Fracture energy of ultra-high-performance fiber-reinforced concrete at high strain rates

The fracture energy of ultra-high-performance fiber-reinforced concrete (UHPFRC) at high strain rates (5-92 s(-1)) was investigated, and specimens with 1-1.5% fibers exhibited very high fracture energy (28-71 kJ/m(2)). Evaluation of the rate effects on the UHPFRC fracture resistance, including fracture strength (f(t)), specific work-of-fracture (W-s), and softening fracture energy (W-F), indicated that f(t) and W-s were highly sensitive to strain rate, whereas W-F was not. The effects of fiber type, volume content, specimen shape and fiber blending on the fracture resistance at high and static strain rates differed significantly: 1) smooth fibers exhibited higher f(t) and W-s at high rates than twisted fibers; 2) higher fiber volume content did not clearly generate higher W-s and W-F at high rates; 3) notched specimens generally exhibited higher fracture resistance than un-notched samples at both static and high rates; and 4) UHPFRC blending two fibers produced higher W-s and W-F than UHPFRC with mono fiber at high rates. (C) 2015 Elsevier Ltd. All rights reserved.