Pyrite oxidation and expansion in the New Albany black shale have caused serious foundation problems in numerous buildings and structures constructed in the black shale soil horizons in various parts of Kentucky. Pyrite oxidizes, causing various secondary sulfates to form when excavated shale or shale fill is exposed to the atmosphere, water, and humidity; these shales can therefore cause serious problems when used in foundations. These secondary sulfates are sensitive to water and humidity and can form when only minor amounts of water are present in foundation materials. In addition to heaving, these sulfate minerals can also create a mild sulfuric acid in foundation soils. These sulfates form by crystal growth and expansion by volume change, which cause subsequent soil expansion and heaving of any foundation materials when confined. Several structures—schools, hospitals, commercial buildings, water plants, and factories—have had expensive remediation to repair damaged sidewalks, floors, walls, utility conduits, and foundations. One home was condemned and others have severe damage. Repairing these conditions is sometimes more expensive that the original cost of building.

Foundation Failures in Black Shale Soil Horizons

Condemned home in Berea, Ky., and expansive sulfate minerals in black shale.