Kendiliğinden iyileşen çimento-esaslı harçlar için iki bileşenli biyolojik katkı maddesinin geliştirilmesi

Factors affecting the durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks can decrease the service life of concrete structures. Therefore, it is crucial to find alternative methods to detect and recover microcracks, then to repair them before they were developed into wider cracks. Recent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediating cracks by triggering biogenic calcium carbonate (CaCO3). The mineral precipitation was obtained by leveraging the metabolic activity of microorganisms to provide microbial induced calcium carbonate precipitation (MICP). The research done on the possible use of MICP in cement-based systems has showed promising results and the studies suggest this process could be a useful approach for remediation of cracks on the surface of the concrete. The goal of this study was to design a 2-phase biological self-healing agent for cement-based materials. For this specific goal, vegetative Sporosarcina pasteurii (S. pasteurii) cells were immobilized on the selected natural minerals or lightweight aggregate (LWA). Herein, the bacterial cells were immobilized on diatomaceous earth, bentonite, sepiolite and pumice, to remediate flexural cracks on mortar in early ages (14 and 28 days after mixing). To obtain the 2-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur (CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. Additional evaluations were conducted with water absorption test and viability assessment. Precipitated formations were further examined with scanning electron microscopy (SEM) analysis. With this approach, the cracks on mortar surface were sealed with the biogenic precipitate and the water absorption capacity of the so-called self-healed mortar was decreased compared to its counterpart cracked mortar samples. Calcite was found to be the dominant precipitate in the remediated cracks. At last, the bacterial cells immobilized on various protection barriers were viable and functional for extended time periods.