Austroads bitumen road models

Austroads’ long-term pavement performance (LTPP) study has exceeded its initial objectives, facilitating the development of multiple prediction models to assist in pavement maintenance.

Austroads has released the final report of the study, which was established in 1994-95.

The long-running project monitored the structural and functional performance of a range of in-service sealed granular, asphalt and concrete pavements.

LTPP monitoring helps with understanding pavement behaviour under different traffic loading and environmental conditions.

Prediction of pavement performance under various conditions is a critical element in managing high-cost pavement assets in terms of the potential cost savings on maintenance and rehabilitation activities.

The LTPP study had four primary objectives. The first was to enhance road asset management strategies by using improved pavement performance models.

The second was to compare the performance of a range of Australian pavement sections with sections in the United States that had been established under the Strategic Highway Research Program Long Term Pavement Performance (SHRP-LTPP) Program.

The third objective was to compare the performance of accelerated loading facility (ALF) test pavements with actual road pavement performance.

Finally, Austroads sought to investigate the quantitative influence that various maintenance surface treatments had on long-term pavement performance, as determined by the long-term pavement performance maintenance (LTPPM) portion of the study.

The final report reveals that the study more than fulfilled its original objectives, resulting in additional outcomes.

Among these outcomes were a number of new models and modelling approaches.

The study saw the development of an asphalt and seal life prediction model based on bitumen hardening from more than 257 asphalt and 124 seal samples collected across the country.

The study also developed rutting and roughness progression factors and the calibration of the HDM‑4 road deterioration (RD) models for rutting and roughness under Australian conditions.

Interim works effects (WE) models for a wide range of surface treatments, as well as interim network-level functional and structural RD models for flexible pavements, were installed in the pavement management system used by the NSW, Victorian and Western Australian road agencies.

A probabilistic RD model development using a decision tool software @Risk was also developed.

The study enabled Austroads to trial a new probabilistic modelling approach using a data condensation technique known as stochastic information packet to explore the possibility of adopting the approach in a pavement management system.

A comparative analysis of in-service LTPP pavement data from Victoria, Queensland and South Australia using ALF experimental data confirmed that pavement performance predictions made from the ALF pavements were generally comparable with the performance of in-service pavements.

Additionally, a comparison between the asphalt pavement performance of the LTPP sites and the US SHRP‑LTPP sites showed that the US non-freezing zone and Australian pavements experienced similar structural and functional deterioration.

Austroads also investigated the influence of maintenance and surface treatments on pavement performance, based on the data collected from eight LTPPM sites from 1998 to 2018.

It found that, as expected, periodic maintenance treatments such as geotextile reseals, polymer modified binder (PMB) reseals and normal reseal treatments helped reduce the rate of deterioration in terms of roughness, rutting and cracking.

Over the course of the study, guidelines were developed for the establishment and monitoring of LTPP and LTPPM sites.

Austroads hopes the LTPP data will be frequently used by researchers and academia inside and outside Australia.

View the Long-term Pavement Performance Study final report here.

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