Mechanical and durability properties of natural fiber-reinforced geopolymers containing lead smelter slag and waste glass sand

Owing to the low tensile properties of concrete, the use of internal fibers received significant attention in concrete production. In recent years, using renewable and eco-friendly natural fibers has become a viable alternative to synthetic fibers. Toward this direction, the behavior of natural fiber-reinforced geopolymers containing industrial by-products and waste-based sands is presented in this study. Industrial by-products, namely fly ash (FA) and ground granulated blast furnace slag (GGBS), were used as binders and waste-based sands, namely lead smelter slag (LSS) and waste glass sand (WGS), were used as fine aggregates in geopolymer mortars reinforced with natural fibers (i.e., 1% coir, ramie, sisal, hemp, jute and bamboo fibers, as well as 2% ramie fiber by volume fraction of fine aggregates). The flowability, mechanical properties (i.e., compressive strength and direct tensile strength), durability properties (e.g., water absorption), and drying shrinkage of the mortars were investigated. The results reveal that, at a given binder and fiber type, geopolymers containing WGS experience higher strength and lower water absorption than those containing LSS and natural river sand (NS). LSS-incorporated geopolymers exhibit a lower drying shrinkage when compared to the geopolymers prepared with WGS and NS. It is also found that geopolymers containing 1% ramie, hemp and bamboo fiber, and 2% ramie fiber exhibit higher compressive and tensile strengths and a lower drying shrinkage than unreinforced geopolymers, with those containing 1% ramie fiber exhibiting the highest strength and lowest drying shrinkage. These findings are promising and have significant potential for the use of natural fibers in the development of structural-grade construction materials, in which binder and aggregate are replaced with industrial by-products and waste-based materials.