Experimental study of GPC using ultra super-pozzofine M-500 siliceous fly ash

The construction industry is under increasing pressure to reduce its environmental footprint, particularly due to the high carbon dioxide emissions associated with Portland cement production. Geopolymer concrete has emerged as a promising low-carbon alternative, utilising industrial waste materials such as fly ash as binders. While previous studies have explored the mechanical properties of geopolymer concrete, limited attention has been given to its microstructural behaviour using ultrafine siliceous fly ash and the optimisation of alkaline activator dosage. This study addresses these gaps by investigating five geopolymer concrete mixes incorporating ultra super-pozzofine M-500 Class F fly ash with varying alkaline activator solution to fly ash (AAS/FA) ratios. The results reveal that an AAS/FA ratio of 0.6 yields the optimum correlation between early-age compressive strength of 61.77 MPa at 28 days and workability with slump value of 86 mm, while higher ratios lead to diminished performance due to microstructural instability. These findings offer valuable insights for designing high-performance, sustainable concrete mixes and contribute to advancing geopolymer technology for eco-friendly construction.