Everyday Uses of Rocks and Minerals - Shelf 11
The concrete that makes up most of the urban landscape is actually an artifical reconstruction of a naturally occurring rock, conglomerate. To make concrete, we mix sand and gravel, with cement. Cement is created by heating ground limestone with other minerals. When hot enough, the limestone releases carbon dioxide and becomes quicklime, the primary ingredient in cement. When the quicklime in cement reacts with water, it forms a stable crystal: this is what happens when concrete 'dries'. The process of making cement from limestone releases carbon dioxide, consequently, the cement industry is second only to power production in the release of carbon dioxide gas into the atmosphere.