Performance Evolution and Chloride Adsorption Efficiency of Seawater Mixed Cement-Based Materials Subjected to Ohmic Heating Curing under a Severely Cold Environment

Abstract

Many coastal areas in cold regions are suffering from the concrete construction crises due to lack of freshwater and inhibition of hydration reaction under negative temperature. In this research, ohmic heating (OH) curing has been proposed to prepare carbon fiber strengthening seawater cement mortar (CF-SWCM) at −20°C. Two-day OH-cured CF-SWCM at −20°C endowed the compressive strength of 61 MPa, gaining an increase of 50.2% with three-day room temperature (RT) cured freshwater sample. Further, 28-day compressive strength results revealed the priority of OH curing and seawater mixing on accelerating the early-age strength development without scarifying long-term strength. Moreover, microscopic examinations indicated that OH curing could improve the hydration degree and achieve refinement of a C-S-H structure with higher mean chain length in CF-SWCM. Besides, two-day OH-cured CF-SWCM exhibited great potential on immobilizing free Cl− with the binding ratio of 35%, meeting an increase of 100% with that of three-day RT-prepared CF-SWCM. The detailed mechanism behind the advantage of OH curing on improving binding efficiency and distribution homogeneity of Cl− was also clarified based on the alternative electric field generated by OH curing. This work highlights the specific effect of OH curing on immobilizing free Cl− inside seawater-mixed cement mortar, making a breakthrough toward coastal concrete construction in a cold region with promising performance.