Flexural behavior of hybrid ultra-high-performance concrete

Abstract

Ultra-high performance fiber reinforced concrete has superior mechanical and structural properties but the major drawback of this new construction material is its high cost. This research presents an experimental study to investigate the flexural behavior of hybrid ultra-high-performance concrete with different steel fibers' volume fractions, cast in full and partial depths of specimen's cross sections to exploit the advantages of steel fibers in optimal way. The variables studied included the percentages of steel fibers used (0, 1, 2 and 3) % and the fraction of depth containing the steel fibers (0.25, 0.5, 0.75 and 1). Experimental results show that the failure load increases with the increase in the fraction of depth where the steel fibers were distributed. This increase was more significant as the fraction of depth increases from 0.25 to 0.5 and 0.75. As it reached the 0.75 the increase was none pronounced, and the failure load was almost similar to that of full depth. Therefore, it can be concluded that the maximum effective fraction of depth would be 0.75. It was noted that the different distribution of the same amount of the steel fibers within the depth of the section greatly affects the specimen load capacity and using the steel fibers in the tension zone effectively enhances the flexural performance of UHPFRC. The results also indicate that increasing the steel fiber volumetric ratio from 0% to 1%, 2% and 3% the percentages of increase in the failure load (Pf) with respect to the control specimen were 156%, 261% and 389%, respectively.