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Purpose This paper aims to review the effect of using recycled aggregates (RA) on the properties of recycled aggregate concrete (RAC) following the steady rise in global demand for concrete and the large generation of construction and demolition waste. Design/methodology/approach This study reviewed relevant literature of research work carried out by previous researchers, leading to a deeper understanding of the properties of both RA and RAC. The properties of RA and RAC reported in the various studies were then compared to their corresponding natural aggregate (NA) and natural aggregate concrete, as well as the specifications provided in different codes of practice. In addition, the mix design methods appropriate to RAC and the cost implication of using RA were reviewed. Findings Findings show that the contribution of RA to strength appears inferior in comparison to NA. The shortcoming is attributed to the mortar attached to the RA, which raises its water absorption capacity and lowers its density relative to those of NA. However, it has been reported that the use of regulated quantity of RA, new mixing and proportioning methods, the addition of admixtures and strengthening materials such as steel fibres, can improve both mechanical and durability properties of RAC. Cost evaluation also showed that some savings can be realized by using RA instead of NA. Originality/value This research serves as a guide for future works and suggests that the use of RA as aggregate in new concrete is technically possible, depending on the mix design method adopted.

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This paper presents the study carried out using the extended Equivalent Mortar Volume (EMV) mix design technique, for concrete made of recycled aggregates (RA) and steel fibre (SF). The expansion of the EMV approach is necessary to encourage the use of fine recycled aggregates (FRA) in concrete manufacture. To this end, the same replacement ratio obtained for coarse recycled aggregates (CRA) using the EMV principles, was applied to the FRA for concrete production. Furthermore, SF was added to improve the mechanical behaviour of RA-concrete developed with this method. Altogether, four mixes were developed using a constant waterto-cement ratio of 0.42 thus: reference mix labelled conventional concrete (CC) prepared with natural aggregates (NA); crushed aggregate concrete (CAC) mix designed with the conventional method and made of 100% RA; blended aggregate concrete (BAC) mix prepared with the EMV guide and composed of both NA and RA; and steel fibre-reinforced blended aggregate concrete (SFRBAC) mix prepared by adding optimum SF to the BAC mix. Then, cubical, cylindrical and prismatic specimens were produced from the mixes to investigate different properties of concrete. The experimental results show that the mechanical properties of concrete are not adversely affected by the presence of FRA. Also, the EMV mix design provision offers a better result than its companion conventional approach, even with about 30% reduction in cement content. The addition of SF mainly controlled crack development and induced a ductile failure mode.