Optimization of geopolymer synthesis using coal fly ash for enhancement in properties as sustainable and durable construction material

Coal-based power plants produce a huge quantity of fly ash, which requires a huge amount of revenue. The same practice is conducted at the SEPCO coal power plant in Karachi; this study was conducted to address the disposal issue productively and to determine the potential of coal fly ash for the development of sustainable, ef - ficient construction materials. In this study, work was conducted on the effect of alkali activator concentration on fly ash-based geopolymer, examining the morphological properties of the geopolymer material at the micro level using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis to develop a durable and environmentally friendly material for the construction industry. The obtained material formed was a porous, amorphous-structured material with regular micro-and macro-pores, resulting in reduced density and potentially enhanced properties. EDX analysis revealed lower incorporation of sodium (Na), silicon (Si), and aluminum (Al), indicating a limited dissolution of fly ash and poor formation of the geopolymeric gel as well as higher levels of unreacted oxides, such as calcium (Ca), iron (Fe), and residual quartz reflects an underdeveloped geopolymer matrix due to lower concentration of alkaline activator solution. In contrast, the 8 M geopolymer shows significantly higher concentrations of Na, Si, and Al, which are key elements in the formation of N-A-S-H gel networks. The improved Na/Al and Si/Al ratios in the 8 M sample point to more complete dissolution of the raw material and better integration into the geopolymer framework. FTIR analysis indicated the chemical environment of GP, with broad peaks in the 3336 cm -1 range suggestive of hydroxyl groups as well as new peaks for carbonate and bicarbonate groups. These changes indicate improved surface properties and reactivity, making GP more suitable for various applications. BET isotherm analysis confirmed the presence of mesoporous material in GP, with an average pore size of 60 µm, porosity of 30.8%, and a BET surface area of 25 m²/g, respectively. This research underscores the potential of CFA-derived geopolymers as a sustainable and high-performance alternative for construction materials.