Pyrite Test

The presence of pyrite in rock aggregates used as backfill can lead to problems if exposed to certain conditions. Aggregate particles containing large amounts of pyrite can react with oxygen and water and are likely to expand, crack and crumble over time. This expansion can lead to cracks in the overlying concrete slab. The thrust can even lift it. In garages or other ground level slab building sections, the thrust can also be to the sides and affect the foundation walls.

Essentially, it is a series of tests to assess the quality of the crushed stone used as backfill under the concrete slab. These tests allow the determination of the Pyrite Swelling Potential Index (IPPG in French) which is a number corresponding to the swelling potential of the backfill material. This number ranges from 0 to 100. For example, if the IPPG is between 0 and 10, the swelling potential is negligible. If it is between 80 and 100, the swelling potential is extremely high.

Demand for pyrite testing is generally concentrated in the greater Montreal area since the problematic quarries are mostly located there. The Montérégie (south shore of Montreal) is where most cases are located. Certain areas of Montreal such as Rivière-des-Prairies, Pointe-aux-Trembles and the west of the Island (Pointe-Claire, Dollard-des-Ormeaux, etc.) are also known risk areas. Finally, cases are also found in Laval, in the Basses-Laurentides and Lanaudière (Repentigny, Legardeur, etc.).

No. The result obtained during the pyrite test, the Pyrite Swelling Potential Index (IPPG in French), is calculated according to the types of rock in the backfill and not according to what remains to react in the future. This therefore means that the IPPG will not vary over time. However, the age of the building is a criterion that the professionals at Sedexlab consider when writing the conclusions of the report.

Chemical analysis is another type of test that allows getting a better grasp on the progress of the chemical reaction in the backfill material. This test is complementary to the IPPG and cannot be done alone. It is often called “the 2nd stage”. This additional test will give an estimate of the progress of the pyrite oxidation reaction. Is it just at the beginning? Moderately advanced? Or finishing off? In cases where a chemical analysis is deemed necessary, professionals at Sedexlab will offer it to you as the IPPG results are put out.

Although there is no law requiring a pyrite test to be performed, it is almost always required in cities and towns deemed most at risk, often by buyers, real estate brokers, banks, notaries, or home inspectors. Cracks in the concrete floor are often a good indication of the presence of pyrite, but the absence of cracks does not necessarily mean the absence of pyrite. By performing the pyrite test, you will be informed about the future potential for damage associated with the oxidation of pyrite and you will also be protected against future claims for latent defects.

The number of tests (or samplings) will depend on the layout and size of your home. In the case of an average-sized single-family home without a garage, a single sampling will suffice. An additional sampling will be required if your house has a garage or any other added section with a ground level concrete slab. In short, a sampling is required per level of concrete floor. Also, please contact us for a quotation for larger buildings such as commercial, industrial or multi-unit condo or rental buildings.

Once the backfill sample has been taken, our technicians will fill the hole with certified crushed stone. They will then plug the top of the hole with fast-setting concrete. In the event that there is floor covering, our technicians will put the floor back in place before leaving.