Resistance of self-consolidating concrete to sulfuric acid attack with consecutive pH reduction

Self-consolidating concrete (SCC) is increasingly being used in numerous concrete applications some of which are vulnerable to sulfuric acid attack. The mixture design of SCC is different than that of normal concrete, and thus its long-term durability characteristics are still uncertain. This study aims at investigating the resistance of a variable range of SCC mixture designs to sulfuric acid attack. The main test variables include the cementitious materials type (single, binary, ternary and quaternary binders), the sand-to-total aggregates mass ratio, and the inclusion of fibre reinforcement (single and hybrid). The investigation comprised two consecutive 6-week phases of immersion of test specimens in sulfuric acid solutions with a maximum pH threshold of 2.5 and 1.0, respectively. In total 24 SCC mixtures were tested. The study reveals that the rate of attack, as expressed by mass loss versus time, is controlled by different factors at each exposure phase. The advantages of blended binders and hybrid (steel + polypropylene) fibres in improving the resistance of SCC to sulfuric acid attack are highlighted. Microanalysis conducted upon test termination elucidates the damage mechanisms, and it is shown that there is no direct correlation between the rate of attack expressed by mass loss and the compressive strength loss after exposure to sulfuric acid.