Forensic Study on the Cracking of New Jersey's Long-Term Pavement Performance Specific Pavement Study Sections

In 2010, New Jersey's long-term pavement performance (LTPP) Specific Pavement Study (SPS-5) sections closed out. Before the rehabilitation of these pavement sections, an extensive coring and forensic study was conducted to characterize the material properties of the virgin and the 30% reclaimed asphalt pavement (RAP) asphalt mixtures used on the project. Along with field cores, raw materials (i.e., aggregates, binder, loose mix) were procured from FHWA-LTPP Materials Reference Library. Visual distress surveys from the LTPP database were collected and used to compare the mixture performance with the general field performance. Overall, the field performance indicated that the virgin and the 30% RAP sections initiated cracking within 1 to 3 years of each other, given the section evaluated. Once cracking began, however, the 30% RAP sections cracked at a faster rate than the virgin sections; this behavior resulted in higher crack counts even though the 30% RAP section had a softer binder (i.e., AC-10 versus AC-20). The overlay tester (OT), disk-shaped compact tension [DC(T)], and low-temperature indirect tension and creep compliance were used to characterize intermediate and low-temperature cracking properties of the mixtures. Asphalt binder characterization included performance grading, master stiffness curves, and linear amplitude sweep (LAS) testing to characterize the stiffness and fatigue properties of the asphalt binders. The material testing program showed that the mixture test results matched the observed field cracking performance better than the asphalt binder testing conducted on the extracted and recovered asphalt binders. The OT and DC(T) tests appeared to be the most sensitive to the cracking performance differences between the virgin and 30% RAP mixtures, while the LAS test appeared to rank the fatigue performance of the 30% RAP mixture better than that of the virgin mixture, which contradicted the observed field performance.