Performance characteristics of micro fiber-reinforced geopolymer mortars for repair

Fiber reinforced geopolymer materials are recently being considered as prominent sustainable repair materials for concrete retrofitting/repair due to their good bonding properties. The addition of fibers to geopolymers materials may considerably improve their mechanical properties but they also effect on physical properties such as setting, workability, density, porosity. It is crucial to understand these characteristics of micro fiber reinforced geopolymer mortars before optimizing the micro fiber for geopolymer mortars for repair. In this study, the effects of micro fiber type and fiber volume fraction on the physical characteristics and on flexural behavior are investigated. In addition, the influence of different heat curing durations on the properties of micro fiber reinforced geopolymer mortars is also examined. Six types of micro fibers (high-strength steel, waste steel wool, polyvinyl alcohol, polypropylene, polyester & carbon) at low fiber volume fractions of 0.5%, and 1.0% are considered to study the physical properties (workability, and total porosity) and flexural behavior of fly ash-based geopolymer mortars. High strength steel fibers imparted the least change in workability whereas with polyester fibers the flow was the lowest. Porosity as well was highest for polyester fiber reinforced mortars followed steel wool and polypropylene. Significant improvements in the flexural behavior and compressive strength due to micro fiber reinforcement are noted particularly in steel and polyvinyl alcohol fibers. Deflection hardening was observed for mortars with 1% polyvinyl alcohol fibers, and for both 0.5% and 1% steel fibers. The overall flexural performance of polyester, steel wool, and carbon fibers reinforced geopolymer mortars was dismal. Increasing the duration of heat curing from 4 h to 24 had little change in total porosity and compressive strength. In flexural behavior however, the effect of prolonged heat curing was more noticeable. (C) 2019 Elsevier Ltd. All rights reserved.