Over many years, it has been demonstrated that the application of engineering judgment has been a significant aspect of the continuing use of naturally occurring materials in roads and regional airports in Western Australia. The information contained in this document has been assembled so that, where possible, engineering judgment can be supported by relevant tests and an understanding of the significance of the test results. Materials such as laterite and calcrete (pedocretes), clayey-sands and scree gravels, are discussed against a background of “conventional” selection criteria, strength tests and critical service applications.
This document has not been prepared to provide specifications for general use in the application of natural materials in roads. Rather, one of its aims is to guide personnel involved in the preparation of specifications, towards practical criteria, which do not exclude useable resources. Wherever possible, Main Roads Western Australia practices have been incorporated into this guideline.
This document has been produced by a working group from the Western Australian Pavements Group (a subcommittee of Australian Geomechanics Society comprising Consultants, Main Roads WA, Local Government, Material Suppliers and Researchers). It is an update of the 2003 document published by Main Roads WA. New data has been included and the scope expanded to cover unsealed roads and minor airports.
“Although laboratory experiments may be thought indispensable for a complete knowledge of metalling materials, they are, however not sufficient to define the coefficient of quality of such material” Bredtschneider et al. (1911)