Concrete damage due to pyrrhotite in the Trois-Rivières area (Québec, Canada): Investigation of existing buildings

In the Trois-Rivières area, about 2000 buildings whose the concrete was manufactured with aggregates containing pyrrhotite was the subject of litigation. At the beginning of a trial started in 2009, the experts representing all defendants grouped together and adopted a number of protocols relating to inspection, visual damage assessment, core sampling, and laboratory testing. The aggregate pyrrhotite content is obtained from the concrete sulfur content, the pyrrhotite/pyrite/chalcopyrite ratio, and other parameters related to the concrete mixture. In a 2014 judgment, the Court required compensation to all owners whose concrete was made with aggregates containing 0.23 vol.% of pyrrhotite or more, whether or not their concrete was damaged. The intrinsic heterogeneity of concrete in terms of sulfur and sulfide contents, from one core to another, but also within a single core, leads to a significant variability of the aggregate pyrrhotite content obtained. Consequently, the 0.23 vol.% limit appears highly questionable.