Pyrite removal



The presence of pyrite in the backfill under the concrete slabs or in the concrete produces sulfuric acid, a substance which causes the bursting of the stone and swelling of the backfill.

Fuel (Oil)

Earth contaminated with fuel that pollutes indoor air and the groundwater.



  • Cracks in the basement and in the garage foundations
  • Cracks and uprising of the basement and the garage floors
  • Presence of white powder near the cracks


  • Fuel odors (fumes) in the air
  • Presence of oil on the surface



Use of backfill containing pyrite (stone non DB certified)


Old heating oil tanks buried or leaking.



A laboratory test shows if the stone in the backfill has a high swelling potential. If this is the case, you must excavate the backfill and replace with crushed stone – DB certified (without swelling potential).


The backfill should absolutely be removed.

Work to be performed

Pyrite and/or fuel.

  1. Crush the damaged existing concrete.
  2. Remove the backfill or any contaminated soil.
  3. Spread and compact a new backfill of stone DB certified.
  4. Make a new concrete slab.

Bisson Expert uses miniature excavation equipment in order to maximize the effectiveness of secure operations.

More information

Typical case of pyrite removal in the basement and in the garage foundations in Montreal.

Karpowicz family  

Gaudreau family 

Picture description

The pictures on the right provide a summary of the different steps involved in the process of eliminating pyrite. The first picture depicts the process used to protect the asphalt. On the second picture, we can see a garage slab with a pyrite problem (that should be removed). The third picture emphasizes on the slab support. The fourth picture details the new backfill. On the fifth picture: the installation of the drain. Lastly, on the sixth picture, we can see the new slab being laid after the pyrite problem was solved.