Direct Estimation of Air Void Content from Gyratory Compaction History

A computational approach is offered and explored for estimating the air void content of asphalt mixtures densified in the Superpave gyratory compactor. It entails fitting a sigmoidal function to the compaction history records of specimen height vs. gyration level. The compaction progress is then extrapolated mathematically to infinite number of gyrations for which the air void content is theoretically zero. The fitted densification curve is then used to estimate the air void content at any finite gyration level of interest. Different asphalt mixtures consisting of both dense and coarse aggregate gradations are
compacted to assess the approach. At this point of development, based on comparison with measured air void contents, acceptable estimations are obtained only for densegraded mixes. It is envisioned that the ideas proposed herein will be programmed into future gyratory equipment to provide operators with an estimated air void content immediately after compaction.