This report presents the findings from the performance analysis of two types of pavements commonly used in North Carolina, aggregate base course (ABC) pavements and full-depth asphalt (FDA) pavements. The main objective of this research project is to examine the NCDOT's assumptions that the required M&R strategies and life costs of the two types of the pavements are the same. In order to complete the inherent tasks to meet this objective, the North Carolina State University (NCSU) research team identified field sections in North Carolina that include both types of pavement (ABC and FDA) and analyzed and compared the performance data of the sections. In addition, the NCSU research team collected and tested material samples from the field using the performance test methods. The team established a database that contains information about the identified sections, for example, their material properties and performance data, as an additional product for the future recalibration of the AASHTO Pavement ME design program. Analysis of the NCDOT's Pavement Management Systems (PMS) database revealed that the performance of the pavements is affected statistically by the pavement structure and traffic volume. This study employed two parameters, the so-called 'structural number' (SN) and asphalt layer thickness, to represent the structural effects. The study used the annual average daily traffic (AADT) data in the PMS database to show the effects of traffic volume on pavement performance. The NCSU researchers developed an index parameter, the pavement deterioration index (PDI) that is related to the SN, asphalt thickness, and design AADT, for analysis. The PDI can be used to determine the best time to apply M&R treatments. The PDI is proportional to the AADT and inversely proportional to the SN and asphalt concrete layer thickness. In other words, the pavements with higher PDI values have relatively short performance years for M&R treatment. The appropriate time to perform M&R treatment is when the pavement condition rating (PCR) decreases to the trigger value of 60 percent. The analysis results show that the PCR for each of the two types of pavement has a unique negative relationship with the PDI. As a result, the time for M&R treatment can be predicted by applying the trigger PCR value of 60 percent on the pavement type specific relationship between the PCR and the PDI. Once the M&R treatment time is determined, LCCA can be used to determine the costs of different types of pavements. |
