The CREATE ACT3 project was based on an innovative patented technology of Carbonova which con[1]verts GHG (namely CO2 and CH4) into carbon nanofibers (CNF). As part of this consortium, Sika technology AG (STAG) had the task to evaluate the implementation of those CNF into various technologies and product lines covering its core activities in specialty chemicals towards systems and products for bonding, sealing, damping, reinforcing, and protecting in the building sector and motor vehicle industry. STAG's primary focus in the CREATE project was on reintegrating CNFs, produced from the CO2 emissions during cement production, into cement as part of a circular economy concept. This led to the development of a robust strategy that utilizes the high shear forces in cement mills to efficiently disperse CNFs into the cement matrix. Various sources and types of CNFs were evaluated, some of which showed promising strength improvements. Key characteristics that enable effective dispersion and integration into cement matrices have been identified and understood. Additionally, attempts were made to use CNFs to enhance the electrical conductivity of cement matrices, using a custom-designed experimental setup. However, the results so far have been disappointing, as the high quantities of CNFs required to reach the percolation threshold, further exacerbated by poor dispersion, have hindered success.
Main findings («Take-Home Messages»)
- A highly efficient, low-energy strategy has been developed to disperse carbon nanomaterials in cement matrices, making use of the high shear forces present in cement mills.
- Key properties of carbon nanomaterials (CNOs) have been identified, showing their potential to significantly enhance the strength of cement-based materials. Once optimized, these improvements could help reducing the clinker factor in cement and concrete, thereby lowering the associated CO2 emissions from cement production.
- However, due to the very low concentrations of CNOs that can be incorporated into cement compared to the vast CO2 emissions from cement production, this recycling of carbon should not be considered a form of circular economy and has a negligible impact on the decarbonization of the construction sector.