Recycling and multi-recycling high performance concretes as coarse aggregates for making new high-performance concretes

This research work aims at assessing the physical-mechanical properties of recycled and multi-recycled high-performance concrete as aggregates for making new high-performance concrete (HPC). Different concretes have been made with aggregate substitutions of 50%, 75% and 100% of recycled and multi-recycled high-performance concrete as coarse aggregates. A natural aggregate high performances concrete of around 75 MPa was first fabricated and then crushed to produce recycled concrete aggregates for making a first cycle HPC recycled aggregates concrete of 73 MPa. After assessing its properties, this concrete was in turn crushed to produce a second-cycle recycled HPC aggregate for making a two-cycle recycled aggregates HPC of 71 MPa. The results show that, after two cycles of recycling, HPC keeps almost the same physico-mechanical properties as the parent concrete, even when 100% of recycled concrete aggregates were used. The hardened recycled cement paste was as strong as the natural aggregates used or even stronger, since traces of crushed aggregates were observed. This has resulted in recycled HPC properties similar to those of the original high-performance concrete. Recycling high-performance concrete into coarse aggregates for making new high-quality concrete appears to be a valuable aggregate supply resource, which fully fulfills the challenge of sustainable concrete construction that responds to the quest for sustainable development.