Effects of Temperature and Pressure on Hot Mixed Asphalt Compaction: Field and Laboratory Study

A field and laboratory study was carried out to study the effect of pressure and temperature on the compaction of asphalt pavements. Density, temperature, number of passes, and type of roller were recorded in the field at four different paving projects in Wisconsin, with binder and mixture samples obtained from each project. Compaction in the field occurred at temperatures that ranged from 125 to $60°\mathrm{C}$ . Densification was achieved only for temperatures above the $70–80°\mathrm{C}$ range. Roller contact pressures were estimated between 300 and $700\mathrm{kPa}$ during the compaction process. Laboratory compaction was performed with Superpave gyratory compactor using the field compaction temperatures and contact pressures. The lab compaction results confirmed that below a certain temperature limit densification decreased significantly. Binder testing was performed to determine the binder viscosities in the full range of field compaction temperatures observed. The upper limit of viscosity for significant reduction in densification was estimated to be $50\mathrm{Pa}\mathrm{s}$ . A procedure for identifying the lowest temperature at which acceptable densification rate can be achieved is proposed based on testing using the dynamic shear rheometer. The determination of the lower temperature limit for compaction is an important task that is absent in the current specifications.