Extended application of the equivalent mortar volume mix design method for recycled aggregate concrete

Abstract

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 water- to-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.