Monitoring ageing of bituminous binders

Abstract

Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.

The failure of the rolling thin film oven test (RTFOT) protocol to simulate the short-term ageing (STA) of in situ asphalt binder accurately for different binder types, can be attributed to the significantly different mixing, transport and compaction temperatures used for different asphalt mixes. The RTFOT procedure can be modified to accurately predict the STA of binders for a specific road construction scenario. The modification of the procedure constitutes the first step in the establishment of a modified protocol for a binder type/class. The method used for monitoring the ageing of binders should be applicable to all binder types, considering that the properties of modified binders often have opposing or juxtaposed ageing effects which result in irregular changes in the measured property with ageing. This paper evaluates a method of rheologically following the ageing of both modified and unmodified binders, based on a single temperature/frequency point. Ultimately data from a number of contract sites would need to be collated; repeatability and accuracy established for the proposed method, before a final protocol is determined.