No abstract

A non-microbial means of carbonate precipitation to heal cracks in concrete is evaluated in this paper. Enzyme induced carbonate precipitation (EICP) that relies on plant-derived urease enzyme is used to catalyze the reaction between calcium chloride and urea to precipitate calcium carbonate. The faster rate of carbonate precipitation and the absence of microbes makes this method attractive to surface applications for crack healing of concrete. Notched mortar beams, where pre-cracking is induced, are subjected to EICP solutions with different CaCl2 concentrations and a fixed molar ratio of urea-to-CaCl2 of 1.2. X-ray diffraction and thermal analysis of samples collected from the vicinity of the notch clearly demonstrate the presence of calcium carbonate in the cracks. A flexural strength enhancement of about 33% is observed for mortars treated with an EICP solution made using 0.5 M CaCl2 as compared to the mortars that are just moist cured, while the fracture toughness doubled. The strength and fracture parameters (fracture toughness, and critical crack tip opening displacement) scale well with the carbonate content. Digital image correlation (DIC) is used to quantify the reduction in crack extension after the beams are treated with the EICP solution.