Effect of synthetic fibers on the properties of geopolymers based on non-heat treated phosphate mine tailing

Abstract In this paper, the use of synthetic fibers as reinforcement of geopolymer matrix produced from phosphate mine tailings was investigated. Non-heat-treated phosphate sludge (PS) was mixed with metakaolin (MK) in a ratio of 50% by weight, then blended with the alkaline activator to produce the geopolymer slurry; after that, the fibers (polypropylene (PPF) and glass fibers (GF)) was added in quantities of 0.25, 0.50, 1 and 1.5%. The effect of the incorporated amount and fiber type on the geopolymer matrix in terms of fresh and handed state properties, such as workability, microstructure, morphology, flexural properties, and bulk density on the geopolymer composite was studied. The results indicate that the geopolymer composites’ flexural strength increases with increasing the amount of the fibers, it was also found that the inclusion of a maximum amount of 1% of polypropylene and glass fibers increased the flexural strength of the geopolymer composite by 278% and 26%, respectively. Besides, the addition of PPF leads to a highly ductile composite and provides a better fracture mode compared to GF. While, the partially and/or unreacted PS particles prevent the geopolymer composite from the considerable decrease of apparent density (slight loss of 5%), resulting from a reinforcing role as well. Microstructural analysis of the geopolymer composite shows a compact microstructure and an acceptable interfacial bond of the fibers with the geopolymeric binder. The current research findings indicate that PS-based geopolymers can reach high ductility with the appropriate reinforcement material. volume.