Physical and Structural Characterization of Sustainable Asphalt Pavement Sections at the NCAT Test Track

Abstract

A sustainable pavement can be defined as a safe, efficient and environmentally friendly pavement that meets today’s transportation needs without jeopardizing the ability to meet such needs in the future. Recent advances in this area include technologies that focus on low consumption of energy for production and placement, conservation of natural resources, noise reduction and improvement of the quality of stormwater runoff. As state agencies have begun to transition from an empirical pavement design method to a mechanistic-empirical (M-E) approach, it has become necessary to further evaluate the material properties and structural characteristics of these newer technologies. This research study evaluated physical and structural properties for different sustainable pavement sections placed at the National Center for Asphalt Technology (NCAT) Test Track. The Test Track was reconstructed in the summer of 2009 and part of the experiment included six new structural sections built using several sustainable technologies, including warm mix asphalt (WMA), high RAP mixes and porous friction courses (PFCs). All pavement sections were embedded with a gauge array to measure horizontal asphalt strain, vertical aggregate base pressure and vertical subgrade pressure in the center of the outside wheelpath. During trafficking operations, falling weight deflectometer (FWD) testing was performed three times per month to quantify the seasonal behavior of the pavement layer moduli. Strain and pressure measurements were taken weekly under live traffic loads and under different environmental conditions. In general, the results indicated that pavement responses changed significantly for high RAP and PFC sections compared to the control, but not for virgin WMA sections. Overall, laboratory tests performed on plant produced mixtures suggested that inclusion of high RAP percentages may increase susceptibility to fatigue and thermal cracking, while the use of WMA technologies could increase rutting susceptibility. However, some results varied depending on the test method used and did not correlate well with field performance. Caution must be taken when using laboratory test to evaluate the performance of sustainable mixes. Field performance measurements showed that rut depths were influenced by the use of sustainable technologies, but all sections performed well overall with under 12.5 mm of rutting. No cracking or indication of moisture damage had been observed in any of the sections at the conclusion of the research cycle.