Effect of adding chitosan capsules produced by ionotropic gelation on the mechanical properties of mortars

ABSTRACT

To ensure the viability of bacteria in the biomineralization process for crack filling and healing, protection from the heat (generated by cement hydration) and the retraction (during hardening) of the microorganisms is required. Superabsorbent polymers, as chitosan, known for their resistance during mixing and water storage capacity, are suitable bacteria carriers. This study aimed to determine the optimal percentage of chitosan capsules and its effects on the physical and mechanical properties in mortars. Mortar formulations containing 0.5%, 1.0%, and 1.5% of chitosan capsules (relative to the total cement weight) were developed keeping the original granulometric distribution. Analysis of variance (ANOVA) for each individual property and post-hoc tests with corrections of Bonferroni and Tukey demonstrated that the formulation significantly impacted both properties through aging. Formulations AQ-0.5C and AQ-1.0C (0.5% and 1.0% of capsules respectively) maintained the flow levels comparable to the original formula. AQ-0.5C showcased the most favorable outcomes, exhibiting mechanical resistance up to 10% higher than the capsule-free original formula. Even slightly inferior results, AQ-1.0C still presented a higher strength mechanical up to 5% over the original formula. These results indicate the potential use of the ionotropic gelation to produce spores with bacteria to be applied in biomineralization for sealing cracks.

Keywords:
Mortar; cracks; bacterium; biomineralization; chitosan