Browsing by Author "Pandey, D."

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    Impact of Hemp Fiber on Mechanical and Durability Characteristics of Bacterial-Based Cement Mortar
    (Springer Science and Business Media Deutschland GmbH, 2025) Pandey, D.; Chaudhary, P.; Palanisamy, T.
    Natural fibers are currently highly valued due to the need for environmentally friendly alternatives. Integrating self-healing bacteria with natural fiber-reinforced mortar creates a unique and sustainable building material that enhances strength and facilitates crack repair. This study evaluates the performance of natural fiber and bacteria in improving the mechanical properties and durability of impaired mortars. The methodologies adopted include a bio-based approach incorporating directly added bacteria and a bio-based strategy utilizing bacteria and fiber reinforcement. Bacteria were identified from a suitable environment and directly added to the cement mortar, along with varying percentages of hemp fibers (0, 0.25, 0.5, and 1). Intentionally induced cracks, subjected to 80% peak compressive stress, undergo water curing with regular monitoring. The effects of hemp fiber content and pH value of acid attack on the mass loss of tested concrete were investigated. The results indicate that the Bacillus strain, Bacillus licheniformis, achieves higher values in compressive strength and lower values of sorptivity tests by 26% and approximately 7%, respectively, with the incorporation of 0.5% hemp fibers leading to a 25–30% increase in 28-day compressive strength. Microstructural investigation reveals that microbial-induced precipitation of various calcium carbonate polymorphs densifies the porous microstructure of the cement matrix. The process was analyzed using SEM imaging to observe bacterially induced carbonate crystals, while FTIR spectroscopy was employed to reveal the variety of CaCO3 crystals formed and to predict the bonding mechanisms responsible for calcium carbonate formation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
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    Pozzolanic Reactivity, Hydration and Microstructure Characteristics of Blended Cementitious Composites Comprising of Ultrafine Particles
    (Springer Science and Business Media Deutschland GmbH, 2022) Snehal, K.; Das, B.B.; Sudhi, A.; Pandey, D.
    Performance of ultrafine fly ash (UFFA, 5–10 µm) and fly ash (FA, 45–50 µm) particles in cementitious composites was investigated individually as well as in combination. To study the physicochemical behaviour of blended cementitious composites, engineering properties and pozzolanic reactivity test were conducted. Further, characterization techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) were employed. The results showed good amplification in the development of early compressive strength and durability on admixing ultrafine particles of fly ash (UFFA) in cementitious system. Particle size and specific surface area of UFFA greatly influenced on the phase assemblages of cementitious composites, i.e. due to enriched pozzolanic reactivity which reduced Ca/Si atomic ratio (≤ 1.82) in the pore solution of cementitious matrix. On contrary, the presence of UFFA particles in cementitious composite mix developed disjoining pressure in addition to self-desiccation thereby induced early age cracks and also reduced the workability in correspondence to that of FA particles. Further, use of UFFA in conjunction with FA particles, cementitious composites showed much superior performance in terms of both physical and chemical characteristics, which necessitates the crucial need of admixing micron and submicron size particles in the design of sustainable and high-performance cementitious composites at this point of time. © 2022, The Author(s), under exclusive licence to Shiraz University.