A flotation-based approach to the quantification of pyrrhotite in concrete aggregates

Abstract

Pyrrhotite-bearing aggregates are a major cause of internal sulphate attack (ISA) in concrete. The concentration of pyrrhotite is usually too low to permit direct accurate quantification. Hence, safety restrictions put on aggregates are expressed in terms of the total sulphur content. This paper outlines an analytical approach in which froth flotation is employed to produce a bulk sulphide concentrate amenable to direct quantification of pyrrhotite. The concentration of pyrrhotite in the concentrate is expected to be more than an order of magnitude higher than that of the original sample. Aided by mass balancing based on conventional sulphur analysis, a safe and more accurate estimate of the maximal concentration of pyrrhotite in the original feed can be obtained. This could facilitate better resource utilization. Extensive work is required to develop and optimize the specific flotation procedure in order to obtain a robust analytical protocol.