Browsing by Author "Mishra M.C."

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    Neutralization of Red Mud with Organic Acids and Assessment of Their Usefulness in Abating pH Rebound
    (2020) Mishra M.C.; Rao B.H.
    This study provides a practical and efficient alternative to neutralize the exorbitant pH of red mud (>11.5) followed by long-term sustenance of the neutralization. The usefulness of organic acids (oxalic acid and citric acid) as standalone additives and admixed with lime in mitigating red mud alkalinity was investigated. The efficiency of these acids in terms of posttreatment pH rebound for curing period up to 180 days was monitored. The neutralization treatment produced pH reduction with simultaneous accentuation of coagulation and precipitation of hydrates, which was determined from scanning electron microscope (SEM) analysis. The uniqueness of the study lies in proposing the rebound rate of pH (RRP) and rebound termination period (trt). The observed results offer distinctive insight into the factors affecting red mud chemistry including the role of lime as an additive. It is recommended to use 2.0 M oxalic acid or 2.5 M citric acid for neutralizing red mud. For improved microstructure, it is warranted to resort to a combination of 5% lime and 2.0 M oxalic acid. � 2019 American Society of Civil Engineers.
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    Performance of Lime Stabilization on Extremely Alkaline Red Mud Waste under Acidic Environment
    (2019) Mishra M.C.; Sateesh Babu K.; Reddy N.G.; Dey P.P.; Hanumantha Rao B.
    Excessive pH (>11) and inconsistent engineering properties because of the chemicomineralogical composition of red mud warrant devising an alternate approach to render it more environmentally benign. In this study, the performance of lime stabilization coupled with oxalic acid, which acts as a neutralizing agent, was explored systematically to improve the long-term strength and to reduce the alkalinity of red mud. The mechanisms governing the behavior of additives along with their effects were investigated by examining the mineralogical, elemental, and morphological characteristics. The results suggest an effect of sodalite and alumina on the inconsistency in dry unit weight and claylike behavior of red mud. A reduction in pH was found to be instrumental during early phases of lime stabilization and in precipitation of cementitious hydration products, leading to strength gain in the long term in red mud. Moreover, the addition of lime and oxalic acid was found to yield more encouraging results than lime treatment alone, and hence this is recommended to be used for red mud stabilization. The obtained results were substantiated by comparison with code provisions. � 2019 American Society of Civil Engineers.