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

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.