• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1075-1082
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• 2008

Recently, coal ashes which are increasing annually are buried in ash ponds as industrial wastes. However, buried coal ashes can pollute ground water and ground due to leachate from coal ashes, which are serious environmental problem. Even though a lot of researches on recycling of coal ashes have been conducted, only 15% of coal ashes are recycled up to now. And those recycled coal ashes are not bottom ashes but fly ashes. So in this study, it was proved that Bottom Ash can be used as an alternative material to O.P.C(Ordinary Portland Cement) according to laboratory test results and test field construction. Also bottom ash is more economical and environmentally friendly than O.P.C.

• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.5-12
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• 2009

This study presents static and dynamic strength of coal ashes collected from disposal site of power plant. Main compositions of coal ashes were bottom ashes. In order to evaluate static and dynamic characteristics of coal ash, NGI direct-simple shear tests, cyclic simple shear tests and direct shear tests were conducted. The strengths of coal ashes from those tests were compared to those of sands. Bottom ashes among coal ashes used for this study were classified as sand from the grain size distribution and show higher strength properties than the sands. For utilization of coal ashes in civil engineering project, mixing coal ashes with sandy soil using batch plant is inconvenient and the cost is higher than the spreading sand layer and coal layer alternately. In order to simulate both mixing type and layered type construction, sands and coal ashes were mixed with volume ratio 50:50 and prepared sand and coal ash layers alternately with the same volume ratio. From the tests mixed coal ashes-specimen shows slightly higher static and cyclic strength than the layered specimen at the same density. The higher strength seems due to the angular grain of bottom ashes. The cyclic stress ratio at liquefaction decreases rapidly as the number of cycle increases at mixed specimen than that of layered specimen.

• Journal of Soil and Groundwater Environment
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• v.18 no.7
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• pp.32-40
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• 2013

This study was objected to evaluate the potential impact on the groundwater environment of the coal bottom ash used as fill materials on the land surface. From four coal-fired power plants, bottom-ashes were collected and analyzed through sequential extraction and column leaching tests following the meteoric water mobility procedure. The column tests shown leaching heavy metals including Pb, As, B, Cu, Zn, Mn, Ni, Ba, Sr, Sb, V, Cr, Mo, and Hg. The relatively high concentrations of B, Sr, Ba, and V in leachate were attributed to both the higher concentrations in the bottom ash and the relatively higher portion of leachable state, sorbed state, of metals. Bottom-ash samples from the D-plant only show high leaching potential of sulfate ($SO_4$), probably originated from the coal-combustion process, called the Fluidized Bed Combustion. Consequently, to manage recycling bottom ashes as fill materials, an evaluation system should be implemented to test the leaching potentials of metals from the ashes considering the absolute amount of metals and their state of existence in ashes, and the coal-combustion process.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.4
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• pp.299-308
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• 2000

This study analyzed solid wastes generated from a school. The emission potential of hazardous pollutants generated from incineration of the school solid wastes (SSWs) was analyzed. Components of the SSWs were identified and the SSWs were classified into combustible and non-combustible wasts. The combustible wastes consisted of papers of 56.5^ plastics of 30.2% woods of 7.1% and fibers of 6.1% based on weight of the wastes. The moisture content and the ash content of the combustible wastes were 18~20% and 11~13% respectively. The combustible wastes of the SSWs were incinerated by using a small-scale incinerator. Fly and bottom ashes and volatile organic compounds (VOCs) were collected from the incineration. Also the metal leaching experiments on the fly and bottom ashes were performed, In analysis of metals leached from the ashes the total amounts of metals leached in the acid solution (pH=3) were much greater than those in the neutral solution (pH=5.8~6.2) For the same amounts of the fly and bottom ashes the total amounts of metals leached from the fly ashes were much greater than those from the bottom ashes. The VOCs produced from incineration of the SSWs consisted of aromatics of 42.1% aliphatic alkenes of 26.3% oxidized forms of 17.3% and aliphatic alkanes of 14.3% In addition the considerable amounts of hazardous air pollutants (e.g benzene chloro-benzene and chloro-alkanes) and compounds (e. g, aliphatic alkenes) with high potential of ozone or photochemical smog formation were identified from the incineration experiment of the SSWs.

• Journal of the Korean Society of Combustion
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• v.8 no.1
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• pp.1-8
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• 2003

The behavior and characteristics of heavy metals at different streams in a MSWI(Municipal Solid Waste Incinerator) with a capacity of 100tonnes/day were investigated by measuring the concentration of heavy metals and gases and analyzing their leaching data from ashes. Metal components of Cr, Cu, Cd and Pb were in higher concentrations in the fly ashes collected after the water spray tower than in the bottom ashes. It was due to condensation by a lower temperature with water spray cooling. Metal contents in the bottom ash became higher for finer particles as expected. The mass balance of heavy metals in different stream was estimated from the analyzed data in bottom ash and collected dusts at different locations. For the lower volatility of metals such as Pb, Cu, Cr, 88-97% of them remained in the bottom ash, while Cd and Hg escaped from the combustor with remaining in bottom ash of 18.4 and 0.8%, respectively. In most cases the leaching rate of fly ash showed higher values than that of bottom ash, with the their average acidities of 9.8 and 11.9 respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.133-137
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• 2007

Ecological lightweight aggregates were made in order to recycle the dredged soils from the seaside construction area and the bottom ashes from the power plant. Various physical and chemical analysis were performed on them to identify their possibility for applying lightweight concrete fields. Lightweight aggregates were made of bottom ashes and dredged soils from Yongheung Island which is located 20km west away from Seoul, and all the raw materials were milled before mixing. The physical and chemical properties such as density, absorption rate, stability, alkali latency reaction, heavy metal leaching of the lightweight aggregates were tested and analysed by following the KS standard procedures. From the size analysis, the coarse aggregates showed a suitable fit on standard particle ranges; however, the fine aggregates showed a large deviation from the standard. The absorption rates were increased with decreasing weight of the aggregates. All the aggregates were turned out to be safe by the stability and heavy metal leaching test; however, some of the aggregates were confirmed on the border of harmless and possibly harmful region through the alkali latency reactivity test.

• Asian Journal of Atmospheric Environment
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• v.4 no.2
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• pp.80-88
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• 2010

In order to offer a better understanding of air pollution of China as well as East Asia we attempted to characterize the chemical properties of the raw coal materials mined in China and their combusted bottom ashes generated from coal fired power plant. To this end, we measured the chemical characteristics of individual bottom ashes and feed coal fragments collected at a coal fired power generator which was operated with the raw coal dug at a coal mine in China. The chemical properties of these two sample types were determined by a synchrotron radiation X-ray fluorescence (SR-XRF) microprobe method. Through an application of such technique, it was possible to draw the 2D elemental maps in and/or on raw coal fragments and fired bottom ashes. The pulverized fine pieces of feed coal mainly consisted of mineral components such as Fe, Ca, Ti, Ca, and Si, while Fe was detected as overwhelming majority. The elemental mass of combusted bottom ash shows strong enrichment of many elements that exist naturally in coal. There were significant variations in chemical properties of ash-to-ash and fragment-to-fragment. Although we were not able to clearly distinguish As and Pb peaks because of the folding in their X-ray energies, these two elements can be used as tracers of coal fire origin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.177-186
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• 1992

In this study, the proper mixing ratio of fly ash to bottom ash is evaluated and bearing capacity of this mixed ash is examined for use of highway embankment and subgrade materials in large quantities. Independently of the mixing ratio of fly ash to bottom ash or the method of compaction test, maximum dry density ${\gamma}_{dmax}$ and CBR value of anthracite mixed coal ash is greater than that of bituminous mixed coal ash. The mixed ashes to contain more fly ash than that of which the ratio of fly ash to bottom ash is 8 : 2, are slaked readily when the water contents of compaction are greater than optimum moisture content O.M.C. The proper mixing ratios of fly ash to bottom ash are about 5 : 5 to 6 : 4. Coal ashes mixed with these ratios exhibit proper physical and geotechnical properties for use of highway embankment and subgrade materials, and enable coal ashes to be used in large quantities.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.173-178
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• 1993

The most appropriate mixing ratio of fly ash to bottom ash obtained from compaction characteristics and CBR values is varying from 5:5 to 6:4. But these mixed ashes are frost-susceptible materials according to judging by the paticle-size distribution because of a lot of silty-size paticles. In this study, the frost-susceptibility of compacted coal ash with proper mixing ratio is examined experimentally for use of subgrade materials. And, the efforts have been made to find proper cement addition in making these mixed ashes frost-insusceptible. It was revealed that these mixed ashes are frost-susceptible, and 4% of cement content is required to be made frost-insusceptable. It was found that amount of frost heave of these mixed ashes decreases with the unconfined compressive strength, and increases with log k if the permeability coefficient k is as low as the water into the freezing front of these mixed ashes is restricted.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.21-27
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• 2015

Due to the population growth and development of industry, waste from household and industries has increased. As the advanced countries experienced these problems, they have already started research on recycling methods of waste incineration ashes. Domestic recycling rate of incineration ash became up to 80 percent as high as the level of developed countries, but the recycling was limited to fly ash for admixture in concrete. In case of bottom ash, most of bottom ash was reclaimed in the landfills. Therefore, basic physical property and mechanical experiments for bottom ash were conducted in this study to evaluate the possibility of incineration bottom ash as an alternative construction materials. Bottom ashes from three different landfills with two different incineration methods were tested. Incineration methods are Stoker type Incinerator and Pyrolysis-Melting Treatment. Bottom ash can be used as an alternative granular material for construction based on the basic physical property and mechanical characteristics similar to those of sandy materials. However, the incineration method should be considered since it can affect the material and mechanical characteristics of the incineration bottom ash.