Development of a Simple Test to Determine Workability and Field Compaction Temperatures of Asphalt Concrete

A simple and easy-to-use test method to determine workability of asphalt mixtures was developed. This new method, called ‘Dongre Workability Test’ (DWT – pronounced DWIGHT), uses the Superpave Gyratory Compactor (SGC) to measure workability. DWT is conducted under displacement control at the rate of 0.05 mm/s in the gyratory compactor using 4224 g of asphalt loose mix. No gyrations are used in the DWT. Workability of asphalt concrete, expressed in kPa units, is defined as the slope of the non-linear stress (kPa) versus volumetric strain (%) curve calculated at 600 kPa stress level. DWT is able to resolve differences in workability due to aggregate gradation, asphalt binder grade, warm mix additives and polymer modification. A chart was also developed as a part of this study to establish field compaction temperatures using the workability values (on-mat and off-mat rolling temperatures for field compaction). Using this chart and the DWT workability values at two test temperatures (200°F and 300°F), field compaction temperatures were successfully predicted for various warm-mix, hot-mix and polymer modified asphalt mixtures. DWT may also be used to calculate the temperature reduction by the use of warm-mix additives.