Long-Term Performance of CRCP over OGDL in Illinois

Throughout the 1980s, many State Highway Agencies (SHAs) adopted open-graded drainage layers (OGDLs) as a means of combating moisture-related distress on portland cement concrete (PCC) pavements. The Illinois Department of Transportation (IDOT) performed an initial evaluation of OGDLs in 1993 that indicated the potential to improve pavement performance. Up to that time, most OGDLs had been installed beneath jointed plain concrete pavements (JPCP) but not on continuously reinforced concrete pavements (CRCP). Consequently, in 1990, IDOT constructed an experimental project on I-39 in LaSalle County to study the performance of alternative OGDLs beneath CRCP designs. The experimental project included one control section and three experimental sections in each direction of the highway, for a total of 8 sections. The base for the two control sections was a 4-inch cement-treated base, while the bases for the experimental sections included 4- and 5-inch asphalt- (northbound) and cement- (southbound) treated OGDLs with and without a 3-inch dense-aggregate separation layer. The common pavement structure placed on each base type was a 10-inch CRCP featuring 0.7% longitudinal steel. Plastic pipe underdrains were placed at the bottom of the base and along the PCC shoulders, with outlets installed every 500 ft. The performance of the sections has been periodically monitored since initial construction with the most recent testing performed in 2023. This case study summarizes the performance of the experimental CRCP designs constructed on the OGDL base layers and presents the critical lessons learned in terms of their construction, placement, durability, and longevity.