Trade Journals for the Concrete Industry

Recycled concrete aggregates (RCA) produced from concrete of known properties are often considered to be of lower quality than natural aggregates but of higher quality than recycled aggregates (RA) obtained from construction and demolition waste. However, the use of RCA has still generally been limited to non-structural applications. The research discussed in this paper entailed the production of concrete con- taining a fraction of coarse RCA produced from high-strength concrete waste of uniform, known properties supplied by a precast concrete manufacturer. The intention thereof was to investigate the use of RCA in structural concrete and the validity of existing guidelines on RA con- crete, which typically specify low replacement ratios. Various replacement ratios (15%, 30%, 40%) were considered across two water-binder ratios and two different moisture states of RCA (dry and pre-saturated). The resulting strength, deformation and permeability (and therefore durability) properties of concrete were found to be equivalent to that of the reference concrete, independent of RCA content. Based on the experimental research, this publication proposes recommendations for using recycled precast concrete waste as coarse aggregate in the production of new precast elements.