Behavior of ultra-high performance concrete under true tri-axial compression

Abstract

Confinements have been adopted to alleviate the brittleness of ultra-high performance concrete (UHPC). However, as the foundation of confinement mechanism, the research on behavior of UHPC under tri-axial compression is rather limited. Furthermore, the confinement mechanism of PE fiber-strengthened UHPC (PE-UHPC) has not been reported yet. To this end, conventional and true tri-axial compression tests were performed for 22 UHPC cubes with different PE fiber lengths and various lateral confining stresses. The typical axial stress-strain curve has a long elastic ascending stage, a relatively short plastic ascending stage and a steep post-peak decline stage. Increasing the lateral confining stresses could extend the elastic ascending stage, and make the plastic ascending stage longer and clearer. Furthermore, the reinforcement effect of longer PE fibers became more pronounced with increasing lateral confining stresses. However, only increasing intermediate principal stresses with minor principal stresses unchanged had minor effect on the axial strain-volumetric strain behavior.