Abstract

This paper presents the environmental problems related to portland cement manufacturing. The burning of cement clinker releases particulate and SO₂, NO_X, and CO₂ gaseous emissions. Sulfur dioxide and nitrogen oxides are the main sources of acid rain which is a regional-scale problem. Anthropogenic emissions of carbon dioxide are related to global warming due to the greenhouse effect. Hence, the only way to attenuate the environmental impact due to cement clinker burning is by means of its partial substitution by blending materials with additional economical, technological, and geological benefits. In this sense, the Brazilian cement industry has continuously been modernized, producing blended portland cement in which the cement clinker is replaced by variable amounts of blending materials, depending on the cement type. Moreover, the Brazilian industry has used dry processes to burn raw meal, because it is thermally more efficient than is the wet process and therefore releases less CO₂ to the environment as well as saves fuel. A classification and technological characteristics of common Brazilian blending materials are presented. Blending materials in this classification are arranged, according to their origin, in two large groups: industry byproducts and mineral deposits. The production profile of the Brazilian cement industry is characterized by composite portland cement manufacture with standardized amounts of active additions such as slag, pozzolan, and limestone. By using the Brazilian production of composite portland cement which sums up to 95% of its total production, estimates of CO₂ reduction as well as economical and geological benefits are presented.