Organic matter is ubiquitous in the environment and exists in many different forms. Reactions involving organic matter are diverse and many have significant economic and environmental implications. In this research, calorimetric techniques were used to study organic- inorganic reactions in two different systems. The primary objectives were to elucidate potential mechanism(s) by which: (i) natural organic matter (NOM) influences strength development in lime-stabilized soils, and; (ii) plant-derived biochars reacts with cations in aqueous environments. Natural organic matter influenced strength development in lime-stabilized soils through the direct inhibition of the formation of pozzolanic reaction products. The degree of inhibition was dependent mainly on the type of pozzolanic reaction product, and the amount and source of organic matter. The formation of the pozzolanic reaction product, calcium silicate hydrate II (CSH2) was less affected by NOM, than was the formation of CSH1. For a given pozzolanic product, the inhibition increased with NOM content. The effect of organic matter source followed the order fulvic acid> humic acid&gt; lignite. Formation of CSH pozzolanic reaction products decreased by 50-100%, 20-80% and 20-40% in the presence of ?2% fulvic acid, humic acid and lignite, respectively. Cation interactions with plant-derived biochars were complex and depended both on the nature of the cation and biochar surface properties. Reactions involving the alkali cation, K+; occurred via electrostatic ion exchange, on deprotonated functional groups located on the biochar surface and; were exothermic with molar heats of reaction (?Hads) between -3 and -8 kJ mol-1. In contrast, reactions involving the transition metal cation, Cd2+ were endothermic with delta Hads between +10 and +30 kJ mol-1. Reaction mechanism(s) for Cd2+ varied from ion exchange/surface complexation in biochars formed at <350 oC, to an ion exchange/surface complexation/diffusion-controlled mechanism in biochars formed at >/=350 oC. For a given cation, differences in sorption characteristics were attributable to temperature-dependent or plant species dependent variations in the properties of the biochars.

Trimethylamine, (CH3)3N, (TMA), odors are often associated with limed and polymer conditioned sludges. This odor has a fishy smell and can be a nuisance to the community surrounding a wastewater treatment plant or land application site. Several factors are thought to determine the amount of TMA generated from limed biosolids. These are, the presence of cationic polymer, the polymer dose, the time between addition of polymer and lime stabilization, shear imparted on the sludge in the dewatering process and dewatered cake solids concentration. All of these were investigated in this study. The results showed that TMA could be generated from sludge that did not contain polymer but the concentrations were low compared to sludge conditioned with cationic polymer. As the polymer dose increased, the TMA increased. Shear also showed to play an important role for TMA production. In addition to higher shear increasing the polymer demand, shear in itself can increase TMA generation. However, the most important factor in generating TMA was the time between conditioning and liming. If this time was minimized, little TMA was produced, even at high polymer doses. Data also suggests that methanogens play an important role in the breakdown of TMA. / Master of Science

Modification of black cotton soils by chemical admixtures is a common method for stabilizing the swell-shrink tendency of expansive soils. Advantages of chemical stabilization are that they reduce the swell-shrink tendency of the expansive soils and also render the soils less plastic. Among the chemical stabilization methods for expansive soils, lime stabilization is most widely adopted method for improving the swell-shrink characteristics of expansive soils. Lime stabilization of clays in field is achieved by shallow mixing of lime and soil or by deep stabilization technique. Shallow stabilization involves scarifying the soil to the required depth and lime in powder or slurry form is spread and mixed with the soil using a rotovator. The use of lime as deep stabilizer has been mainly restricted to improve the engineering behaviour of soft clays Deep stabilization using lime can be divided in three main groups: lime columns, lime piles and lime slurry injection. Lime columns refer to creation of deep vertical columns of lime stabilized material. Lime piles are usually holes in the ground filled with lime. Lime slurry pressure injection, as the name suggests, involves the introduction of a lime slurry into the ground under pressure. Literature review brings out that lime stabilization of expansive clays in field is mainly performed by mixing of lime and soil up to shallow depths. The use of lime as deep stabilizer has been mainly restricted to improve the engineering behaviour of soft clays. Use of lime in deep stabilization of expansive soils however has not been given due attention. There exists a definite need to examine methods for deep stabilization of expansive soils to prevent the deeper soil layers from causing distress to the structures in response to the seasonal climatic variations. In addition, there exists a need for in-situ soil stabilization using lime in case of distressed structures founded on expansive soil deposits. The physical mixing of lime and soil in shallow stabilization method ensures efficient contact between lime and clay particles of the soil. It however has limitation in terms of application as it is only suited for stabilization of expansive soils to relatively shallow depths. Studies available have not compared the relative efficiency of the lime pile technique and lime-soil mixing method in altering the physico-chemical, index and engineering properties of expansive black cotton soils. To achieve the above objectives laboratory experiments are performed that study: 1. the efficacy of lime piles in stabilizing compacted black cotton soil specimens from Chitradurga District in Karnataka. The efficiency of lime piles in chemically stabilizing the compacted black cotton soil mass was investigated as a function of: a)amount of lime contained in the lime pile b)radial migration of lime from the central lime pile c)migration of lime as a function of soil depth 2. the relative impact of the lime pile technique and lime-soil mixing method in altering the physico-chemical, index and engineering properties of expansive black cotton soil. The organization of this thesis is as follows After the first introductory chapter, a detailed review of literature performed towards highlighting the need to examine stabilization of expansive soils using lime pile technique is brought out in Chapter 2. Chapter 3 presents a detailed experimental programme of the study. 25 mm and 75 mm diameter lime piles were installed in the compacted soil mass to study the influence of amount of lime contained in the lime pile on the soil properties. The amount of quick lime contained in the 25 mm and 75 mm lime piles corresponded to 1 % and 3 % by dry weight of the soil mass respectively. Radial and vertical migration of lime from the central lime pile was examined by sampling soil specimens at different radial distances from the central lime pile and at different depths of soil sample. At a given depth and radial distance, migration of lime was estimated by comparing the exchangeable cation composition, pH and pore salinity of the treated soil with that of the natural (untreated) black cotton soil specimen. Alterations in the soil engineering properties at a given depth and radial distance were evaluated by comparing the index properties, swell potential and unconfined compressive strength of the lime pile treated soil specimen with those of the untreated specimen. To compare the relative efficiency of lime mixing and lime pile technique in altering the swelling behaviour of black cotton soil, batches of black cotton soil specimens were treated with 1 % and 3 % quick lime on dry soil weight basis. The compacted soil-lime mixes were cured at moisture contents of 31-34 % for a period of 10 days. The physico-chemical, index and engineering properties of the 1 % lime mixed specimens are compared with those of the 25 mm lime pile treated specimens. The properties of the 3 % lime mixed soil specimens are compared with those of the 75 mm lime pile treated specimens. Chapter 4 examines the efficacy of lime piles in stabilizing compacted black cotton soil specimens from Chitradurga District in Karnataka. Experimental results showed that controlling the swell potential of deep expansive soil deposits is possible by the lime pile technique. Treatment with lime pile caused migration of dissociated calcium and hydroxyl ions into the surrounding soil mass. In case of 25 mm lime pile, the experimental setup allowed measurement of migration of lime up to three times the lime pile diameter. In case of 75 mm lime pile, the experimental setup allowed measurement of migration of lime up to 1.6 times pile diameter. In both experiments, migration of lime was also uniform through out the soil depth of 280 mm. Migration of calcium and hydroxyl ions increased the pore salinity and pH of the treated soil mass. The increase in pH caused clustering of additional exchangeable calcium ions at the negative clay particle edges. The increased pore salinity and exchangeable calcium ions reduced the diffuse ion layer thickness that in turn suppressed the plasticity index and the swell potential of the compacted expansive soil. The laboratory results hence bring out that lime pile treatment in the field can substantially reduce the swell potential of the soil at least to a radial extent of 2 to 3 times the lime pile diameter. The 75 mm lime pile contained lime content in excess of the initial consumption of lime (ICL) value of the black cotton soil - namely 2.6 %. Laboratory results showed that migration of hydroxyl ions even from the 75 mm pile could not elevate the soil pH to levels required for soil-lime pozzoIonic reactions (pH ≥12). The very low solubility of lime in water (< 1 g/litre) and the impervious nature of the black cotton soil are considered to have impeded efficient interactions between lime and soil in course of treatment of the expansive soil with lime piles. Absence of soil-lime pozzolonic reactions precluded the formation of cementation compounds in the lime pile treated soil specimens. Cementation compounds formed by the soil-lime pozzolonic reactions are responsible for the much higher strengths of lime stabilized soils. Consequently, treatment with 25 mm pile had no impact on the unconfined compressive strength of the black cotton soil. Comparatively, treatment with 75 mm lime pile slightly increased the strength of the treated soil due to increased inter-particle attraction and particle flocculation. Chapter 5 compares the relative efficiency of the lime pile technique and lime-soil mixing method in altering the physico-chemical, index and engineering properties of expansive black cotton soil. Experimental results showed that mixing of soil and lime promote stronger chemical interactions between lime released hydroxyl ions and clay particles than that achieved by diffusion of lime from a central lime pile. The more alkaline pH of the lime mixed soil specimens rendered the clay particle edges more negative. Consequently, more calcium ions were adsorbed at the clay particle edges of the lime mixed soil specimens imparting them higher exchangeable calcium contents than the lime pile treated soil specimens. Also, at 3 % lime addition, the pH of the lime-mixed soil was sufficiently high (in excess of 12) to cause dissolution of silica and alumina from the clay lattice necessary for the formation of cementation compounds. The stronger lime modification reactions plus the lime-soil pozzolonic reactions (applicable for soil treated with lime content greater than ICL value) achieved by the lime mixing technique rendered the expansive soil much less plastic, much less expansive and much stronger than the lime pile treated specimens. The results of the laboratory study hence suggest that if a choice exists in the field between conventional method of spreading-mixing-compacting of soil-lime mixes and treating the ground with lime piles, the former technique should be adopted because of its greater efficacy in stabilizing the expansive soil. Chapter 6 summarizes the findings of the study.

The aim of the present investigation is to improve the geotechnical properties of dispersive soil by reducing their dispersivity after elucidating the important mechanisms controlling the dispersivity of the soils. Dispersive soils have unique properties, which under certain conditions deflocculate and are rapidly eroded and carried away by water flow. These soils are found extensively in the United States, Australia, Greece, India, Latin America, South Africa and Thailand. The mechanism of dispersivity of soils is a subject matter of great interest for geotechnical engineers. In the earlier days clays were considered to be non erosive and highly resistant to water erosion. However, recently it was found that highly erosive clay soils do exist in nature. Apart from clayey soil, dispersivity is also observed in silty soils. The tendency of the clays to disperse or deflocculate depends upon the mineralogy and soil chemistry and also on the dissolved salts in the pore water and the eroding water. Such natural dispersive soils are problematic for geotechnical engineers. They are clayey soils which are highly susceptible to erosion in nature and contain a high percentage of exchangeable sodium ions, (Na+). It is considered that the soil dispersivity is mainly due to the presence of exchangeable sodium present in the structure. When dispersive clay soil is immersed in water, the clay fraction behaves like single-grained particles; that is, the clay particles have a minimum of electrochemical attraction and fail to closely adhere to, or bond with, other soil particles. This implies that the attractive forces are less than the repulsive forces thus leading to deflocculation (in saturated condition).This weakens the aggregates in the soil causing structural collapse. Such erosion may start in a drying crack, settlement crack, hydraulic fracture crack, or other channel of high permeability in a soil mass. Total failure of slopes in natural deposits is initiated by dispersion of clay particles along cracks, fissures and root holes, accelerated by seepage water. For dispersive clay soils to erode, a concentrated leakage channel such as a crack (even a very small crack) must exist through an earth embankment. Erosion of the walls of the channel then occurs along the entire length at the same time. Many slope and earth dam failures have occurred due to the presence of dispersive soils. Unlike erosion in cohesionless soils, erosion in dispersive clay is not a result of seepage through the pores of clay mass. However, the role of type of clay and its Cation exchange capacity in the dispersion of soil is not well understood. Data on the presence, properties, and tests for identification of dispersive clays is scarce. Hence, an attempt is made, in this thesis, to develop reliable methods to identify these soils and understand the extent of their dispersivity as well as to develop methods to control their dispersivity. The present study deals with the characterization of a local dispersive soil collected from southern part of Karnataka State. This study has focused on comprehensive tests to assess the dispersivity of the soils by different methods and to methods to improve geotechnical properties by reducing the dispersivity of the soil. An attempt is made to reduce the dispersivity of soil by using calcium based stabilizers such as lime, cement and fly ash. The mechanism of improvement in reducing the dispersivity of the soil with calcium based stabilizers has been studied. One of the important mechanism by which the dispersivity of the soil is reduced is by inducing cementation of soil particles. The differences in effectiveness of different additives are due to their differences in abilities to produce cementitious compounds. Although all the additives increased the strength of the soil and reduced the dispersivity of the soil, cement was found to significantly reduce the dispersivity of the soil, compared to the other two additives lime and fly ash. Cement is more effective as sufficient cementitious compounds are produced on hydration without depending on their formation. A detailed review of literature on all aspects connected with the present study is given in Chapter 2. A comprehensive description of dispersive soils present worldwide has been brought out in this section. Based on this survey, the scope of the present investigation has been elaborated at the end of the chapter. To understand the reasons for dispersivity of the soil and to estimate its degree of dispersivity, it is essential to assess standard methods to characterize the soil. Chapter 3 presents a summary of material properties and testing programs. The results of geotechnical characterization of the soil, the index properties of the soilspecific gravity, sieve analysis, Atterberg’s limits are discussed in Chapter 4. The physico chemical characteristics play an important role in determining the amount of dispersivity of the soil. Dispersive soils have two main characteristics which define its dispersivity chemically. These are Sodium Adsorption Ratio (S.A.R) and Exchangeable Sodium Percentage (E.S.P). The two characteristics are determined from the Cation exchange capacity of the soil. Exchangeable Sodium Percentage is defined as the concentration of sodium ions present in the soil with respect to the Cat ion exchange capacity of the soil. And Sodium Adsorption Ratio is used to quantify the free salts present in the pore water. Since Atterberg’s limits and grain size analysis do not help in identifying dispersive soils or in quantifying its dispersivity, two other tests- Emerson Crumb test and double hydrometer test were carried out on the soil. Emerson crumb test is a simple way for identification of dispersive soils. In this test, a crumb of soil measuring about 1mm diameter is immersed in a beaker containing distilled water and the subsequent reaction is observed for 5 minutes. It is solely based on direct qualitative observations. Depending on the degree of turbidity of the cloud formed in the beaker, the soil is classified in one of the four levels of dispersion in accordance with ASTM-D6572. Since this test is mainly a qualitative test and does not help in quantifying the dispersivity, it cannot be depended upon completely in identifying a dispersive soil. Another test double hydrometer test, which helps in quantifying the dispersivity of the soil, was also conducted on the soil. This test involves in conducting the particle size distribution using the standard hydrometer test in which the soil specimen was dispersed in distilled water with a chemical dispersant. A parallel hydrometer test was conducted on another soil specimen, but without a chemical dispersant. The dispersing agent used for the experiment was sodium hexametaphosphate. The percent dispersion is the ratio of the dry mass of particles smaller than 0.005 mm diameter of the test without dispersing agent to the test with dispersing agent expressed as a percentage. The double hydrometer test was carried out according to Double Hydrometer Test (ASTM D4221). Apart from the conventional tests, attempts are made to consider shrinkage limit test and unconfined compression test to determine the dispersivity of the soil. For this purpose, the shrinkage limit of the soil was determined with and without dispersing agent. The initial shrinkage limit of the untreated soil reduced on treating it with dispersing agent, thus indicating that the soil had further dispersed on addition of dispersing agent. In order to carry out the unconfined compression strength, the maximum dry density and optimum moisture content was determined through the compaction test. The soil was then treated with dispersing agent and compacted at the optimum moisture content. The soil exhibited high degree of dispersion through the strength test. Hence it is necessary to stabilize the soil with additives. Detailed experimental program has been drawn to find methods to improve the geotechnical properties and to reduce the dispersivity of the soil. Chapter 5 presents the investigations carried out on the dispersive soil with lime. The importance of lime stabilization and the mechanism of lime stabilization have been discussed initially. Commercially obtained hydrated lime was used in the present study. The soil was treated with three different percentages of lime 3, 5 and 8. The curing period was varied from one day to twenty eight days. The effect of addition of lime on various properties of the soil such as pH, Atterberg’s limits, compaction test and unconfined compression test is elaborated in chapter 5. The pH of the soil was maximum on addition of 3% lime. On further addition, the pH decreased and remained constant. The liquid limit of the soil increased on adding 3% lime and decreased with further lime content. The compaction test conducted on the soil showed an increase in maximum dry density of the soil and reduction in optimum moisture content with 3% lime content. On further increase in the lime content, the soil showed a decrease in the maximum dry density and increase in optimum moisture content. The unconfined compressive strength of the soil also increased on increasing lime content upto 5%. The variation in strength of the soil with respect to curing period was also compared. Optimum lime content arrived at based on the above conducted tests was 3%. The effect of lime in reducing the dispersivity of the soil through shrinkage limit test and unconfined compression test is also presented in this chapter. Details of the efforts made on the soil with fly ash are presented in Chapter 6.The fly ash used for stabilization of Suddha soil was of Class F type. This type of fly ash contains low reactive silica and lime. The effect of varying fly ash content on the properties of Suddha soil by varying the percentage of fly ash from 3 to 10 percentages is discussed in this chapter. The tests conducted on fly ash treated Suddha soil were pH test, compaction test, Atterberg’s limits and unconfined compression test with varying curing period. The fly ash treated Suddha soil was cured from one day to twenty eight days for the unconfined compressive strength analysis. The pH of the soil system increased with increasing percentage of fly ash. The increase in liquid limit was marginal on addition of fly ash. The maximum dry density of fly ash treated Suddha soil decreased continuously and the optimum moisture content of the treated soil increased with increasing fly ash content. The unconfined compressive strength of Suddha soil increased with increase in fly ash content upto 8% and then decreased for fly ash content of 10%. For all the percentages of fly ash added, the strength of the soil increased with increase in the curing period. The effect of fly ash in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. It was seen that on increasing the fly ash content, the soil treated with dispersing agent showed an increase in the shrinkage limit. Also, the same trend was observed for the unconfined compression strength to determine dispersivity. Optimum fly ash was determined as 8% with the help of all the tests conducted on the soil. Since the improvement in the properties of the soil with lime and fly ash was not very high, Cement was also considered as another additive used for stabilization of Suddha soil. It is known that soil with lesser amount of clay content will respond well with cement. The effect of cement addition on various properties of Suddha soil has been brought out in Chapter 7. It was found that addition of cement had positive effects on all the properties of Suddha soil. The pH of the soil increased for all the percentages of cement addition. The liquid limit of the soil increased on increasing the cement content. The shrinkage limit also showed a similar trend. The optimum moisture content of the soil decreased on increasing the cement content for Suddha soil and the maximum dry density increased for cement treated Suddha soil. The soil showed the maximum dry density at 8% cement content. The unconfined compression strength conducted on cement treated Suddha soil increased significantly for higher cement contents and also with curing period. Suddha soil when treated with 8% cement content exhibited maximum strength in comparison to other percentages. Also, the effect of cement in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. The shrinkage limit of the soil increased for all percentages of cement content, even in the presence of dispersing agent. Through the unconfined compression strength for dispersivity, it could be seen that 8% cement treated Suddha soil had the least dispersion. Optimum cement content was derived as 8% with the help of the tests conducted on the soil. A comparison of effect of all the additives on the strength of the soil as well as effect of the additives in reducing the dispersivity of the soil is discussed in Chapter 8. The effect of additives on the shrinkage limit of the soil with and without dispersing agent has been compared. The variation in shrinkage limit of the soil when treated with the additives was due to the different mechanisms involved in reducing the dispersivity by each additive. The effect on the unconfined compression strength of the soil treated with the additives with and without dispersing agent is also brought out in this chapter. It was noted that the dispersion exhibited through shrinkage limit test was lesser as compared to the percentage dispersivity exhibited through unconfined compression test. Hence it could be said that dispersion of the soil is due to loss of cohesion than volume change behavior. Also, the unconfined compression strength of the soils with respect to curing period is compared. The percentage dispersivity calculated through these tests is summarized and compared. With the help of this it could be said that to control the dispersivity of the soil, it is necessary to enhance the strength of the soil. The general summary and major conclusions drawn from the thesis are presented in Chapter 9.

This thesis focuses on the calculation of costs arising from the shallow foundations using different ways of stabilizing the foundation soil. At the same time also assesses the impact of a method based on the total construction cost and compares the differences in the calculated price. On a specific contract, this work tries to show all the pros and cons of both types of foundations. Assigned values and findings are particularly important for potential investors who are dealing with the amount of their future costs to order a return on that investment. The work shows differences in competitive tendering prices, prices calculated using BUILDpowerS, the amount of the grant awarded and consequently the difference in price determined in accordance with the existing legislation, which will have a contract after its completion and the price calculated.

No description available.

No description available.

Hazardous waste substances are solid, semi-solid or non-aqueous liquids that exhibit characteristics of corrosivity, reactivity, ignitability, toxicity and infectious property. Major available options for management of hazardous waste include direct disposal into landfill or chemical treatment/stabilization of wastes prior to landfill disposal. Hazardous wastes are accepted for direct disposal in engineered landfills if they conform to the chemical concentration limit criterion (determined by water leach test followed by estimation of the concentration of the contaminant) and compressive strength (the material should have compressive strength > 50 kPa) criterion. Lead is classified as extremely toxic metal. Elevated levels of lead in water (surface and ground water) primarily arise from industrial discharges, and aerial deposition. During its residence in surface water bodies, the lead may interact detrimentally with aquatic life or be abstracted into public water supplies. According to National drinking water standards, the permissible limit of lead in drinking water is 0.05 mg/l. Deposition of air-borne lead, disposal of sewage sludge on land and disposal of industrial effluents on lands are major sources of lead contamination of soils. When incorporated in soil, lead is of very low mobility. Lead retained in soils can be slowly leached to the groundwater thereby impacting human health if consumed for potable needs. Alternatively lead deposited in soils can be absorbed by vegetation (crops/trees) and can impact human health on their consumption. Given the negative impacts of lead contamination on human health, the strong affinity of soils to retain deposited lead and the possible release for human consumption, this thesis focuses on characterization and chemical stabilization of artificially lead contaminated soils in the context of their disposal in hazardous waste landfills. The main objectives of the thesis are: characterize artificially lead contaminated soils for water leachability of lead and undrained strength characteristics as per CPCB (Central Pollution Control Board) guidelines in the context of disposal criteria in hazardous waste landfills. Artificially lead contaminated soils in compacted and slurry states are used in the thesis. Red soil (from Bangalore District, Karnataka) and river sand are used in the preparation of compacted and slurry specimens. The red soil and red soil-sand specimens are artificially contaminated in the laboratory by employing aqueous lead salt solutions as remolding fluids. Lead concentrations of 160 to 10000 mg/l are used in this study. The results of characterization studies with artificially lead contaminated soils help identify contaminated soil materials that require chemical stabilization prior to disposal into engineered landfills. Based on the results of characterization studies with artificially lead contaminated soils, lime stabilization coupled with steam curing technique is resorted to immobilize lead in the red soil-sand slurry specimens and mobilize adequate undrained strength to meet the criteria for disposal of lead contaminated soils in hazardous landfills. After this first introductory chapter, a detailed review of literature is performed towards highlighting the need to undertake chemical stabilization of artificially lead contaminated soils in Chapter 2. Chapter 3 presents a detailed experimental program of the study. Chapter 4 presents the physico-chemical and mechanical characterization of the artificially lead contaminated soils. The ability of artificially contaminated soils to release (artificially added) lead during water leaching is explained using lead speciation results performed using the Visual MINTEQ program. Experimental results illustrated that contamination of compacted red soil and red soil + sand specimens with significant lead concentrations (21 to 1300 mg/kg) resulted in major fractions of the added lead being retained in the precipitated state. Results of water leach tests revealed that lead concentrations released in the water leachates are far less than (0.0011 to 0.48 mg/l) limits prescribed by CPCB (2 mg/l) for direct disposal of lead contaminated materials into hazardous waste landfills. Unconfined compressive strengths developed by the lead contaminated red soil and red soil-sand specimens were significantly higher (100-2700 kPa) than the strength requirement (> 50 kPa) for direct disposal of hazardous wastes in engineered landfills. Lead contamination did not affect the unconfined compression strengths of the specimens as matric suction prevalent in the unsaturated compacted soils had an overriding influence on the cementation bond strength created by the lead precipitates. Visual Minteq tool was helpful in predicting the amount of added lead that was converted to insoluble precipitate form. However the amounts of water leachable lead determined experimentally and predicted by Visual Minteq were very different-Visual Minteq predicted much higher amounts of water leachable lead than experimentally determined. Experimental results revealed that the levels of lead released by the red soil-sand slurries in water leach tests were in excess (13 to 36 mg/l) of the permissible lead concentration (2 mg/l) for direct disposal of hazardous waste in landfills. Owing to water contents generally being in excess of their liquid limit water contents (w/wL ratio > 1) the slurry specimens exhibited undrained strengths below 1 kPa. Lime stabilization and steam curing of the contaminated slurry specimens was therefore resorted to control the leachibility of lead and increase undrained strengths to acceptable limits. Chapter 5 deals with lime stabilization of artificially contaminated slurries that do not meet the leachate quality (lead concentration in water < 2 mg/l) or compressive strength (> 50 kPa). Procedures are evolved for lime stabilization of such artificially contaminated soils to meet both the water leachate quality and compressive strength criteria. Lime stabilization together with steam curing of the lead contaminated slurry specimens effectively immobilized the added lead (2500 mg/kg) and imparted adequate compressive strengths to the contaminated red soil-sand slurry specimens. The lime stabilized contaminated specimens released marginal lead concentrations (0.03 to 0.45 mg/l) in the water leach; these values are much lower than permissible limit (2 mg/l) for disposal in hazardous landfills or values exhibited by the unstabilized specimens (13 to 38 mg/l). Lime addition rendered the contaminated specimens strongly alkaline (pH values ranged between 10.68 and 11.66). Combination of the experimental and Visual Minteq results suggested that precipitation of lead as hydrocerrusite in the alkaline environments (pH 10.68 to 11.95) is not the sole factor for marginal release of lead in water leach tests of the 4, 7 and 10 % lime stabilized contaminated specimens. It is possible that fraction of lead ions are entrapped within the cemented soil matrix. Water leach tests performed at range of pH values (pH 2.5 to 9.6) with 7 % lime stabilized specimens suggested that immobilization of lead as hydrocerrusite or as entrapment in the cemented soil mass in the lime stabilized specimens is practically irreversible even on exposure to extreme pH conditions. The lime stabilized contaminated specimens developed unconfined compressive strengths ranging from 100 kPa (4 % lime stabilized 40 % red soil-60 % sand specimen) to 1000 kPa (10 % lime stabilized 100 % red soil specimen). The significant growth of compressive strength upon lime stabilization is attributed to growth of inter-particle cementation bonds by the CAH (calcium aluminate hydrate) and CSH (calcium silicate hydrate) compounds formed by lime-clay reactions, slight reduction in void ratios and growth of strong inter-particle cementation bonds the during steam curing at 800C. The results of this thesis bring out a procedure to immobilize high concentrations of lead and develop adequate compressive strength of lead contaminated slurry specimens by lime stabilization + steam curing technique. The red soil acted as pozzolana in reactions with lime, while, steam curing accelerated the lime-soil reactions. The procedure can be extended to non-organic slurry wastes that are devoid of pozzolanic material (example, lead contaminated smelting sands). In slurry wastes devoid of pozzolana, materials such as fly ash can be added and the reactions between lime and fly ash would immobilize lead + develop adequate compressive strength. Also, similar to the methodology being adaptable for any non-organic slurries, it can also be extended to other toxic metal bearing wastes, example, zinc, cadmium and nickel.