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Reheating and oven-aging procedures of plant-produced asphalt mixtures in laboratories are important topics to consider as performance testing of mixtures becomes more popular among agencies. Differences between laboratory equipment and procedure could significantly affect performance properties. The objective of this study is to investigate the influence of sample size, oven type, and variation in reheating/aging temperatures on the results of two performance tests on plant-produced mixtures. A selected mixture was tested for volumetric properties and performance using Hamburg wheel-tracking (HWT) and semi-circular bending (SCB-IFIT) tests. Results show that reheating mixtures uncovered and in smaller containers could significantly reduce the time to achieve aging temperature, and could make the process more efficient and consistent. In addition, aging using three different oven types showed that temperature within ovens can vary significantly depending on the location of the sample inside the oven, which affects the time required to reach the target temperature, and thus may also influence the aging of the sample. The mixture volumetric properties show that the effect of various heating conditions is marginal. Using the developed reheating/aging procedure of this study, the results of the HWT and SCB-IFIT tests showed no substantial effect of oven type on rutting and cracking resistance. The overall results indicate that there is a need to standardize the conditions of reheating, sample geometry, and to verify uniformity of temperature in ovens. Such standardization can further reduce variability and thus should be part of the AASHTO/ASTM standard procedures for quality control, or of laboratory equipment calibration procedures.

Wheel tracking tests have seen a vast increase in usage among various state department of transportations for measuring rutting resistance of mixtures that already meet volumetric property requirements. With the increase in using recycled materials and warm mix additives, it is clear that using volumetric properties alone to approve asphalt mixture designs is a risky approach. Wheel tracking tests are among the most widely used methods for evaluating rutting resistance, and the AASHTO T324 (Hamburg Wheel-Tracking [HWT]) is the most widely accepted and followed procedure used today in the U.S. However, there are challenges using the HWT, among which the most difficult are the poor repeatability, time required to complete the test, and the sample preparation details. This study reports on an alternative wheel tracking method called the Rotary Asphalt Wheel Tester (RWT) that can successfully address the challenges currently faced with using the HWT. The method requires no cutting of the gyratory samples, significantly reduces time to complete a sample, and appears to offer acceptable repeatability of the results. The method has existed for more than 15 years, available commercially, but used only in a few labs, and one acceptance criterion is already developed by one agency. The study includes evaluating an expanded set of mixtures tested at two temperatures, and two air voids. The results of the RWT are compared with the results of the HWT for numerous mixtures and they show that similar qualitative ranking can be achieved.