An index was developed for evaluating the acceptability of initial overlay smoothness based on surface profile measurements. The proposed index predicts the change in overlay service life due to differences between the target surface profile assumed in the design and the as-built profile. From theoretical considerations, the change in overlay life, based on reflection cracking, was found to be a function of the fracture characteristics of the overlay mix and the variability in vehicle dynamic loading due to unevenness in the surface profile. The index for evaluating initial overlay smoothness was applied using profile data from actual overlay projects. Using the final surface profile, the index is applicable to projects where the overlay thickness is more than 64 mm or where surface preparations, such as milling to grade or in-place recycling, are used to correct or remove existing surface distress. Implementation of the proposed index in a smoothness specification will require the use of surface profilers and the simulation of vehicle dynamic loads from measured profiles.
Abstract