Çimento-esaslı harçlarda kendiliğinden iyileşmenin sağlanması için 2 bileşenli biyolojik katkı maddesinin geliştirilmesi

Abstract

Self-healing in cementbased mortars were obtained through biomineralization.  The bacterial cells were immobilized on pumice and diatomaceous earth  There was app. 40% reduction water absorption upon crack healingRecent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering biogenic calcium carbonate (CaCO3) precipitation. This paper summarizes a study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on both diatomaceous earth and pumice, to remediate flexural cracks on mortar in early ages (28 days after mixing). Figure A. Visual analysis of the cracks in 28-day old specimens (a) Stereomicroscopy image of sample containing bacterial cells and DE (b) Stereomicroscopy image of sample containing bacterial cells and pumice(c) SEM image of sample containing bacterial cells and DE (d) SEM image of sample containing bacterial cells and pumicePurpose: Throughout the literature, studies showed that among several alternatives such as diatomaceous earth (DE), metakaolin, zeolites and expanded clay could be suitable for protection of the bacteria based on their effects on compressive strength and setting, in particular DE was found to be effective in self-healing of cracks. A correct choice of the protection barrier and application methodology are of crucial for further development of self-healing concrete. This study presents a comparative study on the possible use of a mineral additive (DE) and a porous lightweight aggregate (pumice) as a protective barrier for bacterial cells. Theory and Methods:To obtain a two-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 stereomicroscopy imaging, ultrasonic pulse velocity (UPV) analysis and water absorption testing. Results:Cracks with an average width of 0.4 mm in 28-day old mortar specimens were almost completely filled by bio-based precipitate depending on the curing regime. Cracks were sealed even in sample including relatively smaller dosage of nutrients and bacterial cells in presence of moisture. Moreover, the duration of crack healing was approximately 21 days, which was almost half of the duration to remediate the cracks when cells were directly incorporated to the mix. Conclusion:With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the socalled self-healed mortar decreased compared to its counterpart cracked mortar samples.