Resistance to external sodium sulfate attack for early-opening-to-traffic Portland cement concrete

The results of a study on sulfate resistance of early opening-to-traffic concretes with accelerating admixture, also known as fast-track concretes (FTC), are presented. A total of 11 concretes made with four different cement factors and three different cement types were investigated at both opening and maturity (28 days) ages. Upon curing, the test samples were immersed in a 5% sodium sulfate solution. Length change, mass loss, and compressive strength were monitored for a period of 270 days to evaluate the performance of the test specimens exposed to severe sulfate attack. The influence of immersion period, curing age and cement type and factor on bulk characteristics and sulfate resistance were evaluated.The study produced FTC with excellent sulfate resistance. Length change of FTC incorporating accelerating admixture increased with increasing immersion age and stabilized within 3 months from initial contact. No mass of concrete residues nor notable strength loss were found in any opening time fast track concretes used in the investigation.