Properties of Bacterial Silica Fume Concrete

Abstract

Ingress of harmful chemicals such as Chloride and sulfate may severely damage the structural properties of concrete as well as corrosion of embedded steel which results in failure of concrete structures. The microstructure of concrete has a direct influence on its durability and strength. Thedurability and strength of concrete can be improved by using a technique which involves bacterial induced calcite precipitation. Bacteria are capable of precipitatingcalcium carbonate crystalswhich enhances the microstructural properties of concrete thereby reduction in permeability of concrete. The premier objective of this work is involved with the use of Ureolytic bacteria in concrete which could make it more durable. Thebacteria present in the concrete rapidly sealed freshly formed cracks through calciteproduction. The bacterial concentration was optimized to 105 cfu/ml.In concrete mix, cement was replaced withsilica fume in 5% 10% and 15% by weight of cement.The experimentswere carried out to estimate the effect of bacteria on the compressivestrength, water absorption, porosity, rapid chloride permeability and sorptivity of concrete made with silica fume up to the age of 28 and 56 days. The test result shows thatinclusion of bacteria enhanced the compressive strength by 12%, reduced theporosity, water absorption and sorptivity by upto 55% of the silica fume concrete. The improvementin compressive strength was due to deposition ofcalcite precipitated by bacteria within thepores which was scanned by electron microscopy and characterized by XRD and revealedcalcium carbonate precipitation. This precipitation also reduced the chloride permeability inconcrete with silica fume.The bacteria improve the impermeability of concrete by improving its pore structure and thereby enhancing the life of concrete structures.