Experimental investigation on shear behavior of PVA-ECC keyed joints

Keyed joints play a critical role in ensuring the overall behavior of a precast concrete segmental bridges. However, these joints can exhibit poor shear capacity and durability as well as brittle failure. Polyvinyl alcohol fiber-reinforced engineered cementitious composites (PVA-ECCs) exhibit high shear strength and ductility as well as excellent fracture performance, making them attractive for use in the joints of segmental bridges. This study fabricated 16 Z-shaped specimens with number of keys (one, two, or three), concrete materials (normal concrete or PVA-ECC), and types (monolithic, epoxy, or dry) to investigate their failure modes, cracking loads, shear capacities, residual capacities, and shear stress-vertical displacement curves. The results indicated that the keyed joints exhibited shear failure at the root of a shear key, and an increase in the number of keys increased the residual strengths and ductility of both the dry and epoxy joints, but it had a negative effect on the shear strengths. When PVA-ECC was applied instead of normal concrete, the cracking resistance index for all joints improved significantly and the shear strengths and ductility of the monolithic and keyed epoxy joints increased. Generally, the shear strengths of the epoxy joints were 6.3-29.1% higher than those of the corresponding dry joints; however, the ultimate displacements of the epoxy joints were 46.6-72.4% lower. Finally, a method for calculating method of the shear capacities of keyed PVA-ECC joints was proposed and verified to accurately predict the behaviors of previously tested joint specimens.