Compressive strength of fly ash based geopolymer utilizing waste completely decomposed granite

An attempt to recycle construction waste soils in southern cities of China was presented in this study, where completely decomposed granite (CDG) was utilized to replace fly ash in the production of environment-friendly low-carbon geopolymers. Five crucial parameters were identified and incorporated into the experimental design using the Taguchi method, including fine and gravel particle content of CDG, fly ash content, water-binder ratio, and curing temperature. Test results demonstrate that the newly formulated geopolymer can achieve a compressive strength of up to 14 MPa with a relatively high usage of CDG. The strength initially increases and then stabilizes with an increase in fine particle content. However, no significant relationship is observed between the compressive strength and gravel particle content. Higher curing temperatures and greater fly ash content lead to increased strength, while the strength initially decreases and then slightly increases with changes in the water-binder ratio. To examine the significance of these factors, Analysis of variance (ANOVA) were conducted and a correlation heatmap was drawn, revealing the following order of significance: curing temperature > fly ash content > water-binder ratio > fine particle content > gravel particle content. Furthermore, a robust strength prediction model was modified through multiple regression analysis. Another two additional groups of tests were performed to validate the proposed model, demonstrating the model's strong performance, particularly for curing ages beyond 14 days.