Crunching the Numbers
Cost is often the No. 1 factor that public works departments must consider, but basing assessments solely on upfront costs can be dangerous. Cost of the raw material may fluctuate daily or may be difficult to acquire locally (think of rising oil costs or shortages of portland cement). Both ACPA and NAPA encourage public works departments to look at the long-term costs of maintenance and rehabilitation when deciding which material to specify. Because estimates show that 25% of roads in cities across the United States must be either rehabilitated or completely replaced in the next two years, public works officials must take a close look at how those costs are going to affect them in the long run.
The reconstruction of Walden Avenue and Union Road with concrete pavement in Cheektowaga, N.Y., resolved longstanding and expensive problems associated with asphalt pavement rutting and shoving.
Credit: Photo: L&S Construction LLC
Haislip said that asphalt is more common for a department to specify than concrete. “Asphalt over concrete—that's the standard,” he said. “That's what they've been doing for so long.”
But because it's the “standard” doesn't necessarily make it the best option for all applications. Concrete may be better in some instances, the first of which is new construction. In urban metropolitan areas, where new roads are being built and existing roadways are being expanded, using concrete may be a good way to minimize future inconvenience. “Funding is a big challenge, however,” said Haislip. “People are looking for short-term fixes, which have a political impact.”
Another place to use concrete paving is where underground utilities need to be redone. When separating sewer and drainage pipes (no more combined sewers), the public works department must dig out the roadway, which could present a good opportunity to go in and place longer-life pavements.
Asphalt also can be specified as a long-term solution. “Some pavement types must be completely removed and reconstructed when they reach the end of their design life, but total removal and reconstruction due to structural failure of a thick asphalt pavement is rare,” said Margaret Cervarich, vice president of marketing and public affairs with NAPA. “With a thick asphalt structure, it is possible to obtain a ‘Perpetual Pavement,'one that can last indefinitely, with the only rehabilitation being milling of the surface followed by an asphalt overlay.” Perpetual Pavement is a relatively new type of asphalt concrete pavement designed to resist structural fatigue distress for at least 50 years. Maintenance is limited to replacement of the surface course.
Next page: Overlays to the Rescue