12-years bending tensile stress corrosion of high-performance concrete under high salinity brine conditions

Based on the comprehensive renovation project of Xining High-Speed Railway Station in China as the application background, this study investigated the high-concentration Na ⁺-Cl ^--SO ₄ ^2- type brine with a salt content of 180 g/L underground in the Xining Basin as the corrosion medium. Through the strength grade C40-C60 High-performance concrete (HPC) small beams (100 mm×100 mm×400 mm) and reinforced small beam components (85 mm×100 mm×500 mm, the thickness of steel reinforcement cover is 15 mm) with air-entraining agent, rust inhibitor and double-mixed air-entraining agent and rust inhibitor added, a 12-year stress corrosion test with a bending tensile stress level of 0–0.70 was carried out, and the changes of the strength, relative dynamic elastic modulus ( E _rd), resistivity of concrete and the natural potential difference of reinforced concrete beams were tracked and tested. The bending tensile stress corrosion behavior of plain HPC and reinforced HPC beams in high-concentration brine was studied. The research shows that in the high-concentration brine environment, under the 12-year bending tensile stress corrosion of the plain HPC at an initial bending tensile stress ratio of 0.30 and the reinforced HPC beams at an initial bending tensile stress ratio of 0.70, the E _rd of plain HPC and the reinforced HPC beams are always greater than 90 %, and the compressive corrosion coefficient ( K _c) of the plain HPC is always greater than 0.8. After 12 years of bending tensile stress corrosion, by using the method of natural potential double-electrode equivalent gradient and the method of concrete resistivity to judge the probability of reinforcement corrosion in the reinforced HPC beam is relatively low, indicating that even if the cover thickness is only 15 mm, the protection effect of HPC on reinforcement is still good. Therefore, reasonably designed plain HPC and reinforced HPC beams demonstrate high resistance to brine corrosion and stress corrosion, providing reliable durability for the comprehensive renovation of Xining High-Speed Railway Station and its underground engineering facilities.