International First In Situ Stabilised Crushed Rock for Heavy-Duty Port Pavement with 3 + lifts

Australia is currently experiencing the largest infrastructure boom in its history, with an estimated $1,177 billion of engineering work being undertaken in the last 10 years with no sign of slowing. The Port of Melbourne Rail Transformation Project currently under construction is a prime example of being limited by competing major projects and supply chain issues. The primary pavement for this project is a cement bound crushed rock (approx. 800 mm thick) with a 200 mm proprietary asphalt wearing course designed to withstand the loading from reach stackers. Due to the constraints put on this project from the competing goliath projects, access to suitable plant-mixed cement-treated crushed rock material was not possible. Therefore, an international first innovative approach of using multiple lifts of in situ stabilisation was developed to overcome the supply chain issues and still deliver a pavement that conformed to the facility’s strict performance and maintenance requirements. The new method was developed in consultation with WSP experts from Australia, New Zealand, and the UK. Rather than having the material mixed at a batch plant and brought to site ready for final compaction, unbound granular material was delivered to site and in situ stabilised. In situ stabilisation isn’t new to Australia, but due to the total thickness of the pavement, it was required to be undertaken in at least three lifts. This paper will provide an overview of the key points from the specification WSP developed for the contractor to deliver the innovative approach, and the test method adopted to determine if the crucial interlayer bonding criteria is met.