Papers by Hanumantha Rao B
Waste and Biomass Valorization, 2020
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Developments in geotechnical engineering, 2017
Neutralization is essential for high alkaline wastes like red mud for its effective utilization. ... more Neutralization is essential for high alkaline wastes like red mud for its effective utilization. As such, the process of neutralization involves treating the red mud with either chemicals or other waste materials. Among several factors that affect the efficiency of the treatment, surface charge characteristics and particle diameter parameters predominantly influence the performance of the neutralization. The present study focuses on examining the surface charge properties which include flocculation and dispersion and determining the particle size characteristics which include mean particle diameter under variable pH conditions. Surface charge properties are interpreted from zeta potential, ζ, measurements made on suspensions prepared with red mud waste at different pH values. The average particle diameter is obtained from the grain size analysis established on the same suspensions using the zeta potential analyser. Results indicate that the zeta potential increases with pH up to a certain pH value of 4 and then begin to fall with the further increase in pH. The zeta potential turned into negative (up to a maximum value of −48 mV) at pH value of 6.6, which denotes the point of zero charge for the red mud, from the initial positive (from a maximum of +41.8 mV) value. However, the value becomes stabilized when the pH is 10 and above. An average particle diameter of (a) 65–150 nm at pH of 3.96 and above 9.00, indicating a complete dispersed state of the grains, and (b) 1660 nm, 2176 nm and 1080 nm at pH of 1.15, PZC (i.e. pH of 6.6) and pH of 7.48, respectively, indicating likely agglomeration of the grains, was recorded with the change in pH of the suspension. The study finds that the waste possesses surface charge characteristics, which appear to be greatly influenced by the pH.
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Journal of Hazardous, Toxic, and Radioactive Waste
In bauxite residue (BR), the abatement and rebound of pH when ameliorated with different amendmen... more In bauxite residue (BR), the abatement and rebound of pH when ameliorated with different amendments have been reported as prime concerns. In addition, to the best of the authors' knowledge, no research has focused on the characterization of BR during the decrease and rebound in pH, which happens over an extended period. This characterization is essential to convert posttreated residue into green construction materials and to affirm that it does not pose a threat to the environment. This study aimed to investigate two important points. The evaluation of the efficacy of commonly and widely employed conventional additives and mineral acids while mitigating the pH of the residue and its characterization included sedimentation and leaching with a change in pH. The uniqueness of this study lay in the exploration of the latter point and pH rebound for ≤180 days. Cement, gypsum (G), fly ash (FA), and ground granulated blast furnace slag (GGBS) as conventional additives, and nitric (HNO 3) and hydrochloric acids (HCl) as mineral acids were selected to ameliorate BR. A significant pH rebound with time occurred from 6.59 to 9.51 and 7.54 to 9.78 when treated with 1M HCl and HNO 3 , which indicated the influence of the curing period and ameliorant on the alkalinity. Conventional additives, except for G, and their combinations proved ineffective when mitigating and maintaining pH within acceptable limits (i.e., 8.5). Settling analysis revealed accelerated particle settling at pH 4.5-7.0, which indicated implications for the safe disposal, washing, or slurry thickening of BR. The extensive leaching studies for potentially toxic elements (PTEs), which were further endorsed with a field case study, demonstrated that the amended residue was environmentally safe to be used as a construction material.
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Lecture Notes in Civil Engineering, 2020
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Lecture Notes in Civil Engineering, 2019
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Proceedings of the 8th International Congress on Environmental Geotechnics Volume 3, 2018
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Waste and Biomass Valorization, 2020
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Journal of Hazardous, Toxic, and Radioactive Waste, 2019
AbstractExcessive pH (>11) and inconsistent engineering properties because of the chemicominer... more AbstractExcessive pH (>11) and inconsistent engineering properties because of the chemicomineralogical composition of red mud warrant devising an alternate approach to render it more environmentall...
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Géotechnique Letters, 2018
Previous studies revealed that the geotechnical properties of red mud waste (RMW) closely resembl... more Previous studies revealed that the geotechnical properties of red mud waste (RMW) closely resemble that of conventional soils. Due to the predominant presence of exchangeable sodium, the RMW tends to exhibit high-dispersion behaviour. In this study, mitigation of the dispersion characteristics of RMW using eco-friendly biopolymers was investigated. Two types of biopolymers, namely guar gum (GG) and xanthan gum (XG), in 0·5, 1, 2, 3 and 4% (by weight), were selected for the study. The untreated and polymer-amended RMW samples were subjected to cylindrical dispersion crumb tests for examining the dispersion phenomenon, and the hardened samples were further analysed for microstructure, mineralogical and elemental compositions. Turbidity and pH of water in the crumb tests as well as consistency limits of untreated and polymer-amended RMW were also tested. The microstructural analysis revealed an increase in particle aggregations with an increase in the biopolymer content, while elementa...
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Geo-Chicago 2016, 2016
This paper focuses on evaluating the compaction characteristics of untreated and treated red mud ... more This paper focuses on evaluating the compaction characteristics of untreated and treated red mud waste in a comprehensive way. Chemical solutions such as NaCl and HCl were used to treat the red mud waste. A series of standard Proctor (SP) and modified Proctor (MP) compaction tests were conducted on identical samples of (a) untreated and (b) NaCl and HCl treated samples. It has been observed that among standard Proctor and modified Proctor test, the latter one yields reproducible compaction curves especially on untreated red mud waste. The results also showed significant variations in the value of maximum dry density and optimum water content between NaCl and HCl treated samples. Further, it has also been found that compaction energy can considerably influence the density characteristics of the red mud waste.
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Journal of Hazardous, Toxic, and Radioactive Waste, 2020
Abstract In this paper, citric acid (CA) is chosen as an additive for the treatment of bauxite re... more Abstract In this paper, citric acid (CA) is chosen as an additive for the treatment of bauxite residue, a by-product generated by the aluminum industry. The potential of CA to improve geotechnical ...
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Scientific Reports
Microlevel properties such as mineralogical and chemical compositions greatly control the macro b... more Microlevel properties such as mineralogical and chemical compositions greatly control the macro behaviour of expansive soils. In this paper, the combined effect of mineral (i.e. montmorillonite, MMC) and chemical contents (i.e. Ca and Na in their total (T), leachable (L) and exchangeable form (CEC)) on swelling behaviour is investigated in a comprehensive way. Several 3-dimensional (3D) graphs correlating MMC and Ca/Na ratio, together, with swelling property (swelling potential, Sa, and swelling pressure, Sp) are developed. 3D plots, in general, portrayed a non-linear relationship of Sa and Sp with MMC and Ca/Na ratio, together. It is hypothesized that swelling initially is triggered by chemical parameters due to their quick and rapid ionization capability, but the overall swelling phenomenon is largely controlled by MMC. It is importantly found that expansive soils are dominant with divalent Ca++ ions up to MMC of 67% and beyond this percentage, monovalent Na+ ions are prevalent. F...
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Lecture Notes in Civil Engineering
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Lecture Notes in Civil Engineering
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Geotechnical Research
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Indian Geotechnical Journal
Red mud waste is generally transferred to the storage area in a slurry form with solids content v... more Red mud waste is generally transferred to the storage area in a slurry form with solids content varying from 15 to 40%. Due to arise of a variety of environmental and climatic conditions in the due course of time, settling behaviour of particles as well as properties of settled particles changes. Thus, understanding of the settling behaviour of waste particles becomes essential after disposing the waste into the pond. In addition, studies related to the settling behaviour of particles become important during the extraction of alumina from bauxite ore (i.e. in settlers). In the present study, efforts are made to investigate the settling behaviour of red mud waste particles when exposed to different aqueous environmental conditions. For testing purpose, a series of differential free swell tests were conducted considering aqueous environmental conditions such as tap water, distilled water, kerosene, NaCl solutions of 1.71 and 3.42 M, and HCl solutions with a pH range from 1 to 4, respectively. In addition, efforts are also devoted to characterizing the post-exposed sediment samples to ascertain possible changes in the mineralogical, morphological , and elemental compositions of the particles. Results reveal that aqueous environment has a considerable effect on the settling behaviour of particles, while the effect of pH found to be trivial. The analyses of characterization studies disclose a marginal to considerable changes in elemental, phase compositions and morphological characteristics of the post exposed particles.
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Indian Geotechnical Journal
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International Journal of Geotechnical Engineering
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Journal of Geotechnical and Geoenvironmental Engineering, May 1, 2010
ABSTRACT To establish soil-water characteristic curves (SWCCs) of fine-grained soils, researchers... more ABSTRACT To establish soil-water characteristic curves (SWCCs) of fine-grained soils, researchers have employed geotechnical centrifuges. However, most of these studies were confined to small acceleration levels and as a result the suction, psi, created in the soil mass was extremely low (< 100 kPa). Hence, researchers have resorted to ultracentrifuges, which are capable of generating psi approximate to 300 kPa. However, the volume of the soil mass used in these centrifuges is too small to be representative of field conditions and determination of moisture content of the soil specimen is done by invasive and destructive techniques. Under these circumstances, utility of electrical measurements (i.e., voltage across two points in the soil mass) for determining soil moisture content, which has the distinct advantage of being both nondestructive and noninvasive and facilitates development of the SWCC, seems to be quite promising. Validity of the technique has been demonstrated by comparing the resultant SWCC, for kaolin, vis-a-vis the SWCCs reported in the literature and those obtained from the pedo-transfer function (PTF). Further, unsaturated hydraulic conductivity (k(u)) of the kaolin was determined by employing various PTFs available in the SoilVision database and using the relationship proposed by Corey in 1977. It has been observed that the k(u) values obtained from these relationships match extremely well for psi <= 3000 kPa.
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International Journal of Geosynthetics and Ground Engineering, 2015
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Papers by Hanumantha Rao B
Read More: http://ascelibrary.org/doi/abs/10.1061/9780784480151.003