Pore structure evolution and chloride ion permeability of concrete under sulfuric acid

In the long-term use of underground reinforced concrete pipelines, the structure is subjected not only to high-frequency fatigue loads from external vehicles but also to the influence of internal corrosive environments. Although some studies have focused on the performance changes of concrete in corrosive environments, the quantitative research on the permeability and pore characteristics of concrete remains unclear. This study systematically analyzes the effects of corrosion duration on mass loss, volume loss, surface roughness, corrosion depth, and chloride ion permeability of concrete specimens through prolonged sulfuric acid corrosion experiments. The results indicate that both mass and volume loss rates of the concrete increase linearly with the corrosion duration, indicating a progressive structural degradation. Surface roughness measurements, conducted using laser 3D scanning technology, reveal a linear increase in roughness over time, with a corrosion rate of 0.0084 mm/d. Phenolphthalein solution tests show that corrosion depth also increases linearly over time, with a fitting variance of 0.97. Chloride ion permeability tests demonstrate a non-linear trend in diffusion coefficients, with an initial deterioration followed by optimization and subsequent overall degradation, but with a general linear increase, the equation is [[EQUATION]], with a fitting variance of 0.98. The findings indicate that corrosion leads to increased porosity, enhanced surface roughness, and greater chloride ion permeability, accelerating structural degradation. This study provides critical insights for the durability assessment and protective design of concrete in corrosive environments.