Antimicrobial Activity and Toxicity Profile of Fly Ash Geopolymer in Comparison with Conventional Construction Materials: An Experimental Study

An alkali-activated geopolymer (GP) was synthesized from coal fly ash b direct template and cured at 60 °C for 24 h. The obtained GP was characterized by XRD, FTIR, and SEM-EDS, confirming the formation of an amorphous aluminosilicate network. The biological activities were evaluated compared to three reference construction materials: ordinary Portland cement mortar (OPC), fired clay brick (CB), and vitrified ceramic tile (CT). Antimicrobial activity was assessed against Escherichia coli, Staphylococcus aureus, and Aspergillus niger. The fly ash GP revealed a high marked inhibition zones (45 mm for E. coli, 38 mm for S. aureus) and 100% fungal inhibition greater than standard antibiotic controls. This effect is attributed to the high alkalinity of GP and ionic composition of its leachate, rather than specific antimicrobial agents. Toxicity was evaluated using the Artemia salina lethality assay across a concentration range of 5 to 0.15 mg/mL, and zero lethality was induced. Mean survival remained 100% (± 0%) in triplicate assays statistically indistinguishable from negative controls. The study proves that fly ash GP has a strong antimicrobial action and exhibits a high biological activity in a sensitive toxicity screen. But an environmental assessment analysis in real-world applications are needed.