Use of MICP with active bioslurry for restoration of fragmented ceramic artifacts: Mechanical and fracture behaviors study

Ceramic artifacts, as significant cultural relics, are highly vulnerable to damage due to their inherent fragility and brittleness. Prolonged exposure to environmental and anthropogenic factors further increases their susceptibility to breakage. Microbially induced calcium carbonate precipitation (MICP) presents a promising approach for restoring these fragmented materials. This study explores the application of active bioslurry, produced via MICP, for artifacts restoration and evaluates its effectiveness through mechanical tests (tensile and bending strengths) and microscopic analysis. The production of bioslurry was first optimized by varying initial pH levels and concentrations of calcium chloride (CaCl 2 ) and urea. The optimization process included factors such as bioslurry mass, urease activity, and calcium conversion rates. The results identified that the optimal condition was 400 mmol/L of CaCl 2 and 440 mmol/L of urea with a pH of 9.25. The mechanical testing revealed significant improvements in tensile and bending strengths over curing periods ranging from 12 to 72 hours. The average tensile strength ranged from 0.4 MPa to 1.2 MPa, while the bending strength ranged from 0.8 MPa to 1.4 MPa. Scanning Electron Microscopy (SEM) analysis indicated that the microstructure of the bonding layer evolved with the curing time. Failure probabilities of the restored ceramic fragments were modeled using the Weibull distribution, and the absolute error between the experimental and fitted values was minimized using the maximum likelihood estimation and least squares methods. The findings provided valuable insights into optimizing MICP-based bioslurry for ceramic restoration and demonstrated its potential as a viable alternative for the conservation of historical artifacts.