Pavement

This report examines the selection of an appropriate laboratory compaction device for stone mastic asphalt (SMA). The laboratory compaction of the SMA mix is crucial as the volumetric properties are selected based on the results from laboratory samples, which should replicate volumetric properties that are similar to those achieved during field compaction. Therefore the mix design relies heavily on the applicability of the laboratory compaction method.

While this project focused on the selection of an appropriate laboratory compaction device for SMA, due to the complexity of this task it was necessary to also investigate compaction temperatures. The method described in European Standard EN 12697-10 and the achieved air void contents were used to assess the compactibility of bituminous mixtures. Based on the outcomes of this study, it is suggested that Australian Standards are harmonised in terms of the required mixing and compaction temperatures, and the requirements for laboratory mixing and compaction temperatures should be selected as a function of the binder type.

It was found that for SMA applications the Gyropac compactor is not capable of achieving the same level of compaction (i.e. air void content) as the Servopac. When using the Servopac according to AS 2891.2.2, it was found that 250 gyratory cycles would be applicable for preparing SMA samples in the laboratory. However, this value requires validation. The design air void content achieved using the Marshall compactor at 50 blows may replicate field conditions and a further decrease of the air void content is possible when using 75 blows; this needs to be considered when using the Marshall compaction.