Sustainable Concrete: Impacts of Existing and Emerging Materials and Technologies on the Construction Industry

Cement production generates about 5 percent of global manmade carbon dioxide (CO₂) emissions (ca. 1 ton of CO₂ per ton of cement made) and is the second-largest industrial process-related source of CO₂ emissions in the United States. In response to environmental concerns related to global warming, the cement and concrete industry has been gradually shifting towards more sustainable materials and technologies. The primary objective of this paper is to provide an overview of the main directions of sustainable concrete technology; namely, reduction of the CO₂ footprint of concrete materials, adaptation of performance-based specifications, and utilization of high-performance concrete. Specific methods of CO₂ reduction in concrete, some of which are still under development, include supplementary cementitious materials, limestone filler, binder content reduction through optimization of aggregate gradation, "low CO₂" cements, and cement-free binders (geopolymer concrete). In view of emerging environment-conscious policies and regulatory changes gradually being adopted by owners and specifiers, the concrete construction industry is facing significant challenges.