Comparing humidity cell and mass flux testing for a sulfide-bearing cement-treated slate

Acid-producing waste rock can be an abundant by-product of urban construction and its environmental impact necessitates proper disposal. A potential technique to limit acid drainage from this waste rock is cement-based solidification and stabilisation (s/s). For urban projects, leaching tests (e.g. mass flux testing) are used to evaluate the performance of a cement-treated material, while for mining projects, humidity cell testing is often performed. The purpose of this paper is to compare these two methods of performance testing to examine the leachate generate from a pyritic slate rock obtained from an excavation project. Based on the humidity cell and mass flux testing performed, cement-based s/s was effective in neutralising the pH of the effluent leachate and slowing or preventing the release of most examined contaminants. Notable exceptions were sulfur and sulfate, which were detected in significantly higher concentrations in the binder-treated samples. It was noted that humidity cell testing may produce an eluate with more concentrated potential contaminants than mass flux testing for s/s monoliths as mass flux is likely more indicative of performance of the s/s monolith.