Assessment of Distress in Conventional Hot-Mix Asphalt and Asphalt-Rubber Overlays on Portland Cement Concrete Pavements: Using the New Guide to Mechanistic-Empirical Design of Pavement Structures

The purpose of this study is to assess the way distresses are predicted by using the new Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures (design guide), developed under NCHRP Project 1–37A. Two pavement sections were used: a conventional hot-mix asphalt reconstruction and an asphalt–rubber overlay on a portland cement concrete (PCC) pavement. The design guide does not include rehabilitation design for asphalt–rubber overlays. However, many large-scale asphalt–rubber overlays on interstate highways in Arizona have been built and monitored for performance, providing an opportunity to determine to what degree the design guide can predict their performance. The input data for both types of pavements were derived from two different projects on the same highway, Interstate 40. The actual data measurements that summarize the pavement performance were compared with calculated values obtained by using the design guide. Three pavement performance parameters were evaluated on the basis of the available data: rutting, cracking, and international roughness index (IRI). Rutting was one of the distresses that the design guide predicted more accurately. The fatigue cracking prediction, evaluated with Level-3 data input, was not accurate; future analysis should consider calibrated fatigue models for the different mixtures. The predicted IRI results differed from the actual measured field performance because of inaccurate distress prediction. The Arizona experience using asphalt–rubber overlays to rehabilitate aged PCC pavements has been successful. For that reason, a calibration process that allows the use of the asphalt–rubber mixtures in the design guide should be considered in the future.