Queformat solves problems related to pyrite

Pyrite is a relatively common problem in Quebec, particularly on the South Shore of Montreal. The Association des consommateurs pour la qualité dans la construction (ACQC) describes its impact as follows:

“Pyrite (FeS2) is a very common mineral. Traces of it are found in the sedimentary rock used to make crushed stone, a backfill material, in regions where swelling is an issue. Under the combined presence of humidity, oxygen and heat, pyrite oxidizes to produce sulphuric acid. This acid reacts with the calcium carbonate (e.g. limestone) found in the crushed stone. The ensuing chemical reaction results in the formation of sulphate and possibly gypsum. This gypsum can crystallize, causing the stone to burst and the pyritic backfill to swell; it can also cause the concrete slab itself to swell and even crumble. The resulting swelling may heave the slab and interior structural supports resting upon it. This in turn can damage the floors and interior walls of the upper levels. The higher the pyrite percentage and the greater the thickness of the pyritic backfill, the greater the production of sulphuric acid and sulphates; and, ultimately, the more serious the swelling problem. For this reason, swelling is usually worse in residential garages, where the layer of backfill is thicker than under the basement slab.”

Queformat is Quebec’s leading specialist in the identification and resolution of pyrite problems.

Accredited by the Comité technique québécois d'étude des problèmes de gonflement associés à la pyrite, a committee formed to study the problem, Queformat can carry out in-depth petrographic studies to precisely determine the swelling risks of sub-slab backfill.

Queformat’s experts have the building knowledge and geotechnical, environmental and materials engineering expertise required to rigorously assess your particular situation. Thanks to our knowledge and independence, we can suggest made-to-measure solutions, whatever your conditions. Contact us