Alternative processing procedures for recycled aggregates in structural concrete

• Recycled concrete aggregates (RCAs) present higher porosity than natural ones.
• The higher porosity of RCAs results in a higher water absorption capacity.
• Autogenous cleaning process is considered to reduce water absorption.
• The influence of the process duration on the concrete properties is investigated.
• Both workability and strength are enhanced by the process under consideration.

As sustainability is becoming a fundamental requirement for all modern industrial activities, upcoming environmental research efforts should be intended at both enhancing the efficiency in the use of raw materials and reducing the carbon footprint. The present research activity has been launched at the Federal University of Rio de Janeiro (UFRJ, Brazil) for demonstrating the feasibility of “ecological concrete” for structural use, characterised by a significant replacement of natural aggregates with recycled ones, which are produced from processing Construction Demolition Waste (CDW). Particularly, this work explores alternative processing procedures and investigates their influence on the relevant physical and mechanical properties of the resulting aggregates and concrete mixtures. Therefore, particle size distribution, bulk density attached mortar content as well as the associated water absorption capacity of recycled aggregates were monitored to scrutinise the effect of such processing procedures. Subsequently, a series of concrete batches was produced for evaluating the influence that alternative processing procedures for recycled aggregates have on the main mechanical performance in a fresh and hardened state. Results reported in this paper show the feasibility of “autogenous cleaning”, which removes surface impurities and reduces particle heterogeneities, usually characterising the morphology of a recycled aggregate matrix. It shows that the considered cleaning procedure significantly reduces the gap between the performance of recycled aggregate concrete (RAC) and ordinary ones, both in terms of workability at the fresh state and strength at the hardened state of concrete mixtures.