Durability of Green Concrete Composed of Fly Ash, GGBS, Quarry Dust, and RCA after Acid Exposure

Abstract

Green concrete utilizes industrial waste resources as fine and coarse aggregates, to partially replace cement in concrete using supplemental cementitious materials. The primary goal of the present study was to explore the acid durability of green concretes with different compressive strengths of 30 and 40 MPa. In green concrete, fly ash and ground granulated blast furnace slag (GGBS) were adopted as SCMs, and quarry dust (QD) and recycled coarse aggregates (RCA) were adopted as replacements for fine and coarse aggregates, respectively. The acid durability assessment was carried out by immersing concrete cubes in H2SO4 and HCl solutions followed by residual compressive strength comparison. For comparative study purposes, the same grades of ordinary concrete were prepared, tested, and subjected to similar acid exposure. The microstructural investigation was also accomplished by employing field emission scanning electron microscopy (FE-SEM) analysis and energy-dispersive X-ray spectroscopy (EDS). It was found that concrete with 30% GGBS and 20% fly ash and the remaining 50% ordinary portland cement as cementitious materials along with 40% QD and 30% RCA as aggregate replacements gives adequate compressive strength and performs better in aggressive environments as compared to traditional concrete. These mixes were found to have denser microstructures with silica-rich, calcium silicate hydrate (C-S-H) gel.