A Toowoomba-based transport engineering expert hopes to help industry fine tune its use of foamed bitumen for road repairs by providing a better gauge of material performance.
The University of Southern Queensland’s faculty of engineering boasts a laboratory-scale plant designed to determine the ideal foamed bitumen properties to suit various base materials.
USQ lecturer and researcher Dr Kathirgamalingam (Soma) Somasundaraswaran initiated the purchase of the $90,000 Wirtgen-manufactured WLB 10S about a year ago after being involved in a road rehabilitation research project on the Oakey-Pittsworth Highway.
He believes there is good potential for Queensland industry to reuse existing, in-situ pavement material with foamed bitumen for rehabilitation work rather than bringing in new material, as required under current Austroads and Main Roads standards.
Focus on testing protocols
“I am interested in developing testing protocols to determine the suitability of a wide range of local materials from existing pavements including reclaimed asphalt pavement (RAP) and granular bases/sub-bases of different sizes and qualities,” Dr Somasundaraswaran said.
“Recently, one of my masters students completed a project titled: Evaluation of strength characteristics of foamed-asphalt mixtures with RAP materials.
“I am sure that the Austroads FBS (foamed bitumen stabilisation) design requires additional laboratory performance testing.”
Dr Somasundaraswaran said he planned to assign further such work to students this year to help build up testing methods for using RAP.
“We can test it and, if the results are good, develop protocols to start using it,” he said.
This would mean reduced time and construction costs as well as the environmental benefits of recycling.
Process becoming easier
Foamed bitumen is produced by injecting water into hot bitumen, resulting in spontaneous foaming.
While this used to be difficult, the process had been become easier with the introduction of purpose-made machinery, Dr Somasundaraswaran said.
He said FBS was widely used for rehabilitation work throughout Queensland, with the Department of Transport and Main Roads conducting its first trial of the process on a 1.6km section of the Cunningham Highway in 1997.
The rapid evolution of the technology presented many challenges, particularly regarding adapting different specifications, construction standards and design approaches for using materials from existing pavements, Dr Somasundaraswaran said.
Cost-effective and durable
Cold recycling with foamed bitumen in road rehabilitation works was highly cost-effective and produced high-quality, durable base layers, he said.
Other advantages in using foamed bitumen stabilisation included an increase in the shear strength of granular pavement and relatively greater fatigue resistance.
Dr Somasundaraswaran said lower moisture contents were required in compaction, minimising wet spots, and the pavement could tolerate heavy rainfall with minimal surface damage under the traffic.
“And it is carried out in situ and hence is quicker than other methods of rehabilitation such as an overlay,” he said.
However, the construction process requires attention to detail.
Dr Somasundaraswaran said operators and supervisors must have specialist training and more experience for successful application of FBS.