Biyomineralizasyon ile kendiliğinden iyileşen çimento-esaslı malzemeler

Factors affecting the durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack when stress is applied. Recent research in the field proposes that it might be possible to develop a smart, cement-based material that can self-heal itself. Self-healing is the ability of concrete to heal the cracks without any external intervention. Self-healing property of concrete can be obtained via different approaches. Use of biomineralization is a novel technique to provide self-healing in cement-based materials. Biomineralization is a biochemical process in which microorganisms stimulate the formation of minerals.In this system, calcium carbonate (CaCO3) is induced by leveraging the metabolic activity of microorganism and self-healing is obtained by sealing of the cracks with CaCO3. A limited number of studies have been conducted to evaluate self-healing by biomineralization as means of recovery in compressive strength. However, there is not enough information regarding the influence of this system on flexural strength. In addition, none of the previous work to date studied the interactions amongst concrete admixtures, biomineralization, and the resultant self-healing ability. At last, the durability of the CaCO3 precipitate under weathering conditions is controversial. The goal of this study was to investigate these abovementioned issues in depth and fill the knowledge gap in the literature. The ultimate goal was to take novel method one-step further into practical use.In this study, the bacteria was introduced to cement paste with its growth media without any additional manipulation such as encapsulation. With this approach, the flexural cracks on mortar surface were sealed with the CaCO3, the permeability of the healed specimen was decreased compared to the cracked samples. However, there was no significant flexural strength regain after crack healing. This was attributed to the soft and brittle nature of theCaCO3 as well as the weak bonding between the precipitate and the mortar. The precipitate, CaCO3, was found to be durable against rain and freeze-thaw cycles. However, the resistance of the CaCO3 sealant against sunlight was lower than its resistance to other weathering conditions.