Effect of slag on mechanical and microstructural properties of fly ash-based geopolymer concrete containing recycled aggregate

Abstract

Abstract In India, major cities have aged infrastructures that produce significant construction and demolition (C&D) waste. This trash has an adverse impact on the environment and poses challenges for disposal. To address the same, recycled aggregates (RA) are considered in place of natural aggregates (NA), and geopolymer binders, namely fly ash (FA) and slag, are used as sustainable alter to ordinary Portland cement (OPC) for the preparation of geopolymer concrete (GPC) at ambient curing condition. In this study, the engineering and permeability characteristics of GPC were examined using compressive strength, tensile strength, and water permeability. Further, the microstructural properties of the prepared mixes were assessed by adopting X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The test results revealed that the blended mixing of FA and slag enhanced the mechanical and water permeability properties of GPC. The highest compressive and tensile strength is 37.65 MPa and 5.06 MPa at 28 days curing period at an optimum mix of F70S30, 10M NaOH, and Na2SiO3 to NaOH of 2.0. At the same time, the minimum water penetration depth was measured as 11 mm. Thus, adding 30% with FA accelerated the reaction mechanism, densified the GPC matrix, and enhanced strength.