Advancement In Oxidation Test For Sulphide-Bearing Aggregates In Concrete

A research program was carried out to optimize test conditions that can lead to the oxidation of sulphide phases in aggregates. The goal was to accelerate the oxidation and its subsequent sulphate attack. Different relative humidity levels, sample moisture content, sample mix design, and the use of an oxidizing agent were attempted. It was found that oxidation takes a relatively long time, and the expansion obtained is relatively low. Out of the attempted conditions, testing mixtures of cement paste with the coarse aggregate—after being soaked in an oxidizing agent to achieve 30% of its absorption capacity—showed a relatively fast expansion. Vacuum-saturated concrete mixtures with an oxidizing agent showed an accelerated expansion. Some of the test conditions produce expansion in mixtures with non-sulphide aggregate, which requires further investigation.