Effects of fiber content on mechanical properties of UHPFRC with coarse aggregates

Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is a relatively new construction material with superior mechanical properties. The addition of fibers in UHPFRC has been recognized to significantly enhance its tensile strength, post-cracking ductility and energy absorption capacity. This study investigates the influence of fiber content on the mechanical properties of UHPFRC with coarse aggregates. By applying the Brouwers design method, UHPFRC with a maximum particle size of 8 mm is achieved. The incorporation of coarse basalt aggregates reduces the powder volume fraction in the matrix, and hence brings economic and environmental benefits. Experiments are conducted to investigate the effects of fiber content on the tensile and compressive strengths, as well as the flexural behavior of the UHPFRC. The results show that the compressive strength of the UHPFRC is almost independent on the fiber content. On the contrary, the tensile and the flexural strengths are significantly increased with the increase of the fiber content, and consequently the toughness of the UHPFRC composite has a prominent enhancement with the addition of the steel fibers as well.