Novel Pyrrhotite Detection Method in Concrete Aggregate

Pyrrhotite is an iron sulfide mineral found in diverse rock types. Its presence in the aggregate used for concrete construction can produce damaging effects associated with oxidation of pyrrhotite in the presence of water and oxygen. Available methods of detecting pyrrhotite do not suit routine field applications. This project will develop a portable test system based on NMR relaxometry principles for nondestructive field detection of pyrrhotite in aggregate and concrete. NMR relaxometry provides information on the physico-chemical environment within solids with different pore system characteristics. Background studies of soil and the work on aggregate and concrete conducted in the course of preparing this proposal have demonstrated that the presence of pyrrhotite produces distinct and quantifiable effects on the NMR relaxation parameters. The proposed Phase I project will tailor the design and operation conditions of a portable NMR to suit the targeted application. A systematic experimental program will be planned and implemented in order to devise a test protocol and data analysis procedures for accurate and reliable detection and quantification of pyrrhotite in aggregate and concrete. The results will be used to assess the potential of the approach to meet the targeted requirements of the development effort.