An updated specification for polymer modified binders (PMBs) and crumb rubber modified binders has been published by Austroads.
PMBs consist of bitumen blended with a synthetic polymer or crumb rubber and are used to enhance the performance of binders on heavily trafficked or distressed pavement surfaces.
The test method has been revised following a review of current PMB manufacturing, testing and application experience.
The updated test method includes an alternative Standards Australia method to determine viscosity at 165 °C, a stress ratio binder property and a definition for field-produced crumb rubber modified binders.
The consistency and elastic recovery binder properties have been removed, and the rubber content by analysis binder property for the class S45R binder has been replaced with a stipulation that this binder class be manufactured from crumb rubber derived from used vehicle tyres.
The framework has been produced by an Austroads working group and is based on test procedures that have been in use throughout Australia for several years.
The specification aims to achieve satisfactory design performance in the field for both sprayed seal surfacing and asphalt pavement applications.
Specification limits are framed around the results of nationally coordinated field trials and laboratory studies, supplemented by Austroads jurisdiction experience.
The Specification Framework for Polymer Modified Binders can be found here.
