The Evangelical Hospital located in Lewisburg, Pennsylvania has experienced distress in the form of cracked floor slabs and displaced structural steel due to swelling of the underlying fill material and natural bedrock formation. The bedrock consisted of black, pyritic, calcareous shale from the Marcellus Formation of the Hamilton Group (Devonian Age). The fill materials beneath the cracked concrete floor slabs consisted of the weathered shale fragments from this formation. Although mitigating the structural distress has been attempted, the building continued to experience problems relating to the swelling of the underlying bedrock materials. The expansion of the shale could be attributed to the oxidation of the pyrite, which produced sulfuric acid. The sulfuric acid, in turn, reacted with the calcium carbonate (calcite) in the shale partings producing the mineral gypsum. Since gypsum has approximately twice the molar volume of calcite, the result is an expansion or swelling of the shale. Various laboratory tests were conducted on the shale in an attempt to simulate the swelling processes. The failures and successes of the laboratory testing have given new directions for additional research to further educate Geotechnical Engineers unfamiliar with the expansive nature of pyritic shale
