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TMR investigation reveals why failed spray seal became a tar trap

By intouch * posted 04-09-2018 11:20

  

A review probing why bitumen ‘melted’ on a Far North Queensland road, damaging dozens of vehicles, has found the road surfacing material, atmospheric conditions and traffic management were to blame.


Screen_Shot_2018-09-04_at_11_11_47_AM.pngIn early July, drivers travelling on Millaa Millaa-Malanda Road an hour and a half south of Cairns became ‘glued’ to the newly spray sealed road surface. Pictures emerged of sticky tar-coated tyres and the road became strewn with rubble, which drivers say resulted in chipped windscreens. Authorities were forced to close the road for a short time while repairs were made.

Transport and Main Roads (TMR) Minister Mark Bailey said the investigation was undertaken by an independent expert, in consultation with the TMR and its contractor, COLAS.

“The report concludes the issue was caused by a number of different factors, including spray seal rates, spray seal mix, aggregate size, variable underlying surface texture and higher levels of moisture,” Bailey said.

“The report also identified that the road was affected in-part due to traffic management during brooming of aggregate that had come loose. 

“Traffic management on the day allowed south bound vehicles to stop on exposed binder where stripping of aggregate had occurred.

“During this time, vehicle tyres became stuck to the exposed binder and this contributed to the seal binder lifting.”

Bailey said TMR required all seal designs to be undertaken by designers who have completed the Australian Asphalt Pavement Association (AAPA) Sprayed Sealing Selection and design course.

“The department works alongside AAPA and will look at the recommendations from the investigation through its existing strategic alliance,” Bailey said.

 “We have now developed and circulated additional guidance for immediate implementation to help manage seal risks.

“TMR will look closely at the recommendations and learnings from the independent report to determine what additional steps may be needed to ensure this does not happen again.

“Measures may include updating TMR’s specifications, increasing the use of crumb rubber (recycled tyres) in seals and introducing a registration or similar system for contractors.

“We may also conduct research into the risk associated with sealing in a range of challenging conditions with the Australian Road Research Board.”

As of Monday 27 August, 51 claims had been submitted to TMR from people seeking compensation for damage caused by tar and 112 for stone chips.

A similar incident was reported on a stretch of the Bruce Highway between Rockhampton and Mackay in August. 

Bailey said the second incident was still under review and it was too early to say if the cases were connected.


READ THE REPORT HERE

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