Ultra-high performance concrete (UHPC) for closure pours between precast concrete deck panels
Lim, Sung Yeob
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Ultra-high performance concrete (UHPC) is a relatively new type of concrete that has been implemented in bridge construction in many states. UHPC has improved mechanical properties such as higher compressive and tensile strengths than conventional concrete. In bridge construction, UHPC can be used as joint pour between precast structural elements such as deck panels and bulb-T girders. The usage of UHPC can significantly reduce construction time and long-term maintenance cost of bridges. However, commercially available UHPC is prohibitively expensive and, therefore, is not currently widely in bridge construction. For this reason, many studies have worked to develop a non- proprietary UHPC mix design. Often, silica fume is used as a key component in UHPC, however, it is not easily accessible in Georgia. This research focuses on developing and evaluating a non-proprietary UHPC mix design using locally-available materials in the state of Georgia. Metakaolin and Type F fly ash are used as supplementary cementitious materials (SCMs) instead of silica fume. In this investigation, a UHPC mix is designed, implemented, and tested to meet baseline mechanical properties. The mix design demonstrates the required 28-day compressive strength of at least 18,000 psi and tensile strength of at least 750 psi. The UHPC mix then underwent testing to further investigate its feasibility in a structural application. Precast concrete deck panels were joined together by a closure pour filled with UHPC and these panels were tested to determine UHPC joint performance. The deck panel specimen tested in this research has demonstrated that the non-proprietary UHPC performs satisfactorily in a structural load test. Further research is needed to better evaluate and validify the integrity of the non-proprietary UHPC mix developed in this investigation.