Experimental Investigation on Hybrid Steel Fibers Reinforced Self-compacting Concrete under Flexure

Using the self-compacting concrete (SCC) can shorten the time and decrease the costs of the building process. The incorporation of the randomly distributed steel fibers into brittle SCC improves its tensile parameters. The steel fibers can be effective in delaying propagation of micro- or macro-cracks according to geometrical parameters of fibers. To attract all types of cracks the fibers with different geometrical parameters should be used simultaneously. In the present paper, the influence of the combinations of straight and corrugated steel fibers with different lengths (6 mm, 35 mm) and cross-sectional shape on the compressive strength and flexural behavior of SCC was investigated. The total fibers volume ratio varied from 1.0% to 3.0%. Among the rheological parameters of self-compacting concrete, the hybrid fibers reinforcement did not influence workability but pronouncedly decreased passing ability. Thus, the mixes reinforced with the highest fibers volume ratios did not satisfy the requirements for the SCC. Based on the mechanical test results no apparent difference in the compressive strength was noted. The results showed that the flexural parameters were pronouncedly enhanced in the HFR-SCC due to the hybrid fiber addition and at low dosage rates depended on the proportions between the two applied types of fibers. However, using the highest summary amounts of fibers did not cause further increase in flexural parameters.