Thursday, 16 March 2023
A new report from Austroads documents the findings of the first stage of a project which is reviewing the laboratory fatigue performance of locally manufactured asphalt mixes against the performance predicted by the Shell relationship used in Australia and New Zealand.
The mechanistic-empirical design system in Austroads Guide to Pavement Technology Part 2: Pavement Structural Design uses a laboratory fatigue relationship developed by Shell in the 1970s to predict the fatigue life of asphalt layers.
Ross Guppy, Austroads Transport Infrastructure Program Manager says the testing specimens used 40 years ago are no longer representative of the modern mixes used in Australia and New Zealand today.
“Shell’s test was based on specimens from the US and Europe and did not include asphalt mixes with polymer modified binders, reclaimed asphalt pavement or other recycled materials that are becoming more common practice today,” Ross said.
The project used modulus and fatigue data collected from asphalt suppliers and road agencies to benchmark the laboratory fatigue performance of the mixes against the performance predicted by the Shell laboratory relationship.
The benchmarking analysis found that the current Shell laboratory fatigue relationship overpredicted the laboratory fatigue performance of conventional dense graded asphalt (DGA) mixes used in Australia and New Zealand. Consequently, new preliminary fatigue relationships were developed for DGA manufactured with conventional binders and EME2 asphalt. Further research work and additional fatigue testing are still required to refine and validate these relationships prior to implementation.
“To date, no evidence has been provided to suggest that the thickness design outcomes achieved by using the in‑service Austroads asphalt fatigue model are unacceptable or that asphalt layers have historically been over‑designed. However, the report is an important step in moving the asphalt laboratory fatigue relationship forward with our changing asphalt mixes and technology,” Ross said.
Download: Asphalt Laboratory Fatigue Relationship: Stage 1 Utilisation of Existing Data
Join us for a webinar on 22 March 2023 with researchers Joe Grobler and Dr Negin Zhalehjoo and project manager Peter Bryant.
The session will cover the findings of the project, including the preliminary fatigue relationships developed for locally manufactured asphalt mixes with conventional (unmodified) bitumen.
No charge but registration is essential.
Can’t make the live sessions? Register and we’ll send you a link to the recording.