DEVELOPMENT OF SUSTAINABLE BACTERIAL FLYASH CONCRETE USING THE TECHNIQUE OF MICROBIOLOGICAL INDUCEDCALCITE PRECIPITATIONSANTOSH ASHOK KADAPURE, GIRISH S. KULKARNI AND K.B. PRAKASH
Flyash is a solid waste left behind by combustion of pulverized coal in thermal power plants. Fly ash acts as a partial replacement material for both Portland cement and fine aggregate. An experimental investigation is done on technique of microbial calcite precipitation in fly ash-amended concrete. This paper presents the results of the investigation done on the effect of various dosages of Bacillus pasteurii on properties of normal and flyash concrete such as compressive strength, water absorption, sorbtivity and chloride permeability of concrete. Cement was partially replaced by 10%, 20% and 30% with fly ash by weight. Experiment was conducted for varying cell concentrations of 0,103, 105 and 107 cells/mL. At the fly ash concentrations of 0%, 10%, 20% and 30% in concrete, bacterial cell enhanced compressive strength by 25.08%, 19.8, 20.18% and 18.6 % respectively for 7 days, in comparison with control specimens. Microbial deposition of a layer of calcite on the surface of the concrete specimens resulted in substantial decrease of water uptake and chloride permeability compared to control specimens without bacteria. Scanning electron microscopy (SEM) analyses illustrated both the stages of crystal growth and the crystalline structure of highly impermeable calcite layer (CaCo3) crystals on the surface of the cement mortar cube specimens. Thus a sustainable concrete can be produced by technique of biomineralization which gives us dual environment friendly advantages. First, use of flyash-a solid waste reduces depletion of natural resources and also reduces the energy-intensive manufacturing of other concrete ingredients, leading to savings in both energy usage and emissions of greenhouse gases. Secondly, MICP biochemical process enhance strength and durability of fly ash-amended concrete further provides greener and economic options.
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