Recycled concrete production. Multiple recycling of concrete coarse aggregates

Abstract

Recycled aggregates, such as the ones used in making the sub-base and base layers of roads and the ones used as replacement of natural aggregates in concrete production, may give an important contribution towards decreasing the negative consequences that production and dumping of construction and demolition waste nowadays impose on the environment. Within the research work being carried on at Instituto Superior Técnico (IST) in Lisbon, the results of an experimental research project are presented in this article. Its main purpose was to demonstrate the technical sustainability of multiple recycling of coarse stone aggregates originally obtained from the demolition of existing concrete elements to make new concrete with no further consumption of any coarse natural aggregates. The results, in terms of compression strength and workability, show that concrete produced after multiple recycling of aggregates has approximately the same characteristics as the one obtained after only one cycle, thus proving that the process can be reproduced with no further limitations.