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    PAVEMENT CONDITION INDEX
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By using pavement preservation treatments such as micro surfacing (shown here), in conjunction with mill-and-fill cycles, agencies can save up to $500,000 per two-lane mile over a 50-year period when compared to mill-and-fill-only programs. To most effectively stretch the budget, target up to 40% of paving dollars to preservation. Photo: ISSA

PAVEMENT PRESERVATION TREATMENTS AT-A-GLANCE

Micro surfacing — A mixture of aggregate, asphalt emulsion, water, and additives applied in a smooth layer over existing pavement. When applied early in the pavement's life cycle, it can cost-effectively extend surface life by seven or more years.

Slurry seal — Applied to existing pavement by a spreader box linked to the surface slurry-mixing unit. Used over newly laid pavements, slurry seal will prevent surface distresses such as the effects of weathering. Existing distresses in older pavements — surface cracking, raveling, loss of matrix, increased water and air permeability, and slipperiness due to flushing and aggregate polishing — can be corrected with a slurry application.

Chip sealing — A bituminous binder covered with clean graded aggregate, applied to an existing asphalt surface.

Crack treatments — Specialized materials are placed into prepared cracks to prevent water and incompressible intrusion into the cracks and underlying pavement layers and to reinforce the adjacent pavement. Used for pavements that primarily have working cracks (greater than 1/8-inch annual movement).

A constant sell

“Few engineering schools have classes that address pavement preservation, or even hot-mix asphalt,” Tarsovich says. “We work to educate the guys coming out of college and becoming DOT engineers. The concept isn't hard to understand; it's not a hard sell — but it is a constant one.”

In Overland Park, Kan., Civil Engineer Matt Laipple, PE, oversees a detailed pavement management program. He notes that, in a perfect world, agencies would target a portion of their budget to preventive maintenance, rather than reactive maintenance, beginning three to five years after initial construction.

“While the specific funding allocation will vary between agencies, the concept of investing in a street while it's still in good, serviceable condition can be used across the board,” says Laipple. “Although many people outside of the industry have a difficult time understanding the need to put funds into a street that is in perfectly good condition — especially when there are many other worthwhile endeavors to spend those funds on.”

The continued extensions of SAFETEA-LU without reauthorization loom large in everyone's minds. And the fact is that reauthorization will likely happen soon — but at lower funding levels than the industry would like. Budgets will continue to be smaller than they were five years ago. But if pavement preservation techniques can stretch budgets and treat more lane-miles in a good economic climate, the same will hold true when budgets have declined.

“In these times, if an organization can budget 30% to 40% of their surface treatment budget to preservation, they are doing well,” says Byrne. Kent County allocates at least 30%.

“We compare pavement preservation to painting a house,” says Laipple. “It helps public officials and residents understand what we're doing. A mill and overlay is similar to the idea of removing the siding from your home every 25 years and replacing it with new siding. It's cheaper and more efficient to paint the siding and preserve it over time.”

— Contributed by the International Slurry Surfacing Association (www.slurry.org).