Calcium carbonate labeling for the characterization of self-healing cracks in cement-based materials

Biomineralization has been widely used to develop self-healing cement-based materials for infrastructure maintenance. To characterize the crack repair depth of cement-based materials after microbial self-healing, we used two methods to label calcium carbonate, the main product of microbial mineralization. One method involved the adsorption of Cu2+ by microbial calcium carbonate to form Cu-2(OH)(2)CO3, which surrounded the repair products. The other method involved labeling the mineralized products by doping them with Eu3+ to form CaCO3: Eu3+. X-ray diffraction was used to analyze bicarbonate before and after labeling in solution and in the cement-based materials. Fluorescence excitation and emission spectroscopy was used to analyze CaCO3: Eu3+. X-ray computed tomography was used to characterize the depth of the repair products in cement-based materials labeled using the two methods. Both labeling methods indicated a similar repair depth of 3 mm, demonstrating that these methods can be used to evaluate the efficacy of microbial self-healing in cement-based materials. (C) 2021 Published by Elsevier B.V.