Copper slag

This Is Copper

Design Studio ThusThat worked with waste from the copper industry to design a series of objects that demonstrate its potential as an alternative to cement, which has a much lower carbon footprint.

Copper is ubiquitous, yet entirely invisible. It is the oldest metal used by humankind, with ancient uses dating 8000 years ago due to its malleability and antimicrobial properties (indeed, even against viruses). Today, it is crucial for a renewable future: a wind turbine alone can have up to 5 tonnes of copper, and 10 tonnes of copper are needed per kilometre of highspeed rail.

But copper production--and even recycling--comes at a cost; our increasing demands also mean increasing amounts of waste. Roughly 40 million tonnes of slag--a waste of the refining process from both mines and recycling plants—are produced each year and piled in massive black mounds.

Working with scientists from KU Leuven, Studio ThusThat uses slag to create what is called a ‘geopolymer’. Geopolymerisation is an innovative technology that uses common inorganic compounds to create high-performance alternatives to standard cement. This waste-based alternative has up to 80% less CO2 footprint than standard cement while matching it in strength. During their research, the designers experimented with various processes and techniques in order to explore the different properties and characteristics of the material. For instance, the individual parts of their “molten” chair are joined together with molten copper, exploiting the material's unusually high resistance to heat and thermal shock. Another example is the “Sparkly Black” chair that was cast directly into a pile of coarse copper slag, using the raw material itself as formwork, a process that is inspired by the traditional metal sand casting techniques.

This Is Copper is part of an ongoing investigation into mining and metals through which the designers hope to tell a more complete story about both the primary metals as well as their material backstories.

Making process

Slag is used as both aggregate and cementitious binder, forming an inorganic polymer concrete (also known as a "geopolymer"). The slag is atomised into a powder, and activated in the presence of an alkali, setting off an inorganic polymerisation reaction. This material makes use of the inherent high-temperature industrial process of refining copper (both in mining and recycling), providing a silica structure that allows for polymerisation without the need for any additional thermal treatment.

Text submitted by the maker and edited by the Future Materials Bank. For information about reproducing (a part of) this text, please contact the maker.