In Australia, the traditional material specifications and construction standards for quality unbound granular base materials have been continuously reviewed following feedback on performance from the field to take into account variations in material types and quality, traffic loading, construction methods, plant development and testing procedures. However, over the past few years there has been a substantial increase in the use of alternative aggregate sources of less than premium quality (such as marginal materials, industrial residues, incinerator ashes, wastes, recycled materials, etc.) and mechanical/low binder content stabilisation aggregates. For these new materials, the selection of the appropriate requirements of material specification and construction standard has become a problem of increasing concern to both the owners (State Road Authorities) and contractors. In addition, there are other new requirements directly related to field performance (e.g. resilient modulus and permanent deformation as adopted in the current Austroads mechanistic pavement design procedures), which are not catered for in the traditional material specifications and construction standards. To overcome these problems, advanced laboratory repeated load testing methods for engineering properties of the materials have been used as the basis in the establishment of new requirements of material specifications and construction standards. Full-scale pavement trials have also been conducted to establish the relationships between laboratory engineering properties and in-service material performance and validate new requirements of material specifications and construction standards.
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