Fracture and Mechanical Properties of GGBFS-Based Geopolymer Concrete Incorporating Rice Husk Ash and Natural Zeolite

Abstract

Geopolymer concrete (GPC) cured under ambient conditions is a sustainable alternative to conventional cement concrete in building and construction applications. Despite its potential, few comprehensive studies, to our best knowledge, have been conducted on its fracture behavior, which is a critical feature in evaluating the ductility and integrity of a structure in structural engineering. In the present study, the fracture energy of ground granulated blast furnace slag (GGBFS)-based GPC was investigated by incorporating various amounts of rice husk ash (RHA) and natural zeolite (NZ) with two different ratios of alkali activator solutions using a wedge splitting test (WST). Further, an extensive examination of mechanical properties was conducted, encompassing compressive strength, splitting tensile strength, and ultrasonic pulse velocity (UPV) at the termination of a 28-day curing period. Results revealed that increasing the sodium silicate to sodium hydroxide (SS/SH) ratio from 2 to 2.5 improved all mechanical properties and increased the fracture energy of all specimens. However, adding RHA and NZ decreased all examined properties. Specifically, for an SS/SH ratio of 2.5, substituting 10% RHA and NZ decreased the fracture energy by 27% and 10%, respectively. Additionally, the findings indicated a positive correlation between fracture energy and the compressive strength of GPC. Subsequently, a comprehensive evaluation of destructive and nondestructive tests established reliable relationships facilitating the estimation of fracture energy in GPC, characterized by a notably high coefficient of determination (R2) value. Finally, microstructural analyses X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy were performed to further validate the results. GPC have garnered significant attention due to their potential to reduce carbon dioxide emissions and utilize industrial waste. This study investigated the fracture and mechanical behavior of GPC made from GGBFS. Key properties of GPC were analyzed, focusing on the effects of replacing RHA and NZ with GGBFS, and the impact of the sodium silicate to sodium hydroxide ratio. The findings demonstrated that adjusting the sodium silicate to sodium hydroxide ratio enhances the mechanical properties and fracture energy of GPC. However, substituting RHA and NZ with GGBFS led to a decrease in these properties. These findings show that different pozzolans significantly affect the properties of GPC. These results are crucial for structural engineering, as fracture energy is linked to the ductility and integrity of structures. Further, the study provided formulas for predicting fracture energy using mechanical parameters and nondestructive tests. These relationships can aid in improving the analysis and engineering design of structures. Overall, this study aids construction engineers in gaining a better understanding of the mechanical and fracture properties of GPC structures.