Two family businesses from Limburg (Belgium) – Orbix in Genk and Betonagglomeraten Gubbels Masterbloc in Maasmechelen (both Limburg) – have launched a world-first: they produce CO2 ‘absorbing’ construction blocks based on slag from the steel industry.
The finished products are bricks in which cement has been replaced by CO2 as a binding agent. The bricks are injected with CO2, and they also continue to absorb CO2 from the air, even after construction.
Years of research and development preceded the production. The technology was developed by the recycling company Orbix in Genk. Orbix had been processing steel slag from steel manufacturer Aperam for years.
In 2004, the company’s R&D manager made a special discovery: the fine residual fractions of the steel slag hardened. Research showed that the hardening process was caused by the addition of CO2.
The technology based on carbonation was further developed in collaboration with several knowledge institutions – the Flemish Institute for Technological Research (Vlaams Instituut voor Technologische Onderzoek, VITO), among others – and in 2011, the so-called ‘Carbstone’ technology was patented.
How are the stones made? Orbix provides concrete manufacturer Masterbloc with Carbinox powder – the brand name of the component. In the Masterbloc factory, the powder is mixed with gravel, sand, and water, and the mixture is compressed in the desired shape.
After the molding process, the blocks are dried in a drying chamber where they are injected with CO2 at a temperature of at least 40°C.
The Carbstones offer numerous advantages. The bricks store and absorb CO2 and are completely circular. They have the same qualities and technological characteristics as conventional bricks. They’re equally strong and rain- and frost-resistant.
They’re even CO2-negative because more CO2 is absorbed than emitted during production. Moreover, they can offer a structural solution for the CO2 emissions of companies.
“And, there’s another important advantage,” CEO Bjorn Gubbels explains in the newspaper Het Belang Van Limburg. “By using CO2 as a binding agent, we are no longer dependent on cement prices.”
Interest in the technology is high, and Orbix is ready for international commercialization. The bricks fit in with the trend toward sustainable materials in the construction industry.
Orbix’s technology is also suitable for other building materials, ranging from clinkers and tiles to roof tiles and sewer pipes.