Prospecting For Expansible Shale

Manufacture of lightweight concrete aggregate from common shale is one of the most rapidly growing industries in the field of nonmetallic or industrial minerals. Although expanded shale" has been in use since it was developed by Stephen J. Hayde in 1917, it was not until after World War II that it became a substantial competitor with other aggregates. There are some 70 plants now producing this aggregate in the United States, approximately half of them in states west of the Mississippi River. Expanding plants throughout the U. S. are grouped around major urban centers such as Los Angeles, New York, Chicago, and Denver. Concrete made with expanded shale aggregate combines the desirable features of low weight with relatively high strength, making it especially useful in concrete block, in structural concrete for multi-story buildings and in a variety of specialized concrete products such as prestressed panels and beams, and storage tanks. As the cost of construction continues to rise, lightweight concrete will probably be used in increasing quantities because of its low cost relative to the more traditional construction materials such as wood, brick and steel