The Mechanical and Fracture Characteristics of Low Fiber Content Slurry-Infiltrated Fiber Concrete

It is well known that fiber additives provide concrete with significant ductility after the peak load depending on the fiber content. However, due to workability and balling effects, the maximum usage limit of steel fibers is about 3% by volume. To overcome these obstacles, a cement-based slurry is infiltrated into the vacancies between steel fibers, which is a special type of fiber-reinforced concrete named SIFCON. Although the flexural response of SIFCON has been studied well, fracture characteristics have not been dealt with in depth. In this work, three-point static tests were conducted on notched beams produced with SIFCON with steel fibers (i.e., 0, 2.5, and 5.0% by volume). Fracture formations from the beginning to the end of the experiment were traced with the digital image correlation method. Test results show that the crack mouth opening displacement (CMOD)-to-net vertical deflection ratio was constant for the fiber ratios of 2.5 and 5.0%. It was also revealed that steel fibers significantly improved the fracture energy but slightly changed the initial fracture toughness of SIFCON. Nonlinear sectional analysis was also performed using several tensile models for fiber-reinforced concrete. The numerical results indicated that the peak load in the experiment was best estimated by the RILEM TC162-TDF tension model.