Uniaxial tensile stress–strain behavior of seawater sea-sand recycled aggregate concrete: influences of sea-sand replacement ratio and curing age

This study investigates the uniaxial tensile behavior of seawater sea-sand recycled aggregate concrete (SSRAC) considering sea-sand replacement ratios (0%–100%), curing ages (7–360 days), and curing environments (standard and seawater immersion). Uniaxial tensile tests and microstructural analyses (SEM, XRD, MIP) were conducted. The results show that at a 100% sea-sand replacement ratio, the tensile strength, peak strain, and elastic modulus increase by 13.61%, 11.56%, and 8.20%, respectively. Short-term seawater immersion curing slightly enhances the tensile properties, whereas long-term immersion led to a decline in peak stress and elastic modulus due to an increase in harmful pores. Microstructural analysis revealed that salt ions in sea-sand accelerated cement hydration and formed Friedel’s salt, which filled the pores, but harmful pore volume fraction rises with age. A predictive model for the uniaxial tensile stress-strain curve of SSRAC, applicable to different sea-sand replacement ratios and curing ages, was established.