Direct Biaxial Behavior of Ultra-High-Performance Concrete

Ultra-high-performance concrete (UHPC) is known for its high strength and advanced durability. Due to the unique formulation of this material, including a fine cementitious matrix and distributed steel fibers, UHPC displays different material behavior than conventional concrete. This paper examines the biaxial tension-compression behavior of UHPC using a novel biaxial test method and compares results to biaxial failure criterion of conventional concrete. A total of 62 specimens were tested to evaluate the effects of curing regimes and fiber orientations. While the compressive strength of UHPC increased significantly when steam treated, tensile strength did not increase to the same degree. Controlled fiber orientation provided more compressive stress resistance than random fiber orientation with the presence of increasing tensile stress. Comparing UHPC results to biaxial failure criterion recognized for conventional concrete, the Mohr-Coulomb biaxial failure criterion was shown to be a conservative model for UHPC for all fiber orientations and curing regimes.