Enhanced biodeterioration and biofouling resistance of nanoparticles and inhibitor admixed fly ash based concrete in marine environments

Abstract

In this paper, we report the enhanced biodeterioration and biofouling resistance of a modified fly ash based concrete, formulated by the addition of fly ash, nano-TiO2, nano-CaCO3, and corrosion inhibitor into conventional concrete. After six months of exposure in natural seawater, the modified fly ash based concrete showed a three to four order reduction in aerobic and anaerobic bacterial density, which was confirmed by epifluorescence and confocal microscopic investigations. The FESEM micrographs showed a characteristic surface morphology with uniform distribution of more calcium silicate hydrate (CSH) gels and aluminate hydrates, absence of discontinuities, pits, and cracks on the modified concrete surface which helped to resist the ingress of aggressive ions from seawater. The comparatively lesser reduction in surface pH, low water/cement ratio, better bulk thermal properties, and low surface roughness facilitated the improvement in the antimicrobial and antifouling properties of modified concrete. The addition of nanoparticles and inhibitor increased the hydration of cement resulting in the formation of more portlandite which got converted into more hydration products, producing a pore free morphology. The inherent photocatalytic activity of nano-anatase TiO2 and bactericidal activity of sodium nitrite due to the presence of reactive nitrogen species (RNS) together enhanced the biofouling and biodeterioration resistance.