Modeling the Development of Permanent Deformation in Asphalt Interlayers of Unbonded Concrete Overlays of Concrete Pavements

Abstract

Unbonded concrete overlay of concrete pavement (UBOL) is an effective rehabilitation method involving the construction of a new concrete pavement over a deteriorated concrete pavement, separated by an interlayer. While UBOL is used in practice to improve the structural capacity of existing concrete pavements, the performance of the interlayer is not currently accounted for in the pavement mechanistic–empirical design process. Therefore, the objective of this research is to improve prediction of UBOL performance by accounting for the effects of asphalt interlayer consolidation on the development of longitudinal cracks in the wheelpath. First, a laboratory investigation was performed using beams cut from in-service pavements in Michigan, Minnesota, and Pennsylvania to assess the susceptibility of permanent deformation of asphalt interlayers. This data was utilized in conjunction with a finite element analysis to develop/calibrate a permanent deformation prediction model for dense graded asphalt interlayers. The framework of the model follows that of the permanent deformation prediction model for asphalt surface pavements incorporated into the American Association of State Highway and Transportation Officials (AASHTO) Mechanistic–Empirical Pavement Design Guide. In addition, a field analysis was conducted, using the Long-Term Pavement Performance (LTPP) database, to assess longitudinal cracking in the wheelpath caused by permanent deformation in asphalt interlayers. The laboratory-calibrated permanent deformation model was then validated using the performance data for UBOLs in the LTPP database and deformation thresholds for asphalt interlayers were established. This research resulted in the development of a framework for the prediction of longitudinal crack development in UBOLs because of permanent deformation in the asphalt interlayer.