| Description |
Portland cement is manufactured from a clay and limestone mixture that is calcined in kilns. Portland cement does not contain free silica. Kiln emissions include carbon monoxide and sulfur dioxide. The hexavalent chromium found in cement may originate from the refractory lining of the kilns. [ILO Encyclo, 3:93.1-93.52] Raw materials in Portland cement: chalk, limestone, clay, shale, and acid sulfates; Typical composition: 64% Calcium oxide, 21% Silicon dioxide, 6% Aluminum oxide, 3% Iron oxide, 3% Magnesium dioxide, 2% Sulfur dioxide, and 0.002% Chromium; Also contains Cobalt and Nickel; [http://www.ohici.nl/pdf/health_effects_of_construction_materials.pdf] |
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