In July 1998 Austroads released the new Provisional Guide for Selection and Design of Asphalt Mixes. The mix design procedure is intended to replace Marshall mix design method currently used in Victoria. The new Austroads procedure includes a new volumetric design procedure based on gyratory compaction and new performance type laboratory tests to determine modulus, fatigue, deformation, and moisture sensitivity for heavy duty asphalt mixes. An Austroads/Australian Asphalt Pavement Association Working Group has recently released new test methods and all state road authorities are now in the process of implementing the requirements of the new Austroads Guide. Over the past few years VicRoads has undertaken a research project to use the new performance tests to obtain sufficient data to conduct a review of the presumptive moduli used for mechanistic design of asphalt pavements and to "benchmark" performance properties of heavy duty mixes for future specification purposes. Relationships between moduli determined by different methods on laboratory prepared specimens and specimens extracted from field trials after 12 months aging and trafficking have been developed. An attempt has also been made to indicate possible specification limits for modulus and fatigue life of commonly used heavy duty asphalt mixes. (a)
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