The performance of a pavement is affected by the type, time of application and quality of maintenance it receives. Preventative timely maintenance slows the rate of pavement deterioration due to traffic and environmentally applied loads. Delays in maintenance and deferred maintenance increase the quantity of defects and their severity so that, when corrected, the cost of repair is greater. Continued deferral of maintenance and rehabilitation action shortens the time between overlays and reconstruction.
The traditional method for protecting a deteriorating pavement, reducing roughness, restoring skid resistance, and strengthening the pavement structure of a flexible pavement is with an overlay of hot mix asphalt. It is typical practice of most states Department of Transportation (DOT) to place a thin hot mix asphalt overlay, 1.5 inches thick, when considering the need for restoring skid resistance and protecting a deteriorating pavement. The total overlay thickness will vary depending on the type of roughness components present in the pavement profile.
Where strengthening the pavement structure is the primary objective for the overlay, thin overlays are seldom cost effective, even if several are placed over a period of several years, primarily because thin overlays cool quickly and therefore are more difficult to compact. Also, thin overlays are generally prone to de-bonding from the existing surface. Therefore, it is imperative, when pavement strengthening is needed, that the engineer perform;
A. an adequate analysis to establish the condition of the existing pavement,
B. determine the strength properties of the existing pavement material,
C. determine the length of the performance period required for service and based on the traffic to be served,
D. and then determine overlay thickness.
Only by using good engineering design procedures and sound life-cycle cost analysis can the most effective combination of overlay design thickness and future maintenance activities be determined.
A smooth asphalt pavement saves in vehicular wear and makes drivers happy. Hot mix asphalt pavements go down quickly and are open to traffic faster, saving labor costs and costs due to user delays. The use reclaimed asphalt pavement (RAP) in the road base, base course, or surface course can make those dollars go even further, while sustaining the environment.
Initial costs, maintenance costs, long-term costs, user delay costs, residual costs. They all add up to one thing: Hot Mix Asphalt is the lower cost pavement, hands down.