Mechanistic–Empirical Model for Cracking Prediction in Unbonded Concrete Overlays on Concrete Pavements

Abstract

Unbonded concrete overlays (UBOL) are a preferred rehabilitation solution for distressed concrete pavements because the remaining pavement can be used as a strong support layer while an interlayer between the UBOL and the existing pavement mitigates potential distress reflections. Nevertheless, UBOL, as other types of jointed concrete pavements, experiences fatigue cracking as a major distress because of critical stress inflicted by traffic and environmental loading. Therefore, for proper UBOL performance, a cracking model that considers the specific UBOL characteristics is necessary. The AASHTO Mechanistic–Empirical Pavement Design (AASHTO M-E) cracking model, although the most advanced model for UBOL design currently available, still presents significant limitations. The model considers only transverse cracking, ignoring longitudinal cracking which has been reported by Departments of Transportation. Additionally, UBOL unique design features such as the effect of temperature variation throughout the existing concrete slab thickness and different interlayer properties are overlooked, resulting in crack predictions with unreliable trends. To address these issues, this paper proposes a modified UBOL cracking model. The proposed model was developed with a new approach for stress analysis and damage calculation considering different positions in the UBOL as well as modifications of the temperature data processing, and built-in curl analysis. The model was calibrated and validated using Long-Term Pavement Performance UBOL sections, and two sensitivity analysis are presented with a modified reliability analysis.