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The art of pavement preservation

The art of pavement preservation

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    When properly used to improve surface friction and prevent water penetration, agencies report chip sealing allows them to maintain the most square yards of pavement per dollar spent. Photos: International Slurry Surfacing Association

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    By consistently devoting budgetary dollars to pavement preservation treatments, such as micro surfacing, agencies can maintain four to five times more lane-miles than if they only focus on rehabilitation.

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    The International Slurry Surfacing Association (ISSA) has applied a hypothetical cost scenario to the Pavement Condition Index chart developed by the Army Corps of Engineers. In this example, a road that receives three preservation treatments over a 25-year period at $2/square yard will remain in good condition for a total cost of $6/square yard.If the road is left untreated for 11 years and pavement preservation is used as reactive maintenance to preserve the pavement, the cost will be approximately $4/square yard. Waiting this long to apply a treatment generally leads to a deteriorated road-base structure, so the reactive maintenance treatment will only last about four years, when it will require yet another treatment or rehabilitation. In comparison, if nothing is done for 12 or more years, a mill-and-fill (mill and overlay) or full rehabilitation will be required at a cost upwards of $12 to $16/square yard.

According to Matt Laipple, PE, civil engineer with the public works department in Overland Park, Kan., his young community is lucky. City officials and staff have always understood that pavement preservation is necessary to keep road quality high and life-cycle costs low, and have been using pavement preservation techniques for the past 50 years.

“Many communities use mill-and-overlay — removing the top 2 inches of asphalt — on a 10- to 15-year cycle to provide a new wearing surface on asphalt pavement,” he says. “We can preserve nearly five times more lane-miles of pavement with micro surfacing or chip seal for the same cost. Other maintenance treatments may extend that figure further.”

Laipple says the goal of using pavement preservation techniques rather than wholesale mill and overlay (or mill-and-fill) is to keep the pavement's life-cycle cost low while maintaining serviceability and user satisfaction. Without some form of preventive maintenance program, it's not uncommon for an asphalt pavement to need complete reconstruction after 20 to 30 years.

While a regular mill-and-fill program will extend pavement life just as well as a preventive maintenance program, the life-cycle cost between the two approaches is dramatically different. Using recent local pricing and discounting future activity costs to present value with a 4% discount rate, the difference is $400,000 to $500,000 per mile of two-lane street over a 50-year period. That may not seem like a lot over 50 years, but multiply it by the number of miles in an agency's street network, and it adds up to serious dollars,” Laipple adds.