Articles written in Sadhana

    • Bacterial based admixed or spray treatment to improve properties of concrete


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      The capability of calcite precipitation by microbes is a well-known natural phenomenon and is now successfully employed to improve properties of concrete. The calcite precipitation by microbes will be affected by the process in which bacteria is introduced into concrete. The present study highlights different ways ofmicrobial incorporation into concrete and its effect on the properties of resultant concrete. The bacteria were introduced into concrete either during casting or curing of concrete. The efficiency of the proposed microbial treatment was monitored in terms of strength development, water impermeability, pH of the pore solution, microstructure and level of CaCO3 precipitated. It was observed that both admixed treatment or spray treatment during curing were effective in calcite precipitation. The procedure involving spraying of bacterial culture onto concrete surface was efficient as well as economical.

    • Assessment of mixing performance in a spiral micromixer with different inlet path configurations


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      This article presents a numerical analysis of mixing and pressure drop in a spiral micromixer with four different inlet flow path configurations. Micromixers Type 1 and Type 2 (M-Type 1 and M-Type 2) have Y-shaped and T-shaped entry into the main channel with fluid entry into a spiral channel at 90°, whereas, inMicromixers Type 3 and Type 4 (M-Type 3 and M-Type 4), the entries of fluid are in line with spiral channel. The mass fraction contours of the species, velocity vectors, mixing efficiency, and pressure drops are analyzed for Reynolds number in the range 1 ≤ Re ≤ 100. The results show that the mixing efficiency first decreases with the increase in Re and then increases with Re values. In contrast, pressure drops and mixing performance increase with the increase in Re values irrespective of the micromixer design. Higher mixing is observed inmicromixers having Y-shaped inlets. The mixing efficiency of 97.2% is observed in M-Type 3, followed by 94% in M-Type 1. In M-Type 2 and M-Type 4, the values of mixing efficiency are 89% and 90.3%, respectively. The mixing performance of micromixers in M-Type 1 and M-Type 3 is lower than M-Type 2 and M-Type 4.

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