13th International Conference on Fracture June16–21, 2013, Beijing, China -5test and loading test. Figure 1. UHPC precast specimen with 8 opening holes 3. Results and Discussion 3.1. Flexural Strength The ASTM C 1018 Standard Test Method for Flexural Toughness and First-Crack Strength of Fiber-Reinforced Concrete (Using a Beam with Third-Point Loading) was one test used to determine the flexural and tensile properties of UHPC at a specific steel fiber concentration of 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 percent by volume. The small-scale concrete prisms had dimensions of 160 mm × 40 mm ×40 mm were used in this test. During the test, the load on and the deflection of the prism are monitored. These data are then used to determine the cracking failure and flexural strength response of the UHPC concretes. The flexural strength test was performed on prisms from all two curing regimes. Table 4 shows flexural strength of UHPCs in comparison with different steel fiber concentration at normal curing and heat water curing. The result of the entire UHPC heat water curing treatment comparison is that UHPC exhibits significantly enhanced flexural strength compared with standard normal curing of UHPCs. The application of the heat water or steam treatment is clearly beneficial; however, this procedure is also not always necessary as long as the user is willing to accept its strength and durability in loss. Compared with the flexural strength of UHPCs in Table 4, the experimental result shows the UHPC containing up to 2.5% steel fiber content is reached the predetermined effect at particular load level of 30 kg/m2 flexural strength. Final tensile failure of UHPC generally occurs when the steel fiber reinforcement begins to debond from and to pull out of the UHPC matrix. Steel fiber has a tremendous effect on flexural strength of UHPC concretes. Test results from Table 4 showed that the effect of steel fiber on the flexural strength was apparent. All the UHPC concretes with 2.5%, 3.0% and 3.5% by volume steel fiber replacement showed significantly higher flexural strength than those of the control one (UHPC0) with the same curing condition at all ages. Figure 2 displays the photo of prism UHPC2.5 with crack extension and failure after flexural test.
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