University of California Pavement Research Center

This report describes a laboratory testing study that compared the performance of a control mix, produced and compacted at conventional hot-mix asphalt temperatures, with a mix containing Rediset^TM WMX warm-mix additive (referred to in this report as Rediset), produced and compacted at approximately 35°C (63°F) lower than the control. Key findings from the study include: No problems were noted with producing and compacting the Rediset mix at the lower temperatures in the laboratory. The air-void contents of individual specimens were similar for both mixes, indicating that satisfactory laboratory-mixed and compacted specimens can be prepared with the warm mix. Interviews with laboratory staff revealed that no problems were experienced with preparing specimens at the lower temperatures. Improved and safer working conditions at the lower temperatures were identified as an advantage. The laboratory test results indicate that use of the Rediset warm-mix asphalt additive assessed in this study, produced and compacted at lower temperatures, does not significantly influence the performance of the asphalt concrete when compared to control specimens produced and compacted at conventional hot-mix asphalt temperatures. In the shear, fatigue, Hamburg Wheel Track, and Cantabro tests, the results and trends in the results indicated similar performance between the two mixes, and between the two mixes and the Control mix tested in an earlier study on warm-mix asphalt undertaken for the California Department of Transportation (Caltrans). Minor differences in the results of these tests were attributed to the inherent variability of these tests and less oxidation of the binder in the Rediset specimens due to its lower mixing temperature. In the Tensile Strength Retained Test, the Rediset mix had significantly better moisture resistance compared to the Control mix in this study as well as the Control mix in the earlier Caltrans study. The laboratory testing completed in this study has provided no results to suggest that Rediset^TM WMX warm-mix additive should not be used to produce and place asphalt concrete at lower temperatures. These results should be be verified in pilot studies on in-service pavements. The results of the Tensile Strength Retained test indicate that the use of Rediset could improve the moisture resistance of moisture sensitive mixes. This should be investigated further along with additional Hamburg Wheel Track tests on oven aged/cured samples to assess the effect of shortterm curing on the results of this test.