Upgraded $159m Sturt Highway falling to pieces
Michael Milnes From: The Advertiser March 03, 2011 12:00AM
SECTIONS of the $159 million upgrade to the Sturt Highway have been ripped up and relaid because the road is falling apart.
The Advertiser has been told 13km, or more than 20 per cent, of newly-laid bitumen is breaking down in places because of "high traffic loads and hot weather".
Of the 17km dual carriage highway between Gawler and Daveyston, 13km of lanes in both directions are affected, with the stone asphalt breaking down within months of the highway re-opening.
Transport, Energy and Infrastructure Department spokeswoman Alissa Smith said the stone asphalt was breaking down mainly in the outside lanes in some places.
"The stone mastic asphalt used in the road works is relatively new technology," Ms Smith said.
"DTEI does not believe there is any one specific cause and it is likely a combination of issues, including extreme temperatures and high traffic loads in the first few days of it being laid as well as the bitumen quality and issues with the asphalt mix design.
"The top 35mm of asphalt is affected and the department is working with the contractor to identify the solution and work to fix the problem."
The project began in January 2008 and was completed last July, four months ahead of schedule and under budget.
"Remedial work started on February 21 and is scheduled to be completed by March 4. A commercial arrangement has been reached between DTEI and the contractor (Boral) to rectify this issue and work will be completed within the original budget, with no extra cost to the taxpayer," Ms Smith said.
An engineer for Boral was unavailable for comment yesterday about the technology and type of asphalt used in the project.
The Northern Expressway was constructed using the same method and materials as the Sturt Highway but Ms Smith said it was constructed under different terrain and weather conditions.
"The Sturt Highway was constructed during a drought period in South Australia with higher temperatures, whereas the Northern Expressway was constructed during the wetter seasons with much lower temperatures," she said.
"The problems with the Sturt Highway were identified during a heatwave approximately six months after its completion and the Northern Expressway has been operational for approximately seven months and has had no issues of this nature."
The Asphalt Institute of America said the life span of an asphalt or bitumen road was at least 12 years but could be more than double that, depending on variables such as traffic and weather.