This summer, we researched a mineral known as pyrrhotite, an iron-sulfide prone to oxidation and subsequent deterioration. It has been implicated in the cracking of foundations in homes across northeastern Connecticut. Such damage can require renovations running into the thousands and even hundreds of thousands of dollars. Therefore, pyrrhotite testing of concrete has been a major subject of focus in the Environmental Science Program, with the main objectives being to develop a comprehensive method for measuring pyrrhotite contamination and estimating probable-effect-concentrations.
Current Trinity sampling methods utilize a combination of X-Ray Diffraction (XRD), Carbon Nitrogen and Sulfur analysis (CNS), and magnetic susceptibility to determine mineralogy and sulfur concentration. In short, sulfur concentration is an indicator of pyrrhotite concentration, but pyrrhotite is not the only sulfur-bearing mineral present in concrete samples. Thus, the objective this summer was to determine the extent to which other sulfur-bearing minerals contribute to overall sulfur concentration. The process involved calibration/adjustment of the CNS analysis method in conjunction with XRD analysis. Our overall goal is to provide a more comprehensive quantification of pyrrhotite in concrete. We also worked on understanding the relationship between pyrrhotite and its oxidative products. Such knowledge is key to achieving better risk assessment as well as establishing a time scale for concrete deterioration.