Diversifying two-stage mixing approach (TSMA) for recycled aggregate concrete: TSMAs and TSMAsc

Recycling demolished concrete as recycled aggregate can be applicable to most construction applications. Lower-grade applications, including sub-base and roadwork, have been practicing in many countries; however, higher-grade activities are rarely discussed. This paper develops two mixing approaches by adding silica fume into certain percentages of Recycled Aggregate (RA) in the pre-mix procedure, named as two-stage mixing approach(silica fume) (TSMAs) and adding silica fume and proportional amounts of cement into certain percentages of RA in the first mix, named as two-stage mixing approach(silica fume and cement) (TSMAsc). Experimentation highlights that improvements have been recorded resulted from the use of various RA percentages from both TSMAs and TSMAsc. The additions of silica fume and proportional cement content in the pre-mix on TSMAs and TSMAsc can fill up the weak areas in the RA and thus develop a stronger interfacial layer around aggregate, and hence a higher strength of the concrete. It, thus, concludes that TSMAs and TSMAsc can provide alternative methodologies for further improvement in quality of this recyclable material.