Concrete degradation mechanisms by sulfuric acid attack

Abstract

Concrete degradation may occur from biochemical processes, especially in the case of sewage system networks, owing to the production of biogenic sulfuric acid by certain types of bacteria. This study aims to investigate the residual mechanical properties of concrete exposed to sulfuric acid solutions of different concentrations (0·5%, 1% and 3%). Two concretes were produced: a standard concrete, with a water/cement (w/c) ratio of 0·83, and a high-performance one, with w/c of 0·28. The samples were cured for 28 d and evaluated for immersion periods of 28 and 84 d. During immersion, changes in pH and the weight loss of the specimens were monitored. After immersion, the residual mechanical properties were evaluated by compressive and splitting tensile tests. Composition and microstructural changes were evaluated by phenolphthalein solution, X-ray diffraction and scanning electron microscopy. Results show a higher mass loss in the concrete specimens with a higher percentage of cement, as well as a greater percentage reduction of the mechanical strength.