Multi-criteria study for recycled concrete aggregate separation process

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Abstract

Construction and demolition waste stream has generated news materials that may be reintroduced into new concrete, e.g. as recycled aggregates. The specific feature of recycled concrete aggregates (RCA) is the presence of hardened mortars influencing their behaviour. This study aims to distinguish processes that allow the complete separation and quantification of attached mortar. The laboratory developed method has to be transferable on a wider scale to be exploited on a real recycling platform. This study is linked to the RECYBETON National Research Project involving public research laboratories, institutes and private companies. Several methods are tested in laboratory conditions to determine their efficiency. They are based on mechanical, chemical and physical principles. The definition of this efficiency concept and the mortar content denomination are also discussed. Originality of this study consists in optimizing hot or cold thermal processes combined with a mechanical treatment. To perform that, a multi-criteria phase experiment was carried out and several values of the multi-criteria parameters were optimized. Results allow for a thorough knowledge of treatment efficiency. However, it appears that not any one method is 100% satisfactory as aggregates are never completely cleaned and/or are damaged.