PAVEMENTS – Stabilisation practices in Queensland

The stabilisation of road construction materials has been extensive across Queensland, with a number of stabilisation technologies currently available, each with distinct benefits and limitations. In Queensland, the selection of a stabilisation treatment for a given application is heavily influenced by traditional local practice and there has not been a state-wide effort to characterise relative performance over time. NACOE research has delivered significant cost savings by providing state-wide consistency in the selection of the appropriate stabilisation method, and aligning design to international best practice. 

 The early focus of this research was in plant-mix cement modified bases and in situ foam bitumen stabilised bases. With the majority of roads treated with these technologies currently in good to excellent condition, including several that have exceeded the original service life estimates. Testing of a subset of this network indicated that many pavements have significant structural capacity remaining. 

 Foam bitumen in particular has been utilised in flood-prone locations due to its ability to withstand prolonged inundation. Pavements treated shortly before Cyclone Debbie in early 2017 exceeded expectations and minimised reconstruction costs after this major event. 

 Stabilisation technologies provide long-term performance benefits at a significantly reduced cost to full-depth asphalt, and as such increased utilisation of these technologies can result in significant reductions in both construction and maintenance expenditure.  An economic analysis has shown that utilising a cement modified base can lead to savings of $50 to $130 per m2 when compared to a similar standard hot mix asphalt base layer, which translates to savings of up to $1 million per kilometre treated. 

 As an outcome of this research, five new technical notes have been developed, to cover the different stabilisation practices in Queensland.  These notes will provide guidance to practitioners regarding best practice for the investigation, design and construction of these technologies.  

 NACOE has established that much of the stabilisation practice adopted by TMR is now best practice nationally.  Using TMR as a benchmark, AustStab have moved to harmonise foam bitumen stabilisation practices and specifications across Australia.