Proving the effect of abiotic processes on the repair of cement composites with carbonates precipitated in the presence of bacteria

PRELUDIUM 23

Funding Organization: National Science Centre

Project title: Proving the effect of abiotic processes on the repair of cement composites with carbonates precipitated in the presence of bacteria

Agreement number: UMO-2024/53/N/ST8/03779

Project implementation period: 01.04.2025 - 31.03.2028

Principal Investigator: dr inż. Martyna Janek

Project value: 207 888,00 PLN

Funds granted for Lublin University of Technology: 207 888,00 PLN

Abstract: The formation of cracks in cementitious composites is one of the biggest drawbacks and threats to these materials. In recent years, the method of repairing cracks of cementitious composites with the products of the MICP process - Microbially Induced Carbonates Precipitation, is gaining popularity. The process is based on the use of selected strains of microorganisms that, under the appropriate microenvironment conditions and in presence of nutrients and precipitating precursors, are able to precipitate carbonate mineral phases that fill cement matrix cracks. Although this method is considered to be very effective, the cementitious matrix environment is highly unfavourable for microbial activity and all studies carried out up to now have indicated a reduction in cells capable of preserving viability under these conditions. Due to the inconsistencies in the reported high rates of repair of cementitious composites with a drastic decrease in the viability of microorganisms in this particular environment, the project authors set out to prove the significant influence of abiotic processes (occurring without the involvement of microorganisms) in the formation of carbonate precipitation products in the environment of cementitious composites. The overall research plan for the project is to analyse the products of carbonate precipitation in the presence of three types of bacteria, both in a controlled and cementitious composite environment. For this purpose precipitates formed from the solutions of bacteria, nutrients and precursors initiating the metabolic activity of the bacteria will be determined. Possible loss of reaction products and the effect of environmental conditions on the process will be determined on the basis of stoichiometric calculations of the amount and type of products of the designed reactions. Subsequently, the produced (bio-based) healing agents will be used as components of cement mortars to determine changes in the microstructure of cement mortars and the possibility of healing cracked mortar structures with precipitation products. The preparation of mixtures with a variable content of healing agent components, also bacteria presence, will enable the determination of the real influence of each of them on the possibility of healing damaged cement mortars. A crucial part of the research will be the analysis of the solid phases - the carbonates produced in the healing process. These products will be comprehensively examined in terms of chemical and phase composition (XRD, XRF, SEM-EDS, XPS), with the detailed analysis with synchrotron techniques. Then, modelling the energetics of carbonate formation by the microorganisms used, both when used alone and in the presence of compounds present in the cement matrix will be carried out for verification of the mechanisms involved in the carbonate precipitation process, including the stages and transition products, and the influence of compounds present in the cement matrix on the carbonate precipitation process. The research will lead to a complete study of the identification of the products of abiotic and biotic carbonate precipitation, the determination of the actual contribution of microorganisms to the precipitation of crystalline forms in the presence of cementitious composites, and the influence of (bio-based) healing agents on the changes occurring in their matrix. The subject matter of the project addresses an important and current research problem and the proposed project will provide new knowledge in the area