Closed-loop recycling of recycled concrete aggregates

Reduce, reuse and recycle for environment recovery and respect are the key principles of a sustainable construction material. Much research has been conducted regarding the use of recycled concrete aggregates (RCA) in concrete mixes recycled from parent concrete of natural source aggregates, referred here as first generation. Recycling the RCA forming a second loop of recycling concrete is referred here as the second generation of RCA. This study concentrates on the properties of the second generation concrete. The concrete mixes considered in this study are conventional mixes made of 100% natural aggregates (NA), mixes containing up to 20% replacement of NA with RCA, producing first generation concrete and mixes containing up to 20% replacement of NA with aggregates obtained by recycling the first generation concrete (R-RCA), producing the second generation concrete. Properties that have been studied are workability, absorption, compressive and tensile strengths. The results show that the use of RCA and R-RCA has an adverse effect on concrete properties. Results show that the use of up to 20% replacement of NA by RCA or R-RCA instead of NA is allowed for producing concretes of accepted quality. The second generation RCA performed better than the first generation RCA. It is also shown that the closed-loop recycling is possible and advantages maintaining the sustainability of the natural resources and the environment.