Chloride resistance of prestressed high-strength concrete pipe piles subjected to different curing conditions and chloride concentrations

Prestressed high-strength concrete (PHC) pipe piles are widely used in coastal regions, but chloride ingress in marine environments threatens their durability and structural safety. This study examines the effects of different curing methods, normal, steam, and high-temperature autoclave, on the chloride resistance of PHC concrete using electric flux test. A critical chloride concentration of 4.5% was identified, and accelerated deterioration tests were conducted to evaluate compressive strength loss under varying curing conditions. Phase production and microstructural analyses were also performed to reveal the mechanisms behind different curing conditions. Results indicate that steam and autoclave curing enhance cement hydration and initial mechanical properties of PHC but increase its permeability and susceptibility to chloride ion penetration compared to normal curing. Chloride penetration is the most severe at moderate chloride concentrations (~4.5%), with higher levels showing reduced ion migration. Although intensive curing improves early strength and stiffness, it accelerates mechanical degradation under chloride exposure, highlighting a trade-off between short-term performance and long-term durability.