Ultra High-Performance Fiber-Reinforced Concrete (UHPFRC): a review of material properties and design procedures

This paper does a review of the recent achievements on the knowledge of UHPFRC properties and in the development of design procedures. UHPFRC is defined as a new material, with unique properties (high ductility, low permeability, very high strength capacity in compression, higher toughness) in comparison to conventional concrete. It is important to know both material and mechanical properties to fully take advantage of its outstanding properties for structural applications. However, since this is a new material, the current design codes are not well suited and should be reviewed before being applied to UHPFRC. In the first part, the following material properties are addressed: hydration process; permeability; fibers role; mix design; fiber-matrix bond properties workability; mixing procedure; and curing. In the second part, the mechanical properties of the material are discussed, together with some design recommendations. The aspects herein examined are: size effect; compressive and flexural strength; tensile stress-strain relation; shear and punching shear capacity; creep and shrinkage; fracture energy; steel bars anchorage and adherence. Besides, the tensile mechanical characterization is described using inverse analysis based on bending tests data. In the last part, material behavior at high temperature is discussed, including physical-chemical transformations of the concrete, spalling effect, and transient creep. In the latter case, a new Load Induced Thermal Strain (LITS) semi-empirical model is described and compared with UHPC experimental results.