Experimental study on indoor simulated deterioration of sandstone of Xiaofowan statues at Dazu Rock Carvings

The sandstone of Xiaofowan at Dazu Rock Carvings in China has severe weathering. To solve this problem, three experiments are set up based on the local environment: wetting-drying cycles, freeze-thaw cycles (saturated group and dry group) and acid rain cycles (pH=2.6, 4.1, 5.6). In this study, the mass, surface hardness and P-wave velocity are measured to explore the weathering degree of sandstone over multiple experimental cycles (for a total of 45 periods, 320 days), and the surface microstructure of the sandstone is photographed (60 times). The X-ray diffraction (XRD), scanning electron microscope (SEM) and water absorption are executed to analyze the weathering mechanism of sandstone. The color change is detected through the color difference tests. The experimental results show that the main damage phenomenon of the sandstone is granular disintegration. The primary bedding and argillaceous mass of sandstone are first affected by weathering. The mass, surface hardness and P-wave velocity of the sandstone gradually decrease. The damage by water is performed on the sandstone from the surface to the inside. The damage degrees affecting the sandstone weathering are in turn as follows: acid rain cycles, freeze-thaw cycles, wetting-drying cycles. Therefore, the results of this study may provide a basis for the protection of Xiaofowan statues at Dazu Rock Carvings.