Assessment of the effect of fiber percentage in glass fiber reinforced slag-based geopolymer

Fibers can increase the ductility of geopolymer materials, acting as reinforcements to improve mechanical properties. These improvements depend on fiber content and quantity. This study evaluates the impacts of different percentages of glass fiber on a GBFS (ground blast furnace slag) geopolymer matrix. The glass fibers were used on the critical length of 20 mm, obtained by pull-out test in previous studies. Percentages of 0.25%, 0.50%, 0.75%, and 1.00% of glass fiber in mass were tested in fresh state, by flow measurement, and in hardened state, by variation of shrinkage, water porosity and response of composites under flexural and compressive load conditions at 7, 14, 28, and 90 days. The mixture resulted in a high porosity geopolymer paste. In addition, an analysis of variance (ANOVA) was performed to evaluate the statistical significance of fibers in compressive strength. The results show that increasing percentages glass fibers, until 0.75%, enhances mechanical properties. Percentage of 1.00% started to show accumulation of branch of multifilament fibers which contribute to higher drying shrinkage. The ANOVA test showed that the percentage of fibers can influence the compressive strength. With the results, the optimum percentage of fibers for his composite mixture was found at 0.75%.