How can we reduce our carbon footprint and build more resilient roads?

Local solutions to create more sustainable highways

Infrastructure is the go-to, low-hanging fruit for economic growth and recovery. These outcomes are important when grappling with a crisis like Covid-19. But can we push our infrastructure projects to deliver benefits that also contribute to a resilient future for all?

Sometimes, it’s the context-specific solutions that drive the most innovative responses and generate both socioeconomic and environmental advantage.

During a conversation with Curtin University, our Australasian geotechnics team, led by Sergei Terzaghi, saw an opportunity to approach a long-standing Australian infrastructure issue in a way that pairs waste with want. The idea was straightforward: replace carbon heavyweights (like cement mixtures) with environmentally friendly by-products from the local sugarcane industry.

Australian soils along the low-lying east coast are highly vulnerable to acidification. This weakens infrastructure, particularly roads, and makes it difficult for our engineers to deliver resilient and sustainable solutions. Due to the massive amounts of soil involved in road construction, it’s not feasible to replace the contaminated earth, so huge volumes of cement and lime are added as stabilisers. This is not an ideal fix given that ordinary Portland cement accounts for 8% of global carbon emissions, and the production of lime results in toxic elements.

The residue from the burning process is sugarcane bagasse ash (SBA). Some SBA is used as fertiliser in the agricultural industry, but the team is researching its potential for further reuse as an additive to traditional soil stabilising agents.

“An added benefit is that reusing these materials could boost local economies,” Sergei notes.

After some preliminary studies, the team moved to Curtin University’s Civil Engineering lab. Here, Curtin’s project lead Dr Amin Chegenizadeh conducted a series of experimental tests investigating how different mixes of SBA and cement affected the mechanical characteristics of the acid sulphate soil. The team first tested the compressive strength of macroscopic samples that had been submerged in acid sulphate baths. Then, they analysed the micro-interactions between the soil particles, acid sulphate and SBA additions using electron microscopy and energy-dispersive x-ray spectroscopy.

Testing provided a lot of information and positive results: with the correct treatment, replacing a portion of cement with SBA did assist in the stabilisation of the acid sulphate soils. And, it’s an approach that could work across the globe. 

“It can be applied in any location where SBA by-product is locally available, like India and Brazil,” says Dr Mahdi Keramatikerman, the engineer who initiated the idea and led the project. “But it has to be localised and regularised because both the SBA and the contaminated soils have specific, potentially unique, characteristics.” 

“Another great thing about this project is that it links up with several Sustainable Development Goals. It’s a collaborative project, and it takes an innovative approach to reuse materials. And beyond soil acidification, there is a whole range of issues, like adverse clay mineralogy, that this circular solution may help to address,” said Sergei. 

How a circular economy framework can drive sustainable change

This research shows how we are bringing sustainable change and circular economy principles to highway infrastructure. However, creating the touchpoint between a global sustainability agenda and local solution is not simple. To achieve far-reaching resilient outcomes we need clear processes. This is where our Outcome-led Design framework comes in. Claudia Prior, Infrastructure Engineer in our Brisbane office and co-creator of the framework, explains:

The framework is a database of context-specific indicators, interventions, and metrics that enable users to correlate the trade-offs between a project’s cost, time, economic, social, and environmental benefits. By helping our highway planners and engineers make informed choices that are based on Sustainable Development Goals, we are now able to build more sustainable highways.

And it’s having a real impact across a range of projects. The Yatala South Interchange Exit 41 upgrade, in Queensland, used the framework to raise sustainability awareness in early design. This allowed for a smooth integration of green specifications that went beyond the standard requirements, such as using more recycled materials.

What does the future of road infrastructure look like? Can we drive good stimulus through a holistic approach? The road to sustainable, resilient, construction is multi-lane and underpinned by both experimentation and a strong foundation of knowledge. Using circular economy approaches coupled with outcome-led design, we could see issues like soil acidification shift from being a weakness to a positive that boosts local economies and provides a beneficial impact so that future generations can travel safely into their future.