Development of Non-Proprietary Ultra-High Performance Concrete (UHPC) Prestressed Bridge Girders

Project summary:

Bridge girders made of ultra-high performance concrete (UHPC) allow for members with shallower depths to achieve longer spans as well as reduced substructure and grading costs while still achieving required under-bridge clearances. Additionally, bridge service lives are extended due to the reduced permeability and increased tensile strength of UHPC. This project focuses on identifying and eliminating barriers to the development and implementation of precast, prestressed concrete bridge girders in Minnesota and Wisconsin using non-proprietary UHPC made of local material resources. The main objectives of the project are summarized below:

1. Work with the producers of MnDOT's and WisDOT's precast, prestressed bridge girders to identify and characterize locally available materials. Use particle packing theory and lessons learned from similar work performed by the Precast/Prestressed Concrete Institute (PCI), Federal Highway Administration (FHWA), Texas, Iowa, and Montana Departments of Transportation, and others to proportion a non-proprietary UHPC mixture.

2. Optimize UHPC mixture design through laboratory trial batches focused on reaching a desired flow through reducing water and mindful use of high-range water reducers (HRWR), and then validate through compressive strength, flexural strength, and workability retention testing.

3. Through in-plant test batches, verify the UHPC mixture can be batched, mixed, formed, placed, finished, cured, and transported at the precast plant utilizing existing facility equipment. Cast short, full-section specimens to ensure flow and consolidation and verify performance by monitoring compressive strength, flexural strength, and shrinkage.

4. Design and fabricate a full-section girder at each plant and transport the girders to the University of Minnesota Twin Cities (UMTC) Galambos Structural Testing Laboratory, where decks will be cast on the girders. The girders will be monitored for time-dependent effects and tested to investigate their flexural and shear strengths.

5. Verify the mechanical performance of the mixture (e.g., compressive and tensile strengths ductility, modulus of elasticity), time-dependent behaviors (i.e., creep and shrinkage), and durability (i.e., rapid chloride permeability) of the UHPC.

6. Develop a specification based on lessons learned, PCI's recommendations, and the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Guide Specifications for Structural Design.