Tuesday, 17 July 2018
Austroads has released the final report of a five-year project to improve the Austroads design procedures of foamed bitumen stabilised (FBS) materials and identify distress modes of FBS pavements from in-service trial sites.
The report:
- summarises the development of four improved test methods published in late 2017
- investigates the influence of compaction method, moisture content and other factors on the mix design moduli
- compares laboratory mix design moduli with those from field cores
- details the construction and performance monitoring of six trial sites in Western Australia, South Australia, Victoria and New South Wales and describes the distress modes observed at the sites
- investigates improvements to the Austroads structural design method.
The major project conclusions were:
- the mix design methods of foamed bitumen stabilised (FBS) materials have been improved and harmonised.
- mix design indirect tensile moduli are similar to very early-life values and well below cured field values.
- fatigue cracking is a distress mode for FBS pavement layers and needs to be considered in structural thickness design.
- despite identified deficiencies, the fatigue life predictions using Austroads interim thickness design method appear reasonably consistent with the observed field performance based on the limited information available from field trials. The use of very conservative FBS design moduli with the asphalt fatigue relationship, together with empirical guidance on particle size distribution, plasticity and maximum binder contents, appears to result in FBS pavement layer depth based on the limited performance information available.
Report link: Design and Performance of Foamed Bitumen Stabilised Pavements