Study on the mechanical properties and sulfate resistance of desert sand-supersulfated cement mortar with different curing methods

Desert sand supersulfated cement (DS-SSC) mortar suitable for western saline-alkali environments was designed using desert sand (DS) and supersulfated cement (SSC). The production process of SSC reduces carbon emissions and saves energy, and its excellent resistance to sulfate erosion is highly compatible with the building needs of western saline-alkali areas. At the same time, the western region contains abundant DS resources, and the use of local materials has reduced transportation costs, making up for the shortage of natural sand resources. This article investigates the effects of DS content and early curing methods on the mechanical properties and sulfate resistance of DS-SSC mortar, and analyzes its degradation mechanism. The results showed that 25 % DS reduced the porosity of DS-SSC mortar, improved its mechanical strength and salt erosion resistance. After 28 d of standard curing, the compressive strength was 34.4 MPa, which increased to 53.3 MPa after 28 d of MgSO4 erosion. Hot water curing accelerates hydration and promotes the transformation from larger to smaller pores, while carbonization curing leads to the decalcification of C-S-H gel, which destroys the network structure and leads to the transformation from smaller to larger pores. The main erosion product of MgSO4 is gypsum, which is initially fill but later expand. The salt erosion coefficient of SC-S25 was 1.55 at 28 d and decreased to 0.97 at 180 d. Carbonized mortar undergoes secondary decalcification under sulfate erosion, resulting in a weakened internal structure. The salt erosion coefficient of CC-S25 at 180 d is only 0.61.