Use of Iron and Steel Byproducts

Three byproducts of the iron and steel industries can be used in the manufacture of portland cement: foundry sand, mill scale, and slag. Foundry sand can provide silica and possibly iron for the production of clinker. Mill scale contains iron oxides that can replace other iron-bearing materials in the kiln feed. Slag contains high percentages of calcium oxide and silicon dioxide and varying amounts of aluminum oxide and iron oxides. All of these components are needed in the cement manufacturing process. Select slags can be interground with the portland cement to produce a blended cement product. Foundry sand and some slags can replace natural stone as an aggregate in portland cement concrete. From 115 operating plants reporting in the PCA publication: 2006 U.S. and Canadian Portland Cement Industry:Plant Information Summary, 12 plants were using foundry sand and 38 plants were using mill scale as a raw material in the manufacture of clinker. In the U.S., 55 plants were using slag either as a clinker raw material or in blended cements.