Development of Design Procedures for Lightly Bound Cemented Materials in Flexible Pavements

Austroads: Transport Research and Trends

The addition of a small amount of cementitious binder to non-standard granular materials may result in a fit for purpose base or subbase at a significantly lower cost than crushed rock complying with standard specifications. Such lightly bound cemented (LBC) materials have particular use in pavement rehabilitation and heavy patching as they are less susceptible to block cracking and crocodile cracking than cemented materials.

The binder content and strength of LBC materials are significantly lower than heavily bound cemented (HBC) materials. Austroads’ recent report, which reviewed the performance of selected Queensland pavements with LBC bases, has shown that it is possible to design and construct a low-strength material with base thickness and subbase support sufficient to limit the extent of the micro cracking development that leads to macro-cracking.

Considering the use and performance of LBC for moderate to heavily trafficked roads, a structural design method was developed for pavements containing LBC materials and HBC materials in the post fatigue cracking phase of life, including:

• A new elastic characterisation method, applicable to LBC materials and HBC materials in the fatigue cracked state, including methods to vary the design modulus according to the design modulus of the layer supporting the cracked material and the thickness and modulus of the overlying bound materials.
• Design charts to select LBC base thicknesses to inhibit the development of block cracking and crocodile cracking, with the minimum thickness varying with design traffic loading and the support provided by the layer under the LBC base.

This webinar, presented by Dr Geoff Jameson and Dr James Grenfell, explains the structural design method in detail, including its development and application.