Spraying for long life with SAMI Bitumen

This is the SealCoat technique road managers can employ to help extend the life of original surfaces.

Colas Solutions and SAMI Bitumen are working together to extend the life of Australia’s road network with safer and more sustainable solutions using bitumen emulsion-based techniques.

Road asset owners can often be faced with the dilemma of having to maintain ageing bituminous sealed road networks with limited funds.

The challenge has to be managed while trying to preserve natural resources, meet community service expectations and manage the backlog of routine maintenance.

According to Trevor Distin, Colas Technical and Marketing Manager, the majority of lightly trafficked residential roads are surfaced with either bitumen spray seals or thin asphalt.

“The deterioration of these roads is mainly due to surfacing distress caused by oxidation of the bitumen than vehicular traffic,” he says.

Mr. Distin says the properties of bitumen, like other organic substances, are affected by the presence of oxygen, ultra violet light and changes in temperature.

He adds that when these environmental conditions interact with the chemical makeup of bitumen, the binder in the surface starts to harden.

“This phenomenon is more pronounced in hot climates like what we experience in Australia, making low-trafficked bitumen surfaces more prone to premature cracking and stone loss during their in-service life,” Mr. Distin explains.

“These circumstances can lead to an increased expenditure on road maintenance to retain the integrity and functionality of bituminous surfaces.”

Mr. Distin says there are various techniques road asset managers can employ to help extend the life of original surfaces.

“Changing elements in the design and construction to reduce the impact of bitumen oxidisation of the seal and asphalt used in the original surfacing and timeous intervention during the service life are effective,” he says.

According to Mr. Distin, timeous intervention involves treating an ageing surface to prevent the ingress of water to extend its life, and therefore delay the cost of more expensive and resource-hungry maintenance activities such as pot hole repairs and resurfacing.

“Working in conjunction with SAMI Bitumen, Colas Solutions has developed a range of specialised timeous intervention bitumen emulsion-based treatments that provide safe and sustainable management options for the Australian road network,” he says.

“The typical treatments range from using dilute SAMI Bitumen emulsion enrichments to applying a thin coating of special polymer modified bitumen emulsion to thin layer micro surfacing.”

According to Jason Williams, Colas Solutions General Manager, SealCoat is an example of one of these collaborative technologies.

“SealCoat is a polymer modified mineral filled emulsion designed to extend the life of existing bituminous surfaces,” Mr. Williams says.

“By combining SealCoat’s high adhesive characteristics with polymer modifiers and varied quantities of solids, SealCoat seals and protects the road.”

Being an emulsion, SealCoat it is not heated, but applied at ambient temperatures. “The advantage of this is speed of application and fast drying, which then helps traffic get back on the road,” he says.

“During the application process, the macro texture of the initial surface is filled with the emulsion and fine sand to the point of oversaturation, covering the exposed aggregates in the process.”

According to Mr. Williams, in-house Colas testing shows that SealCoat reduces the permeability level of asphalt and increases skid resistance.

“The surface of flexible asphalt pavements designed for a 20-year life commonly have a functional life of between 12-15 years between major maintenance treatments,” he says.

“A mid-life surface treatment of SealCoat can potentially delay those more expensive periodic treatments.”


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