Research on the early fracture behavior of fly ash-based geopolymers modified by molybdenum tailings

Abstract

Due to the existence of abundant broken silicon-oxygen bonds on the surface, metal tailings have been successfully applied to produce novel green cementitious materials. In this paper, research on the damage mechanism of modifying fly ash-based geopolymers by molybdenum tailings is proposed, which not only realizes the reutilization of metal tailings but also reveals the damage mechanism of fly ash-based geopolymers. The effects of molybdenum tailings content on the compressive strength , flexural strength and deflection of fly ash-based geopolymers were researched by mechanical testing and digital image correlation technology (DIC). The early fracture behavior was analyzed by using acoustic emission (AE) technology for fly ash-based geopolymers that were modified with three different contents of molybdenum tailings. Finally, the micromorphology characteristics were analyzed by scanning electron microscopy (SEM), and the toughening mechanism induced by molybdenum tailings was elucidated. The results show that introducing 20% molybdenum tailings leads to significant enhancements of 79% in flexural strength and 145% in deflection in comparison to the pristine fly ash-based geopolymers. Molybdenum tailings can be dissolved in alkali activators, which are then adhered and grown as nanorods on the inner wall of the smooth pore structure. The molybdenum tailings finally fill in the pores and densify the microstructure, thus reducing the formation of macrocracks and corresponding structural damage of the fly ash-based geopolymer specimens during loading, and significantly improving the fracture-resistance. • Molybdenum tailings can be dissolved by the alkali activator. • Molybdenum tailings fill in the pores and densify the microstructure of fly ash-based geopolymers. • The fracture-resistance of fly ash based-geopolymers is significantly improved with the addition of molybdenum tailings.