ABSTRACT
BACKGROUND: Biocement, calcifying bacteria-incorporated cement, offers an environmentally-friendly way to increase the cement lifespan. This work aimed to investigate the potential use of Lysinibacillus sp. strain YL towards biocement application in both theoretical and experimental ways. METHODS AND RESULTS: Strain YL was grown using calcium acetate (Ca(C2 H3 O2 )2 ), calcium chloride (CaCl2 ) and calcium nitrate (Ca(NO3 )2 ). Maximum bacterial growth of ~0.09 hr-1 and the highest amount of CaCO3 precipitation of ~8.0 g/L were obtained when using Ca(C2 H3 O2 )2 . The SEM and XRD results confirmed that biogenic CaCO3 were calcites. The bulk, Young's and shear moduli of biogenic CaCO3 calculated via the VRH approximation were ~1.5-2.3 times larger than those of ordinary Portland cement. The Poisson's ratio was 0.382 and negative in some directions, suggesting its ductility and auxetic behaviors. The new model was developed to explain the growth kinetic of strain YL in the presence of Ca(C2 H3 O2 )2 , whose concentration was optimized for biocement experiments. Strain YL could increase the compressive strength of cement up to ~50% higher than that of the uninoculated cement. CONCLUSION: Strain YL is a promising candidate for biocement applications. This work represents the trials of experiments and models allowing quantitatively comparison with large-scale production in the future.
