Using Basegrade Stabilisation to Rehabilitate Thin Local Roads - Stabilised Pavements of Australia

Abstract

Sealed flexible pavement structures typically consist of a wearing surface, a base layer and a subbase layer to protect the subgrade from damage caused by traffic loads. Local government urban roads in Australia often only have a base layer sitting directly on the subgrade. When the thickness of the existing granular base layer is deemed too thin to satisfy rehabilitation design requirements, the base and subgrade layers can be insitu stabilised simultaneously with an appropriate binding agent. This is termed Basegrade Stabilisation (Young, 2020). Basegrade stabilisation not only provides an economical solution to local government asset owners, but offers another sustainable asset management approach that fits within the circular economy framework. National and international literature supports the use of basegrade stabilisation since the 1980’s in Australia, however no mix design procedure previously existed. Experimental research completed in 2020 developed a mix design procedure to allow practitioners to confidently evaluate an existing pavement structure and select a trial mix design for laboratory testing. Nine pavement types were examined in the research. They comprised three subgrade materials of varying plasticity and subgrade proportions of 20%, 35% and 50%. Three binders were added to the nine pavement types at various application rates. They were lime/cement/flyash triple blends, slag/lime blends and cement/flyash blends after lime pre-treatment. The mix design procedure developed consists of ten mix design trials for selection, based on preliminary assessment of the untreated basegrade structure. This paper explores the background of basegrade stabilisation and the subsequent development of a new mix design procedure and how it can apply to a local council asset management plan with a focus on rehabilitation of thin local council sealed roads.