Investigation of mechanical properties of geopolymer beam elements produced with different fiber compositions

In this study, a total of 5 geopolymer concrete beams, including macro steel fiber full zone, macro steel fiber tensile zone, micro steel fiber full zone, micro steel fiber tensile zone and fiberless control mixture with a total fiber content of 1% by volume, were produced using blast furnace slag. The effect of using fiber in the full region and tensile region of the produced geopolymer beams on the mechanical properties under loading was investigated. In the study, sodium silicate and sodium hydroxide were used together as activators. Sodium hydroxide solution was prepared at a concentration of 10 moles. 13 mm long micro steel fiber and 60 mm long macro steel fiber were used as fiber type. In order to determine the optimum mixing ratios in the first stage, basalt, hemp, glass fiber, macro and micro steel fibers were produced in samples of 40*40*160 mm size with 0.25%, 0.50%, 0.75% and 1% fiber ratios for precasting. At the end of 7 and 28 days, the changes in compressive and bending strengths were examined and the mixture ratio that gave the best results was determined. In order to optimize the best mixing ratio, sodium silicate (Na2SiO3) was added to the mixture as a plasticizer and activator. Significant increases were observed in compressive and flexural strengths after the additions. Considering the displacement criteria of the beams after the bending test, the most effective displacement was observed in the steel fiber. Steel fiber increases the energy absorption capacity of concrete and makes it exhibit ductile behavior. In order to use fibers economically, regional examinations of macro and micro steel fibers in concrete were carried out. If we compare the use of full zone fiber in the beam for macro and micro steel fiber, micro steel fiber exhibited better strength than macro steel fiber, but macro steel fiber provided the best load bearing continuity. If the tensile region is compared, micro steel fiber performed better than macro steel fiber in terms of both strength and load bearing continuity.