Improving the flexural and post‐cracking behavior of fly ash‐based concrete using hybrid steel fibers

Abstract The conventional concrete beam has been known to fail in a brittle manner when subjected to flexural loadings, and as such limits the structural performance of traditional concrete beams. Although adding steel fibers increases the ductility and energy‐absorbing capabilities of fiber‐reinforced concrete, it is still limited by the amount of cement used. Therefore, the use of High Volume Fly Ash concrete provides a more environmentally friendly alternative to using large amounts of cement and, as such, reduces the significant environmental impact from the emissions produced during the production of cement. HVFA concrete inherently has low ductility properties due to its brittleness. The addition of hybrid steel fibers may provide an opportunity to improve the flexural behavior of HVFA concrete, thus increasing its potential to be used as a viable material for structural applications. It has been reported that hybrid steel fibers can improve the flexural performance, but their influence on HVFAC remains unexplored. The total fiber content varied between 0% and 2% by volume of concrete, with hybrid fibers combined in a 1:1 mass ratio for all mixes. This ratio was selected based on previous studies demonstrating an optimal balance between micro‐crack resistance and pull‐out resistance. It was observed that incorporating just 1% hybrid fibers significantly regains the strength loss of the HVFA concrete. It was concluded that adding 2% hybrid fibers to HVFAC greatly enhances the flexural performance of concrete beams by increasing load‐bearing ability, decreasing crack width, and improving strain capacity.