Transfer & Development Lengths in Prestressed Self-Consolidating Concrete Bridge Box and I-Girders

Self-consolidating concrete (SCC) is a workable yet stable concrete which flows easily and consolidates under its own weight. Its unique properties can substantially reduce the labor required to pour complex or heavilyreinforced structural members. Over the past decade, the American precast industry has taken significant strides to adopt SCC in commercial projects, though concern about early-age bond behavior has limited the material’s application in prestressed members. A general need remains for further research on the bond properties of SCC in full-scale prestressed members. The wide array of specimen types and SCC mixture designs utilized in practice further underscores this need. To explore the application of SCC in Illinois bridge construction, the Illinois Department of Transportation (IDOT) and Illinois Center for Transportation (ICT) sponsored a three-phase study investigating the bond behavior of steel strands in pretensioned bridge box and I-girders. In the first phase, 56 pullout tests were conducted to compare the performance of seven-wire strands embedded in SCC to that of strands in normallyconsolidated concrete (NCC) blocks. In the second phase, transfer lengths of prestressing strands in two 28-ft. SCC hollow box girders and two 48-ft. SCC I-girders were determined experimentally. In the third phase, development lengths of strands in the four girders were determined through a series of iterative flexural tests. This report details the experimental program for the study’s three phases and compares results to current requirements of the American Concrete Institute (ACI) and the American Association of State Highway and Transportation Officials (AASHTO). The results of this study may prove fundamental to the safe application of SCC within the state of Illinois’ prestressed concrete industry.Illinois Department of Transportation ICT R27-56published or submitted for publicationnot peer reviewe