High performance concrete (HPC) with higher compressive strength (in the range of 8,000 to 10,000 psi) and increased durability is rapidly gaining acceptance for bridge construction. The goal of this project was to implement and demonstrate the economic benefits of the HPC technology in bridge design and construction in North Carolina, thereby providing a greater value to the public. Specifically, the project monitored the production of HPC in typical plant and field conditions, confirmed the feasibility of producing HPC bridge girders and decks, and validated the expected behavior of bridge superstructures built with HPC girders and decks.
As of December 1999, 29% of the nation's 585,542 highway bridges have been rated structurally or functionally deficient, according to the Federal Highway Administration http://www.fhwa.dot.gov////bridge/defbr99.htm. To replace some of these deficient bridges or to construct new bridges, it has been found that high performance concrete (HPC) can be utilized to great advantage in terms of structural efficiency and durability. However, there is a need for more field data on high performance concrete and on the structural behavior when high performance concrete is used.
In 1997, the Federal Highway Administration (FHWA) initiated a program to demonstrate the application of high performance concrete to bridges throughout the United States. The North Carolina Department of Transportation (NCDOT) participated in that program and chose a bridge on U. S. Highway 401 in Raleigh crossing the Neuse River as the site for demonstration. The original design of the bridge with the conventional concrete called for six lines of girders. By using HPC, it was possible to eliminate one line of girders for the entire length of the bridge, thus achieving significant savings for the initial cost of the bridge.
The objective of this research is to monitor the behavior of four prestressed HPC bridge girders used in this NCDOT demonstration project during their casting and to study the properties of the concrete used in the girders. This report provides details of the testing of the concrete and field instrumentation of the bridge girders. Comparisons are made between the experimental and theoretical results and conclusions are provided.