Mechanism of Salt Swelling Weathering of Sandstone Subjected to Cyclic Imbibition of Saline and Drying

Investigating the pore structure modification and damage features of porous rocks under cyclic imbibition of saline and drying is the premise of building up a full picture of rock weathering. In this study, we designed the experiments on the imbibition-drying cycle under 6 concentrations of Na₂SO₄ solutions, and tested difference in dry mass, imbibition mass, P-wave velocity, NMR T₂ spectrum and three-dimensional morphology in sandstone after 30 cycles. The following conclusions were obtained: ①During the imbibition-drying cycle, the salt crystals initially blocked the pores, and the crystals continued to accumulate, which ultimately led to the destruction of the pores and the gradual deterioration of the physical properties of the sandstone. With the increase in number of cycles, the test parameters such as difference in drying mass, imbibition mass and P-wave velocity of sandstone exhibited a three-stage variational trend.②The rate of variation in above test parameters at each stage is proportional to the concentration.③The crystallization occurs in both capillary imbibition and drying. With the increase in cycles numbers, the generation, accumulation, recrystallization and enlargement of crystals contributes to mineral grains shedding on the surface of sandstone. The morphology was proportional to the number of cycles and solution concentrations.