| dc.description.abstract | A comprehensive study involving rut potential of Hot Mix Asphalt (HMA) was conducted. Both cylindrical and beam specimens
of HMA were prepared using a Superpave Gyratory Compactor (SGC) and an Asphalt Vibratory Compactor (A VC),
respectively. Mixture rutting performance was determined in the Asphalt Pavement Analyzer (AP A). Initially, rut tests
were conducted on three laboratory-prepared HMA for 8000 cycles of loading with I 00 psi hose pressure, 100 lb wheel
load, and 50 seating cycles. The rut values (8,000 cycles) varied between 2.0 mm and 6.4 mm. Rut depths were found to be
sensitive to temperature when compared that to asphalt content.
Subsequently, this study evaluated rut potential of ten plant-produced mixes. Three of these mixes were of type A and six
type B insoluble and one Type C. Only one mix showed a rut depth of more than 4 mm. The A VC beam specimens showed
higher rut depth compared to cylindrical specimens. The AP A rut test data were analyzed to identify the important
contributing factors. Type A mixes were sensitive to percent asphalt content, where as Type B insoluble mixes were
sensitive to material passing number 200 sieve.
This research investigated the relationship between rheological and mechanical properties for various Oklahoma
unmodified and modified binders based on the asphalt mixture's rutting performance. The tests result showed that binder's
Performance Grade (PG) affects mixture performance significantly. In general, modified binder showed better performance
compared to the unmodified binders. Modified binders of same PG grade did not show the same performance when test
parameters were held constant. Binder's viscosity and rut factor (G'/sin8) did not show significant effects on rutting
performance of both modified and unmodified binders. Linear and nonlinear regression analyses were performed to
investigate the contribution of binder properties to rutting. The nonlinear regression prediction of rutting was better than the
linear prediction.
This study identified the most significant factors from a number of factors, which affect rut potential of HMA. Seven
factors: binders PG, specimen type, test temperature, moisture, wheel load, asphalt content, and hose pressure,. each at two
defined levels were incorporated in a Superpave mix. Rut tests were designed to be the elements of an experimental matrix.
The matrix test results were analyzed statistically. The analysis results showed that binders PG, specimen type, test
temperature, and moisture, affected a mixture's rutting performance significantly. This study developed and described a
statistical procedure to design and analyze an experimental matrix of test results.
This research investigated the repeatability and reproducibility of laboratory test data. An inter-laboratory study was
performed on rut tests using the AP A between the 'asphalt design laboratory' at the Oklahoma Department of
Transportation (ODOT) and the 'asphalt laboratory' at the University of Oklahoma (OU). The tests result showed no
significant variability in the collected data from two laboratories. This study developed a rut database for future model
development. The AP A rut results ofHMA materials, which were used in a road section (funded by ODOT) of the National
Center for Asphalt Technology (NCAT) Test Track at Alabama, were also included in the rut database. | |
