There are practical guides to complete home repair, building swimming pools, landscaping, and just about anything else one could imagine doing.

Now, Virginia Tech civil engineer Richard Weyers and his colleagues have completed a several-hundred page fix-it manual for concrete bridges that could save taxpayers billions of dollars.

The project began five years ago when the National Research Council's Strategic Highway Research Program awarded Weyers a $2.7 million contract to study the rate of corrosion deterioration of concrete bridges in the U.S. and how to protect, repair, and rehabilitate concrete bridges from de-icing salt corrosion.

Bridge corrosion has increased since the 1950s, when de-icing salts began to be used in greater quantities to keep highways ice-free during the winter. The salt seeps through the concrete in bridge decks. When the salt concentration reaches a threshold level, corrosion starts. This is a chemical process in which salt, aided by moisture, reacts with iron in the steel reinforcing bars to form iron oxides rust. Several times larger in volume than the original steel, the rust exerts pressure on the concrete, which eventually "spalls," creating potholes.

However, corrosion does not usually prove to be a safety threat. Because the resulting cracks and potholes produce a bumpy ride, bridge decks are often repaired long before major structural damage occurs. Though the substructure or supporting columns can also be corroded, the bridge isn't a hazard unless repairs are neglected for a long time.

The most recent estimate to repair all of the nation's bridges is $78 billion. The manual presents a few dozen methods that the authors estimate could save as much as 20 percent of the $30 billion needed just for concrete bridges.

As part of the research, 20 men and women inspected 65 bridges in 11 states in the east and the Midwest. Weyers chose locations that represented various types of problems state highway agencies face as they attempt to maintain the nations's infrastructure. The team of 11 undergraduates and seven graduate students counted the number of cracks, potholes, and patched areas on each bridge deck. They used sounding hammers and chains to detect cracking and impact hammers to drill for concrete samples to analyze later in the lab.

All the conditions assessment data was used to develop a deterioration model that can be used to predict and define the service life of bridges. Weyers, director of the Center for Infrastructure Assessment Management at Virginia Tech, and colleagues developed the model because, "Engineers haven't been able to tell precisely when a bridge reaches the end of its service life," says Weyers. "Our model looks at how fast salt diffuses through various types of concrete, how long it takes for the concrete to crack once corrosion begins, and how long it takes for the bridge to reach the end of its service life."

For example, the report outlines how to protect the various bridge parts from corroding by using specific sealers, coatings and polymer concrete deck overlays. The guide also addresses how to provide a longer lasting new bridge deck riding surface through the use of conventional concretes, new corrosion inhibiting concretes, and rapid polymer concrete systems. These measures will also account for a reduction in a traveler's delay time. And the guide looks at how to best remove deteriorating concrete and how to select the most economic methods to use, based on the present assessed condition of the various concrete bridge components.

Also as a result of the "bridge tour," civil engineering faculty member Imad Al-Qadi developed a technique using ultrasound to non destructively determine the condition of rubberized asphalt sheets widely used to protect against salt penetration. This sheet, called a preformed membrane, is spread over the concrete bridge deck before bituminous concrete is laid down for a driving surface.

In the past, whenever the surface needed replacing (usually every 10 to 12 years), the membrane layer had to be ripped up at the same time and replaced too even if it had many more years of service left in it. There was no way to know how good the membrane remained.

Now, engineers can assess whether the membrane needs to be replaced. If it's still serviceable, workers need only remove part of the top asphalt layer and lay down a new driving surface. This reduces repair costs and saves materials.

And being able to make preformed membranes last 20 or 30 years instead of 10 helps the environment. "You're extending the life of something that would otherwise end up in a landfill," says Weyers.