Pavement on residential streets in Lakewood, Colo., may soon consist of 30% recycled asphalt. Photo: City of Lakewood

Last summer, Lakewood, Colo., infrastructure engineer Chris Jacobsen ran a test project using 30% recycled asphalt for a 1½-inch surface overlay. That's a one-third increase over the previous 20% limit allowed in Lakewood, a Denver suburb with a population of 150,000.

“We monitored the results, and the 30% mix met all the design requirements for the 20% mix,” says Jacobsen. “We saw no problems with the consistency of the mix.”

Although the city is very strongly considering an increase to 30% recycled material on residential streets, its specification will remain at 20% for arterial and collector streets. Jacobsen could not provide savings numbers because the 30% test was run on asphalt bid at the 20% rate, and new bids have not come in for the 30% material.

If the price of oil and asphalt binder remain at current levels or higher, the use of recycled material is certain to increase. Mix design engineers and equipment manufacturers have the technology; they're just waiting for specifications to change.

— Brown is a freelance writer in Des Plaines, Ill.

Reap the savings

The higher the cost of asphalt binder, the more recycled asphalt pavement (RAP) is worth. That's because it contains about 5% binder that replaces new, more expensive asphalt. If aggregates cost $13 per ton and binder costs $250 per ton (which is low), then David Lippert, an Illinois DOT materials and research engineer, figures RAP is worth $20.85 per ton after subtracting $4 per ton to process the recycled material.

If you add 20% of that recycled asphalt to a mix, the savings amount to $4.17 per ton of mix. But if you double the amount of recycled material to 40%, the savings jump to $8.34 per ton.

Those are significant numbers when you consider that hot mix pavement now averages well over $50 per ton as paved.

Source: David Lippert

Build now to beat inflation

Bonds help Ohio fund future road projects.

Assuming that highway construction costs will increase by about 30% between now and 2010, the Ohio DOT (ODOT) decided to increase its bonding authority and build more roads sooner, rather than later.

Last July, ODOT boosted its bonding authority by $600 million over the next three years. The department has identified $221 million worth of projects to begin this year, rather than waiting to build them between 2008 and 2010, says Lindsay Komlanc, Columbus-based spokesperson for ODOT. Other new projects are yet to be named.

“We determined that the cost of interest would be less than the rate of inflation in highway costs,” says Komlanc. “So we decided to issue GARVEE bonds, in part because we can use our federal funds to pay those bonds.” GARVEE bonds, or Grant Anticipation Revenue Vehicle Bonds, have been used in several states to overcome political, technical, and legal barriers to bonding.

Looking ahead, ODOT projected three inflation scenarios for highway costs. The most conservative of those assumed “relatively stable” costs at 23% inflation over the next three years. The most aggressive scenario envisions a 41% increase by 2010. So the state split the difference and assumed 30%.

“With these new scenarios the inflation rate will be 66% greater than our original plans,” says Komlanc.

To arrive at the $600 million figure, the state first reviewed its existing spending plans, and came up with $105 million in savings. For example, $43 million in planning and research was redirected to construction. An Interstate highway widening project was canceled, and another was deferred.

“By taking into account the public benefit of getting the projects earlier, it tipped the scales in favor of issuing the bonds,” says Komlanc.