We have known about the mineral binder magnesia for some time. Why is it not more widely used?
KONRAD SCHÄFER: Magnesia binders, also known as Sorel cement since their discovery in France in the 1850s, have been in use since about 1950. Their applications include magnesia screed for durable industrial floors and stonewood flooring for comfortable commercial and residential spaces. Portland cement, developed in 19th century England, became a more popular material thanks to its superior water resistance, the ability to bond with steel without causing corrosion, and a simpler manufacturing process. In view of the high CO₂ emissions from cement production, the search for alternatives has now resumed.
Which residual materials can be used and which are excluded?
KONRAD SCHÄFER: Magnesium binder is a hard-binding agent that can be used to develop new materials in combination with almost all dry fillers. These can be mineral or organic waste materials, which are then returned to the material cycle. Even mixed or impure waste materials from landfills can be upcycled in this way. It is virtually impossible to use moist or wet materials, however, as they can influence and even disrupt the chemistry of the bond.
It is claimed that the final product absorbs more CO₂ than is released during the production process.
KONRAD SCHÄFER: Magnesite is the most common mineral found in the Earth's crust. Current research indicates that the production of magnesia binders has a positive CO₂ balance, from mining and firing at around 800°C to the final hardening of the product. Once the binder sets, the magnesium hydroxide reacts with the surrounding air to absorb and bind CO₂. This process, known as carbonation, leads to a denser microstructure, which increases the strength of the product.
Can the material also be recycled at the end of its useful life?
KONRAD SCHÄFER: Yes – it can be shredded into different grain sizes and returned to the material cycle. The development products presented here demonstrate that blast sand and bark waste, which would otherwise have to be disposed of, can be recycled into new materials. These products enjoy a unique aesthetic and possess superior attributes, such as high strength, low weight, water resistance and durability. Finally, all products are non-flammable and high-temperature resistant.
Do the surfaces have to be sealed?
KONRAD SCHÄFER: It's always a good idea to protect surfaces. More rigorous protection is recommended for worktops, while impregnation is sufficient for wall panels. We are currently developing a special range of interior design materials, including wall, floor and worktop surfaces.