Review of mechanistic pavement design procedures to produce sustainable pavement designs for heavy duty pavements

Deep strength asphalt pavements with fully bound cementitiously treated sub-base are commonly used for heavy duty urban pavements. There is an increasing demand for thin asphalt surfaced unbound granular pavements incorporating highly flexible polymer modified binder (PMB) asphalt mixes (in lieu of sprayed sealed surfacing) for medium to heavy duty pavements in outer metropolitan areas and rural cities related to cost, safety and reduction of traffic noise. This raises two important questions in regard to the current pavement design procedures: Are heavy duty asphalt pavements requiring an overall thickness of asphalt of up to 400 mm of asphalt sustainable in the future or should we be making better use of thicker bound cement treated sub-bases? For medium to heavy duty pavements, should we develop a more robust pavement design procedure for design of unbound granular pavements with thin flexible asphalt surfacing systems with a high level of waterproofing? This paper presents a series of example pavement designs based on input information from both Victoria and Queensland together with some variations to the pavement design procedures provided in Part 2 of the Austroads Guide to Pavement Technology and relevant State Road Authority design supplements. The material presented is intended to identify areas where further review and enhancement of the current mechanistic pavement design philosophy and procedures may be required. It also attempts to provide a lead for determining the direction of future pavement research in Australia aimed at lowering overall carbon emissions associated with pavement design and construction and to conserve our premium bituminous products by limiting their use to upper pavement layers and the surfacing