Red mud for ceramics

Materials World magazine
,
11 Mar 2019

A team of designers has used bauxite residue from the alumina industry to create ceramics, glazes and geopolymer concrete. 

By using the waste product from the alumina industry, bauxite, a team of four designers from the Royal College of Art in London, UK, has created ceramics, glazes and geopolymer concrete.

Kevin Rouff, one of the four designers, told Materials World that the initial draw to bauxite, also known as red mud, was due to the large amount of it available and its colour. ‘As soon as we looked at satellite images of the red mud sites, we were hooked. As we explored the large body of research on the material and its history, we understood that there was room for designers to have an impact. We saw that the designer could balance between academic research, industry, and the public; designers benefit from the flexibility to use the material in ways that might not make sense for research or commercial purposes. And lastly, the small community of experts in red mud also contributed to our interest, as we were quickly introduced to key researchers and stakeholders,’ he said.

To be able to create the ceramic clay and glazes that later turned into tableware such as mugs, plates, bowls and teapots, the team has to lay the red mud out to dry before grinding it and then several rounds of sieving out the impurities.

‘We even tried using flour mills or stomping it with bags on our feet as winemakers might do,’ Rouff explained.

Finding the correct combination of red mud and clay bodies required several rounds of testing, to see the behavior and performance. ‘The goal was to find a body that was workable, had plasticity, sintered evenly, and, of course, didn’t crack. To our surprise, pure red mud, when worked properly, can do just that, without the addition of other clays.

‘Using traditional ceramicist methods, it can be made into fairly workable clay bodies--the kind one might normally think of with hand-formed ceramics and the “potter’s wheel”. These mechanical techniques, like wedging, essentially build internal macro structures of the alumino-silicate layers, increasing the strength and plasticity,’ Guillermo Whittembury, designer on the project, explained.

The designers were also able to create a liquid clay body, a slip, which can be cast into plaster moulds. ‘Slip casting worked particularly well with red mud and allowed us to standardize the process to some degree for understanding where and why things didn’t go as planned,’ according to Rouff.

The most challenging product to create was the glaze, Rouff told Materials World. Each firing gave different results, several factors played part in this. Temperature, minute recipe changes and even the position in the kiln influences the result.

‘In reality, there was a great deal of testing until we got the right proportions and methods. Our prior lack of experience in ceramics likely played to our advantage, as we had to learn from observation. Given limited facilities, we also had to understand exactly each part of the process.

‘For instance, in developing the concretes, red mud is reduced in a furnace to a slag-like material with the right chemistry for alkali-activation as a geopolymer mortar but necessitated a very small particle size. We initially reduced our material with charcoal in a metalsmith furnace, and we fashioned our own ball mills using pipes, skateboard wheels, a drill, and bicycle inner tubes as the belt drives. This might seem scrappy, but it leads to a better understanding of how to work this material,’ Rouff said.

The design team hopes that their project using waste will inspire more applications for waste materials.

Whittembury said, ‘There is a lot of potential at the larger scale with building materials like bricks. Research in the past has shown how red mud is also viable aggregate and road paving, although as a team, we find that rather flat.’

Joris Olde-Rikkert and Luis Paco Bockelmann was also part of the project together with Rouff and Whittembury

The team is now embarking on their own individual projects. Rouff’s next project will examine and explore several waste streams to scrutinise how things are made. At the moment, he is looking at the copper industry.