Experimental Study on Salt-Bearing Sandstone Samples Under the Change of Temperature and Humidity Cycle

Salt crystallization is a common type of disease in grottoes. Due to the change in temperature and humidity, the soluble salt originally existing in sandstone will have a negative impact on the protection of rock relics. In this study, sandstone samples containing Na2SO4 solution and distilled water were used to study the difference in sample damage under the condition of temperature and humidity cycle changes. It was found that the damage degree of samples containing soluble salts was much higher than that of salt-free samples, especially under the influence of freeze-thaw cycles. With the increase of freeze-thaw cycles, the internal friction angle and wave velocity of sandstone decrease linearly, while the surface hardness, tensile strength, and cohesion decrease exponentially. In addition, the damage caused by freeze-thaw cycles and dry-wet cycles develops from the inside to the outside of the rock sample, which is manifested by the increase in the number of macropores and the emergence of new pores. The different combinations of several effects lead to different changes in pore structure and mineral composition of the samples under the four conditions. The research results are helpful in providing a scientific basis for the disease control of stone cultural relics.