Sulphuric acid exposure of conventional concrete and alkali-activated concrete: Assessment of test methodologies

Abstract Biogenic sulphuric acid corrosion can lead to significant degradation of Ordinary Portland Cement Concrete (OPCC) and cause significant damage to wastewater infrastructure. Recent studies have suggested that alkali-activated concrete (AAC) has improved durability compared to OPCC in a range of aggressive environments. In this study, the resistance of both OPCC and class F fly ash based AAC to sulphuric acid is investigated in order to develop a simple laboratory test method, capable of indicating the susceptibility of both materials to biogenic acid corrosion. Tests that provide an indication of the susceptibility of cementitious materials to corrosion (change of mass, length, compressive strength, and cross-section) are undertaken under exposure to 1% (pH = 1.0) and 3% (pH = 0.52) sulphuric acid concentration for 495 and 112 days respectively, to establish the ability to accelerate testing. Further, characterization tests are conducted to investigate the change of specimens at the microstructural level. The indicators of susceptibility to corrosion are discussed based on their potential advantages and limitations as well as application to both OPCC and Class F fly ash based AAC. The results show that although the alkali-activated matrix partially retains strength after sulphuric acid attack, the coarse aggregates in the alkali-activated concrete are more prone to attack than those in an OPC matrix. It is also shown that using a higher concentration sulphuric acid accelerates the degradation of specimens sufficiently to perform an indicator test within 90 days.