Rapid Assessment of High RAP Mix with Bio-based Rejuvenators Using Ultrasonic Pulse Velocity Testing and Hamburg Wheel Tracking Testing

Abstract
Ultrasonic pulse velocity (UPV) is a popular non-destructive testing (NDT) technique for the rapid assessment of materials and infrastructure conditions without causing any damage. UPV is less time-consuming and labour-intensive than conventional inspection techniques commonly applied to the field- and lab-produced asphalt concrete specimens. In this study, different asphalt mix specimens were produced with 50% Reclaimed Asphalt Pavement (RAP) and four bio-based rejuvenators. A control mix with 20% RAP was also prepared with a verified Job Mix Formula (JMF). During the volumetric mix design, the ease of compaction was observed on rejuvenated high RAP mixes in terms of the reduced number of gyrations compared to the control mix. However, the compaction temperature and conditioning time of the high RAP mix was kept the same as the control mix. The volumetric requirements as per Ontario Provincial Standard Specification (OPSS) 1151 were met for the mixes. This paper attempted to use UPV measurements on the rejuvenated high RAP mix and control mix specimens to examine the condition of these mixes, especially those with reduced compaction effort. Different wave characteristics, including group P-wave velocity and peak-to-peak (PTP) amplitude of the first arrival P-wave in the time domain signal, and spectral area, peak spectral magnitudes, peak frequencies in the Fourier spectra, were evaluated to compare the different mixes. After performing UPV tests, the Hamburg Wheel-Track Testing (HWTT) was performed on the same specimens. The results provided a rapid evaluation of the high RAP mixes at high frequency (low temperature) and high temperature (low loading frequency) domains.