Project 1.1 (2019)

Advancements and Innovations in unbound pavements with thin surfacing- large scale and pre-implementation testing

Road pavements with unbound (untreated) bases of natural gravels or crushed rock are the most common type of pavement structure in Australia. The majority of those roads are unsealed while most of those which are sealed have been done so with thin asphalt or a sprayed seal; thinly-surfaced. While these pavement types have proven to be very cost effective over many decades, increasing road freight demand (both load frequency and axle mass) and a changing, more adverse climate and environment are factors which require improved performance. Improving the performance of thinly surfaced unbound granular pavements is therefore of great significance.

The surfacing of road pavements acts as a durable wearing course for vehicles, as well as a waterproof barrier to protect the pavement from its second biggest damaging agent, water. The strength of unbound layers relies on interparticle friction, which degrades in the presence of water as it acts as a lubricant, and in some cases washes out finer particles breaking down the material matrix.

To create a waterproofing layer, sprayed bituminous seals are applied (in most cases). The process involves spraying a thin layer of bituminous binder onto the prepared pavement structure to waterproof it. Stone chips are immediately spread and rolled into the surface to provide a hard-wearing surface and friction to help vehicles’ steering and braking manoeuvres. Thin asphalt offers a more expensive but more durable means of road surfacing. Thin asphalt surfacing provides a capacity to withstand horizontal shear forces from vehicles and to reduce the stress on the unbound material of the pavement structure.

Project Objectives

1. Contribute to improved design practice for thin bituminous surfaced unbound granular base road pavements in order to optimise life-cycle costs in the provision, use and maintenance of these pavements.

2. Develop a cohort of pavement technology research engineers, trained in both academic and industry environments, who can tackle R&D problems of the future, particularly the use of laboratory and large-scale testing to facilitate implementation of R&D in industry.

3. Use industry-led research to provide research opportunities related to the industry project.

Chief Investigators: 
  • Professor Jayantha Kodikara (LCI - Monash University)
  • Dr Ha Hong Bui (Monash University)
Industry partners: 
Partner investigators: 
Michael Shackleton (ARRB Group Ltd)