Issue 42

A. Jadidi et alii, Frattura ed Integrità Strutturale, 42 (2017) 249-262; DOI: 10.3221/IGF-ESIS.42.27 255 Figure 5 : The impact of fiber content on the 28-day tensile strength of steel fiber-reinforced concrete. Figure 6 : Impact of steel fiber content on 3-day tensile strength of steel fiber reinforced concrete. Figure 7 : Tensile toughness of cylindrical samples. As shown in Fig. 6, application of steel fibers has increased short-term tensile strength of concrete in all cases . According to Fig. 6, 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=30 and crimped steel fibers L/D=50) with 3.98 MPa and 73.79% tensile strength increase according to Fig. 6. Pictures below show samples after splitting test. The tensile toughness of concrete has significantly increased and concrete behavior become softer. As shown in Fig. 8, the 28-day tensile strength of mixture designs has remarkably changed. It is worth noting that the use of steel fibers has contributed to concrete long-term tensile strength increase in all cases. According to Fig. 8, the 28-day tensile strength of all samples has increased. Based on these results, the highest 28-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 7.02 MPa and 77.72% tensile strength increase. However, according to Fig 8, the use of steel fibers has contributed to concrete tensile strength increase in all cases. Based on Fig. 9, the 7-day tensile strength of all samples has increased. Based on these