Development of Ultra High Performance Fiber Reinforced Concrete mixture

Formulation process of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is described in this paper. Materials locally available in the European Union were used throughout the optimization process. The mixture was also developed without any special curing, such as elevated temperature, pressure or vapor. The optimization process consisted of two steps. In the first step a cementitious matrix was optimized with respect to its maximal compressive strength, flexural strength and workability. The key element in the optimization process was to achieve maximal particles packing density, to choose efficient enough high-range water reducer (HRWR) and to decrease water binder ratio as much as possible. In the second step of the optimization process short, high tensile strength steel fibers were added into the matrix that showed highest workability and strength. The resulting compressive strength of UHPFRC mixtures exceeded 150 MPa after 28 days, average secant modulus of elasticity was in the range of 55 GPa and direct tensile strength in range of 10 MPa. During the optimization process mixtures with 1, 2 and 3% of fibers by volume were tested. It was found that with respect to acceptable workability and superior mechanical performance the optimal fiber content is between 2 and 3% by volume.