Browsing by Author "Rao B.H."

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Biopolymer amendment for mitigating dispersive characteristics of red mud waste
(2018) Reddy N.G.; Rao B.H.; Reddy K.R.
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 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. � 2018 ICE Publishing: all rights reserved.
Characterization of coarse fraction of red mud as a civil engineering construction material
(2017) Alam S.; Das S.K.; Rao B.H.
Red mud is a highly alkaline (pH > 11) industrial solid waste produced by aluminum industries during extraction of alumina using Bayer process. The unutilized red mud stored either in slurry form or in dry stacking takes vast tract of usable land and has an adverse effect on the quality of ground water, surface water and also on animal and plant life. An attempt has been made here to characterize the coarse fraction (>75 ?m) of red mud as an alternate construction material (medium value utilization). Different physical, chemical and morphological properties are investigated and the results are compared with Indian standard sand. The morphology using particle size analyzer is elaborated and correlated with engineering properties like shear strength and flowability parameters. In addition, chemical properties like pH, electrical conductivity, total dissolve solids (TDS), zeta potential, lime reactivity and leachate analysis are also investigated along with thermal property and are compared with that of Indian standard sand. The result of zeta potential test shows that the point of zero charge of red sand lies between the pH values of 5.5�6.5. Based on the lime reactivity, the red sand is found suitable as fine aggregate for cement and concrete. Low thermal conductivity of red sand reveals that it can dissipate the heat more efficiently. Leachate analysis shows that most of the heavy metals are within acceptable limit except Al. Based on the present study, the red sand can be used as a sustainable construction material there by utilizing the industrial waste and conserving natural resources. � 2017 Elsevier Ltd
Compaction and consolidation behaviour of untreated and treated waste of Indian red mud
(2018) Reddy N.G.; Rao B.H.
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�42M 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. � 2018 Published with permission by the ICE under the CC-BY 4.0 license.
Correlations between swelling and suction properties of expansive soils
(2015) Rao B.H.; Sahu R.L.; Das S.K.
Expansive soils have long been identified as problematic soils because these soils cause potential damage to civil engineering structures mainly due to their significant volumetric deformation under seasonal moisture fluctuations. Hence, establishment of swelling characteristics such as swell potential and swell pressure of these soils becomes essential. Although, several methods have been developed, recent studies demonstrate that the prediction of swelling characteristics from suction measurements seems to be promising. Incidentally, both these properties are strongly influenced by physical, chemical and mineralogical characteristics of a soil. Apart from this studies also reveal that stress strain behavior of expansive soil is affected by soil suction. Further, most of the swell prediction methods are not standardized, while suction measuring techniques have been well established with standard guidelines. In the present study, an attempt was made to correlate suction properties with swelling characteristics of expansive soils. Correlations between (a) swell potential and (b) swell pressure versus suction measured at natural moisture content, optimum moisture content and air entry value (AEV) were developed. Results demonstrate that suction measurements are quite useful to predict the swelling characteristics of expansive soils, quickly and easily. � 2015 Taylor & Francis Group, London.
Determination of Swelling Characteristics Using Soil Water Characteristic Curve Parameter
(2016) Tahasildar J.; Rao B.H.
Several studies demonstrate that the swelling characteristics of expansive soils can be determined from suction properties like initial suction, suction measured at optimum water content, and parameters of soil water characteristic curve (SWCC). The present study deals with the determination of swell potential (S) and swell pressure (Sp) from one of the parameters of SWCC, i.e. slope of SWCC (nslope). Swelling parameters S and Sp were measured from swelling experiments and nslope was computed from SWCC. The obtained data when plotted show that nslope varies linearly with S and Sp, validating the McKeen (Proceedings of the 7th international conference on expansive soils, vol 1, Dallas, pp 1�6, 1992) proposed methodology on the expansive soil classification system. Furthermore, results reveal that expansive soils which exhibit greater swell potential and swell pressure also show higher suction potential or vice versa. In addition, efforts were also made to investigate the influence of suction pressure range on nslope. To achieve this, SWCCs established for different suction pressure range have been compiled from the present study as well as from literature and plotted into a single graph. It has been observed that the value of slope of SWCC (a) varies greatly at low suction pressure, especially when it is below 1500�kPa, and (b) found consistent when the suction pressure exceeded this value. � 2016, Indian Geotechnical Society.
Development of relationships between swelling and suction properties of expansive soils
(2018) Tahasildar J.; Erzin Y.; Rao B.H.
In this paper, an attempt is made to correlate swelling properties of expansive soils with their suction properties. To achieve this, both swelling, using a conventional oedometer apparatus, and suction, by dew point potentiameter, WP4, properties were measured on different soils used in the study. With the help of data obtained from experimental investigations, plots were drawn against individual swelling parameters (viz., swelling potential, S, swelling pressure, S p , & free swell index, FSI) vs. suction property like (a) air-entry value, AEV, (b) initial suction, ? i , (defined as suction measured at natural water content that is determined at the time of collection of a soil from the field) and (c) suction measured at optimum water content, ? OMC , in order to develop generalised empirical relationships between swelling and suction properties. It has been observed that AEV and ? OMC exhibits a linear relationship with S and S p , whereas ? i exhibits a tri-linear relationship with S and a linear relationship with S p , respectively. The study finds that AEV and ? i , the former parameter is to estimate S p & FSI, and the latter one is to estimate S of a soil, are the best useful suction parameters to relate them with the swelling properties. Additionally, efforts were also devoted to predicting the swelling properties (viz., swelling potential and swelling pressure) from suction properties by adopting to an artificial neural network (ANN) modelling tool. Overall, the results demonstrate that resorting to suction properties is a quite promising option for predicting the swelling properties of expansive soils. � 2016 Informa UK Limited, trading as Taylor & Francis Group.
A device to study the simultaneous heat and moisture movement in soils
(2016) Rao B.H.
Studies of simultaneous heat and moisture movement in soils are essential to characterise the thermal stability of the medium and to understand the soil water dynamics in the vadose zone. Although, many laboratory, analytical and mathematical models have been developed, small-scale laboratory tests found to be quite useful in understanding the behaviour of model materials and evaluating the influence of various interrelated parameters on heat and moisture movement in the soil mass. This paper presents the usefulness of a simple device (i.e. a thermal probe) that can be employed to study the simultaneous heat and moisture movement in kaolin. The device, which was fabricated in-house, is easy to use, handy and cost effective. It imposes a line-heat source of thermal flux in the soil mass that creates a thermal gradient causing moisture movement to take place from higher to lower temperature regions. It has been noticed that the device is very efficient and quite useful to carry out experiments related to simultaneous heat and moisture movement in soils. Further, attempts were also made to demonstrate the distinct advantage of electrical properties to measure the instantaneous moisture content of kaolin in a non-destructive and non-invasive manner. ICE Publishing: All rights reserved.
Environmental geotechnology: An indian perspective
(2015) Rajesh S.; Rao B.H.; Sreedeep S.; Arnepalli D.N.
Infrastructure development and industrialisation have led to an ever increasing demand for energy and tremendous generation of industrial and municipal solid wastes in India. With indiscriminate human encroachments, the impact of disasters such as rainfall-induced landslides, river/coastal erosion, flash floods and cloud bursts is quite high. In order to minimise the harmful impact of these issues, there needs to be development of sustainable optimal solutions, which are best suited to the regions concerned, employment of new construction materials like geosynthetics and state-of-the-art techniques. As such, in dealing with such problems that have direct bearing on geoenvironment, an interdisciplinary approach needs to be developed, which is the starting point of environmental geotechnology as �applied science to research and resolve�. In view of this, this paper discusses a few key geoenvironmental engineering issues and challenges pertaining to the Indian context.
Establishment of water retention properties of granite saw dust using ultracentrifuge
(2014) Rao B.H.; Kumar S.; Ghosh S.
Granite Saw Dust (GSD) is produced during the process of cutting/sawing of large granite blocks and polishing of granite slabs. It mostly contains finely crushed rock substance that is treated as waste material and disposed off on topsoil, indiscriminately. As a result, it significantly affects the geotechnical and geochemical properties of topsoil. Thus, its existence becomes a cause of environmental concern. Although, GSD can be used as the resource material in construction works, lack of data on its physical, chemical and geotechnical properties becoming an impediment factor for its usage. This paper deals with to the establish Water Retention Curve (WRC) of GSD and locally available sand by employing an ultracentrifuge device. When compared the resultant WRCs of these materials, it has been found that the behaviour of GSD similar to that of sand. Thus, granite saw dust could be used as a replacement for sand, however, in applications where flow properties play a dominant role. In addition, it has also been observed that the rate of capillary rise in GSD is almost ten times lesser than that of conventional sand. � 2014 Taylor & Francis Group.
Influence of aspect ratio on crushing strength characteristics of sand and granite saw dust materials
(2015) Rao B.H.; Meena R.Ch.; Meena N.; Sahu R.L.
Evaluation of crushing strength characteristics of granular materials is essential in order to select these materials for a wide range of engineering applications. However, most of the investigations dealing with such studies have been employing only bulk samples. As such, aspect ratio, among many parameters, is one of the most important parameters influencing the stress-strain behavior of a granular material. In the present study, attempts were made to evaluate crushing strength characteristics of sand and Granite Saw Dust (GSD) materials as a function of aspect ratio. A series of tests were conducted on samples of bulk and various size fractions (i.e. fine and medium) by applying a compressive load of up to 80 kN. Results were critically analyzed to find out the effect of aspect ratio and dominant size fraction on overall mechanical behavior of these materials. The phenomenon of grain crushing was verified by comparing grain-size distribution curves established before and after a sample was subjected to loading. It has been observed that particles of fine size range found to predominantly control the crushing strength characteristics of sand and GSD materials. � 2015 Taylor & Francis Group, London.
A methodology for determining crushing strength of stabilized waste from shear wave velocity
(2014) Rao B.H.; Panda T.
Researchers, in general, resort to crushing strength tests to determine the strength gain by stabilized waste with curing period. However, these tests are not only destructive in nature, but also require testing of several identical samples and sample preparation, which is manually done, is cumbersome. This necessitates the development of an alternate technique that can be employed to measure as well as to monitor the strength gain by stabilized waste with curing period that too in a non-destructive and non-invasive way. Such studies are significantly important for proper characterization, which is a pre-requisite when converting the waste into usable material, and for efficient solid Waste Management. In this direction, application of shear wave velocity that can be correlated with crushing strength seems to be quite promising, and its usefulness to characterize the soil is already well established. With this in mind, an attempt was made in this study to develop a methodology that can be employed to determine the strength gain by stabilized waste by adopting to shear wave velocity measurements. Details of the methodology adopted are presented. It has been observed that strength gain by stabilized waste increases as percentage cement content (PCC) increases. Furthermore, it has been identified that adopting to shear wave velocity measurements are quite useful to decide desired curing period. Also, it has been found that shear wave velocity (Vs) correlates in a well-defined way with crushing strength (?c) of stabilized waste, only, when admixed cement content exceeds 20%. � 2014 W. S. Maney & Son Ltd
Mix design development of fly ash and ground granulated blast furnace slag based geopolymer concrete
(2018) Reddy M.S.; Dinakar P.; Rao B.H.
The paper presents a rational mix design methodology to produce fly ash and ground granulated blast furnace slag (GGBS) based geopolymer concrete under ambient temperature curing condition. Efforts are made to develop the mix design by integrating ACI strength versus water to cement ratio curve of normal concrete, absolute volume method and combined grading concept. The proposed mix design methdology is not only user friendly, but offers also an option to choose between the desired compressive strength and specific alkaline activator content, AAC, to binder solids, BS, ratio or vice-versa. Several samples have been cast and are subjected to experimental investigations in order to produce concrete of required strength and properties. Strength attained by the geopolymer concrete for similar AAC to BS ratio that mimics water to cement ratio of normal concrete has found to be significantly high, in the range from 66 to 32 MPa for AAC to BS ratio from 0.4 to 0.8, respectively. Attempts are also made to propose a modified strength versus AAC to BS ratio curve based on the obtained test results. Finally, the mix design methodology has been depicted in the form of a flow chart, and its usefulness is illustrated with the help of an example. � 2018 Elsevier Ltd
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.
A review of the influence of source material's oxide composition on the compressive strength of geopolymer concrete
(2016) Reddy M.S.; Dinakar P.; Rao B.H.
Off late, geopolymer concrete has gained significant attention in the construction industry because of the benefits that it brings via, by-product waste utilization, reduction in greenhouse gas emission. Studies reveal that the chemical oxide composition of the raw material (viz., fly ash) strongly influences the mechanical behavior and durability properties of geopolymer concrete. However, not many studies have paid attention towards the influence of an oxide percentage in the raw material on the compressive strength of the geopolymer concrete. In this paper, an attempt has been made to study the compressive strength behavior against the percentage of oxides (viz., SiO2, Al2O3, Fe2O3, CaO etc.) present in the raw material which were employed in the production of geopolymer concrete. In this extensive data has been collected from various earlier research publications. Trends for 7 & 28 day compressive strengths against individual oxide component percentages were developed, and it was observed that the strength of geopolymer concrete differs greatly with the variation in percentage of the individual oxide component. Also, each oxide has shown distinct influence on the compressive strength of geopolymer concrete. Further, it has been noticed that the compressive strength of a sample has been predominantly influenced by the percentage of alumina-silicate oxides, and whereas oxides like CaO and Fe2O3 even though lesser in amount compared to alumina-silicate oxides have shown a distinctive effect on the strength built-up. Also, the oxide molar ratios influence on the compressive strengths has been analysed and it was noticed that compared to individual oxide composition its influence is not major on the compressive strength development. Therefore, knowing the typical range of the major oxides percentage required for achieving superior compressive strength will be beneficial in developing concrete mix proportion. � 2016 Elsevier Inc.
Strength and durability characteristic of alkali activated GGBS stabilized red mud as geo-material
(2019) Alam S.; Das S.K.; Rao B.H.
Red mud (bauxite residue) is generated during the Bayer's process of aluminium production in the ratio of one part aluminium to 0.8�1.5 part red mud and is considered as an industrial waste. The storage of unutilised red mud creates a geoenvironmental problem due to its highly alkaline nature (pH > 11) as it contaminates the groundwater as well as surface water. The present paper discusses the strength and durability properties of the stabilized red mud using alkali (Na 2 SiO 3 ) activated ground granulated blast furnace slag (GGBS) and its microstructural property for possible application as a geo-material. One of the major problems associated with the geo-materials is the strength loss and weathering due to the exposure to adverse environment. So, the emphasis has been given to the durability of the stabilized red mud by keeping in mind its various uses in geotechnical construction. The durability studies are performed by considering the effect of wet-dry cycles on compressive strength. In addition, the results of slake durability test and impact strength index are also discussed. The microstructural and chemical investigations are performed using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively, to correlate with the strength and durability characteristics. The chemistry of leachate in terms of heavy toxic metals (Hg, As, Pb, and Cr) as identified by EPA is also studied and it was found that the stabilized red mud is non-toxic. � 2019 Elsevier Ltd