"At the request ot the Bureau of Mines Oil Shale Demcnstration Plant, Rifle, Colorado, the Denver Laboratories made a few tests on the possibilities of using ""spent"" oil shale as an aggregate in concrete. ""Spent"" oil shale is the byproduct remaining after the extraction of the kerogen trom the oil shale. The heat in the extraction process expands the shale, giving it a vesicular structure similar to some of the lightweight aggregates used in concrete. Commercial development of the oil shale will result in enormous quantities of the ""spent"" oil shale which must be disposed of in some manner. One possible use for this material is 'in concrete as a lightweight aggregate."