Pyrrhotite and crumbling foundations
Concrete made with aggregate containing pyrrhotite, an iron sulphide mineral that expands as it reacts with water and oxygen, went into foundations across north-central and northeastern Connecticut from roughly the early 1980s into the 2010s. Deterioration typically appears one to three decades after the pour. The state created the Connecticut Foundation Solutions Indemnity Company to help fund repairs, and sellers must disclose what they know.

