Pavement

This report details investigations that were conducted to verify the new Austroads sprayed seal design guidelines.

To verify the appropriateness of the proposed basic voids factor (Vf), and the initial sealing design approach (and also to validate the necessary assumptions made to develop them), several seals that were constructed using the new approaches in the Northern Territory and Victoria were inspected.

The performance of the sprayed seals designed and constructed with the new or the existing basic voids factor was similar. It was therefore not possible to make a definitive judgement on the appropriateness of the proposed voids factor based on these inspections alone.

A series of double/double initial seals with a modified binder were constructed to investigate whether more robust, longer-lasting initial seals (than traditional initial seals) could be developed. The performance of these seals was generally satisfactory after four years of service life, suggesting that a more durable initial seal is possible utilising this type of sprayed seal.

Inspections of a special double/double initial seal, utilising multiple layers, large aggregate sizes and a highly modified polymer modified binder suggested that new and innovative approaches, using previously-unadvised materials and methods, can be used to design initial seals that perform well in high-stress locations, but only if they are managed and used with care.