| The flexural fatigue strength of concrete is an important design parameter for structures exposed to cyclic loading. Steel and synthetic fibers are sometimes added to improve the flexural fatigue strength of concrete. Presently, the flexural fatigue performance of coarse monofilament self-fibrillating synthetic fiber reinforced concrete has only been studied at low fiber volume dosage (0.1%-0.5%). The primary objective of this research was to evaluate long-term flexural fatigue performance of coarse monofilament self-fibrillating synthetic fiber reinforced concrete to extend the database at higher volume dosages (0.75%-1.0%). The secondary objective was to examine the effect of fiber quantity, at the fracture surface, on the flexural fatigue behavior of synthetic fiber reinforced concrete in order to explain large variation observed in the number of cycles to failure in fatigue testing.;Research revealed that the flexural fatigue behavior of concrete was improved by the addition of coarse monofilament self-fibrillating synthetic fibers. The 2-million cycle flexural fatigue endurance limit of plain concrete was increased by 10% for a fiber addition rate of 0.75% volume and by 15% for synthetic fiber reinforced concrete at 1.0% volume. However, the flexural fatigue performance and endurance limit of plain concrete was reduced after prolonged curing. In comparison to plain concrete, the synthetic fiber addition, at the dosages used in this study, increased the flexural fatigue performance of concrete throughout the complete fatigue spectrum. In addition, there was no significant difference observed in the flexural fatigue performance of the three-year-old and the 28-day-old synthetic fiber reinforced concrete, at a fiber addition rate of 0.75% volume. Furthermore, fiber counts performed on beam specimens revealed no correlation between the number of fibers bridging the fracture surface and the number of cycles to failure.;Results from this research showed that the addition of fibers increases the flexural fatigue performance and the endurance limit of synthetic fiber reinforced concrete. The equations derived from this research will modify the design parameters used for plain concrete and contribute new information to the database of synthetic fiber reinforced concrete subjected to flexural fatigue loading.;The flexural fatigue performance of synthetic fiber reinforced concrete was evaluated for two fiber addition rates: 0.75% and 1.0% volume. The flexural fatigue performance of companion plain concrete specimens was also evaluated to determine the effect of synthetic fiber addition on the flexural fatigue behavior of concrete. Furthermore, the flexural fatigue performance of synthetic fiber reinforced concrete, at a fiber addition rate of 0.75% volume, was evaluated at two different ages (twenty-eight-day-old and three-year-old) in order to calculate effect of age on the flexural fatigue behavior of synthetic fiber reinforced concrete. The number of synthetic fibers at the fracture zone was also counted after flexural fatigue testing. In addition, an equation representing the flexural fatigue strength was determined for each concrete mixture, using regression analysis. |
