Local Calibration of Pavement ME and Performance Evaluation of Pavement Rehabilitation and Preservation Asphalt Overlays in Louisiana

Abstract

Asphalt overlays can be categorized as pavement rehabilitation structural overlays or pavement preservation overlays in terms of the thickness and timing of maintenance activities. Pavement rehabilitation overlay contributes to the structural enhancement of pavements and pavement preservation overlays generally provide functional improvement to an existing pavement. In recent times, the pavement design approach employed by the Louisiana Department of Transportation and Development (LADOTD) has been transitioning from the 1993 AASHTO design procedure to a locally calibrated Pavement ME method. The AASHTOWare Pavement ME (Mechanistic-Empirical) design procedure is considered the modern approach to pavement design. Significant updates have been introduced in the Pavement ME design software in the past few years. Therefore, this study focused on conducting a local calibration of the Pavement ME procedure for asphalt overlays in Louisiana. In addition, performance evaluation of the asphalt overlays was conducted to determine the factors that would have an impact on their performance. In total, 37 rehabilitation asphalt overlay projects and 33 preservation asphalt overlay projects were selected all over Louisiana with different base types and traffic volumes. These projects consisted of mainly three types of bases: soil cement base, crushed stone base and Portland cement concrete base. The pavement performance data were collected from the Louisiana Pavement Management System (LA-PMS) database and the data regarding geographical location, design thickness, and traffic were retrieved from the LADOTD intranet. The field performance of the asphalt overlays was investigated in terms of several design parameters i.e. base type, traffic level, total Hot Mix Asphalt (HMA) thickness after milling, pavement precondition and overlay service life. Manual calibration of Pavement ME was performed for rehabilitation asphalt overlays and a calibrator assistance tool was adopted for the local calibration of preservation asphalt overlays to calibrate the performance models in terms of typical pavement structure, traffic, and weather conditions of Louisiana. The results showed that the existing pavement condition does have an impact on preservation overlay performance since distress in pavements with poor precondition was observed to be higher. The pavement with good precondition and higher asphalt concrete (AC) thickness exhibited higher service life. A case study was performed to determine the optimal timing of preservation overlay applications based on cost-benefit analysis. Fatigue cracking was under-predicted and transverse cracking was over-predicted by the Pavement ME national model for rehabilitation overlays. For preservation overlays, both the fatigue cracking and transverse cracking were under-predicted. Therefore, the performance models were adjusted