Pavement

The purpose of this report is to improve the design of thin asphalt surfaced unbound granular flexible pavements. This report presents the findings of an investigation into the potential alternatives to typical pavement configurations in the context of increasing traffic demands across the road network. It describes the full-scale construction, artificial ageing, accelerated loading, and performance monitoring of two trial sections comprising of conventional bitumen binder and polymer modified bitumen. The results of laboratory performance testing of the materials used in the test pavement is also included.

Due to the absence of asphalt cracking under initial loading, the bearing capacity of the unbound granular layer was reduced by the careful and gradual introduction of water. The test pavement was subsequently subjected to further accelerated traffic loading to determine the deflection/curvature thresholds and the relative performance of the asphalt mix. Mix A10E and Mix C320 sections were terminated at 30,000 and 89,500 load cycles respectively. Cracking of the asphalt developed following 10 mm deformation in the pavement.

The pavement investigation revealed that a high moisture content of the granular materials post wetting caused the deformation and fatigue cracking. The laboratory fatigue lives of the Mix A10E were higher than Mix C320. No significant change in life was observed due to the accelerated artificial ageing process used. With increasing traffic demands on the road network, this report represents a significant contribution to understanding the potential performance risks of thin asphalt surfacing alternative to sprayed sealed. The findings will enable practitioners to make appropriate decisions in the design and implementation of thin asphalt surfaced granular pavements, reducing the likelihood of early failure due to selection and design issues.

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