Fixing imperfections in keyed dry joints between the concrete segments compromise the performance of precast concrete segmental bridges (PCSBs), which needs to consider carefully. In this study, a finite-element model on high-strength concrete single-keyed dry joints in PCSBs was established and validated by experimental results. Parametric studies on fixing imperfections in key, concrete strengths, and confining pressures were carried out based on that model. The numeric results included crack patterns, load–displacements and shear strength. Fixing imperfections—especially at lower surface of keys—reduced shear strength of single-keyed dry joints by the different shear transfer mechanism. Higher confining pressure and concrete strength improved the shear strength, but they mitigated and aggravated the effect of fixing imperfections at lower surface of key on shear strength, respectively. Compared with simulating results, AASHTO standard overestimated the shear capacity of single-keyed dry joints with fixing imperfections at lower surface of key by up to 0.602–22.0%, but greatly underestimated that of the rest. A modified formula with a strength reduction factor was proposed. For six experimental three-keyed dry-joint specimens and 30 numeric single-keyed dry-joint specimens with or without fixing imperfections, the average ratio of code predictions to experimental results was 90.4% and 81.6%, respectively.

To widen bridges, a usual method is to cast joint connections between new and old bridge decks without traffic interruption. The traffic vibrations have negative influence on the quality of joint connections. Shortening the construction time can alleviate the impact on the traffics, a fast-hardening retarding high-early-strength concrete (FRHC) for the connections is in need. In this study, low-alkalinity sulphoaluminate cement (LASC) concrete was modified to gain these characteristics. Based on FRHC concrete, four slab specimens including a monolithic concrete slab and three joint FRHC slabs were cast to investigate their flexural behaviors. With proper splicing details in joint connections, the joint FRHC specimens behaved approximately similar to the monolithic specimen. Combing the laboratory tests and engineering practice, the newly developed FRHC mixture succeeded in fast-hardening, retarding and high-early strength and the joint connections filled with FRHC have a good flexural performance.