Durability of Non-Proprietary Ultra-High-Performance Concrete for Pretensioned Bridge Girders

Abstract

Proprietary ultra-high-performance concrete (UHPC) has predominantly been used in bridge applications in the United States in connections, overlays, and girders. To facilitate further implementation, the Texas Department of Transportation (TxDOT) is supporting research to develop its own cost-efficient non-proprietary UHPC that will provide the same benefits as the proprietary mixes with a specific application to pretensioned bridge girders. This research presents an evaluation of the durability, particularly permeability, of select non-proprietary mixes made with locally available materials in Texas and provides a service life estimation based on the available methods and properties of these mixes.

Resistivity is a non-destructive test that is faster and more user-friendly than conventional permeability tests, while the formation factor is based on a numerical approach to quantify the porosity and pore connectivity. Determining the service life of the considered non-proprietary UHPC mixes provides an additional evaluation for durability. While multiple programs are available for service life prediction, their applicability to UHPC components needs to be better understood. Using available software, a more detailed analysis on the limitations and applicability to UHPC are made. Identifying the limitations of the software in the application to UHPC elements is crucial to the interpretation of the results and the subsequent comparative analysis between mixes used in similar applications.

It is concluded that the non-proprietary mixes studied have excellent permeability characteristics and microstructure development. The resistivity testing provided useful insight into the role of supplementary cementitious materials (SCMs) in UHPC microstructure development. The computed formation factors are used to calculate a diffusion coefficient. This diffusion coefficient aids in service life prediction and allows for a comparative assessment with other concrete mixes. While the limitations in the available software make it impossible to provide explicit results for service life prediction, the service life predictions coupled with the permeability testing indicate that the non-proprietary UHPC mixes have a strong potential to provide a service life exceeding conventional concrete mixes used in similar applications. The results also merit a further discussion for additional bridge applications outside of pretensioned bridge girders.