UC Davis Institute of Transportation Studies

This is one of two reports describing the third phase of a warm-mix asphalt study that compares the performance of two rubberized asphalt control mixes with that of seven mixes produced with warm-mix technologies. The control mixes were produced and compacted at conventional hot-mix asphalt temperatures (>300 F [150°C]), while the warm-mixes were produced and compacted at temperatures between 36°F (20°C) and 60°F (35°C) lower than the controls. The mixes, test track, Heavy Vehicle Simulator (HVS) and laboratory testing are discussed. Key findings from the study include: Adequate compaction can be achieved on rubberized warm-mixes at lower temperatures. Optimal compaction temperatures will differ. Equal and potentially better rutting performance can be achieved provided that standard specified limits for hot-mix asphalt are met. Test results indicate that use of the warm-mix technologies did not significantly influence performance when compared to control specimens. However, the mixes produced with chemical surfactant technologies did appear to be influenced in part by the lower mix production and construction temperatures, which would have resulted in less oxidation of the binder and consequent lower stiffness of the mix. Rutting performance, fatigue performance and moisture sensitivity did not appear to be affected. The warm-mixes produced using water-foaming technologies appeared to have lower moisture resistance compared to the other warm-mixes. Smoke and odors are significantly reduced on warm-mixes compared to hot-mixes, while workability is considerably better on warm-mixes compared to hot-mixes. The HVS and laboratory testing completed in this phase have provided no results to suggest that warm-mix technologies should not be used in rubberized asphalt in California.