About the research
Over the last decade, a new generation of concrete known as ultra-high performance concrete (UHPC) has emerged on the market. This general class of concrete has compressive, tensile, permeability, and other properties that far exceed those of conventional or high-performance concrete (HPC). The major drawback to this material is that its cost is considerably higher. The prospect of using this material has, in fact, prompted the Federal Highway Administration (FHWA) to invest in strategic research related to the use of UHPC. To the credit of Iowa Department of Transportation (DOT) and Iowa county engineers, Iowa has remained at the forefront of this research. In fact, the first two vehicular bridges constructed with UHPC in the US were constructed in Iowa through multi-organizational partnerships.
Up to this point, there has been only one major producer of UHPC: LaFarge. The LaFarge product is a highly engineered concrete mix design sold under the trademarked name Ductal. Likely at least in part due to limited competition, the price of Ductal appears to have changed very little since it was first introduced. As a result, the most recent research activities have focused on identifying ways that small volumes of UHPC can be used in very strategic manners (joint closure pours in bridges, etc.). With this philosophy, the highly desirable properties can be exploited without resulting in significantly higher bridge construction costs.
Engineers and researchers in Iowa have become aware that an alternative UHPC mix design, known as K-UHPC, has been developed at The Korea Institute for Civil Engineering and Building Technology (KICT). Because the material is relatively new to the market, there are many questions regarding its performance, cost, etc. However, preliminary conversations with the developers seem to point to one very important fact: the cost of K-UHPC mix may be considerably less than Ductal. Should this hold true and we can verify that the K-UHPC material does possess the required material characteristics, there would be significant benefits to Iowa.
For example, the Iowa Highway Research Board (IHRB) recently invested in the development of a set of box beam bridge standards using UHPC as a joint filler material. While conventional joint materials are also being explored for applications where “lower service levels” are required, having an alternative to Ductal could mean that even the highest service level could be obtained more economically.
The objectives of the project are to aid evaluation of a new cost-effective UHPC mix design and evaluate the performance of a UHPC bridge design by assisting the Buchanan County Engineer in reviewing the plans for the yet-to-be constructed K-UHPC bridge, characterizing the new UHPC material, assessing the bond/development length for the K-UHPC material, and documenting the durability and performance of a yet-to-be-constructed K-UHPC bridge over a two-year period.