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Received Jan 23, 2018; Accepted Mar 31, 2018
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1. Introduction
Aggressive sulfuric acid is mainly derived from acid rain, industrial environment, and sewage treatment systems [1–4]; further, the physical and chemical reactions between aggressive sulfuric acid and cement hydration products are primary reasons for durability failure of concrete structures [5]. For example, the pH value of inner concrete decreases in a sulfuric acid corrosion environment, which leads to the destruction of the passive film on the surface of reinforcement steel bars, followed by severe steel bar corrosion. Previous studies have shown that water-cement ratio, pH value, type and proportion of cement, coarse aggregate content, mineral admixture, and other factors have important effects on the sulfuric acid corrosion mechanism for concrete [6–13]. In fact, these factors will affect the pore structures of concrete, and the change of pore structures will significantly affect the transport performance of concrete [14–17], which results in a decline in concrete resistance to sulfuric acid corrosion. Being different from the mechanism of sulfate attack on concrete [11, 12, 18, 19], the sulfuric acid corrosion mechanism for concrete is the result of a combined action of dissolved corrosion caused by hydrogen ion (H+) and expanded corrosion caused by SO42− (sulfate ion) [20]. This finding led Böhm et al. [21] to propose a moving boundary diffusion model, which can be used to predict sulfide corrosion rate for concrete. Böhm et al. [21] also studied the influencing factors of sulfuric acid corrosion rate. Based on this, Böhm et al. [22] and Jahani et al. [23] predicted sulfuric acid corrosion rate and corrosion layer thickness for concrete and cement mortar through applying the moving boundary diffusion model [21], which were also verified by experiments. Overall, the sulfuric acid corrosion mechanism for concrete is complicated. This mechanism has been studied by different researchers from different aspects; however, differences between these research results still exist. Therefore, the prediction model for concrete corrosion due to sulfuric acid needs to be further studied.
Based on the theory of reaction boundary layer, this paper presents a sulfuric...