MODELING ESTIMATION OF MICROBIAL DECOMPOSITION OF CALCIUM SILICATE HYDRATE AND CONCRETE BIODEGRADATION

Abstract

Net microbial decomposition of calcium silicate hydrate (C-S-H) that results in the biodegradation of concrete has been analyzed theoretically on the basis of the conservation principle of Gibbs free energy in the microorganism-concrete systems. Microorganisms have been considered to be adhered to concrete surface by forming micro-colonies and bio-films. The growth and decay of microorganisms were expressed using Monod-based equation. It was predicted that the mean density of microorganisms in bio-films reached 6.7×10^<-6>g/cm^3. The bio-film thickness reached 19.5μm. The net microbial decomposition depth of C-S-H in concrete was about 7 to 10μm/year and did not exceed 40μm/year at most, provided that microorganisms of 4×10^<-9> and 4×10^<-8>g/cm^3 adhered to concrete surface.