Evaluating fracture characteristics of ultra-high-performance fiber-reinforced concrete in flexure and tension with size impact

This study highlights the size impact on the fracture characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC) under flexure and tension through a series of experiments. The studied UHPFRC contained 1 % twisted steel macro and 1 % smooth steel microfiber by volume. The flexural specimens were rectangularly prism-shaped, while the tensile specimens were bell-shaped. To assess the size impact, only the volume change was investigated in flexure, while changes in gauge length, thickness, section area, and volume were studied in tension. The partial/total energy, partial/total toughness, and length of the cohesive zone of UHPFRC were determined. First, the studied UHPFRC produced a normal size effect on partial/total fracture toughness, complementary toughness, and microcrack number in both flexure and tension. The hardening fracture toughness was noticeably higher than the complementary toughness. Second, the length of the cohesive zone of UHPFRC was much higher than that of conventional concrete. Third, the Weibull modulus values of UHPFRC for the hardening fracture toughness, complementary toughness, and number of microcracks per 100 mm were drawn based on the Weibull statistical theory. The normal size effect of UHPFRC on these parameters under tensile load was more obvious than that under flexural load.

Automated summary

This study investigates the influence of size on the fracture characteristics of UHPFRC under flexure and tension conditions. The UHPFRC samples contained 1% twisted steel macrofibers and 1% smooth steel microfibers. The study finds that the UHPFRC exhibits a normal size effect on fracture toughness and microcrack number, with the hardening fracture toughness being higher than the complementary toughness. The length of the cohesive zone in UHPFRC is significantly greater than that in conventional concrete, and the size effect is more pronounced under tension load.