Triaxial Behavior of High-Strength Concrete and Mortar

Abstract

Triaxial axisymmetrical compression tests were performed on cylinders of ultra-high-strength mortar. The matrix was reinforced with straight steel fibers (6% by volume) and had a uniaxial compressive strength of 165 MPa (24 ksi). Comparisons were made with similar triaxial strength results on plain high-strength concrete (HSC) and mortar. The Coulomb friction failure criterion was applied to fit the data. The brittle compressive failure of HSC was reflected in the appearance of the failure criterion. The angle of friction governing the behavior under small confinement pressures equaled 51 deg (0.9 rad) instead of 37 deg (0.6 rad), which is typically seen for normal strength concrete. Under increasing confinement pressures, the angle of friction reduced to 30 deg (0.5 rad), attributable to the fact that the crack growth in HSC is only slightly influenced by the aggregate. Finally, the axial and lateral strains corresponding to the ultimate triaxial load were assessed in order to predict the deformations of confined HSC.