Issue 42

A. Jadidi et alii, Frattura ed Integrità Strutturale, 42 (2017) 249-262; DOI: 10.3221/IGF-ESIS.42.27 256 results, the highest 7-day tensile strength exists in samples reinforced with 2.5% hybrid steel fibers (hooked steel fibers L/D=50 and crimped steel fibers L/D=50) with 5.45 MPa and 82.27% tensile strength increase according to Fig. 9. Figure 8 : Impact of steel fiber content on 28-day tensile strength of steel fiber-reinforced concrete. Figure 9 : Impact of steel fiber content on 7-day compressive strength of steel fiber-reinforced concrete. Figure 10 : Impact of steel fiber content on 3-day compressive strength of steel fiber-reinforced concrete. As shown in Fig. 10, the use of steel fibers has contributed to concrete short-term tensile strength increase in all cases. Based on Fig. 10, the 3-day tensile strength of all samples has increased. Based on these results, the highest 3-day tensile strength exists in samples reinforced with 2.5% hybrid steel fibers (hooked steel fibers L/D=50 and crimped steel fibers L/D=50) with 3.88 MPa and 69.43% tensile strength increase according to Fig. 10. As shown in Fig. 11, the 28-day bending strength of mixture designs has remarkably changed. It is worth noting that the use of steel fibers has contributed to concrete long-term bending strength increase in all cases . According to Fig. 11, the