Effect of nutrient types on the hydration of cementitious materials with co-cultured bacteria

This study investigated the effect of nutrient types on the hydration of cementitious materials incorporated with co-cultured bacteria. The medium consisted of co-cultured bacteria (Sporosarcina pasteurii and Bacillus thuringiensis), urea, nutrient, and calcium lactate. Different nutrient types were added in the form of a bacterial culture solution or medium solution in the mixing process of cementitious specimens. Thirteen different types of specimens were fabricated with various media, dry-cured for 56 days, and subsequently, isothermal calorimeter analysis, X-ray diffraction analysis, and thermogravimetry analysis were performed to investigate the hydration kinetics and hydrates of the specimens. Finally, compressive strength of the specimens was measured. When bacteria, calcium lactate, and each nutrient were incorporated, as a comparison of compressive strength with the control specimens on the 28thday, 8% compressive strength was increased when TSB was incorporated, but NB and YE were incorporated, the compressive strength decreased by 21% and 22%. The results showed that the incorporation of nutrients and co-cultured bacteria suppressed the hydration of the specimens, whereas the reduction in compressive strength caused by delayed hydration was significantly compensated by CaCO3 amount which was increased by 3.3 times owing to the bio-mineralization of the co-cultured bacteria with TSB.