Department of Civil Engineering

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Author: search.filters.author.Lahoti, MukundSubject: search.filters.subject.Fly ash

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    Investigating the potential reactivity of fly ash for geopolymerization
    (Elsevier, 2019-11) Lahoti, Mukund
    This study investigated potential reactivity of fly ash for geopolymerization. A combined dissolution of fly ash in NaOH in conjunction with HCl extraction of fly ash-NaOH residue is proposed in this study to more accurately estimate the total reactive content and reactive Si/Al ratio of fly ash. Results show that the total reactive content of fly ash used in the current study is about 68.80%, similar to the amorphous content (66.28%) obtained using quantitative XRD and XRF. The values of reactive Si/Al ratios are between 2.65 and 2.98 depending on the duration of dissolution. The reactive Si/Al values differ significantly from the total Si/Al ratio (1.63) calculated using XRF results and also differ from the vitreous Si/Al ratio (3.75) calculated using combined XRF and XRD results. The results suggest that total or vitreous Si/Al ratio should not be used for mix proportioning of fly ash geopolymers as is generally used for metakaolin-based geopolymers. Instead, the reactive Si/Al ratio determined based on the current study should be used for fly ash geopolymer mix design.
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    Tailoring sodium-based fly ash geopolymers with variegated thermal performance
    (Elsevier, 2020-03) Lahoti, Mukund
    Sodium-based fly ash geopolymers show great fire resistance potential and commercial advantage for structural applications. Hence, in current research, tailoring of sodium-based geopolymer mix design without changing the fly ash source has been studied. It was found that a wide variety of residual compressive strength ranging from significant reduction (~80%) to maintaining significant enhancement (~150%) after being exposed to 900 °C was observed. The contributory mechanisms were discovered by investigating their chemical stability, pore structures, volume stability, and strength endurance prior to and after exposure to high-temperature using different microstructure characterization techniques including XRD, FTIR, MIP, dilatometry, and SEM. Crack formation due to moisture migration, pore shrinkage, and re-crystallization of nepheline adversely affected compressive strength. Matrix densification due to shrinkage of pore and stronger inter-particle bonding due to viscous sintering, favored compressive strength gain. This work discusses at length these competing mechanisms influencing the residual compressive strength.
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    Kiln-fired clay bricks synergizing nickel–chromium plating sludge and fly ash: mechanical characteristics and cradle-to-gate life cycle assessment
    (Springer, 2022-09) Bhunia, Dipendu; Routroy, Srikanta; Singhal, Anupam; Lahoti, Mukund
    Life cycle assessment (LCA) of novel fired clay bricks with synergistic co-valorization of nickel-chrome plating sludge (NCPS) and fly ash (FA) is reported. 0%, 20%, and 37.5% FA was added to improve sludge-deteriorated mechanical properties. Sludge bricks (SBs) exhibited compressive strength of 11.03 MPa, 17% water absorption, nil efflorescence, and permissible heavy metals’ leaching, complying with standards as first-class bricks. LCA was performed with the ReCiPe-2016 method, utilizing the primary experimental data, government reports, and the Ecoinvent v3.8 database. LCA analysis revealed that compared to clay bricks, SBs caused 30%, 43%, and 51% lesser harm to ecosystem quality, human health, and resource categories in the endpoint assessment. Kiln emissions, coal, clay, and transportation were chief contributors, but their cumulative endpoint impacts significantly reduced (38%, 52%, 55%, and 45%) on switching to the SBs. Terrestrial acidification, global warming, photochemical oxidant formation, and particulate matter emissions significantly affected midpoint categories. However, their impacts got reduced by 52–57% with SBs. With global annual clay brick production exceeding 1.5 trillion, agricultural soil mining causes irreversible depletion of nitrogen, phosphorous, potassium, and organic carbon in the soil. SBs utilize only 50% clay, adding substantially to environmental savings. Successful NCPS immobilization in bricks prevents leaching hazards and avoids scientific landfill construction. With a calorific value of 945 kcal/kg, NCPS acts as internal fuel during firing, reducing the external coal requirement. This work establishes the techno-environmental feasibility of recycling NCPS and producing better-performing bricks with lower environmental impacts.
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    Alternative materials for wearing course of concrete pavements: A critical review
    (Elsiever, 2020-03-10) Singh, Ajit Pratap; Sarkar, Askoke Kumar; Lahoti, Mukund
    The existing worldwide road length of concrete pavements is significant. Furthermore, concrete pavements have a number of specific applications, even though they are second to asphalt pavements in terms of current popularity. Besides, asphalt is a rapidly depleting resource, which might mean that concrete is the chief material for the future. However, concrete pavements have their drawbacks, such as high construction cost, low tensile strength, and significant contribution to global carbon-di-oxide emissions. The present study aims to address these drawbacks by reviewing the prominent alternative materials that may be utilized to replace cement and/or aggregates in concrete. The potential of alternatives such as coal ash, silica fume, nano-silica, fly ash, slag, and recycled concrete aggregate is investigated. In addition, the effects of adding fibers (as both fiber-reinforced concrete and engineered cementitious composite) to concrete pavements are discussed. This review will also help pavement engineers and researchers to ascertain which combination of materials to use so that mechanical properties better than conventional concrete are achieved. The specific advantages and disadvantages due to various combinations of materials, in several types of concrete pavements such as conventional concrete, roller-compacted concrete, and self-compacting concrete are discussed in detail.