Mechanical and durability performance of recycled aggregate concrete incorporating low calcium bentonite

Abstract

Concrete produced from recycled concrete aggregates (RCA) has been evolved as a good substitute of natural aggregate concrete (NAC) because of associated environmental benefits and increasing attention towards sustainable development in recent decades. Despite recycled aggregate concrete (RAC) presenting numerous benefits, it has inferior properties compared to NAC. Researchers have reported that mechanical and durability performance of RAC can be improved by using supplementary cementitious materials (SCMs) such as fly ash, silica fume, metakaolin, etc. Low calcium bentonite is a naturally found pozzolana and can be used as partial replacement of ordinary Portland cement (OPC) in concrete. In this study, the effect of bentonite on mechanical and durability behaviour of both NAC and RAC was investigated and compared. RAC was prepared by using RCA as coarse aggregate. Bentonite was used as 0, 5, 10, 15, and 20% by mass replacement of OPC in both NAC and RAC. Workability, fresh density, air content, compressive strength, split tensile strength, water absorption, chloride resistance, and acid attack resistance were investigated. Results of testing revealed that with the incorporation of bentonite, RAC showed significant improvement in the durability and later strength. Bentonite contributed more to strength development and durability of RAC than those of NAC.