Effect of fiber geometric property on rate dependent flexural behavior of ultra-high-performance cementitious composite

In order to examine the rate dependent flexural performance of ultra-high-performance cementitious composite (UHPCC), a number of UHPCC beams containing three straight steel fibers with different aspect ratios of 65, 97.5, and 100 and one twisted steel fiber with an aspect ratio of 100 were fabricated and tested under quasi-static and impact loadings. Test results indicated that the use of long straight and twisted steel fibers resulted in improved quasi-static flexural performance, and their effectiveness was higher at large deflections. The twisted steel fiber was most effective at improving the deflection capacity and the'number of micro-cracks under quasi-static flexural loading. In contrast, long straight steel fibers were more favorable than twisted steel fibers in terms of impact resistance and residual performance after impact damage. A lower sensitivity of the strain rate to the dynamic increase factor (DIF) was obtained for the post-cracking flexural strength than for the first-cracking strength, and the use of twisted steel fibers led to lower sensitivity to the strain rate on the DIF of post-cracking strength than that of straight ones. Finally, the higher strength concrete was less sensitive to the strain rate than the lower strength concrete. (C) 2017 Elsevier Ltd. All rights reserved.