The latest use of the sustainable SAMIGreen polymer modified binder in the manufacture of asphalt for road surfacing has helped to establish a new standard and precedent for environmentally-friendly additive use in New Zealand. Experts from SAMI Bitumen Technologies and COLAS New Zealand explain.

One of the biggest barriers to the use of sustainable methods and materials is perceived risk, compliance and cost. Specifically, compliance with road agency specifications, costs, and a perceived risk of poor performance.

Products such as SAMIGreen are helping to accelerate sustainable material use, while easing the aforementioned barriers associated with ‘going green’.     

SAMIGreen is a bio-based binder developed in Australia about three years ago, built on more than 25 years of European experience.

The biogenic modified bitumen binder’s purpose is to reduce the carbon footprint of asphalt binders. Biogenic components in the binder act as a carbon sink, allowing its life-cycle carbon footprint to be significantly lower, even effectively negative compared to conventional petroleum-based binders.

On top of providing a sustainable alternative to purely petroleum-based binders, SAMIGreen also helps to future-proof the sector, with oil supply and pricing becoming more and more uncertain.

Despite never having been used previously in New Zealand, works at Ha Crescent, Wiri on the Auckland Transport network presented the ideal conditions to conduct a national first use of SAMIGreen.

Ha Crescent was originally designed with a very heavy and extreme‑condition binder. This is due to one end of the road having a quarry, right near a cul-de-sac, which often leads to heavy trucks turning, scrubbing, and shearing the surface while manoeuvring.

Such movement inflicts extreme stress conditions that could quickly expose any weaknesses in the asphalt.

But before works could begin on this project, multiple essential boxes needed to be ticked.

The biggest milestone was receiving product and project approval from Auckland Transport (AT), a recognised benchmark.

One of the key checkpoints that needed to be hit was to prove that SAMIGreen could act as a true substitute to conventional binders. This included evidence that SAMIGreen could be handled, transported, heated, mixed, paved, and compacted exactly like conventional binders.

Project reports and successful outcomes from SAMIGreen’s use in Australia were instrumental in this process, with existing test results and performance data being provided by SAMI Bitumen Technologies.

“There’s a lot of collaboration between SAMI Bitumen Technologies in Australia and COLAS New Zealand,” says Hamidreza Sahebzamani, R&D and Technical Support Manager – SAMI Bitumen Technologies.

“We’re in contact almost every two days, as we’re a major supplier of their binders, not only SAMIGreen. There was close communication when it came to the mix design, laboratory checks and generally providing support where we could.”