A novel approach of biomineralization for improving micro and macro-properties of concrete

The aim of this paper is to investigate the effect of biomineralization in concrete by incorporation of ureolytic sp. (B. megaterium, B. pasteurii) in the absence of substrate and non-ureolytic sp. (B. cohnii) without chemical feed. The related pathway accountable for durability enhancement besides well known, microbially induced calcite precipitation (MICP) was explored. The explored pathway of mineralization resulted in enhancement of mechanical properties, reduction in water absorption (similar to 22%), volume of voids (similar to 24%) and sulphate ion concentration at 180 days (similar to 26%). Field emission scanning electron microscopy revealed thick mineral deposition (microstructural modification) by bacteria at interfacial transition zone (ITZ) with Ca/Si = 1.5. X-ray diffraction and Fourier transform infrared spectroscopy results showed an accelerated formation of hydrated products in the presence of bacteria. Quantification by thermogravimetric analysis, exhibited similar to 16% higher calcium silicate hydrate and similar to 37% more calcium hydroxide formation in bacterial concrete. The additional formation of hydration products facilitated by bacteria, is believed to be the definite reason of densified microstructure and thus, enhanced macro properties of bacterial concrete. (C) 2018 Elsevier Ltd. All rights reserved.