Experimental Investigation of Effect of Recycled Coarse Aggregate Properties on the Mechanical and Durability Characteristics of Geopolymer Concrete

Abstract

With the increased population and industries in the global building sector, two major construction issues must be addressed: (i) Huge construction waste accumulation and (ii) Excessive use of Non-Renewable Resources. Geopolymer Recycled Coarse Aggregate Concrete emerges at a critical juncture in history to address two issues. Firstly, utilizing Geopolymers derived from the waste of industry to replace cement which reduces the use of cement and thus emissions of CO2, and secondly, Recycled Coarse Aggregate can make use of accumulated construction waste while conserving the natural resources. In the current study, Geopolymer Concrete was made with a constant ratio of fly ash and GGBS (50:50), a sodium silicate to Sodium Hydroxide ratio of 2.5, a Sodium Hydroxide concentration of 8 Molarity, an alkaline to binder ratio of 0.4, and different proportions of Recycled Coarse Aggregate that was partially and completely replaced with Natural Coarse aggregate with the percentage of (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%). The test results showed that Recycled Coarse Aggregate can be used as a Natural Coarse Aggregate in Geopolymer Concretes by replacing 70%, with a 28-day compressive strength of 60.02 MPa, which is almost same as 100% Natural Aggregate in Geopolymer Concrete. The reduction in strength after 90 days of exposure to the HCL solution was up to 1.28 percent for Geopolymer Concrete using Recycled Coarse Aggregate. The Compressive Strength of Geopolymer Concrete using Recycled Coarse Aggregate decreased by up to 1.89 percent after the same period of exposure to the Sulphate solution. In this study combination of fly ash, GGBS, 70% Recycled Coarse Aggregate, and an 8 Molarity NaOH concentration-based Gopolymer Concrete was recommended for precast construction with ambient curing.