Study on fresh and mechanical properties for different grades of geopolymer concrete with recycled coarse aggregate

Abstract

In the construction industry, recycled coarse aggregate (RCA) and geopolymer concrete (GC) are been identified as the two main sustainable components to overcome the disposal of construction waste and by-product waste in landfills. These components are also involved to overcome the consumption of ordinary Portland cement and natural aggregates, and the use of dismantled waste in the concrete. The waste material like low calcium fly ash, ground granulated blast furnace slag (GGBS), and RCA were used to develop sustainable GC. In the present study, Natural coarse aggregate (NCA) is partially replaced with 25% RCA to study the different grades (i.e., M20, M30, M40, M50, and M60) of RCA-based geopolymer concrete (RCAGC). Based on several trials, the optimum dosage of GGBS has been replaced with LCF for developing the workability, compressive strength, splitting tensile strength, flexural strength, and compared with limiting values of conventional concrete as per IS code for each grade of RCAGC. Sodium hydroxide (NaOH) and Sodium silicate (Na2SiO3) are used as alkaline liquids to prepare RCAGC. Sodium hydroxide of 8 M, alkaline liquid to binder ratio of 0.5 were used and cured in ambient curing for 7 days and 28 days respectively. It was observed from the results that, as the amount of GGBS content increased, for each grade of RCAGC the workability gradually decreased with an increase in compressive strength. RCAGC achieved 80–85% of compressive strength within 7 days of ambient curing. Splitting tensile and flexural strength tests have been satisfactory as per Indian standards. A polynomial relationship is obtained between the mechanical properties of RCAGC and the limiting values of conventional concrete. RCAGC grades utilize by-products along with recycling coarse aggregate is an effective way in dealing with environmental crises.