Study on Salt Corrosion and Salt Freezing Resistance of Basic Magnesium Sulfate Cement Concrete

By adjusting the water-cement ratio and incorporating mineral admixtures such as fly ash and silica fume, basic magnesium sulfate cement (BMSC) concrete was prepared, and the concrete was immersed in a simulated natural salt lake brine solution. The salt corrosion resistance and salt-frost resistance of BMSC concrete were investigated, and the phase composition and microstructure of BMSC concrete after corrosion and freeze-thaw cycling were analyzed. The results showed that by controlling the water-cement ratio and adding mineral admixtures, optimizing the pore structure of the concrete, and reducing the porosity, the salt corrosion resistance and salt-frost resistance of BMSC concrete could be effectively improved. When the water-cement ratio was reduced from 0.5 to 0.3, the corrosion resistance coefficient increased from 0.64 to 0.88 after 420 days of immersion, and the number of salt-frost damage cycles extended from 75 to 175. The combined use of fly ash and silica fume achieved the best results, with the corrosion resistance coefficient reaching 0.98 and the number of salt-frost damage cycles extending to 250 in the BMSC50 (FS) group after 330 days of immersion. The damage to BMSC concrete in a salt solution environment is mainly physical damage. The invasion of salt ions into the concrete pores leads to crystallization reactions and generates crystallization pressure, which is the core cause of microstructural damage. The freeze-thaw damage of BMSC concrete in a salt solution is essentially a coupled effect of physical frost heaving and physical crystallization of salts.