Durability of recycled aggregate concrete

Abstract

This paper presents the main results of the research carried out to analyse the physical, mechanical and durability properties of concrete incorporating recycled aggregate. One of the most unknown aspects of recycled aggregate concretes is related to their durability in aggressive environments. Also most of the results found in the literature are not comparable due to the heterogeneity of the recycled aggregates, water/cement ratios and types of cement used. In this research, recycled aggregate concrete with partial and total coarse aggregate replacement and reference concretes with 24 water/cement ratios have been cast to study their physical and mechanical properties, behaviour under accelerated carbonation, water and oxygen permeability. The results show, for the same w/c ratio, the influence of the recycled aggregate on the concretes. The durability of the concretes made with recycled aggregate is worse due to the intrinsic porosity of them. These differences decrease for low w/c ratios, as in this case the most influential factor is the low porosity obtained in the new improved cement paste. Considering the mechanical properties, the influence of the recycled aggregate is worse for the high w/c ratios. On the basis of the results obtained, recommendable mixtures for recycled aggregates in aggressive environments will be suggested. Also, an experimental model from the recycled aggregate concretes compressive strength is proposed.