High-Performance Alkali-Activated Binders from Red Soil, Slag, and Fly Ash for Simultaneous Structural Use and Dye Remediation

Abstract This study focused on developing an optimal blended high-performance alkali-activated binder (AAB) mixture using appropriate precursor ratios of fly ash (FA) and ground granulated blast-furnace slag (GGBS), combined with red soil (RS). The study’s main objective was to investigate the potential application of the resulting material as an efficient dye adsorbent for wastewater treatment. Its mechanical strength and durability were assessed to determine its suitability for structural engineering applications. Nine AAB combinations (M1–M9) were developed with varying proportions of GGBS, FA, and RS to concurrently evaluate structural performance and dye removal efficiency. The mix M6 (25% FA + 30% GGBS + 45% RS) exhibited multifunctional attributes, including the maximum dye removal efficiency (85.56% for methylene blue), ideal compressive strength of 38.93 MPa, and a 45% utilization of naturally available RS, rendering it nearly a negative carbon emission material. The X-ray diffraction (XRD) analysis was conducted to investigate the mineralogical transformations and validate dye molecules’ interaction with the M6 matrix. Field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDS) was used to characterize the surface morphology and elemental composition of the M6 AAB before and after due adsorption. Furthermore, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed that the dye removal mechanism is predominantly governed by chemical interactions, indicating a chemisorption process. Integrating wastewater treatment functionality into structural-grade optimized AAB provides a sustainable, circular solution for infrastructure development in water-stressed and pollution-affected regions.