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Sand a short-term fix for melting tar

Oxley Highway sand fix
Oxley beached as

The recent over-application of sand on the Oxley Highway to fix slippery melting tar is a short-term fix that has outraged many riders.

Since we published an article about the thick sand across the road, Roads and Maritime Services have been actively sweeping the road.

However, Motorcycle Council of NSW chairman Steve Pearce says it is “very disappointing to see this work without any consideration for motorcyclists”.

“You could easily come to the conclusion that Melinda Pavey doesn’t want motorcyclists to use this road, remember it was just a year ago when the speed limit was dropped,” he says.Oxley Highway sand fix

Warning signs have also been posted on the area of road 25km west of Gingers Creek not far past the 80km/h zone.

The road began melting a few weeks ago in the heat. These photos were taken when the temperature was 31C.

After the images were posted, RMS spread thick sand over the road in what independent road surface expert and rider Ian Kite says is a short-term fix only.

Melting tar causeMelting tar claims first crash victim Mt Glorious costly repair bitumen fix

The 40-year local government infrastructure manager and lecturer in road construction, pavement design and bitumen sealing says the technical term for the melting tar is “bleeding”.

“The cause of the problem is the aggregate in the seal being completely submerged by the bitumen and allowing the tyres to make contact with the bitumen,” he says.

“This can be caused by a number of factors – usually a combination of several.”Melting tar on Oxley highway sand fix

How to fix the issue

Ian says sand is the “quickest/simplest/cheapest solution” in the short term to absorb the excess bitumen.

Sometimes fine aggregate or crusher dust is also applied.

“The bitumen adheres to the surface of the particles and is no longer free to stick to tyres or present a slick surface,” he says.

He says the photos of the road indicate a high application rate of sand resulting in a loose, unbound surface “not much better than the slick road”.Oxley Highway sand fix

“It’s pretty hard/near impossible to get the application rate just right since the bleeding of the surface is not uniform,” he says.

“Therefore it is usual to over-apply the sand or dust, but sweep off the excess ASAP.

“Until the sweeping is done, appropriate ‘slippery surface’ signage should be in place.

“I would expect the sweeping to be carried out within 24 hours. It may be necessary to re-apply the sand on subsequent hot days followed by sweeping.”

Other long-term solutions require analysis, design and specialist equipment to implement, Ian says.

Treatments include application of a “fog” coat of bitumen, rolling in another layer of aggregate, removal of excess bitumen by water blasting and replacement of the entire seal.

Ian says the analysis, design and resourcing of these treatments may take a couple of months to a year to organise and finance.

Mt Glorious melts

New roadworks on Mt Glorious melting tar reservations bitumen fix
(Photoshopped sign for irony!)

Similar melting tar on the Mt Glorious Rd west of Brisbane in 2017 resulted in at least one rider crashing.

Queensland Main Roads spent months working on the road to fix the issue with various methods.

More information about road conditions across Queensland are available on TMR’s website or by phoning 13 19 40.

  1. Melting Tar is caused by incorrect product specification and or incorrect application. A Freedom of Information Request for the purpose of obtaining information that is in the Public Interest may assist. The Chip Seals (or seal coating, BST, Bituminous Surface Treatment) is the application of a special protective wearing surface to an existing pavement.

    The Chip Seal Process.
    First, asphalt is mixed with about 30% water. This emulsified mixture is then applied to the road using a special spray truck. As soon as the liquid asphalt meets the road surface, the water starts to evaporate.
    Immediately after spraying this asphalt, a layer of crushed gravel is applied by a spreader. The gravel (or chips) has a maximum size of 3/8 inch.
    Next, the gravel is compacted and embedded into the asphalt by rubber-tired rollers. However, even with the high pressure rolling, some gravel will not become embedded in the asphalt.
    The new chip-seal surface can require up to two days to cure properly. Hot, dry weather helps speed up this process in which all of the remaining water in the emulsion evaporates and the asphalt hardens. Traffic can pass over this surface at reduced speeds during the curing process.
    After curing, the loose gravel is swept off the surface. This may take several sweepings.

    Current specifications in use:
    Queensland MRTS18
    New South Wales RMS 106, 107, 116, 3252 & 3253
    Victoria VicRoads 407, 408, 417
    Western Australia Specification 501, 509, 510, 511

    This instance of Melting Tar is a misuse of Public Monies and a presents a danger to the Public with the potential to cause Loss and Injury. Questions should be put to Politicians who are now up for election on the 23 March 2019. Minister for Transport is Andrew Constance. The Minister for Roads is Melinda Pavey.

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