Pyrite is a mineral that can be found in the crushed stone used as fill under concrete slabs in garages and basements of houses. In the presence of moisture and oxygen, pyrite oxidizes and causes swelling of the stone fill.
When expanding, the stone exerts pressure on the slab in the basement or garage, which lifts and cracks. The cracks are often observed in a cross or star pattern and white powder can be detected. The pressure exerted on the slab can also result in cracked walls of the garage and cause major problems.
Pieux Metropolitain’s solution
The complete reconstruction of the slab.
Since the problem comes from the contaminated fill, the only solution is to undo the concrete slab and remove the fill, then replace it with stone that is DB certified, to meet the requirements of a domestic foundation. The concrete slab is then safely rebuilt.