Using Recycled Concrete Aggregates in New Zealand Ready-Mix Concrete Production

Abstract

Motivations for adopting recycled concrete as an aggregate source include the preservation of natural resources, effective utilization of a growing waste stream, and financial and energy savings. Although current New Zealand practices include some use of crushed concrete in road construction, use of recycled concrete aggregate (RCA) in low specification concrete is currently infrequent and the use of recycled concrete as an aggregate source in structural concrete applications is rare. To make such recycling feasible, the properties of RCA must be related to the properties of new concrete that utilizes the recycled aggregates. In response to this need, a study was undertaken to investigate the feasibility of using RCA as a viable alternative to natural aggregate (NA) in the production of concrete manufactured in a conventional New Zealand ready mix concrete plant. Aggregate properties and hardened and fresh concrete properties of RCA concrete were studied and compared with the associated properties derived from NA concrete. Results indicated that RCA is a viable alternative to NA in the production of concrete. Furthermore, it was confirmed that the properties of RCA dictate the hardened properties of the reconstituted concrete and that RCA from certain strength placements limited the resulting possible strengths of concrete produced from it.