Response of Concrete to Sulfuric Acid Attack

Abstract

The response of four different concrete mixes to sulfuric acid attack was evaluated in an accelerated laboratory test program. Small test specimens cut from standard concrete cylinders and a 1 percent sulfuric acid solution with a pH of 1 were used in the test program. Changes in weight and thickness of the test specimens were used as physical indicators of the degree of deterioration, while increase in sulfur content of the test specimens was used as a chemical indicator of the degree of deterioration. The study shows that all three indicators of deterioration are effective measures of concrete response to the acid attack. However, the study suggests that the increase in thickness (expansion) of small specimens (with large surface area-to-volume ratios) may be a more consistent measure than the weight loss of larger specimens when comparing the effects of different sulfuric acid concentrations on concrete. Photomicrographs of the concrete microstructure show that the concrete deterioration starts from the acid-exposed surface and progresses inward. The degree of concrete deterioration is increased by alternate wet-dry cycles of exposure to sulfuric acid. The rate of concrete deterioration along the penetration depth of sulfuric acid could be described by a variation in sulfur concentration with the depth of acid penetration.