Strength and durability characteristics of binary blended recycled coarse aggregate concrete containing microsilica and metakaolin

Abstract

Concrete is an important construction material. However, the consumption of natural aggregates in concrete production is responsible for depleting natural resources. Utilization of construction waste as recycled aggregate to replace natural aggregate in concrete construction is a great way to save the natural aggregate and manage the construction waste in an efficient manner. In the current study, compressive strength, water absorption and electrical resistance of concrete were investigated by replacing the natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) in the ratio of 50% and 100%. In addition, 10% cement was replaced with microsilica (MS) and metakaolin (MK) in RCA concrete mixes. Results show that RCA concrete had lower strength than NCA concrete; however, the strength of RCA concrete was improved by using binary blends of supplementary cementitious materials (SCMs). The SCM’s effect was found to be positive on water absorption and electrical resistivity of RCA concrete, water absorption was reduced, and electrical resistivity was increased. Further, the electrical resistivity results show that inclusion of SCMs reduces the chance of having corrosion in RCA concrete particularly using MK. Moreover, the microstructure investigations revealed that the incorporation of binary blends of SCMs reduces the voids in the RCA concrete and the microstructure of the concrete appears to be dense. Eventually, 100% RCA with binary blends of MS or MK can be used for the production of up to M35 grade concrete for practical concrete construction applications.