Analysis of Pavement Response Data and Use of Nondestructive Testing for Improving Pavement Design

The Maine Department of Transportation (DOT) spends more than $50 million on design, construction, and rehabilitation of asphalt pavements every year. Much of the design procedures are based on 1986 and 1993 AASHTO design guides (1, 2), which are primarily empirical in nature. These guides were developed on the basis of field tests conducted in Illinois in the 1960's. Results from these field tests are not applicable for a different climatic region, and also for today's traffic and construction materials. Furthermore, significant changes in layer properties occur as a result of change in seasons, and it is critical that such changes are determined, documented, and considered properly for design, construction, and load restrictions. Analysis of data from properly instrumented pavement test sections can provide invaluable information for proper design and rehabilitation of pavements. Pavement instrumentation has been used in a number of states including Minnesota, Virginia and Pennsylvania (3, 4, 5). In-place data is absolutely necessary for adopting a more rational design process - such as the Mechanistic-Empirical design method being proposed by the NCHRP (6). Moreover, in many reconstruction projects in Maine, the "new" subgrade consists of a layer of old HMA (remnants of old "pancake" layers) over the soil subgrade - something that is not usually considered in typical pavement structures. Hence, collection and proper utilization of in-place response is crucial for understanding the behavior of these pavements, and hence to test the pavement materials, and model their performance in the most appropriate way.