Evaluation of the Rapid Rutting Test and High Temperature Indirect Tensile Test for practical use in asphalt mix design, quality assurance, and quality control
Abstract
The asphalt industry has a large number of mixture performance tests available to evaluate a mix design's ability to withstand typical pavement distresses. Some of these tests are widely used whereas others tend to fall into the background for reasons such as cost, being time and labor intensive, and most importantly correlating poorly to field performance. This study focuses on the evaluation of two newly proposed asphalt rutting tests, specifically looking at their practicality in use for mix design, quality control, and quality assurance purposes. These tests are the Rapid Rutting Test (RRT) and the High temperature Indirect Tensile Test (HT-IDT). The various asphalt mixtures that were used in this study came from several different asphalt pavement design projects completed by the Missouri Asphalt Pavement Innovations Lab (MAPIL) here at the University of Missouri. These projects include both dense graded and stone matrix asphalt (SMA) mixture types for a total of 11 different asphalt mix designs. Within the 11 used asphalt mixtures, novel materials such as recycled rubber and recycled plastic were implemented as modifiers to the mix designs. In this study, the evaluation of the RRT and HT-IDT was carried out through five individual areas of focus. The first focus area involved correlating the test results of the RRT and HT-IDT to the existing and commonly used Hamburg Wheel Track Test (HWTT). It was found that the RRT showed R2 values ranging from 45 percent to 84 percent for dense graded mixtures and 69 percent to 82 percent for the HT-IDT. Correlations to the HWTT for the SMA mixes were below 30 percent for the RRT and HT-IDT. Next, the effects of reheating on the RRT and HT-IDT testing procedures was evaluated by comparing the results between lab and plant reheated forms of each mixture. It was found that dense grade mixes resulted in -6 percent to 30 percent percent difference and -22 percent to 26 percent when tested in the RRT and HT-IDT, respectively. The next area of focus involved analyzing the effects that the additives and modifiers (rubber, plastic, anti-strip) had on the testing results in the RRT and HT-IDT. These effects were able to be made due to the incorporation of unmodified "control" mixtures being compared to their counterparts who were modified with such materials. It was found that the addition of rubber and plastic had significant increases in performance for dense graded mixtures (RRT and HT-IDT) and the addition of rubber had a negligible effect on performance of SMA mixtures (RRT and HT-IDT). The last area of analysis in this study focused on statistical analysis of the data results for the RRT and HT-IDT. It was found that the RRT and HT-IDT tests showed low coefficient of variation for dense graded and SMA mixtures with COVs ranging from 1 percent to 7 percent and 4 percent to 7 percent, respectively. From the obtained data results, each test shows merit in use for QA/QC purposes due to their very low variation and high repeatability. However, the other section's data results indicate that these tests show promise in rut evaluation but must be further researched before any type of consideration for implementation is made.
Degree
M.S.