Effect of the surface-area-to-volume ratio on dissolution and deterioration of acid-corroded sandstone

Abstract

This study investigates the impact of hydro-chemical action on the deterioration of physical and mechanical properties of rock, with a specific focus on sandstone subjected to HCl, and H2SO4 solutions with pH values of 2 and 5. The research explores the role of the surface-area-to-volume (SATV) ratios of 0.65 and 0.70 in influencing the dissolution and deterioration of sandstone. A chemical kinetic model is developed to explore the diffusion-dissolution mechanism. Following acid corrosion, the porosity of sandstone increases, marked by a decline in small pores (r ≤ 1 μm) and an increase in medium (1 μm < r < 10 μm) and large pores (r ≥ 10 μm). Furthermore, uniaxial compression tests reveal a reduction in peak strength and elastic modulus, an increase in peak strain, diminished brittleness, and enhanced ductility. The study underscores the substantial influence of the SATV ratio, particularly in the case of low pH values in HCl solutions. Following 150 days of corrosion by pH = 2 HCl solution under a SATV ratio of 0.70, the peak stress and elastic modulus decreased by 52.845% and 92.712%, and peak strain increased by 386.186%. The acid-rock reaction is characterized by diffusion and dissolution, with parameters exhibiting a negative correlation with the SATV ratio and a positive correlation with the pH value of solutions. The diffusion is more affected by the SATV ratio rather than the dissolution. The insights derived from this research have implications for the theoretical foundation of safety assessments and disaster prevention in practical engineering scenarios under acidic environments.