Design and field construction of Hawkeye Bridge using ultra high performance concrete for accelerated bridge construction

The Ultra High Performance Concrete (UHPC) consists of sand, cement, crushed quartz, silica fume, superplasticizer, water and steel fibers, with water-to cement (w/c) ratio of 0.24 or lower. By omitting coarse aggregates in the mix, density and mechanical homogeneity can be maximized. Also, adding steel fibers increases durability by producing exceptionally high compressive and tensile strengths. As a result, a bridge using UHPC can be designed slimmer and longer with less amount of steel reinforcements than a conventional concrete bridge. UHPC developed by Korea Institute of Civil Engineering and Building Technology (K-UHPC) was used to build a bridge, named “Hawkeye”, in Buchanan County, Iowa. This paper describes the design and construction process of the Hawkeye bridge which is the first bridge using K-UHPC in the United States. A unique pi-girder design, which is similar to the design previously developed at MIT, was adopted for the Hawkeye Bridge. The Hawkeye Bridge was successfully constructed using K-UHPC, utilizing local cement, sand and ready-mix trucks. Precast pi-girders were made at the Buchanan County, 17 miles (27 km) from the bridge site. A total of six girders were transported to the bridge site and installed in one day. This project not only demonstrated easy field constructability of K-UHPC but also set a great example of Accelerated Bridge Construction (ABC), which would minimize a traffic disruption.