Effect of Fly Ash on the Behavior of Expansive Soils: Microscopic Analysis

Abstract. Transmission electron microscopy (TEM) was employed to obtain morphology, size, composition, and mixing state of background fine particles with diameter less than 1 μm in the Qinghai-Tibetan Plateau (QTP) during 15 September to 15 October 2013. Individual aerosol particles mainly contained secondary inorganic aerosols (SIA-sulfate and nitrate) and organics during clean periods (PM2.5: particles less than 2.5 μg m−3). The presence of KCl-NaCl associated with organics and an increase of soot particles suggest that an intense biomass burning event caused the highest PM2.5 concentrations (> 30 μg m−3) during the study. A large number fraction of the fly ash-containing particles (21.73 %) suggests that coal combustion emissions in the QTP significantly contributed to air pollutants at the median pollution level (PM2.5: 10–30 μg m−3). We concluded that emissions from biomass burning and from coal combustion both constantly contribute to anthropogenic particles in the QTP atmosphere. Based on size distributions of individual particles in different pollution levels, we found that gas condensation on existing particles is an important chemical process for the formation of SIA with organic coating. TEM observations show that refractory aerosols (e.g., soot, fly ash, and visible organic particles) likely adhere to the surface of SIA particles larger than 200 nm due to coagulation. Organic coating and soot on surface of the aged particles likely influence their hygroscopic and optical properties in the QTP, respectively. To our knowledge, this study reports the first microscopic analysis of fine particles in the background QTP air.

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Influence of Fly Ash Fineness on Autoclaved Energy Conservation Block's Performance and Hydration Products

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.599.302 ◽

2014 ◽

Vol 599 ◽

pp. 302-309 ◽

Cited By ~ 5

Author(s):

Bao Guo Ma ◽

Li Xiong Cai ◽

Shou Wei Jian ◽

Lei Su

Keyword(s):

Fly Ash ◽

Microscopic Analysis ◽

Production Performance ◽

Strength Increase ◽

Hydration Products ◽

X Ray Diffraction ◽

Electron Microscopic ◽

Specific Strength ◽

Autoclaved Aerated Concrete ◽

Aerated Concrete

This article discussed the influence of FA fineness on the production performance and usability through the autoclaved aerated concrete slurry gas foaming curve and basic physical properties of blocks; meanwhile, studied the influence of different fineness FA on the composition and morphology of hydration products through X-ray diffraction analysis and scanning electron microscopic analysis, The results show that in the cement-fly ash-lime system autoclaved aerated concrete, the higher fineness of FA, the more water it need, and more sensitive the slurry presents; when the FA residue decrease from 17.8% to 8% through a 0.045mm square hole sieve screen, its specific surface area enlarge from 325m2/Kg to 388m2/Kg, the autoclaved aerated concrete specific strength increase by 53.24% and 40.96% in the case of the same ratio of water and resemble extended degree, respectively. Keep on increasing FA fineness does harm to its specific strength. The crystallinity of tobermorite, which is the main hydration products of autoclaved aerated concrete decreases with the increasing of FA fineness, however, crystallite size become larger.

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Evolution of thermal and mechanical properties of mine tailings and fly ash mixtures during curing period

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0232 ◽

2014 ◽

Vol 51 (5) ◽

pp. 570-582 ◽

Cited By ~ 12

Author(s):

Joon Kyu Lee ◽

Julie Q. Shang

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Fly Ash ◽

Mine Tailings ◽

Mechanical Characteristics ◽

Early Stage ◽

Expansive Soils ◽

Thermal And Mechanical Properties ◽

Curing Period ◽

Compaction Energy

Fly ash is often used as a binder for modifying the properties of geomaterials, such as organic and expansive soils, sludge from water treatment, dredged sediments, mine tailings, etc. Changes in thermal and mechanical properties of compacted mixtures of mine tailings and fly ash are studied over a curing period of 120 h. The study includes the measurement of thermal conductivity, temperature, unconfined compressive strength, and elastic modulus. Effects of the amount of fly ash added to mine tailings, molding water content, and compaction energy on these properties are investigated. Pore-size distribution and surface texture are analyzed to characterize the microstructures of fly ash treated–mine tailings. Relationships between the thermal conductivity and properties that capture packing and mechanical characteristics of mine tailings and fly ash mixtures are established. These observations provide enhanced understanding of thermal, mechanical, and structural properties of fly ash–treated mine tailings, which is associated with the hydration process at the early stage of the mixtures.

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Effect of Fly Ash on Engineering Properties of Expansive Soils

Journal of Geotechnical and Geoenvironmental Engineering ◽

10.1061/(asce)1090-0241(2004)130:7(764) ◽

2004 ◽

Vol 130 (7) ◽

pp. 764-767 ◽

Cited By ~ 178

Author(s):

B. R. Phani Kumar ◽

Radhey S. Sharma

Keyword(s):

Fly Ash ◽

Expansive Soils ◽

Engineering Properties

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Study on Physical-Mechanical Properties and Microstructure of Expansive Soil Stabilized with Fly Ash and Lime

Advances in Civil Engineering ◽

10.1155/2019/4693757 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Sheng-quan Zhou ◽

Da-wei Zhou ◽

Yong-fei Zhang ◽

Wei-jian Wang

Keyword(s):

Mechanical Properties ◽

Fly Ash ◽

Expansive Soils ◽

Expansive Soil ◽

Physical Parameters ◽

Swelling Ratio ◽

Sem Images ◽

Mixture Ratio ◽

Plain Area ◽

Stabilized Soil

Fly ash and lime have been frequently employed to reduce the swelling potential of expansive soils. Laboratory experiments, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used in this study to investigate the stabilizing effect of fly ash and lime on expansive soils in the Jianghuai undulating plain area. The comparison was drawn between the variation laws of physical parameters, mechanical properties, microstructure, and mineral composition of expansive soil before and after being stabilized. Experimental results suggest that, after 5% lime is added based on fly ash, the plasticity index of the expansive soil decreases by 64.9%, the free swelling ratio is reduced to about 10%, the unloading swelling ratio is reduced to nearly 4%, and the stabilized soil no longer exhibits the expansive property. The unconfined compressive and tensile strengths of the stabilized soil increase first and then decrease with the rising in fly ash content. After the addition of 5% lime, both the unconfined compressive and tensile strengths increase significantly. The optimum modifier mixture ratio is obtained as 10% fly ash + 5% lime. The SEM images reveal that the microstructures of the stabilized expansive soil vary from an irregular flake-like and flocculent structures to blocky structures, and the soil samples compactness is enhanced. XRD results indicate that quartz is the main component of the stabilized soil. These are the underlying causes of the rise in the strength. The conclusions of this study can be referenced for the engineering design and construction of expansive soil in Jianghuai undulating plain area.

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Undrained Strength Characteristics of Fibre Reinforced Expansive Soils

Proceedings of International Web Conference in Civil Engineering for a Sustainable Planet ◽

10.21467/proceedings.112.19 ◽

2021 ◽

Author(s):

G. Surya Narayana Kurup ◽

Sona P. S. ◽

Luthfa U ◽

Varsha Manu ◽

Amal Azad Sahib

Keyword(s):

Fly Ash ◽

Expansive Soils ◽

Uttar Pradesh ◽

Strength Characteristics ◽

Fibre Reinforcement ◽

Polypropylene Fibres ◽

Swell Index ◽

Swell Potential ◽

Granular Pile ◽

Deccan Plateau

Expansive soils are those whose volume changes take place while it comes in contact with water. It expands during rainy season due to intake of water and shrinks during summer season. Expansive soils owe their characteristics due to the presence of swelling clay minerals. Expansive soils cover nearly 20% of landmass in India and include almost the entire Deccan plateau, western Madhya Pradesh, parts of Gujarat, Uttar Pradesh, Andhra Pradesh, Karnataka and Maharashtra. The properties that describe the expansive behaviour of soils are free swell index, swell potential and swell pressure. This behaviour has an impounding effect on the bearing capacity and strength of foundation lying on such a soil. Some of the stabilization techniques which are currently being used are physical alternations, sand cushioning, belled piers, under reamed piers, granular pile anchors, chemical stabilization, and fibre reinforcement techniques. This paper focuses on improvement in the strength characteristics of stabilized Chittur soil. The commonly used stabilizer for expansive soils is lime. This paper looks upon alternative materials such as fly ash and polypropylene fibres in order to reduce the lime content. It was concluded from the trials that an optimum combination of 1.5% lime, 10% fly ash and 0.2% polypropylene fibres contribut

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