It appears that the awareness and intentions to use recycled concrete aggregate (RCA) in concrete are expanding over the globe. The production of self-compacting concrete (SCC) using RCA is an emerging field in the construction sector. However, the highly porous and absorptive nature of adhered mortar on RCA's surface leads to reduced concrete strength, which can be removed with the application of various techniques, such as acid treatment. This study investigated the effect of the partial replacement of silica fume by cement and natural aggregate (NA) by RCA with and without steel fibre. The used RCA was treated with magnesium sulphate solution. It was immersed in solutions with different concentrations of 10%, 15% and 20% and for different periods of 5, 10 and 15 days. Sixteen mixes were prepared, which were divided into six groups with or without 1% of steel fibre content. The fresh properties, compressive strength, split tensile strength and impact resistance were examined. The results revealed that the strengths of the mixes with 20% RCA were marginally better than those of the control mixes. The compressive strength and split tensile strength were reduced by 34% and 35% at 60% RCA content, respectively, as compared to the control mixes.
Keywords: magnesium sulphate self-compacting concrete; recycled aggregate; strength; sustainable treatment.