Slag is a byproduct of producing most metals, including copper. When ores are mined, or when secondary sources of metals are recycled, the input is smelted at high temperatures to extract the metal. The molten impurities leftover from this process is slag, a black, glassy rock that closely resembled volcanic stone.

Slag is produced regardless if the metal is made from mining or recycling. As such, slag is an inevitability of our future, and has been amassing in mountainous heaps for centuries; industrial-era slag heaps are still common to the European landscape.

Given the thermal process it has undergone, slag benefits from unique properties, and can be used as an alternative to cement — a ‘geopolymer’ – with up to 80% lower CO2 footprint.

The slag-geopolymer benefits from high thermal resistance, high durability and strength, corrosion resistance, partial recyclability, all the while being made from a waste. The geopolymer is cast in a cold process similar to ordinary cement allowing for a wide array of possible geometries from flat tiles to large monoliths.