STUDY OF RUTTING IN FLEXIBLE HIGHWAY PAVEMENTS IN OKLAHOMA (ABRIDGMENT)

The primary objective of this research was to investigate rutting on high-quality flexible pavements and to detect if possible evidence of contribution of bituminous bound pavement materials to this type of failure. A transverse profile gauge was developed to plot the profile of the pavement surface perpendicular to the centerline. Rut depths could be scaled directly, and humps outside the wheel-path locations could be detected from the transverse profile tracings. Stereo-photography was employed to obtain quantitative estimates of differential wear in the wheel-path locations. Also a visual rating of the pavement surface condition was made at each site to provide additional data for the study of these locations. Sixteen test sites were selected on two Interstate Highway Systems in Oklahoma. Performance of four test sites on flexible pavements constructed of various base course materials was studied. Based on the test procedures employed and the pavement sections studied, six conclusions were drawn: The transverse profile gauge provides a portable and accurate means of obtaining continuous transverse profile tracings of a pavement surface; Profile graphs can provide permanent records of measurement of surface deformations at a specific time in the service life of a pavement; Densification contributed a significant amount to the total surface rut depth; Evidence of lateral creep or instability in the bituminous material layers was found at 11 of the 16 test sites; Surface wear or attrition in the wheel paths on heavily traveled lanes was an important contributing factor to rutting; Base and subgrade deformations influenced the magnitude of rutting at many of the test sites.