On the performance-based approaches to evaluate the oxidation potential of iron sulfide-bearing aggregates in concrete

Abstract

Oxidation of aggregates containing iron sulfide minerals has recently been linked to severe degradation in housing foundations in the northeast United States and the Trois-Rivières area of Quebec, Canada. Existing performance-based approaches mainly rely on the use of oxidizing solutions, which may create harsh environments and lead to unexpected results. This work evaluated the effectiveness of a mortar test by using atmospheric oxygen (a more realistic exposure condition) as an oxidizing agent and employed a design of experiments approach to investigate the effects of relative humidity (50% and 95%), oxygen content (20.9% and 35%), temperature (5°C and 60°C), and water-to-cement ratio (0.45 and 0.65) on the oxidation potential of iron sulfide-bearing aggregates. Results show that length changes of the mortar samples are mainly attributed to drying shrinkage within the experimental duration (more than 400 days), which is highly dependent on the relative humidity levels, whereas minimal to no expansion was observed under laboratory conditions. Recent efforts to simulate iron sulfide deterioration in laboratories by performance-based tests are then reviewed. Their advances and challenges as well as comparison with the proposed test are summarized, leading to a call for further development of experimental methods.