Production of Cast-in-Place UHPC for Bridge Applications

Ultra-high performance concrete (UHPC) is a new class of concrete that has mechanical and durability properties that far exceed those of conventional concrete. The use of UHPC will result in significant improvements in the structural capacity and durability of bridge components. Due to its superior characteristics, UHPC has drawn substantial interest in the bridge community at both federal and state levels. Besides the bridge deck connections applications in multiple states, Federal Highway Administration (FHWA) Every Day Counts (EDC-6) program “UHPC for Bridge Preservation and Repair” emphasizes the use of UHPC for bridge applications due to its excellent mechanical and durability properties. Nebraska Department of Transportation (NDOT) successfully constructed connections/joints in bridge decks for the Primrose East Bridge in 2013, and Belden-Laurel Bridge in 2018. However, the unit cost of UHPC used in these two projects was as high as $13,000/CY, primarily due to the high unit cost of materials, shipping of materials and equipment, and transportation/accommodation for technicians associated with the use of proprietary mixes. The research team has already developed a non-proprietary mix using local materials through a recent completed NDOT project (SPR-P1(18) M072) entitled “Feasibility Study of Development of Ultra-High Performance Concrete (UHPC) for Highway Bridge Applications in Nebraska” with a unit cost at approximately $740/CY. While the development of non-proprietary UHPC mixes could greatly encourage the usage of UHPC, the lack of training and experience in batching and handling the material hinders its widespread use. FHWA and multiple state agencies have recently developed guidelines for the use of UHPC. There is also a current research project sponsored by the Precast/Prestressed Concrete Institute (PCI) for developing UHPC design and production guidelines for precast components in building and bridge applications. Moreover, multiple documents are currently under development through the American Association of State Highway and Transportation Officials (AASHTO), FHWA, American Concrete Institute (ACI) Technical Committee 239 (UHPC), and other state agencies. However, most of these documents are focused on either the design of UHPC components or precast UHPC production. There is a lack of detailed guidelines on cast-in-place (CIP) UHPC production and handling, especially when non-proprietary mixes are used. Due to the large amount of fine powders and the very low water-to-cement ratio in UHPC, the proportioning and batching of UHPC is very different from conventional concrete. Also, while it is generally known that UHPC is very flowable, it is often challenging to achieve the desired workability while maintaining stability. As shown in Figure 2, too high flowability could lead to fiber segregation. On the other hand, the viscous nature of UHPC could lead to a lack of flow and consolidation. Another peculiarity of UHPC is the rapid workability loss due to the high content of high-range water-reducing (HRWR) admixture. The self-consolidation properties of UHPC cannot easily stand for an extended period of time, resulting in issues of concrete transportation and placement. A preliminary study from the investigators shows that guidelines need to be developed to better control the workability and stability of UHPC in both static and dynamic conditions.

    Language

    • English

    Project

    • Status: Programmed
    • Funding: $83996
    • Sponsor Organizations:

      Nebraska Department of Transportation

      1500 Nebraska 2
      Lincoln, NE  United States  68502
    • Project Managers:

      Halsey, Lieska

    • Principal Investigators:

      Hu, Jiong

      Morcous, George

    • Start Date: 20210701
    • Expected Completion Date: 20230531
    • Actual Completion Date: 0

    Subject/Index Terms

    Filing Info

    • Accession Number: 01769365
    • Record Type: Research project
    • Source Agency: Nebraska Department of Transportation
    • Files: RiP, STATEDOT
    • Created Date: Apr 12 2021 2:10PM