Geotechnical Properties Of Fly Ash Research Articles

Study on geotechnical performance of high-grade highway subgrade applied with fly ash

The subgrade filling of high-grade highways requires a lot of earth and stone. If the use of fly ash is used for filling, the purpose of reducing the weight of the subgrade and consuming a large amount of industrial solid waste can be achieved. In order to ensure that fly ash has the possibility of filling, it is necessary to systematically study the road geotechnical properties of fly ash. In this paper, the low liquid limit silty silica-alumina fly ash is taken as the research object, and the road geotechnical properties of fly ash are studied through laboratory tests. The results of the compaction test show that the maximum dry density and optimum moisture content have an obvious linear relationship with the increase in the proportion of fly ash. Small, conducive to the stability of the roadbed. The shear strength of fly ash mainly depends on the internal friction angle, which is much larger than that of ordinary clay. The above test conclusions can provide reference for scientific and economical treatment of fly ash subgrade.

Compressibility of Fly Ash and Fly Ash-Bentonite Mixtures

Environmental protection, one of the most important issues nowadays, forces civil engineers to look for alternative solutions to the known ones. The use of substitute materials as an embankment fill or a ground material under the embankment instead of natural soil follows these trends. A great amount of fly ash is disposed of in landfills. It is a cost-effective material that can be used in construction instead of natural soil. The geotechnical properties of fly ash as a construction material in place of soil need to be examined. It includes laboratory tests to determine the chemical composition and geotechnical characteristics. In the present work, one-dimensional consolidation tests have been conducted to examine the compressibility behaviour of compacted fly ash and fly ash-bentonite mixtures used in the earth structures like road embankments. The analysis of the consolidation phenomenon is useful for predicting the magnitude and rate of settlement of the structure. Materials compacted at OMC to their MDD, according to Standard Proctor, were tested in Rowe-Barden type consolidometer on saturated and non-saturated samples. Coefficients of consolidation have been compared between values derived from log-time and square-root-of-time methods and direct hydraulic conductivity tests. Bentonite amount in fly ash-bentonite mixtures influences the vertical deformation of the sample.

Determination of Geotechnical Properties and Stability of Expansive Soil using Fly Ash

This study was conducted to have a detailed analysis of the geotechnical properties of expansive soil and fly ash from Sipat thermal power plant. It reported the findings of laboratory studies on certain common physical and geotechnical properties. The chemical properties and morphology of the black cotton soil (BCS) and fly ash is also determined using scanning electron microscopy and X-ray diffraction test. The geotechnical test includes determining specific gravity, particle size distribution, moisture content, standard proctor test, free swell index, and Atterberg’s limit. The different compositions of expansive soil with fly ash, yellow soil, moorum, and sand are studied. BCS was evaluated with fly ash, fly ash and sand, BCS with yellow soil, and moorum and fly ash. The study also analyzed the details and results of different tests conducted on soil samples. The results showed that strength and fly ash are inversely proportional; as fly ash increases, strength decreases, and vice versa. Fly ash was added from 20 to 80 % by replacing expansive soil by weight. The results indicated that expansive soil can be stabilized by the addition of fly ash to a limit of 10 to 20 %.
 HIGHLIGHTS
 
 The XRD And SEM results shows the mineral present in the FlyAsh and Expansive soil
 The geotechnical properties of Flyash and expansive soil is determined
 The OMC increases with decrease in densities
 The Particle size distribution curve shows the soil is GW soil
 
 GRAPHICAL ABSTRACT

Interaction of biopolymer with dispersive geomaterial and its characterization: An eco-friendly approach for erosion control

Addition of natural polymer or biopolymer is considered as a novel, cost-effective and eco-friendly soil modification approach mainly pertaining to erosion stability. The present study focuses on the interaction of three types of biopolymer i.e., xanthan gum, guar gum and carboxymethyl cellulose to stabilize two dispersive industrial waste materials i.e., fly ash and coal mine overburden soil. The results found that all the three biopolymers enhanced the index and geotechnical properties of fly ash and mine overburden due to their high viscosity, aggregation, adsorption and cross-linking bond formation. However, the rate of enhancement varies with the type and concentration of biopolymer. The biomodified soil were evaluated for erosion stability against wind and water by performing pinhole test, cylindrical dispersion, surface resistance and water retention test. It concluded that a very minimal fraction, 1% of biopolymer solution could mitigate the dispersiveness of the geomaterial. Additionally, the results of microscopic analysis by scanning electron microscope assist to correlate the morphological changes with the engineering properties of biomodified soil due to the interaction of soil with the long-chained biopolymers strings. Finally, leachate and cost analysis of the biopolymer modified material was assessed to evaluate the efficiency of the biomodification.

Geotechnical Characteristics of HNPC Fly Ash

Fly ash is the solid waste being produced in largest quantities from thermal power plants in India causing pollution of land and water. It requires bulk utilization which is possible in geotechnical applications such as embankments and subgrades. This necessitates the determination of the geotechnical properties of fly ash from different thermal power plants. The present paper investigates the geotechnical characteristics of fly ash from HNPC, Pedagantyada, Visakhapatnam. The physical and index properties of HNPC Fly ash (HNFA) and its OMC and MDD using I.S. Heavy compaction are first determined. The shear strength, CBR and permeability are then determined at OMC. The study also investigates the influence of polyester fibers and lime as admixture to HNFA in different percentages on Compaction and CBR properties to check their effectiveness in improving HNFA for use in embankments and subgrade. The chemical and morphological characteristics of HNFA, including its specific surface, XRD, SEM and FT-IR spectra have also been determined. The study confirms the suitability of HNFA for use in geotechnical applications and verifies the relative suitability of polyester and lime as admixtures for further improvement of the geotechnical properties of HNFA.

Physical, chemical, and geotechnical properties of coal fly ash: A global review

In 2015, fly ash utilization rates were 70% for China, 62% for India, and 50% for the US. This leaves substantial potential for increased utilization. This article summarizes available literature concerning physical and chemical and geotechnical properties of fly ash which affect its options for re-use. Fly ashes are broadly classified worldwide into two chemical types for their industrial applications, mostly in cement industries, namely class C and class F. Class C fly ash, with its higher levels of calcium oxide, generally has self-cementing properties. In terms of global fly ash composition, fly ash from India on average contains higher levels of silicon dioxide than that from the US and China. In terms of particle size, studies report that fly ash more often is poorly graded than well-graded; fly ash from India in particular tends to be poorly graded. Optimum moisture content (OMC) values for fly ashes vary from 11 to 53%, and maximum dry density values range from 1.01 to 1.78 g/cm3. Country-specific trends in terms of fly ash OMC and maximum dry density values are not readily apparent. Fly ash tends to be non-plastic, meaning it will not swell if used as a foundation material for structures. Reported fly ash shrinkage limits range from 38 to 65. Permeability of pure fly ash generally varies from 10−4 to 10-7 cm/sec, and angle of friction varies from 25° to 40°.

Fly ash and kaolinite-based geopolymers: processing and assessment of some geotechnical properties

Fly ash is an industrial waste material of the thermal power plants. At present, India produces about 100 million tons of fly ash per annum and most of them are currently dumped in landfills, thus creating a threat to the environment. In recent years, attempts are made to increase the effective utilization of fly ash in the country. This study reveals the morphological, mineralogical, and geotechnical properties of fly ash and fly ash–kaolinite-based geopolymer materials prepared with low-calcium fly ash (ASTM Class F) and kaloinite with activating solution of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) at different curing conditions. Both the fly ash and the fly ash–kaolinite-based geopolymers are prepared in molds, and the unconfined compressive strength (UCS) for each combination is obtained. The UCS of geopolymers at different concentration of alkali, curing temperature, and time is studied. The microstructural and geotechnical characterization of fly ash and geopolymers are obtained using the X-ray diffraction, X-ray fluorescence, and scanning electron microscope (SEM). The low-calcium fly ash and kaolinite-based geopolymers are found to exhibit excellent UCS as compared to that of other geotechnical materials such as clay. It is also observed that fly ash–kaolinite-based geopolymer exhibits more compressive strength than that prepared only with the fly ash. The compressive strength of the geopolymers increases with the concentration of NaOH up to 12 molar beyond which the strength decreases. The compressive strength of geopolymers increases with the improvement of curing condition. Finally, water absorption test is performed to know the water absorption characteristics of the geopolymers.

Performance of Geotechnical Properties of Fly Ash and Quarry dust Mixtures for use in Highway Embankments with Varying

Performance of Geotechnical Properties of Fly Ash and Quarry dust Mixtures for use in Highway Embankments with Varying

Geotechnical Properties of Fly Ash and its Application on Soft Soil Stabilization

Soil stabilization has become the major issue in construction engineering and the researches regarding the effectiveness of using industrial wastes as a stabilizer are rapidly increasing. This paper briefly describes the suitability of the local fly ash to be used in the local construction industry in a way to minimize the amount of waste to be disposed to the environment causing environmental pollution. Several civil engineering laboratory tests are conducted to study the geotechnical properties of fly ash and strength gain when mixed with local clay sample. A different proportion of fly ash and soil sample cured for 7 days results in a strength gain. A better understanding of the properties of fly ash is gained from the study and the tests indicates an improved strength and better properties of soft soil sample when stabilized.

Geotechnical Characterization of Some Indian Fly Ashes

This paper reports the findings of experimental studies with regard to some common engineering properties (e.g., grain size, specific gravity, compaction characteristics, and unconfined compression strength) of both low and high calcium fly ashes, to evaluate their suitability as embankment materials and reclamation fills. In addition, morphology, chemistry, and mineralogy of fly ashes are studied using scanning electron microscope, electron dispersive x-ray analyzer, x-ray diffractometer, and infrared absorption spectroscopy. In high calcium fly ash, mineralogical and chemical differences are observed for particles, >75μm and the particles of <45μm size. The mode and duration of curing significantly affect the strength and stress–strain behavior of fly ashes. The geotechnical properties of fly ash are governed by factors like lime content (CaO), iron content (Fe2O3) and loss on ignition. The distinct difference between self-hardening and pozzolanic reactivity has been emphasized.

Properties of Fly Ash as Hydraulic Barrier

This study examines the suitability of pozzolanic fly ash as a hydraulic barrier and the use of bentonite to enhance geotechnical properties of fly ash. The behavior of fly ash is studied not only with water but also with different pore fluids, such as acid, alkali, salts, and neutral organic fluid to assess its chemical compatibility. While some geotechnical properties of fly ash meet the requirements of liner material, the disadvantage of using of fly ash alone is that it has a low cation exchange capacity and high hydraulic conductivity. The compressibility of fly ash reduces with alkaline solution but increases with acidic solutions. While alkaline or neutral inorganic solutions do not affect the hydraulic conductivity of fly ash, the addition of dilute acid increases the hydraulic conductivity. Addition of bentonite improves the geotechnical properties of fly ash such as cation exchange capacity, shrinkage and volume change behavior, etc. Fly ash-bentonite mixtures possess low shrinkage and hence do not crack. Compacted fly ash-bentonite mixtures undergo very little volume changes under various stress conditions. The hydraulic conductivity of fly ash is reduced after amendment with bentonite. Though the unconfined compressive strength of the mixture is lower than that of fly ash alone, the fly ash-bentonite mixture still possesses good strength. The compressibility of fly ash bentonite mixtures are lower with different pore fluids studied than with water. The hydraulic conductivity of fly ash-bentonite mixtures are slightly higher in different pore fluids studied than with water.

CBR behaviour of fly ash–murrum mixes

The rapid increase in the demand for power has led to the commissioning of large coal-based thermal power stations in India. The present production of fly ash is about 100 million tonnes, but its utilisation is less than 10% for gainful applications. Mass and effective utilisation of fly ash is possible only through geotechnical engineering applications, which is still not yet been fully developed and understood. In the present investigation an attempt has been made to study the geotechnical properties of fly ash–murrum mixes with special reference its use as sub-base and sub-grade material in pavement construction. Keeping this as the main objective of mass and effective utilisation of fly ash, an experimental study was carried out to understand the effect of murrum addition on the California bearing ratio (CBR) of fly ash both for unsoaked and soaked condition. The study indicates that addition of murrum increases the CBR of fly ash significantly. L'augmentation rapide de la consommation électrique en Inde a mené à la construction de grandes centrales thermiques utilisant le charbon. La production de cendre volante est actuellement d'environ 100 millions de tonnes mais son utilisation représente moins de 10% en applications lucratives. Son utilisation massive n'est possible que dans des applications d'ingénierie géotechnique, qui est toujours en cours d'étude. Nous tentons d'étudier les propriétés géotechniques des mélanges cendre volante-murrum en examinant particulièrement son utilisation comme matériau de base et sous-base dans la construction de chaussées. En considérant comme objectif principal l'utilisation de la cendre volante en gros volumes, nous nous sommes livrés à des expériences pour étudier l'effet de l'adjonction de murrum sur le CBR (indice de portance) de la cendre volante, dans des conditions de non-pénétration et de pénétration. L'étude indique que l'adjonction de murrum augmente de manière importante le CBR de la cendre volante.