Experimental Behavior of Precast Bridge Deck Systems with Non-Proprietary UHPC Transverse Field Joints

Full-depth precast bridge decks are widely used to expedite bridge construction and enhance durability. These deck systems face the challenge that their durability and performance are usually dictated by the effectiveness of their field joints and closure joint materials. Hence, commercial ultra-high performance concrete (UHPC) products have gained popularity for use in such joints because of their superior mechanical properties. However, the proprietary and relatively expensive nature of the robust UHPC mixes may pose some limitations on their future implementation. For these reasons, many research agencies along with state departments of transportation sought their way to develop cheaper non-proprietary UHPC (NP-UHPC) mixes using locally supplied materials. The objective of this study is to demonstrate the full-scale application of the recently developed NP-UHPC mixes at the ABC-UTC (accelerated bridge construction university transportation center) in transverse field joints of precast bridge decks. This study included experimental testing of three full-scale precast bridge deck subassemblies with transverse NP-UHPC field joints under static vertical loading. The test parameters included NP-UHPC mixes with different steel fibers amount, different joint splice details, and joint widths. The results of this study were compared with the results of a similar proprietary UHPC reference specimen. The structural behavior of the test specimens was evaluated in terms of the load versus deflection, reinforcement and concrete strains, and full assessment of the field joint performance. The study showed that the proposed NP-UHPC mixes and field joint details can be efficiently used in the transverse deck field joints with comparable behavior to the proprietary UHPC joints. The study concluded that the proposed systems remained elastic under the target design service and ultimate loads. In addition, the study showed that the use of reinforcement loop splices enhanced the load distribution across the specimen’s cross-section.

Flexural Strength of Thin Slabs Made of UHPFRC

This paper focuses on the determination of the flexural strength of thin slabs made of the Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The load-bearing capacity in bending of elements reinforced only with steel fibers (used as a scattered reinforcement) is primarily influenced by the orientation and distribution of the fibers. A size-effect occurs by these elements. Some special bending tests were executed within the development of precast bridge deck segments for an innovative timber-concrete composite bridge system. The bending tests were executed on the slab strips under similar boundary conditions as by the bridge deck segments. The slab strips of various thickness of 40, 50, 60, 70 and 80 mm were tested in 4-point bending tests with span 1900 mm and in 3-point bending tests with span 600 mm. Half of the test specimens was tested in casting position, the other half was tested upside down. The obtained values of the flexural strength were compared to values from reference bending tests of the beams 150 x 150 x 700 mm, 100 x 100 x 400 mm and 40 x 40 x 160 mm. An influence of the different size of the tested specimen, of the slab thickness, of the span size and of the positioning of the slab with respect to the direction of casting on the flexural strength are evaluated. The experiments are further supported by numerical simulation.