Eco-efficient preplaced recycled aggregate concrete incorporating recycled tyre waste

This experimental study explores the development of highly eco-efficient concrete. This concrete incorporates 50% higher coarse aggregate content compared with normal concrete, thus reducing cement demand, and its granular skeleton is entirely recycled. Moreover, it adopts a unique energy-efficient placement technique whereby the granular skeleton is first preplaced in the form and then injected with a flowing grout, which considerably reduces the energy of mixing and placement. Various mixtures incorporating recycled concrete aggregate along with recycled rubber granules and steel wire fibres retrieved from scrap tyres were made. The mechanical strength and post-cracking behaviour of the eco-efficient concrete were evaluated. While tyre rubber decreased mechanical strength as expected, scrap tyre steel wire fibres enhanced the tensile and flexural behaviour, exhibiting superior energy absorption and ductility compared to the brittle failure of the control mixture. The results provide an insight into the level of recycled tyre rubber and steel wire that could be combined with recycled concrete aggregate to achieve durable and cost-effective eco-efficient preplaced recycled aggregate and rubberised concrete for sustainable non-structural applications.