Mixture optimization of marine concrete with composite expansive CPA: durability and carbon‑footprint assessment

This study optimized the proportions of expansive and filler components in corrosion-resistant preservative admixtures (CPA) and evaluated their performance via compressive strength ratio, expansion behavior, corrosion resistance coefficient, and relative chloride diffusion coefficient. The effects of CPA dosage on concrete workability, strength, chloride and sulfate resistance, and economic-environmental benefits were further investigated. The EB50S50 formulation achieved the best overall balance, with 7 d/28 d compressive strength ratios of 94.0%/103.4%, a 28-d expansion rate of 0.189%, a corrosion resistance coefficient of 1.09, and a relative chloride diffusion coefficient of 0.81. At a water-to-binder ratio of 0.35, the 10% CPA group attained a 60-d compressive strength of 79.3 MPa, a 20.6% reduction in electric flux, and sulfate resistance coefficients of 104% and 97% after 60 d and 120 d of wet-dry cycling. Carbon emission per unit volume decreased from 362.13 to 352.18 kg CO2/kg with increasing CPA dosage; the 10% group reduced strength-normalized carbon emission by 6.68% and recorded the largest radar chart area (1.209). Field verification confirmed good construction adaptability and durability, with a slump loss of only 7 mm and a 20.0% lower 56 d electric flux. A dosage of 10% is recommended as optimal.