Performance assessment of novel high-performance waterproof concrete developed by different admixtures in chloride and stray current coupling environment

Underground reinforced concrete (RC) subway structures in coastal areas are subjected to prolonged exposure to chloride diffusion and stray current environments, posing serious challenges to their durability. Herein, this study designed new high-performance waterproof concrete (HPWPC) made by cement, fly ash (FA), ground granulated blast furnace slag (GGBFS) and a novel cementitious capillary crystalline waterproofing materials (CCCW) developed by our research group, and then investigated the performance development of HPWPC under coupled corrosion environments with chloride diffusion and stray current, incorporating different chloride concentrations (1 % and 5 %) and rebar corrosion rates (0 %, 2 %, 4 %, 6 %, and 8 %). Firstly, this study assessed compressive strength, split tensile strength, water permeability, chloride penetration resistance, concrete time-dependent strain, electrochemical impedance spectroscopy (EIS) and rebar pull-out bond-slip behavior. Finally, the degradation and reinforcement mechanisms were analyzed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and mercury intrusion porosimetry (MIP). The results indicate that adding CCCW and FA/GGBFS obviously improves the mechanical properties and durability of concrete. The optimal performance of concrete was achieved by replacing 45 % of ordinary portland cement (OPC) with 25 % FA and 20 % GGBFS, and adding CCCW equivalent to 4.5 % of the cement content. Additionally, compared to plain concrete, the 7-days compressive strength increased by 9.97 %, the 28-days compressive strength improved by 4.40 %, the 28-days split tensile strength increased by 51.09 %, the water permeability pressure increased by 300 %, the chloride migration coefficient decreased by 94.38 %, and the ultimate bond strength improved by 30.08 %. Additionally, the specimens incorporating a combination of FA/GGBFS and CCCW show higher polarization resistance. SEM-EDS analysis revealed a compact matrix with abundant calcium silicate hydrate (C-S-H) gels encapsulating ettringite (AFt) phases in HPWPC, and MIP results indicated that the porosity of uncorroded specimens and RC specimens subjected to 16-days electrochemical corrosion in 1 % and 5 % chloride concentrations were 2.509 %, 4.643 % and 4.833 %, respectively. More importantly, HPWPC shows greater economic potential and a lower environmental burden. Overall, this study provides new design insights and valuable experimental data for the optimization and design of high-performance waterproof RC structures in complex corrosive environments. • Developed high-performance waterproof concrete (HPWPC) using FA, GGBFS, and CCCW. • Coupled Cl⁻ corrosion and stray current environments was simulated in labs. • HPWPC show higher Cl⁻ diffusion resistance, mechanical strength and lower porosity. • CCCW/FA/GGBFS improve ion conduction resistance and rebar polarization resistance. • Optimized mix design reduced OPC content by 49.45 % with enhanced economic potential.