Active Carbonation of Porous Mineral Binder Systems – A-COMBS

• Applicant: Professor Dr.-Ing. Viktor Mechtcherine
• Subject Area: Construction Material Sciences, Chemistry, Building Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542141112

In light of global warming, it is imperative to establish reliable and cost-effective measures in the field of building materials to reduce the CO2 content in the atmosphere. The carbonation of mineral materials can be such a measure and be very effective. However, in compact mineral building materials with low porosity, the speed of carbonation is very low, and the full potential for carbonation is rarely fully utilized. By foaming, the porosity of mineral binders can be purposefully increased, enabling rapid and almost complete carbonation with minimal technical effort. This research project aims to describe the mechanisms and phenomena present in the active carbonation of porous mineral binders. The essential influencing factors on the carbonation of various binder systems will be recorded and presented in experiments. The temporal development of the phase composition should be understood, and its impact on the mechanical properties pinpointed. The limits of a technically meaningful carbonation concerning desired favorable mechanical properties are also explored. Based on the data developed in the experiments and the geometric characterization of the pore system, a numerical material description for the active carbonation of porous binders is formulated. The application of this modeling to mineral building materials with lower porosity is examined, highlighting the limits of the material description. Experiments are conducted on physically foamed binders with three bulk densities. The binders under investigation are Portland cement, LC3, and magnesium oxychloride. The central method for active carbonation is the permeation of hardened binders aged from 1 to 28 days with CO2-containing gases. The connectivity of the pore system is improved by adding biochar particles. This is intended to accelerate early hardening and reduce structure damage in the young age induced by excessive pressure from the permeation gases. The carbonation of fresh, non-hardened binder foams is investigated using CO2-containing foam and the addition of CO2 during the mixing process. The connectivity of the pores is characterized using computer vision methods based on µCT analyses. The modeling of gas permeation and carbonation is carried out using multi-physical FE methods. The understanding of the processes and transformations during the active carbonation of porous binders and the developed model description provide a fundamental tool for the design of technical processes for the active and large-scale binding of CO2 in permeable building materials.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2436: Net-Zero Concrete
• Co-Investigator: Professor Dr.-Ing. Marco Liebscher