Study on failure characteristics of concrete under simulated acid rain based on nondestructive computed tomography

As the 21st century progresses, industrial development and increasing energy demands have intensified the problem of acid deposition. Over time, the degradation of concrete caused by acid deposition-induced corrosion has become a widely observed issue. However, the impact on the structure and mechanical properties of concrete using nondestructive techniques has not been deeply studied. In a laboratory setting, simulated acid rain solutions with pH values of 0.0, 1.0, and 2.0 were prepared using sulfuric acid to accelerate the corrosion of concrete cubes over periods of 7, 14, 21, and 28 days. Compressive tests were conducted on the corroded concrete cubes, and Computed Tomography (CT) scans were performed both before and after compression failure. Image processing techniques, including various CT thresholds and gray values, were employed to accurately differentiate between substances. This allowed for the detailed observation of the corroded concrete structure in both 2D slices and 3D reconstructions. The results clearly indicate that simulated acid rain significantly impacts the structure and mechanical properties of concrete. Simulated acid rain increases pore heterogeneity, as well as the number and area of pores at different levels. The corrosion layer formed significantly alters the failure mode, with compressive failure primarily occurring within this layer. The cubic compressive strength is highest in concrete soaked in pure water, but it decreases linearly with increasing corrosion time and acid concentration. The main factors leading to the reduction in concrete strength are the formation of the corrosion layer and the increase in pore area due to corrosion. • Using computed tomography (CT) technology for quantitative analysis of corroded concrete. • Studying the impact of simulated acid rain on concrete pore parameters from a non-destructive perspective. • Determining the reasons for the reduction in concrete compressive strength through CT scanning before and after failure.