|Accelerating Infrastructure Innovations|
|Federal Highway Administration > Publications > Focus > March 1997 > Making Concrete More Durable|
|March 1997||Publication Number: FHWA-SA-97-021|
Making Concrete More Durable
Highway agencies in the United States spend $6.5 billion a year on portland cement concrete bridges, pavements, and structures. Much of that money is spent repairing or replacing bridges and pavements damaged by salt, freezing weather, and other causes. New technologies developed and evaluated by the Strategic Highway Research Program (SHRP) can provide highway agencies with better ways to build, maintain, and repair concrete bridges and pavements and make that money go much further, according to the findings of the SHRP assessment project.
In its benefits-versus-costs analysis, the Texas Transportation Institute (TTI) predicted that highway agencies can reap substantial savings by adopting just 6 of the 44 test methods and guidelines SHRP developed for portland cement concrete and structures. The six test methods and guidelines can allow highway agencies to:
Using the six tests and guidelines, State highway agencies can extend the service life of their bridges and cut their bridge monitoring and maintenance costs. How much highway agencies actually save will depend on how quickly they adopt these guidelines and test procedures. For example, TTI predicts that if the products were to be adopted by only one-quarter of highway agencies over a 20-year period, they could save $4 million per year. In contrast, if all highway agencies were using the new tests and guidelines in 20 years, the savings could total $15 million per year.
Extending Pavement Service Life
About 10 percent of the Nation's 208,000 km (129,000 mi) of portland cement concrete pavements are affected by ASR-related cracking or D-cracking. On average, those pavements will require extensive rehabilitation after 10 years of service. In its calculations, TTI assumed that SHRP guidelines for mitigating ASR and D-cracking could extend the service life of affected pavements by 70 percent, to 17 years, thus delaying the need for expensive rehabilitation work.
If only a quarter of highway agencies have implemented these strategies in 20 years, the savings could average $13 million a year. If, instead, half of all highway agencies are using the products in 20 years, the annual savings could total $25 million. If all agencies were to adopt these tools in 20 years, the savings could reach $48 million per year.
Longer-lasting concrete pavements will have even bigger benefits for motorists. More durable pavements will mean fewer work zones that delay traffic. Smoother roads will mean less wear and tear on vehicles. As a result, motorists could save between $38 million and $143 million a year over a 20-year period, depending on how quickly highway agencies adopt the new guidelines.
SHRP products are already proving their value on concrete pavements and structures around the country.
Idaho is using SHRP's chemical test to detect ASR in portland cement concrete pavements and structures. Previously, the State took concrete samples and sent them to a private laboratory for analysis, which cost $300 to $400 per sample and could take a month or more. Thanks to the SHRP test, says Al Stanley of the Idaho Transportation Department, "we spend perhaps $40 to $50 per sample, and we know the results within hours."
The Nevada Department of Transportation evaluated the surface air-flow permeability meter, a new tool for assessing the permeability of concrete over reinforcing steel. Nevada found the SHRP permeability meter to be a labor-saver_it's quick, easy to use, and dependable.
The Kentucky Transportation Cabinet has been evaluating the hydraulic fracture test chamber. The device simulates the effect of freeze-thaw cycles on aggregates, allowing highway agencies to screen out aggregates susceptible to D-cracking. The test takes only days, rather than weeks, and the equipment costs about one-tenth as much as that needed for the conventional test procedure.
TTI predicts that highway agencies should see a quick return on the cost of researching, developing, and implementing the SHRP tools and guidelines for concrete structures and pavements. The institute estimates that this cost will total $55 million over 20 years. Even if highway agencies implement the products slowly, they could still recover that cost in just over 4 years.
In its analysis of the economic benefits of SHRP research on concrete and structures, TTI focused on the following products:
More detailed information on the benefits-versus-costs analysis of the SHRP products, as well as more than 100 case studies of how highway agencies are using those products, are available at the RoadSavers home page.
United States Department of Transportation - Federal Highway Administration