The role of water-to-binder ratio on strength of fly ash geopolymer as sustainable green materials in supporting SDG 13

Disasters caused by global climate change issues have become a global concern. One of the causes is the production of Portland cement (PC). The use of fly ash as a cement substitute in geopolymer applications is one alternative to address this issue. However, the use of fly ash in geopolymers is significantly affected by the ratio of the activator solution to the fly ash. Therefore, identifying the optimal water-to-binder (w/b) ratio is crucial. The fly ash geopolymer (FGP) performance was assessed based on compressive strength at 7 and 28 days. The depth penetration test identified the effect of the w/b ratio on the initial setting time. The w/b ratio was varied from 0.20 to 0.45 with a 0.05 increment. The results found that the w/b ratio significantly affects the strength of FGP. The highest strength was achieved by a 0.30 w/b ratio. Further increasing the w/b ratio tended to decrease strength and the initial setting time. However, the results showed that with a suitable water-to-binder ratio, fly ash can be utilized as a sustainable green material to address the global climate change issue, supporting SDG 13.