Hanumantha Rao B | IIT Bhubaneswar (original) (raw)

Papers by Hanumantha Rao B

Waste and Biomass Valorization, 2020

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.

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.

Lecture Notes in Civil Engineering, 2020

Lecture Notes in Civil Engineering, 2019

Proceedings of the 8th International Congress on Environmental Geotechnics Volume 3, 2018

Waste and Biomass Valorization, 2020

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...

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...

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.

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 ...

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...

Lecture Notes in Civil Engineering

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.

Indian Geotechnical Journal

International Journal of Geotechnical Engineering

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.

International Journal of Geosynthetics and Ground Engineering, 2015

Waste and Biomass Valorization, 2020

Developments in geotechnical engineering, 2017

Journal of Hazardous, Toxic, and Radioactive Waste

Lecture Notes in Civil Engineering, 2020

Lecture Notes in Civil Engineering, 2019

Proceedings of the 8th International Congress on Environmental Geotechnics Volume 3, 2018

Waste and Biomass Valorization, 2020

Journal of Hazardous, Toxic, and Radioactive Waste, 2019

Géotechnique Letters, 2018

Geo-Chicago 2016, 2016

Journal of Hazardous, Toxic, and Radioactive Waste, 2020

Scientific Reports

Lecture Notes in Civil Engineering

Indian Geotechnical Journal

International Journal of Geotechnical Engineering

Journal of Geotechnical and Geoenvironmental Engineering, May 1, 2010

International Journal of Geosynthetics and Ground Engineering, 2015

Previous studies reveal that the geotechnical properties of red mud waste (RMW) closely resemble ... more Previous studies reveal that the geotechnical properties of red mud waste (RMW) closely resemble that of conventional soils. Due to the predominant presence of exchangeable sodium, the red mud waste 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, 1.0, 2.0, 3.0, and 4% (by weight), were selected for the study. The untreated and polymer amended red mud waste samples were subjected to cylindrical dispersion crumb tests for examining the dispersion phenomenon, and the hardened samples were further analyzed 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 particles aggregations with an increase in the biopolymer content, while elemental compositions showed gel formation by GG cross-linking with calcium. As such, GG proved to be more effective over XG in mitigating the dispersion characteristics of the RMW. Overall, this study shows that GG biopolymer has potential to be used for mitigating dispersion and controlling dusting in field applications.

Waste and Biomass Valorization, 2021

In order to conserve natural resources and prevent waste generation, effective utilization of ind... more In order to conserve natural resources and prevent waste generation, effective utilization of industrial wastes and/or by-products for beneficial engineering applications becomes inevitable. In order to accomplish this, extensive research studies, exploring properties and new applications of waste materials in a sustainable and environmentally friendly manner, have been initiated worldwide. Red mud (RM, also known as bauxite residue) is one of the wastes generated by the aluminium industry and its disposal and utilization have been traditionally hindered due to the extreme alkalinity (pH about 10.5–13.5). To date, no comprehensive review on various properties of RM of different origin and associated challenges in using it as a beneficial engineering material has been performed. The objective of this study is first to critically appraise the current understanding of properties of RM through a comprehensive literature review and detailed laboratory investigations conducted on Indian RM by the authors, to assess and identify the potential engineering applications, and to finally discuss associated challenges in using it in practical applications. Physical, chemical, mineralogical and geotechnical properties of RMs of different origin and production processes are reviewed. Mechanisms behind the pozzolanic reaction of RM under different chemical and mineralogical compositional conditions are discussed. Environmental concerns associated with the use of RM are also raised. Studies relevant to leachability characteristics reveal that most of the measured chemical concentrations are within the permissible regulatory limits. Overall, the review shows that RM disposal and reuse is complicated by its extreme alkalinity, which is also noticed to be influencing multiple engineering properties. But with selected pH amendments, the treated RM is found to have significant potential to be used as an effective and sustainable geomaterial. The assessment is majorly based on the characteristics of Indian RMs; hence the adaptation of the findings to other RMs should be assessed on a case-by-case basis. Moreover, field studies demonstrating the performance of RM in various engineering applications are warranted.

Stabilization is one of the most preferred techniques of dealing with expansive soils. Several ty... more Stabilization is one of the most preferred techniques of dealing with expansive soils. Several types of additives have been evolved and are successfully being used for this purpose. This paper evaluates the performance of a variety of additives categorized into (a) cementitious: lime and fly ash (b) non-cementitious: stone dust, and (c) chemical additives: CaCl 2 and Na 2 SiO 3 , when employed to stabilize three types of expansive soils used in the study. Attempts were also made to investigate the influence of valence of cations (viz., monovalent, divalent and trivalent) and mean particle diameter (d50) of additive(s) on percentage reduction of swelling characteristics. Results reveal that each additive exhibits distinct response on the swelling behavior of expansive soils. It has been observed that chemical additives exhibit superior performance over cementitious and non-cementitious additives in reducing the swelling characteristics. Further, it has also been found that valence has profound influence on the swelling characteristics of expansive soils. As such, the degree of reduction of swelling was found significantly high when employed chemical additive consists of trivalent cations than its counterpart additive consists of mono-or divalent cations. Further, efforts were also devoted to correlate mean particle diameter of additives with swelling characteristics, and it was clearly evident from trends that an appreciable decrease in swelling characteristics occurs with decrease in mean particle diameter.

This study deals with the evaluation of the compaction and consolidation characteristics of untre... more This study deals with the evaluation of the compaction and consolidation characteristics of untreated as well as hydrochloric acid (HCl)-and sodium chloride (NaCl)-treated red mud wastes. A series of standard and modified Proctor compaction and one-dimensional consolidation tests were conducted for the study purpose. Sodium chloride solutions of 1·71 and 3·42 M and hydrochloric acid solutions with pH of 1, 1·5, 2, 3 and 4 are selected to treat the waste. Results show that standard Proctor compaction tests yield inconsistent and low dry unit weight values with relatively high optimum water content. On the other hand, modified Proctor compaction test produced consistent dry unit weight values with low optimum water content. There is only a marginal improvement in dry unit weight and compression properties of hydrochloric acid-and sodium chloride-treated samples; however, the treatment proved effective in reducing pH of the waste. It has been noticed that the compressibility of both untreated and treated samples is appreciably low. Results elucidate that parameters such as the size of the particles and their shape, chemical and mineralogical compositions and surface charge properties can influence the compaction and compressibility characteristics of the waste. Overall, the study demonstrates that the red mud waste could be a potential resource material for geotechnical engineering applications.

Environmental Science and Engineering, Springer, Singapore, 2019

Knowledge of consistency limits is considered important in predicting the engineering properties ... more Knowledge of consistency limits is considered important in predicting the engineering properties (viz., swelling, shrinkage, strength, etc.) as well as for identifying and classifying the geomaterials. Determination of these consistency indices becomes even more imperative when selecting geomaterials (soil or waste) as a resource material for constructing earthen structures. This paper focuses on evaluating the consistency limits (or Atterberg's limits such as liquid limit, plastic limit, and plasticity index) of red mud waste admixed with oxalic acid, gypsum, sodium silicate, and the combination of fly ash and gypsum additives in different proportions, in a comprehensive way. The results show significant variations in the value of Atterberg's limits of ameliorated red mud waste vis-à-vis with that of raw waste. It has been inferred that the results reported in the study are of great help in asserting the suitability of the red mud waste in geotechnical engineering applications.

The present study deals with evaluating the dispersion characteristics of red mud by adapting to ... more The present study deals with evaluating the dispersion characteristics of red mud by adapting to chemical analysis methods. For this purpose, the leached aqueous solution has been extracted by suitably diluting the red mud particles with distilled water. The parameters like sodium absorption ratio (SAR) and exchangeable sodium percentage (ESP), which are strong indicators of flocculation or dispersion stability, pH, zeta potential and electrical conductivity, have been measured and employed to assess the dispersive nature of the red mud. The values of SAR and ESP are measured as 54.9% and 98.3%, respectively. The very high values of SAR and ESP demonstrate that the red mud tends to exhibit moderate to high dispersive behaviour. Usually, dispersive soils are not selected as a source material for the construction of earth structures, without adequately stabilizing or treating with chemical additives. As such, the results emphasize that there is a need for treating the red mud with additives like gypsum or alum for mitigating the dispersion behaviour, before its intended use.