Induced swelling of kaolinitic soil in alkali solution

Unexpected swelling induced in foundation soils can cause distress to structures founded on them. In this paper, the swelling of kaolinitic soils due to interaction with alkali solution has been reported. The induced swelling is attributed to the formation of new minerals, which has been confirmed by X-ray diffraction patters and SEM studies. To understand the effect of alkali concentration and duration of interaction, two series of consolidation experiments have been carried out. In series 1, the specimen were remoulded with water and inundated with alkali solutions and in series 2, the specimen were remoulded and inundated with same alkali solutions. A steep compression during loading cycle and no abnormal swelling during unloading cycle has been noticed for the specimen remoulded with water and inundated with 1 N NaOH solutions. The steep compression is due to the segregation or break down of clay minerals due to alkali interactions. In case of specimen inundated with 4 N NaOH solutions, abnormal swelling has been observed during unloading cycle of the consolidation test. New minerals are formed on interaction of soil with 4 N solution as confirmed by X-ray diffraction patterns. These minerals are known to have very fine pores and possess high water holding capacity. The differences in the amount of swelling of samples remoulded with water and remoulded with alkali solution are due to variations in the concentration of alkali and duration of interaction

Chemical Compatibility of Lime Stabilized Indian Red Earth as Liner Material

Geotechnical liners are widely used to contain leachate generated within landfills and minimize the risk of sub-surface and underground water contamination. In this study, an attempt has been made to utilize locally available soil red earth as liner material. The collected red earth contains mostly quartz and kaolinitic minerals. Studies have shown that bentonite content higher than 20% by weight is not usually required. This study aims to assess the red earth with 20% by weight of bentonite as liner material. Further the studies are being carried out to improve the amended material by stabilizing the mixture with 1% by weight of lime. The relative merits of the Ne materials under different physico-chemical environments are studied. The assessment of the liner material is based on their basic and geotechnical properties. The studies reveal that the geotechnical properties of red earth with 20% by weight bentonite stabilized with 1% by weight of lime enhanced,particularly after curing for sufficient period. The pore fluids suchas HCl and $CCl_{4}$ increased volume change. The hydraulic conductivity of soils, which increased on treating with lime initially, decreased withcuring. However, the hydraulic conductivity, of stabilized soilincreased in the presence of HCl and $CCl_{4}$. The strength of stabilized soil is affected with the fluids NaCl and HCl solutions

Geotechnical properties of cement treated illite as hydraulic barrier

Bentonite is widely used for construction of hydraulic barrier in water and waste containment facilities because of its high adsorption capacity and low hydraulic cond. Performance of bentonite is questionable under varied phys. and chem. environment. Illite is one of the, common minerals present in many soils and hence it is important to improve its behavior as liner material. Studies have shown that illite alone is marginally suitable for use as liner material. The properties of illite are influenced by the nature of pore fluid. To improve the properties of illite and reduce the sensitivity of illite to pore fluid characteristics, it has been proposed to stabilize illite with 1% by wt. of cement. In this work the geotech. properties of cement stabilized illite are studied and evaluated from the consideration of liner or as hydraulic barrier requirements. Results have shown that there is a considerable improvement in the geotech. properties of illite on treatment with cement. The liq. limit, plasticity index, shrinkage properties and strength of cement treated illite are improved and also shown increase in optimum moisture content and reduced dry d. with curing period. The properties of cement treated illite are better suited as hydraulic barrier or liner than that of illite alone

2,6-Lutidine-N-oxide complexes of rare-earth bromides

2,6-Lutidine-N-oxide (LNO) complexes of rare-earth bromides of the composition $$MBr_3 .(LNO)_{4_{ - n} } .nH_2 O$$ wheren = l for M = La, Pr, Nd, Sm, Gd, Ho, Er; andn = 0 for M = Y have been prepared and characterised by analyses, conductance and infrared data. Infrared spectra of the complexes indicate that the coordination of ligand to the metal ion takes place through the oxygen of the ligand, and the water molecule in the complexes present is coordinated to the metal. A coordination number of seven has been suggested to all the rare-earth metal ions

4-Picoline-N-oxide complexes of rare-earth bromides

In continuation of our work on the effect of the anion on the coordination chemistry of the rare-earth metal ions, we have now extended our studies to 4-picoline-N-oxide (4-Pie NO) complexes of rare-earth bromides. By ohangi~ the method of preparation Harrison and Watsom (1) have prepared two types of Sm(IIl) complexes and three types of Eu(III) complexes of 4-pioollne-N-Oxide in the presence of perchlorate ions. We have isolated two types of pyridine-N-Oxide complexes of rare-earth bromides, also by changing the method of preparation (2). The effect of the change of the preparative method on the composition of the lanthanide complexes is exhibited in the case of other complexes also (3-6). But our attempts to prepare 4-picoline-N-Oxide of rare-earth bromides having different stoichiometries were unsucessful . The composition of the complexes is the same for all the complexes prepared. The results of the physico-chemical studies on these 4-Pic NO complexes of rare-earth bromides are discussed in the present paper

Consolidation Behavior of Bentonite in Electrolyte Solutions

Volume change behavior of clays in different pore fluids is very important in their use as compacted clay liners for landfills. The present study brings out the variations in the consolidation behavior of bentonite compacted at Proctor’s optimum conditions in different electrolyte solutions. Qualitatively the behavior can be explained using diffuse double layer theory. Existing methods to calculate theoretically e-log p curves based on this theory have been referred to the theoretical curves that agree closely with experimental curves. Clay properties, which are critical in the theoretical prediction of the curves, have been identified. However, the effect of potassium ions, which link bentonite clay particles, cannot be assessed by diffuse double layer theory

Gypsum-Induced Volume Change Behavior of Stabilized Expansive Soil With Fly Ash-Lime

An attempt was made to study the efficiency of fly ash and lime on the volume change behavior of soil to mask the effect of gypsum. Swell and compressibility of soil mixed with 10 % fly ash and treated with various lime contents (0 %-6 %) in the absence and presence of 1 % gypsum after curing for different periods of up to 28 days were studied. It was established that an increase in lime content improved swell and compressibility in the soilfly ash mix but that it led to rapid swelling and increased compressibility in the presence of gypsum, particularly when the specimens were not cured. Higher amounts of lime and a longer curing period were found to be essential to conquer the adverse effect of gypsum. The behavioral changes in the swell and compressibility of both specimens, with and without gypsum, were attributed to consequent alterations in the microstructure by the formation of cementitious products and the growth of ettringite crystal. It was observed that the formation of cementitious compounds with a curing period enables to the compound to overcome the adverse effect of ettringite, leading to control of undesirable volume change behavior

Reliability of illite as a liner material under chemical environment

Landfills are increasingly used to dispose of all types of waste. Leachate generated by precipitation and other liquids within the refuse is free to flow from unlined landfills into surface water and groundwater, potentially polluting drinking water aquifers. Even though clay liners have many limitations, they are still used since they are natural, relatively inert, and generally available; moreover, they are inexpensive, have large attenuation capacity, and resist damage and puncture. A major problem with clay liners is that chem. wastes or leachate may destroy them. This work analyzed illite properties in relation to its use as liner material. The effect of 0.5 normal HCl, NaCl, and NaOH solutions, water, and CCl4 on geotechnical properties of illite was assessed. Results showed illite marginally meets the requirements of liner material; hence, illite alone is not suitable for liner application. The susceptibility of illite liners from changes in effective stress and physicochemistry environments is low. Its sp. surface area and cation exchange capacity are low, making it less desirable for liner application

Effect of zeolitization on the volume-change behaviour of kaolinitic soils

An attempt has been made to study the effect of zeolite formation on the volume-change behaviour of kaolinitic soil. This is studied in terms of two criteria, namely concentration and period of interaction. Conventional consolidation tests have been carried out to determine the extent of change in swell and compressibility of kaolinitic soils remoulded with water and inundated with an alkali solution. It was observed that abnormal swell occurs during unloading when specimens were inundated with a 4N alkali solution. While allowing a longer interaction period at 6.25 kPa, it was found that swelling in kaolinitic soils is induced after time lags of 30 and 15 days on inundation with 1N and 4N alkali solutions, respectively. Equilibrium is reached after 50–70 days in kaolinitic soils, however, and loading was undertaken later. A 16% swelling was observed in kaolinitic soils when inundated with a 4N alkali solution, indicating that zeolitization of kaolinite results in swelling at the seating load provided the period of interaction is sufficient. X-ray diffraction studies confirm the formation of zeolite