Effect of shrinkage reducing admixture on tensile and flexural behaviors of UHPFRC considering fiber distribution characteristics

This study investigated the effect of shrinkage reducing admixture (SRA) on the properties of ultra high performance fiber reinforced concrete (UHPFRC) including fluidity, compressive, single fiber pullout, tensile and flexural behaviors. In addition, the influence of fiber distribution characteristics such as fiber orientation, fiber dispersion, number of fibers, and packing density on the flexural behavior of UHPFRC was evaluated according to the amount of SRA, using an image processing technique that was developed. Three different SRA to cement weight ratios (0%, 1%, and 2%) were investigated on UHPFRC with 2vol.% of steel fibers. The specimen without SRA exhibited the best performance in compressive, single fiber pullout, and tensile behaviors including load carrying capacity, strain capacity, and energy absorption capacity and had a highly densified interfacial transition zone between fiber and matrix. In particular, the flexural strength of UHPFRC varied with the fiber distribution characteristics, rather than the amount of SRA.