National Concrete Pavement Technology Center

Project description

Unbonded concrete overlay (UBCO) is the most widely used rehabilitation option being used as compared to other types of overlays based on its long-term performance, minimal pre-overlay repairs, and relatively easier construction. The implementation of latest pavement performance prediction tools such as the Pavement ME Design [previously called AASHTOware Pavement Mechanistic Empirical (ME) Design guide or MEPDG] has provided the opportunity for designing and performance analysis of UBCOs. The levels of design inputs, for concrete mechanical properties, range from time series data (time series means tested data from 7 to 90 days) of elastic modulus (Ec) and modulus of rupture (MOR) to 28-day compressive strength. This study focuses on evaluating the impact of design input levels for concrete strength and stiffness properties on performance predictions of UBCO using Pavement ME Design. Previous studies have shown that concrete strength properties including compressive strength, Ec, and MOR have significant effects on UBCO performance. The effects of these input levels on predicted faulting and transverse cracking are evaluated for three different paving mixes. The results show that the combination of measured 28-day MOR and Ec yielded predicted distresses that were consistently in close agreement with the predictions using time series data. It became evident that accurate 28-day MOR and Ec values can be used as a less challenging and less expensive alternative to the time series characterization of concrete mechanical properties for UBCO design and performance evaluation.