Using forced carbonation of recycled concrete fractions to improve the performance of new concrete

Reuse of recycled concrete aggregate is often restricted to coarse aggregates, albeit with slight loss in performance. There is growing interest in valorisation techniques to improve the properties of coarse recycled concrete aggregate. One such treatment is accelerated carbonation, which is also being considered for fine recycled aggregates and recycled concrete powder, so maximising reuse potential. This study has evaluated the effect of carbonation on all size fractions arising from crushing end-of-life concrete. End-of-life concrete was crushed in a jaw crusher and then subjected to forced accelerated carbonation. Following sieve analysis, each size fraction was characterised to determine its physical properties (particle size, attached mortar, absorption, and specific gravity). Concrete mixes containing all size fractions of recycled aggregates were subsequently prepared to assess the efficacy of up to 100% recycled concrete aggregate both pre- and post-carbonation treatment. Carbonation significantly improved the characteristics of all size fractions of recycled concrete aggregate, and consequently improved the performance of the resultant concrete prepared with it. Concrete prepared with 100% recycled coarse and fine aggregate outperformed a reference mix prepared with natural aggregates.