Abstract: Datong city, where the Yungang Grottoes is located in, is an important coal producing and coal chemical industry base in China. The SO2 concentration in the Grottoes area exceeds the standard because of air pollution. The feldspar and calcareous cement, which are the main mineral compositions of the sandstone in Yungang Grottoes, are very sensitive to acid. A sulfuric acid solution and sand rock reaction test was carried out to simulate the rock degradation. To study the mechanism of Grottoes rock deterioration caused by sulfuric acid, three steps are included in the test: immersing the sandstone samples into static sulfuric acid solution of different pH values; measuring the solution’s pH value, the mass and wave velocity of sandstone samples during the tests; and comparing the changes of samples’ compressive strength and physical structure before and after the test. Test results show that the sulfuric acid poses very quick degradation on calcium cementation sandstones, and it mainly focuses on damaging the calcium cement. As the reaction cycle increases, the wave velocity declined markedly. Degradation by sulfuric acid is extremely serious on the surface layer of sandstone samples. With the loss of calcareous cement, the rock strength reduces significantly.

Key words: Yungang Grottoes, sandstone, sulfuric acid, degradation