In New Zealand excessive deformation in the wheel paths due to post construction densification has occurred in a number of new pavements constructed in recent years. It is believed that much of the deformation could be avoided if the aggregate layers were to be compacted to a high level of density prior to the road being opened to traffic.
This research project was designed to explore the factors that control the density of unbound granular aggregate and the influence that particle size distribution has on the density, on the compaction process and on the subsequent performance of a pavement. It was carried out in the period between 2004 and 2007.
The results show that it is practical to produce basecourse with a dense grading by blending the normal quarry product with crusher dust or sand. Full scale trials showed that dense graded basecourse could be compacted to a Total Voids content of less than 15% and that the mean depth of ruts after twelve months trafficking was less than 5 mm.