Simplified Assessment Method of Sulfate Ion Diffusion Coefficient in Concrete

Abstract

Due to the widespread use of concrete in construction, the durability of concrete structures is of utmost importance. One of the major factors that can significantly impact the longevity of concrete is sulfate attack. However, there is a lack of sufficient data on the measurement of sulfate diffusivity in cement-based materials, making it difficult to accurately predict and prevent this type of deterioration. To bridge this gap, an experimental study was conducted to investigate the diffusion of magnesium sulfate ions in concrete. The study analyzed the effect of various factors, such as cement content, water-cement ratio, C3A percentage, hydrostatic pressure, curing age, and specimen size, on sulfate ion diffusion. The experiment involved measuring the concentration of magnesium sulfate ions using titration tests at different depths and ages of up to 450 days of sulfate attack. To estimate the diffusion coefficient of sulfate ions, the researchers utilized a solution of the nonlinear parabolic partial differential equation through the error function method, which provided a simplified model. This model considers the three main factors affecting sulfate diffusivity, namely, cement content, water-cement ratio, and C3A percentage. The proposed model shows a good simulation of sulfate ion ingress in concrete compared with previously published models, with the best mean value by 0.987 and the lowest standard deviation by 0.053. The model was further improved by considering the impact of water hydrostatic pressure, exposure area depth ratio of the concrete specimen, and curing age on sulfate.