Durability assessment of quaternary blended recycled aggregate concrete under chloride environment

Abstract

This article describes the durability of Normally Vibrated Concrete (NVC) containing Recycled Coarse Aggregate (RCA) using different mineral admixtures under extreme chloride environment. Further, to make concrete more sustainable by replacing cement and Natural Coarse Aggregates (NCA) with supplementary cementitious materials and RCA respectively without compromising the performance of concrete. For this, cement is replaced partially with Fly Ash (FA), Silica Powder (SP) and Ground Granulated Blast Furnace Slag (GGBS). The percentage of admixtures (FA, GGBS and silica powder) are decided based on the fresh) and hardened (compressive - strength) properties. M30 concrete is prepared using binary mix (OPC + FA), (OPC + GGBS), ternary mix (OPC + FA + GGBS) and quaternary mix (OPC + FA + GGBS + silica powder). Fresh and mechanical properties of concrete prepared from these mixes are determined. Further the best result of the outcomes based on the above mechanical properties is opted as optimum proportion of (FA, GGBS and silica powder) and is replaced in conventional mix to make concrete more sustainable. This optimum proportion is now used as a new conventional mix for replacing natural coarse aggregate with RCA by % weight varying in proportion 0%, 20%, 40%, 60%, 80% and 100%. For the assessment of durability of concrete Rapid Chloride Permeability Test (RCPT) is carried out. Charge passed through the concrete mix, ingress depth, migration coefficient is noted and relationship between compressive - strength and total charge passed for varying percentage of RCA with optimum proportion of admixtures is analysed. From experimental results it is observed that fly ash, GGBS and silica powder significantly improve the mechanical and durability properties of concrete. Moreover, it is also concluded that up to some extent RCA can be used as alternative of coarse aggregate.