Oxidation and Heave of Black Shale

Heave of floor slabs and lightly loaded structures founded on black, pyritic shales has been a severe engineering problem in several places in the world. The geochemical processes responsible for the heaving are generally believed to involve oxidation of ferrous sulphides that produce a variety of secondary sulphates. Additionally, the role of autotrophic bacteria as a catalyst to oxidation weathering processes has received some attention. The purpose of this note is to present additional information in support of the idea that autotrophic bacteria of the Thiobacillus–Ferrobacillus ferrooxidous species are important in catalyzing the oxidation of sulphides in black shale and to suggest gypsum as the actual mineral species causing at least some of the heave.