Investigation of flexural behavior of fibers reinforced geopolymer concrete hallow beams

This study is focused influence of steel and glass fibers on mechanical and structural properties for geopolymer concrete. Furthermore, the effect of hybrid fiber of steel and glass fibers on same these properties was studied also. Where test specimens were manufactured from the geopolymer concrete composites contain of alkaline liquids, 50% fly ash and 50% ground granulated blast furnace slag. The mixtures were designed for 14M molarity and the proportion of sodium silicate equivalent 2.5 than sodium hydroxide and used for producing geopolymer concrete. With this mixture, fibers were added (1%) steel, (0.5%) glass to the full volume of concrete and obtained hybrid fiber by mixing half of amount from both types. The material tests were done for workability, compressive strength (fc') and tensile strength (fsp) for 7, 28 and 56 days. For structural parameters were casted 12 beams (4 solid, 4 circular-hollow and 4 square-hollow) and tested under 3-points monotonic test, for investigation and comparison in terms of Flexural strength, ductility and failure patterns. The experimental test results indicated that there were improved compressive and tensile strength of geopolymer concrete due to use the steel, glass and hybrid fibers. Also these fibers led to improvements in resistance the first crack and ultimate load, ductility increasing, best control on crack patterns and an appropriate converge in the behavior of solid and hollow beams. Key words: Fly ash, Glass fiber, Geopolymer concrete, Hybrid fibers, Steel fiber.