U.S. Portland cement industry, concrete and global climate: Fid-Bau Portal

U.S. Portland cement industry, concrete and global climate

Carroll, D. / Dougherty, A. / Nisbet, M. / O'Hare, A.

Cement is a fine gray powder which, when mixed with aggregates and water, acts as a binder to produce concrete, the widely used construction material. Demand for cement and concrete is determined by the level of construction activity. Construction activity represents about 8% of U.S. gross domestic product. Although the two words 'cement' and 'concrete' are used interchangeably, cement is actually one of the ingredients in concrete. Cement, in combination with water, binds sand and gravel or crushed stone into the rock-like mass known as concrete. Concrete generally contains 10 to 15% of cement by weight. Cement manufacture generates carbon dioxide (CO₂) emissions from calcination of the limestone in the raw materials, and from fuel combustion at the rate of approximately 1 ton of CO₂ per ton of cement. However, cement generally represents a small percentage of concrete meaning that emissions per cubic yard of concrete are relatively low. This paper outlines options for reduction of CO₂ emissions from cement and concrete manufacture by modification of processes and products. The paper discusses Life Cycle Assessment (LCA) guidelines and how they address the issue of allocation of credit for actions taken to reduce CO₂ emissions, such as addition of fly ash to concrete.