摘要: |
In past decades, many state DOTs and the Federal Highway Administration (FHWA) have begun working with ultra-high performance concrete (UHPC), an advanced cementitious material. The Washington State Department of Transportation (WSDOT) has not employed the UHPC in highway bridge applications, such as connection joints for precast concrete decks and girders due to its high cost and lack of experience. In this study, two viable mixtures (A4 and C3) were selected from an array of trial UHPC mixtures produced using local materials (primarily the local fine sand and domestic steel fiber) for extensive performance evaluation. The physical and mechanical properties (including work-ability, compressive and tensile strength, elastic modulus, and shrinkage) of selected UHPC mixtures and their bond properties with the epoxy-coated reinforcing bars were investigated. The two considered mix designs exhibited compressive strength up to 16 ksi, direct tensile strength of 1.1 ksi, elastic modulus of 5,000 ksi, and relatively high bond strength. Shrinkage was also characterized and found to be about 600 mu epsilon which is comparable to that of conventional concrete. Based on the comparisons of material properties and bond strength of two selected mixtures, the mixture C3 outperforms the mixture A4, and it is thus recommended to be used in the second phase of the project study for the structural level testing and evaluation at the University of Washington. |