Flexural performance and toughness of hybrid steel and polypropylene fibre reinforced geopolymer

In this study, the effects of steel and polypropylene fibre hybridization on the flexural performance of fibre-reinforced geopolymer were investigated. Fibre reinforcement has emerged as a way to improve the brittleness of geopolymer. There are currently several types of fibres available on the market. When polypropylene fibre is used, it usually yields a large drop in strength immediately after the first crack, as well as a lower post-peak response, owing to its high flexibility and low stiffness. To resolve these issues, a hybrid system is introduced using fibre with high strength and stiffness such as steel fibre. In the present study, two hybridization systems are investigated: replacement and addition systems. For a replacement system, the polypropylene fibre is replaced gradually with steel fibre at a rate of 0.2% by volume. For an addition system, the steel fibre is added into the mixture at the same rate. The results indicate that the hybridization of steel fibre can improve the flexural response, toughness, and residual strength of polypropylene fibre reinforced geopolymer to different degrees. Both the load dropping and second peak are found to improve almost instantaneously. The toughness and residual strength also increase gradually with an increase in steel fibre content.