There are inherent dangers with the manufacturing process of diesel-based cold mix asphalt that can cause ignition or explosion, risking worker health and safety.

Downer Road Services says it has now ceased production of diesel-based cold mix nationally, and is looking at the development of new, safer cold mix asphalt alternatives.

Historically, diesel has been used as a fluxing agent in the production of cold mix asphalt.

The dosage of diesel allows for the viscosity of bitumen to be lowered enough to be workable at standard ambient temperatures, giving rise to the name ‘cold mix asphalt’.

Diesel has a relatively low flash point (> 61.5°C) – the temperature at which it can ignite.

Depending on the type of asphalt plant, numerous manufacturing and safety controls are implemented to manage the safety risks with using diesel.

Dante Cremasco, Executive General Manager, Downer Roads Services say missing a critical step or plant malfunction during production can lead to safety incidents, such as ignition or explosion, that are all too common in the industry.

“Zero harm to our people and our community is a priority and we believe that any injury is unacceptable and preventable,” Cremasco says. 

“This requires strong leadership and relentless commitment and can be achieved by continuously focusing on managing risks that have the potential to cause harm, learning from our experiences, and positioning our culture where not only leadership teams, but also work teams on the ground have a commitment and capability to manage zero harm.

“Putting that commitment to zero harm into practice, we have made a decision to stop production of diesel-based cold mix nationally.

“The feedback from my team has been of enthusiasm and rising to the challenge of developing a new superior, safer and sustainable alternative.”

Downer’s National Research and Development Laboratory is developing alternative fluxing agents with several options being trialled in the business.

“We are developing an emulsion based approach that will perform better with a longer shelf life and will completely eliminate all risk of ignition or explosion, making it a true cold mix," Cremasco says.

“We urge all asphalt manufacturers nationally to review their safety processes with regard to diesel-based cold mix, and applaud those in our industry who are taking the steps to continually innovate and improve their products and services to make them safer and more sustainable.”