, with post-corrosion effective stress at 51.79 MPa and a safety margin of 21.11 MPa. These results demonstrate that the centrifugally induced layered microstructure plays a critical role in mitigating corrosion propagation. The findings provide a revised durability evaluation paradigm for PHC piles and offer scientifically grounded criteria for landfill foundation design.