A Belgium-based company is using the steel slag byproduct of the steel industry to make concrete blocks. Masterbloc says its product can contribute to the development of a circular economy and is actually CO2-negative as production of the blocks absorbs more of the gas than it emits.




Masterbloc, a building block company based in Maasmechelen, has produced a building material from steel slag left over from the steel industry, according to Het Belang van Limburg. The aim was to create a block which stores CO2 and can help boost the circular economy, company CEO Bjorn Gubbels says.

At its factory, some 8- tonnes of so-called “CO2-bound” building blocks are built per day, accounting for a yearly output of 15,000 tonnes per year. Unlike other materials which have a net negative impact on CO2 emissions, Masterbloc’s product is CO-2 negative, with more CO2 absorbed during production than emitted.

The company plans to rapidly expand production of the building materials in the coming years, with the production process being presented to Flemish Minister Zuhal Demir on 15 December.

Masterbloc utilises technology from Genk-based recycling company Orbix, which has been processing steel slag from stainless steel producer Aperam since 1996.

In 2004, Orbix’s R&D manager, Dirk Van Mechelen, discovered that steel slag residue was hardening after exposure to CO2. Alongside researchers from the Flemish Institute for Technological Research (VITO), the technology was further developed in 2011 and the “Crabstone” process was patented.





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