Swinburne University of Technology to turn coffee grounds into roads

Swinburne University of Technology engineers are experimenting with the potential to turn used coffee grounds into a building material for road construction.

Swinburne University Professor Arul Arulrajah and PhD candidate Teck-Ang Kua have found a way to incorporate ground coffee in road infrastructure by compressing a mixture of coffee grounds and slag (a metal byproduct) with a liquid alkaline solution to create a product as strong as those made using cement.

“I’ve done a lot of research on recycling materials for road construction and the different types of waste products that can potentially be used in pavements or geotechnical applications. Coffee just came about because I’m an avid coffee drinker,” Arul said. “I see baristas throwing away used coffee grounds and I thought: ‘Why not look at this as an engineering material?’”

To determine coffee as possible a road binding material, Arul and Teck-Ang collected used coffee grounds from cafés located around Swimburne’s Hawthorn campus in Victoria.

Arul says on average, the cafes he collects from dispose of about 150 kilograms of used coffee grounds per week. As a “rough estimate” Arul says it could take as much as between 10,000 and 50,000 tonnes of coffee in order to produce 5 kilometres of road.

To test their theory, the Swinburne University researchers dried the coffee grounds in an oven at 50°C oven for five days and sieved the grounds to filter out lumps. Seven parts of the coffee grounds were mixed with three parts of slag and a liquid alkaline solution to bind the contents together, a Swinburne University press release stated. The mixture was compressed into cylindrical blocks that proved strong enough to potentially use as the subgrade material that sits under a road surface.

“We’ve got it up to the level where it is comparable to other road binder materials. The question now is: what do we have to do to make sure it doesn’t break down over time?” Arul said.

As a subgrade – the first layer in pavement – Arul says coffee grounds would contain very low carbon properties because there is no cement present. “It’s a fairly green solution and that’s another angle I’m looking at in terms of its use,” Arul said. “Right now, we’re just looking at is use in subgrades, but we have a few ideas within the road construction space down the track.”

Arul and Teck-Ang are now moving into another testing phase to simulate how the coffee-based material would behave under true traffic conditions. They plan to test its durability for use in certain conditions such as extreme heat and rain.

“What we can do is tick all the boxes from an experimental point-of-view, but I hope to possibly get a commercial entity on board,” Arul said.

Details of the study have been published in Construction and Building Materials

Image credit: Swinburne University of Technology.

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