A new composite material is finding its way into the construction industry. Made from natural stone, carbon fibers and biochar, it is an alternative to reinforced concrete and is characterized by a particularly good CO2 balance.
The DITF is leading the joint project 'DACCUS-Pre'. The basic idea of the project is to develop a new building material that stores carbon in the long term and removes more CO2 from the atmosphere than is emitted during its production.
In collaboration with the company TechnoCarbon Technologies, the project is now well advanced - a first demonstrator in the form of a house wall element has been realized. It consists of three materials: natural stone, carbon fibers and biochar. Each component contributes in a different way to the negative CO2 balance of the material.
Two slabs of natural stone form the exposed walls of the wall element. The mechanical processing of the material produces significant quantities of stone dust, which is very reactive due to its large specific surface area. Silicate weathering of the rock dust permanently binds a large amount of CO2 from the atmosphere.
Carbon fibers in the form of technical fabrics reinforce the side walls of the wall elements, absorbing tensile forces and stabilizing the building material in the same way as reinforcing steel in concrete. The carbon fibers used are bio-based, produced from biomass. Lignin-based carbon fibers, technically optimized at DITF Denkendorf, are particularly suitable for this application due to low raw material costs and high carbon yield, and unlike reinforcing steel, they are not susceptible to oxidation.
As a result, the energy and CO2 balance is much better than for reinforced concrete, making it possible to construct CO2-negative buildings. The third component, biochar, is used as a filler between the two rock slabs, acting as an effective insulating material and a permanent source of CO2 storage.
The natural stone used is a gabbro from India, which has a high-quality appearance and is suitable for high loads, proven in load tests. The biochar from Convoris GmbH is characterized by particularly good thermal insulation values.
The CO2 balance of a house wall made of the new material has been calculated and compared with that of conventional reinforced concrete, resulting in a difference in CO2 balance of 157 CO2 equivalents per square meter of house wall - a significant saving.
