5 10 15 20 25 Number of cracks 1 10 100 1000 Cycles x 1,000 Control Steel fiber: 0.5% Steel fiber: 1.0% Applied load: 60% of ultimate strength 0 Figure 5: Effect of number of load cycles on number of cracks 0.00 0.50 1.00 1.50 2.00 2.50 Crack width - mm 0 100 200 300 400 500 600 700 Cycles x 1,000 Steel fiber: 0.5% Control Applied load: 60% of ultimate strength Steel fiber: 1.0% Figure 7: Effect of number of load cycles on crack width 5 10 15 20 25 Number of cracks 1 10 100 1000 Cycles x 1,000 Control Polyproplene fiber: 0.5% Polyproplene fiber: 1.0% Applied load: 60% of ultimate strength 0 Figure 6: Effect of number of load cycles on number of cracks 0.00 0.50 1.00 1.50 2.00 2.50 Crack width - mm 0 300 600 900 Cycles x 1,000 Control Polyproplene fiber: 0.5% Polyproplene fiber: 1.0% Applied load: 60% of ultimate strength Figure 8: Effect of number of load cycles on crack width broken at 250,000 cycles. On the other hand, the increase of the number of cracks of beams with fibers be less. The difference between concrete with polypropylene fibers and steel fibers in the number of crack is small. Figures 7 and 8 show the crack width with the increase in number of load cycles. In Figure 7, the crack width of concrete with steel fibers is compared with that of control. In Figure 8, the crack width of concrete with polypropylene fibers is compared with that of control. Crack width which shown in these figures is average of the crack width for all cracks of each specimen. The development of crack width of control beam is quite different from that of beam with fibers. The crack width of control beam is over 5 times as wide as that of beam with fibers. The difference between concrete with polypropylene fibers and steel fibers in crack width is small, too. Photos 1 and 2 show the control beam and polypropylene fibers beam just before failure. As clear from these photos, the decline of serviceability of control beam can be confirmed. The failure cycles of fiber’s beams is between 500,000 and 800,000 cycles. It is not clear whether the fibers has played a role in prolonging fatigue life or increasing the capacity of fatigue load, because the fatigue is estimated by the order of cycles when concrete beam is broken not by the number of cycles itself. It is noticed that the number of cracks and crack
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