Quantified sustainability of recycled concrete aggregates

Abstract

The conservation of coarse aggregates has been largely ignored in the USA even though they account for about half of a concrete mix by volume. The production of natural crushed stone, sand and gravel in the USA accounts for over half of all mining, and associated processing and transport operations use energy and adversely affect ecology. Recycled concrete aggregate (RCA) as a replacement for natural aggregate (NA) in concrete structures can improve the sustainability of construction, but many remain unconvinced of the economic viability of RCA use in structural concrete. These two aspects have slowed research into and the practical adoption of RCA in structures. This paper addresses both aspects, presenting an environmental impact index that includes key aggregate production variables (production facility land use, water use, energy demand and carbon dioxide emissions) and detailing economic calculations showing the viability of RCA use in structures. The two biggest findings of this study were that, for the region studied, the environmental impact of RCA use is approximately half that of NA, according to the newly derived index, and RCA is predicted to be able to be sold for approximately the same cost as NA, even if process modifications to meet concrete aggregate standards are emplaced.