Properties of Sugarcane Bagasse Ash Concrete Modified with Bacterial Treatment.

Bacteria-prompted calcite precipitation enhances concrete strength properties and durability performance by creating nuclei crystals in the concrete pore structure. In this paper, the effect of bacterially treated sugarcane bagasse ash (SCBA)-based concrete on concrete's mechanical and permeability properties has been comprehensively investigated. The SCBA was used in concrete as a partial replacement of normal portland cement at two different replacement levels of 10 and 20%, while bacteria content was kept constant at 105 cells/mL (2.96 x 106 cells/oz.). This study used two different types of bacteria, Sporosarcina pasteurii and Bacillus megaterium from the Bacillus subtilis family. After 28 days of curing in water, the blended cement concrete with 10% SCBA showed higher compressive strength compared to the control mixture. Incorporating B. megaterium and S. pasteurii further improved the compressive strength of concrete by 7 and 10% in SCBA 10% concrete. This compressive strength enhancement is due to the continuous hydration process of cement and the pozzolanic reaction of SCBA in concrete. The addition of bacteria further improves the strength by forming calcite crystals and filling the pore spaces in the concrete. Calcite deposition in the pores of concrete subsequently refines and enhances the microstructure of concrete. The deposition of calcite precipitation in the pores blocks the water permeability, which ultimately reduces the porosity and water absorption of bacteriaincorporated concrete. The incorporation of bacteria in concrete also reduces the penetration of chloride ions compared with the control mixture and the concrete treated with only SCBA. Based on the nuclear magnetic resonance (NMR) spectroscopy analysis, the average chain length of calcium-silicate-hydrate (C-S-H) gel was increased by incorporating SCBA in concrete up to a replacement level of 10%. Further addition of bacteria increases the chain length of C-S-H gel and the degree of cement hydration in concrete. [ABSTRACT FROM AUTHOR]