Green is the new black: SAMI

Roads & Infrastructure explores SAMI Bitumen Technologies’ multilayer approach to conscious capitalism via sustainable bitumen supply. 

Conscious capitalism is a business strategy designed to recognise the significance of values-based economics and a social licence to operate.

In the bitumen sector, this usually takes the form of introducing non-traditional repurposed materials into bitumen mixes to reduce the road network’s environmental impact.

To remain viable in the increasingly competitive infrastructure sector, businesses need to achieve symbiosis; by developing a green product that doesn’t compromise performance or trigger cost blowouts.   

SAMI Bitumen Technologies has embraced this concept through technological innovation and experimentation, manufacturing bitumen products through the lens of resource preservation.

Sebastien Chatard, SAMI Bitumen Technologies General Manger, says SAMI’s approach to conscious capitalism is multifaceted.

The diverse process includes the use of crumb rubber to improve bitumen performance properties, using cold bitumen emulsions to reduce greenhouse gases and working to eliminate petroleum cutters from all SAMI binders in service of human health and safety.

“Together, these approaches represent SAMI’s efforts to improve the sustainability of our products, while also ensuring worker safety during the application and maintenance process,” he says.

While sustainability has become something of a buzzword, like circular economy or infrastructure boom, Sebastian says SAMI’s work in this space speaks for itself, and highlights its real commitment to the concept.

“SAMI is a pioneer in crumb rubber modified binder manufacturing in Australia,” he says.

“Continued research and development efforts allow SAMI to supply a range of crumb rubber modified binders to large scale infrastructure projects across the country, namley SAMIseal S45R for sprayed sealing applications.”

Crumb rubber has been used in spray seal binders since the 1970s and is increasingly explored as a cost-effective and ecological tool to increase recycled content in roads.

Mr. Chatard says crumb rubber modified bitumen has improved material properties, making the surface less prone to bleeding, cracking and stone loss.

He explains that engineering compounds commonly found in tyres can be beneficial to binder performance, specifically natural rubber and carbon black, which retard the ageing process.

“This has the advantage of reducing demand for expensive polymers to modify bitumen, while also diverting significant numbers of end-of-life tyres from landfill, or as is sometimes the case, dangerous and flammable stockpiles,” Mr. Chatard says.

While the uptake of crumb rubber is increasing, long-distance travel can restrict application in areas far from the manufacturing point. According to Mr. Chatard, crumb rubber particles can settle out at the bottom of road tankers, which diminishes material quality.

“To address this, SAMI established a technique in early 2016 that produces a crumb rubber modified binder that is more stable during prolonged heating and transportation,” he says.

The product was used for a Queensland Department of Transport and Main Roads resealing project in 2017, and has been consistently used by the department ever since.

“Receiving the National Australian Asphalt Pavement Association’s Innovation Award for the preblended storage stable crumb rubber modified binder is a testament to the technology’s success,” Mr. Chatard says.

Building on its crumb rubber success, SAMI continues to develop application and chemical composition techniques that minimise the company’s environmental impact. Mr. Chatard says increasing the use of cold bitumen emulsion, at the expense of hot bitumen, is an example.

“SAMI’s work to increase emulsion uptake includes mixing and laying micro surfacing, a slurry seal that consist of water, polymer modified emulsion and crushed aggregate, using SealCoat spraying preservation treatments and developing bitumen-stabilised emulsion base course,” he says.

“Increasing the use of emulsions cuts greenhouse gas generation and energy consumption during binder application, and minimises the potential for workers to be burnt by hot bitumen.”

SAMI is also working to eliminate petroleum cutters from binders to decrease explosion risk, workplace injury potential and fume generation during hot binder spraying.

Fumes generated by the use of petroleum cutters contribute to air pollution, acid rain and gas emissions.

“It is standard on-site practice in Australia to use kerosene as a cutback for hot binders when spray-sealing roads,” Mr. Chatard says.

“The practice is designed to reduce the viscosity of the binder and produce a more uniform spray pattern, before spreading single size aggregates when constructing a new surface.”

Mr. Chatard says kerosene cutbacks also prevent aggregate loss on new seals, which are prone to brittle fracture with sudden drops in air temperature overnight.

Despite functional benefits, most developed countries have stopped, and even legislated against, kerosene cutbacks. According to Mr. Chatard, this is due to the associated hazards of adding a low flash point cutter to hot bitumen and climate change impacts via greenhouse gases.

Mr. Chatard explains however that eliminating kerosene cutters in Australia’s present technological environment would lower daily spray sealing production rates and reduce the number of workdays in the spray sealing season.

“The higher costs incurred by eliminating the use of cutters when constructing spray seals will lead to a considerable increase in funding requirements, unless cost-effective substitute technologies can be adopted,” Mr. Chatard says.

“To direct industry practice away from cutters, we need to offer cost-effective alternative solutions to facilitate the construction of sprayed seals in lower pavement temperature conditions.”

To push progress, SAMI is working to develop low-viscosity crumb rubber modified binders that can be sprayed without kerosene when constructing seals.

“Notably, we developed an emulsion Bioprime with no petroleum cutters that has successfully been used on base courses in Western Australia,” he says.

Mr. Chatard says a number of mechanisms are available to avoid kerosene, including synchronised spray and aggregate spreading machines that allow low-temperature hot binder spraying without a cutter, and bitumen emulsion spraying systems with a second bar that sprays a breaking agent to accelerate rapid cohesion development.

He adds that this allows the seal to open to traffic earlier. Working towards infrastructure solutions that are both environmentally friendly and economically assessable is the key driver behind much of SAMI’s research and product development.

“SAMI prides itself on being a forward-thinking and environmentally conscious company. It’s not just hyperbole and corporate buzzwords – we are very committed to making the provision of binders for the road infrastructure sector more sustainable,” Mr. Chatard says.

“I believe our work demonstrates that there are answers to even the most complex questions. Take reclaimed asphalt pavement for example. That material will soon become standard practice.”

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