What Makes a Perpetual Pavement Perpetual

This article offers a description of components of long-life pavements, whose fundamental design is meant to prevent distresses deep in the pavement. Results from studies of qualified Perpetual Pavements from Washington State and Iowa indicated that staged construction and timely rehabilitation increase performance. Specific types of distresses are described, along with successful remedies. Fatigue cracking is addressed based on volume of traffic, with hot mix asphalt (HMA) thicknesses that keep the bending strain below a threshold of about 70 microstrain. Lower volume roads require less HMA. Rutting prevention techniques are described also. Software is available to calculate the most cost-effective formulas for different conditions, and life-cycle cost analysis is discussed.