When you picture the future of construction, your mind probably goes to high-tech composites, robotic bricklayers or modular systems rolling out of factories. But what if the answer to greener, cheaper building materials was sitting in your recycling bin?

That’s the question RMIT University researchers set out to answer when they developed cardboard-confined rammed earth, a material made from nothing more than cardboard, water and soil.

The result: a wall system with just a quarter of the carbon footprint of concrete, at less than a third of the cost.

And for an industry under pressure to slash emissions, reduce waste and deliver affordable housing, it could be a game-changer.

Why it Matters

Australia sends more than 2.2 million tonnes of paper and cardboard to landfill every year. At the same time, cement and concrete production contributes 8% of global CO₂ emissions.

By swapping cement for compacted soil inside cardboard tubes, the RMIT team has eliminated one of construction’s biggest carbon culprits.

Lead researcher Dr Jiaming Ma explains:

“Modern rammed earth construction often uses excessive cement just for added strength. With cardboard-confined rammed earth, we’ve shown that walls can be robust enough to support low-rise buildings without cement at all.”

For builders, that means access to a structural material that is strong, low-cost and recyclable. For the planet, it represents a significant cut in embodied carbon, an area regulators and clients are now scrutinising more closely than ever.

A Tradition Reinvented

Rammed earth is hardly new. From ancient forts in Morocco to contemporary homes in Margaret River, it’s been prized for its durability and thermal mass. The twist from RMIT is combining this age-old method with a circular economy mindset.

Cardboard has been used in temporary shelters before, famously in architect Shigeru Ban’s Cardboard Cathedral in Christchurch after the 2011 earthquake. But the RMIT team is the first to combine cardboard formwork with compacted earth in a way that makes the structure permanent, stable and scalable.

Practical Benefits for Builders

This isn’t just an academic exercise. The team designed the system with job sites in mind:

• On-site manufacturing: Walls are formed by compacting soil and water mix into cardboard tubes. No batching plants or cement trucks required.
• Transport savings: Lightweight cardboard replaces tonnes of bricks and concrete deliveries.
• Thermal performance: Like traditional rammed earth, these walls regulate temperature and humidity naturally, reducing mechanical cooling needs.
• Local sourcing: In regional areas, suitable soils are often abundant. Pair that with recyclable cardboard, and you’ve got a hyper-local building system.

Emeritus Professor Yi Min ‘Mike’ Xie, a world leader in structural optimisation and study co-author, says this could radically simplify logistics:

“Instead of hauling in heavy materials, builders would only need to bring lightweight cardboard. Nearly everything else is already on site.”

Strength and Science

Sceptics will naturally ask: how strong is it?

The team has answered that too. They’ve mapped out exactly how cardboard thickness impacts load-bearing strength, giving builders a formula for designing to spec.

In parallel research, Ma’s group even tested carbon-fibre reinforcement with rammed earth, achieving strengths comparable to high-performance concrete.

While carbon fibre is unlikely to feature in everyday builds, it shows the adaptability of the base concept: start with local earth and cardboard, then scale performance depending on application.

Where Could It Work?

This innovation may first take root in:

• Remote communities: Red soils in regional Australia are well-suited for rammed earth. Add cardboard and you’ve got a solution for affordable, durable housing far from supply chains.
• Climate-conscious builds: Architects chasing Green Star ratings will welcome a material with 75% lower emissions than concrete.
• Low-rise housing and extensions: From garden studios to rural homes, the material’s strength is ideal for single or two-storey projects.

Dr Ma sees the potential as global:

“This reflects the revival of earth-based construction fuelled by net-zero goals. By using what’s under our feet and rethinking waste, we can design buildings that are both resilient and sustainable.”

Barriers to Adoption

Of course, innovation doesn’t enter the construction market overnight. Challenges ahead include:

• Building codes: Getting new materials into the NCC is a multi-year process. Demonstrating fire resistance, durability and compliance will be key.
• Perception: Convincing clients and financiers that “cardboard walls” can be premium, safe and enduring won’t be easy.
• Scale: From pilot projects to mainstream supply, scaling production and quality control will require industry partners.

The RMIT team is actively seeking collaborations with builders, suppliers and government to fast-track testing and real-world pilots.

Why Builders Should Pay Attention

For the Good Builder audience, this isn’t just another sustainability headline. It’s a signal of where the industry is heading.

Builders are under pressure to:

• Reduce embodied carbon in line with NCC 2025 and client demand.
• Find affordable materials amid price hikes in concrete, steel and bricks.
• Show innovation to stand out in a competitive market.

Materials like cardboard-confined rammed earth tick all three boxes. Early adopters could position themselves as leaders in sustainable construction, while also cutting costs on transport and material procurement.

The Good Builder Take

At TGB, we’ve said it before: the next decade in construction won’t be defined by who can build faster, but who can build smarter.

This development from RMIT is more than just clever engineering. It’s a reminder that innovation doesn’t always come from new tech, sometimes it comes from rethinking the simple materials we overlook.

If cardboard and soil can reshape sustainable construction, what other everyday resources could we be undervaluing?

For builders willing to trial, test and champion these materials, the rewards could be significant, not just for their business, but for the industry’s credibility and climate commitments.

Author: TGB Editorial