U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
|Accelerating Infrastructure Innovations|
Publication Number: FHWA-SA-97-023
Date: May 1997
The Lead States team for high-performance concrete (HPC) bridge implementation is making sure that highway agencies have the tools, information, and support they need to build a new generation of strong, durable, and cost-effective concrete bridges with HPC.
For example, one of the stumbling blocks to broader use of HPC is the lack of appropriate American Association of State Highway and Transportation Officials (AASHTO) standards. The Lead States team thus decided that one of its first tasks would be to address that issue. Team leader James Moore, from the New Hampshire Department of Transportation (DOT), explains, "The current AASHTO bridge design standards are adequate for concrete as strong as 10,000 psi [69 MPa], but they may be too conservative for the stronger grades of high-performance concrete." Likewise, Moore adds, AASHTO materials standards do not apply to HPC mixtures. Moore will meet this summer with the AASHTO bridge and materials subcommittees to discuss changes to the AASHTO standards.
To help State highway agencies understand the characteristics and performance of HPC, the Lead States team is refining the current working definition of HPC developed by Charles Goodspeed, Suneel Vanikar, and Ray Cook and published in the February 1996 issue of Concrete International. The definition is essentially a set of performance criteria and associated tests. The team is asking States that build HPC bridges to help amend and expand the definition based on what they learn from their bridge projects.
"The existing definition is a starting point," Moore explains.
The strength and durability of a concrete mix depends in large measure on the cement and aggregates locally available. Thus, materials engineers and bridge designers must keep in mind what can be accomplished with locally available materials "so that they can effectively use HPC to achieve longer life cycles and lower costs," says Moore.
Another of the Lead States team's projects will help highway agencies track the life-cycle cost of HPC bridges. The team is developing a standard form that will help bridge design departments and maintenance departments more accurately assess the benefits versus costs of HPC bridges.
"Not too many States have taken the time to work on the life-cycle costs of bridges. The form will make that easier," says Moore. The form should be ready this fall.
To ensure that information about HPC gets to State highway agencies, the team has asked FHWA to hold at least three regional showcase workshops on HPC each year. The next will be in June (see sidebar).
There are now about a dozen HPC projects under way in the United States, and the Lead States team wants to add to that number. The team is working closely with FHWA's HPC structures technology delivery team, which is charged with identifying good candidates for HPC demonstration projects and directing HPC research, to have at least five HPC projects in progress at all times.
The HPC Lead States team will meet next in September, when all seven Lead States teams will assemble in St. Louis.
For more information on the HPC Lead States team, contact James Moore of New Hampshire DOT (phone: 603-271-2731; fax: 603-271-7025).
High-performance concrete (HPC) is a performance-based approach to specifying concrete mixes that are more durable and, if necessary, stronger than conventional concrete. HPC uses the same basic ingredients as regular concrete, but is mixed and proportioned to yield concrete of the strength and durability needed for a particular bridge or pavement.
HPC may have higher upfront costs than conventional concrete, but it should save money in the long run. HPC's greater strength allows bridge designers to use fewer supports, which can reduce overall costs. HPC's improved durability also means that bridges and pavements will hold up better to traffic, climate, and other forces. In addition, HPC can be easier to place and cure, potentially saving time and money on construction.
HPC has uses in both bridges and pavements, but the applications have different needs. For example, bridge beams require extremely strong concrete, while pavements that carry high traffic loads may require concrete that reaches the needed strength in just a few hours. Thus, agencies and contractors designing HPC pavements face a different set of issues than those designing HPC bridges.
Although the emphasis is currently on HPC bridges, that will change shortly. FHWA's new HPC pavements technology delivery team will soon begin soliciting States to participate in HPC pavement projects.
The Washington State Department of Transportation (DOT) and the Federal Highway Administration (FHWA) will review and explore high-performance concrete (HPC) for bridges in a comprehensive showcase workshop this summer. Scheduled for August 18-20 in Bellevue, Washington, the showcase will include sessions on the structural applications of HPC, the monitoring and evaluation of results, and the cost-effectiveness of bridges built with HPC.
Another important feature of the showcase will be a field review of Washington's recently constructed HPC three-span girder bridge. In addition, FHWA's mobile concrete laboratory will be used to demonstrate state-of-the-art technology for materials selection, mix design, and laboratory and field testing.
For more information on the Washington State workshop, contact Bill Carr at Washington State DOT (phone: 360-705-7802; fax: 360-705-6889; email: email@example.com).
HPC showcase workshops are also scheduled for June 24-26 in Richmond, Virginia, and September 22-23 in Waterville Valley, New Hampshire. For information on the Virginia or New Hampshire workshops, contact Terry Halkyard at FHWA (phone: 202-366-6765; fax: 202-366-7909; email: firstname.lastname@example.org).