Predicting Service Life of Concrete Structure Exposed to Sulfuric Acid Environment by Grey System Theory

This paper investigated the sulfuric acid resistance of concretes with fly ash (FA) replacement ratios of 0, 20, 30 and 40% and coated with two types of concrete surface coatings. As an index for degree of acid corrosion, the acidification depth with corrosion time was evaluated by an accelerated laboratory test. The test program involved continuous acid immersion of specimens and alternate wet–dry cycles of acid exposure of other specimens. The relations between the acidification rate coefficient, its FA replacement as well as the pH value of the acidic exposure solution was investigated while assuming Fick’s 1st law of diffusion. The grey model (GM) for concrete acidification prediction was established by adopting the grey system theory, which comprehensively considered the effects of the FA replacement and pH value of acid. The GM model was then applied to predict the impact of pH value, thickness of concrete cover and surface coatings on the service life of concrete structure in different sulfuric acid environments. It was found that the concrete deterioration due to alternate wet–dry cycles of exposure to acid is more severe than continuous acid immersion, and the water-based protective coatings for as-cast finish concrete (PCC) and the deep penetrating sealer (DPS) were highly effective in reducing the acid attack. Compared with the increase of the thickness of concrete cover, the application of the PCC and DPS coatings significantly extended the service life of concrete.