Flexural behavior of UHPC joints for precast UHPC deck slabs

This study aims to experimentally investigate the flexural behavior of ultra-high-performance concrete (UHPC) joint connection for precast UHPC deck slabs. Twelve full-scale jointed UHPC deck slabs were tested and discussed with respect to their failure modes, load-displacement response, ductile behavior, and cracking characteristics. The experimental variables included shape of the joint connection, steel reinforcement diameter, restraining condition of the precast UHPC slab, and joint interface roughness. The experimental results showed that all specimens exhibited a flexural failure with yielding of steel reinforcement, local UHPC crushing at the top surface, and excessive opening of the flexural crack, but exhibited varying locations of the critical crack between the tests. In comparison to the integral casting detail, the rectangular joint had a lower cracking resistance, post-cracking stiffness, and flexural capacity as well as higher ductility, whereas the T-shaped joint led to a relatively higher cracking resistance, stiffness, and flexural capacity as well as lower ductility. Both joint shapes showed little influence on the specimens’ pre-cracking stiffness. In addition, increasing the steel reinforcement diameter not only improved the flexural capacity of the UHPC joint connection but also improved the cracking resistance (including the cracking load, the load at the crack width of 0.05 mm, and the crack width propagation rate). Moreover, the mechanical performance of the jointed UHPC slabs with different restraining conditions in the precast UHPC slab was similar. Furthermore, improving the interface roughness at the precast UHPC slab is in favor of increasing the cracking resistance, but played little effect on other mechanical characteristics. The present main outcomes might provide a reference for future flexural design on the precast UHPC deck slab with the UHPC joint connection.