A RATIONAL SYSTEM FOR DESIGN OF THICKNESS OF ASPHALT CONCRETE OVERLAYS

A method for designing asphalt concrete overlays is presented that uses (a) the Kentucky proposed design curves, (b) an estimation of future traffic and the associated fatigue (five procedures are given according to type of information available), (c) the stength of the subgrade on the subject project (as determined by laboratory California bearing ratio tests or results of dynamic in-place tests such as road rater measurements), and (d) the present condition of the existing pavement (as determined from dynamic in-place tests, roughness measurements, or the present serviceability index). Deterioration is expressed as reduced thicknesses of new-quality materials that produce the same measured dynamic deflections. The overlay thickness required is the total thickness for the predicted traffic minus the effective or reduced thickness of the existing pavement. (Author)