Impact of Acid, Salt, and Wetting-Drying Cycles on Weathering Deterioration of the Red Sandstone Used for Leshan Giant Buddha China

The red sandstone of the well-known Leshan Giant Buddha is currently undergoing a severe deterioration threat such as frequent wetting-drying cycles, seasonal and occasional acid rain, and widespread sulfate attacks. The variations in the physical properties of the red sandstone and the hydrochemistry of the soaking solution through an accelerated simulation experiment were comprehensively analyzed in the present manuscript, aiming to investigate and gain insights into environmental weathering impact and deterioration mechanisms on the Leshan Giant Buddha. The results presented that the wetting-drying cycle would significantly decrease the physical and mechanical performances of the red sandstone due to the water-rock interaction and the acid or salt compound undoubtedly aggravated this deterioration process. Thereinto, acid corrosion promptly occurred on the surface of red sandstone and ceased upon depletion of the acid compound, which was deemed as a short-term corrosion, while the sulfate attack was a long-term and repeated process damage caused by the swell stress from salt crystallization. Furthermore, a synergistic and mutually reinforcing relationship was established among the coupling actions of water-rock erosion, acid rain corrosion, and sulfate attack, resulting in serious weathering and deterioration that compromised both the historical and cultural significances of the Giant Buddha statue. According to the findings from this work, the application of appropriate weathering prevention materials for waterproofing and desalination should be considered to safeguard the red sandstone, while the optimization of diversion ditches and reconstruction of the covering buildings were the key to prevent the world heritage site Leshan Giant Buddha.