Evaluation of laboratory compaction of hot mix asphalt

As mix design evolves from conventional Marshall design to Superpave and beyond, it is becoming necessary to develop test methods to evaluate the performance of Hot Mix Asphalt (HMA). One such method being developed is the Pavement Technology, Inc. (PTI) Asphalt Pavement Analyzer (APA). However, if the APA is to be used for performance testing, it is imperative that the specimens to be tested in this device are representative of the HMA to be compacted on the roadway. In light of this observation, three laboratory compaction methods employed in the design of HMA were evaluated. The compaction methods evaluated include the rotating base Marshall compactor, the Superpave Gyratory Compactor (SGC), and the PTI vibratory compactor (Model AVC-III). Volumetric properties of compacted specimens obtained from these three laboratory methods were compared with properties obtained from the roadway.

The results of this study demonstrate that the Marshall compactor and the SGC do not produce samples with densities comparable to those currently achieved on the roadway at the time of construction. On the other hand, it is demonstrated that the compaction obtained on the roadway in Tennessee is statistically equivalent to the compaction obtained in the laboratory with the PTI vibratory compactor.

Further, it was observed during the course of this study that the PTI vibratory compactor might be a valuable tool for the evaluation of the relative compactibility of HMA. Further research is warranted to evaluate the potential of this laboratory tool to identify HMA mixes susceptible to compaction problems on the roadway.