By Andrea Barnard

Curtin University’s Pavement Research Group has partnered with Main Roads WA, the City of Canning, the West Australian C&D waste recycling industry and ARRB Group to complete a major study into cement rehydration and the use of recycled materials in road pavements.

Led by Curtin’s Head of Civil Engineering, Professor Hamid Nikraz, with initial funding provided by the City of Canning and the Waste Management Authority, the research helped to develop a better understanding of cement based materials and highlighted the need for further investigation into the management of rehydration of cement in pavements, identifying recycled road-base sourced from demolition materials as a potential solution.

Curtin engineering lecturer and City of Canning special projects engineer, Colin Leek, said the research would address challenges regarding fatigue cracking in pavements, a problem occurring during the rehydration of cement resulting in the binding and shrinking of granular pavement.

“Shrinkage causes cracks and the binding causes increased stiffness. Whilst the shrinkage cracking appears minor, it is a major consideration,” Mr Leek said.

“The rehydration and excessive stiffness is an issue as, in theory, the material if bound may then crack again due to excessive strain caused by traffic loads, and this cracking may be in the form of discrete segments much like the patterns on a crocodile skin.

“This may not be a problem as such, but may in fact be a benefit that can be utilised. All we need to know is how to design for this, and that is the new challenge. The rehydration has been considered before in Australia, but how to effectively manage it has not.”

Mr Leek said his contribution to the ongoing research was invested in ensuring the solutions provided were based on future sustainability, reducing waste and saving of natural resources.

“The use of recycled products is also energy efficient compared to the use of new quarried products,” he said.

“This research will enable the recycling industry to manufacture specific products based on source stock, and for the construction industry to be aware of the performance of each material type produced.

“It may allow for a method to consider the rehydration effect that would permit the design of pavement life over a considerably longer period than is currently the case, thus reducing total resource consumption in the longer term.”

Mr Leek said the research, combined with new pavement design methods developed in parallel by Curtin civil engineering researchers, Dr Peerapong Jitsangiam and Dr Komsun Siripun, would hopefully remove some of the empirical design methods to allow for a more definitive analysis based on real pavement material properties that accurately reflected the stress conditions in the field.

“This is too early to say, but in reality, pavements are probably one of the most uncertain engineering structures we deal with,” he said.

“We do not yet know how to model them accurately, we don’t know how the stress is transferred in the real pavement situation, and we have no relationship between laboratory characterisation and field performance.

“This project will assist in providing another step in the gradual accumulation of knowledge in this area.”

Contacts:

Professor Hamid Nikraz, Civil Engineering, Curtin University
Tel: 08 9266 7573, Email: h.nikraz@curtin.edu.au

Andrea Barnard, Public Relations, Curtin University
Tel: 08 9266 4241, Email: andrea.barnard@curtin.edu.au

Web: http://curtin.edu.au