Response of Concrete to Incremental Aggression of Sulfuric Acid

There is lack of standardized tests for specifically evaluating the resistance of concrete to sulfuric acid attack, which has caused great variability, for example, in terms of solution concentration, pH level/control, etc., among previous studies in this area. Accordingly, there are conflicting data about the role of key constituents of concrete (e.g., supplementary cementitious materials [SCMs]) and uncertainty about building codes' stipulations for concrete exposed to sulfuric acid. Hence, the aim of this study was to assess the behavior of the same concretes, prepared with single and blended binders, to incremental levels (mild, severe, and very severe) of sulfuric acid solutions over 36 weeks. The test variables included the type of cement (general use [GU] or portland limestone cement [PLC]) and SCMs (fly ash, silica fume, and nanosilica). The severe (1 %, pH of 1) and very severe aggression (2.5 %, pH of 0.5) phases caused mass loss of all specimens, with the latter phase providing clear distinction among the performance of concrete mixtures. The results showed that the penetrability of concrete was not a controlling factor under severe and very severe damage by sulfuric acid attack, whereas the chemical vulnerability of the binder was the dominant factor. Mixtures prepared from the PLC performed better than those prepared from GU. While the quaternary mixtures that consisted of GU or PLC, fly ash, silica fume, and nanosilica showed the highest mass losses after 36 weeks, the binary mixtures incorporating GU or PLC with fly ash had the lowest mass losses.