Macroscopic mechanical and microscopic characteristics variations of red sandstone from Qinghai Province with solution erosion

To understand the macroscopic mechanical characteristics of red sandstone and its microscopic damage mechanism with complex chemical environments, this study investigates the chemical corrosion behavior of red sandstone from Qinghai Province. The research focuses on the effects of Na₂SO₄ solutions and distilled water at varying pH levels (2, 7, and 12). Using uniaxial compression, nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) analyses, the results demonstrate significant alterations in the mechanical properties of red sandstone. Specifically, there is a 29.20% reduction in the modulus of elasticity in acidic environments, a 24.63% reduction in alkaline environments, a 23.99% reduction in neutral salt solutions, and a 20.25% reduction in distilled water after 40 days. The study provides detailed insights into the role of ion exchange and salt crystallization, revealing that calcium sulfate precipitates form primarily under acidic conditions, but they are also present in two other salt solutions. Crystallization processes occur in all three salt solutions, highlighting the intricate interplay between mineral dissolution, ion exchange, and crystallization. These findings offer a deeper understanding of the water–rock reaction mechanisms affecting red sandstone. The outcomes of this research are crucial for developing strategies to mitigate chemical erosion in geotechnical engineering, especially for infrastructure exposed to industrial pollution and harsh chemical environments.