• 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 Korea Institute of Building Construction
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• v.17 no.2
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• pp.183-189
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• 2017

The aim of the research is to provide rheological properties of cement paste with various qualities of coal ash including fly ash, raw ash, and reject ash. Generally, fly ash is the well known supplementrary cementitious materials for concrete and is used to improve various properties. Although fly ash is obtained as a byproduct of fire powder plant, still reject ash is wasted from raw ash. In this research, thus, to provide a fundamental information on using not only fly ash but also raw ash or reject ash for cementitious materials, a rheological properties of cement paste was studied with three different coal ash. This research was conducted from particle conditions of three different coal ashes to rheological properties in cement paste phase. According to the expeirment, reject ash was consisted with large and coagulated particles although fly ash was consisted with a small and spherical shaped particles. based on the particle conditions of various coal ashes, rheological behaviors were tested, and it was shown as the coal ashes improved the fluidity of cement paste. Specifically, depending on the particle distributions of cement paste, it is considered that the viscosity of paste can be controlled.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.344-347
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• 2004

The amount of coal ash has been increasing and development of effective use is urgently needed. Various by-products and waste are expected to be used as resources from the point of reduction in environmental load. This is an experimental study to compare the properties of high volume coal ash concrete using the reclaimed coal ash. For this purpose, authors have started work to develop a production method of hardening coal ash concrete. Laboratory tests show that the optimum mixture of coal ash concrete can be determined from multiple regression analysis. According to test results, it was found that the compressive strength of the concrete can be determined by a single curve. And it is obtained from the analysis of the results tested for concrete with the ratio of total power to water and amount of land reclamation ash.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.207-213
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• 1992

In this study, the strength and durability of compacted coal ash with proper mixing ratio of fly ash to bottom ash, such as 5:5 or 6:4, are examined for use of highway embankment and subgrade materials. Right after compaction, the strength of bituminous mixed coal ash is greater than that of anthracite mixed coal ash. The distinguished increase of strength with curing time is observed only in Ho-nam mixed coal ash that contains a lot of free lime, and the strength increase with curing time are not seen or little in the others. The durability in sinking test is good also in Ho-nam mixed coal ash, but satisfactory by adding 2% cement in the others. And it is seen that the effects of the strength increase with adding cement are greater in coal ash with proper mixing ratio than in fly ash or bottom ash respectly.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.211-218
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• 2022

Coal ash is being considered as a source of silica and alumina for cement clinker. The purpose of this study was to investigate the effect on cement clinker sintering by confirming the high-temperature microstructural change according to the firing temperature in the cement clinker sintering process of coal ash. In the coal ash used as a raw material for cement clinker, the shape change of the particle surface was confirmed from the sintering tem perature of 950 ℃. The shape of the coal ash disappeared from the sintering temperature higher than 1250 ℃. It was confirmed that the Al and Fe components of the coal ash were converted to the cement interstitial phase at a temperature higher than 1350 ℃. In addition, the clinker using a large amount of coal ash as a raw material showed a low content of Lime and a high content of Belite in the sintering tem perature range of 1150~1200 ℃. From this, it was confirmed that the formation of calcium silicate mineral proceeds more easily at the initial sintering temperature by the application of coal ash.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1452-1457
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• 2010

Recently, coal ash is used as resources to make controlled low-strength material (CLSM) which a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. Pozzolanic reaction is strongly related with self-cementation of coal ashes. However, this reaction depends on pozzolanic content in fill materials and is disappeared in 2-3 days after placement of coal ash fill. Therefore, state of coal ash fill is commonly very loose and not appropriate for foundations of structures without special treatments. In this study, a coal ash placement device was developed to place coal ashes effectively to improve density of coal ash fills. The device consists of a ribbon type mixer to obtain homogeneous materials mixture and a piston type pump for density control of fill materials. Based on several laboratory test results, more stable coal ash fill state can be obtained with controlling placement pressure.

• Journal of Environmental Impact Assessment
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• v.24 no.5
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• pp.472-486
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• 2015

More than 8M tons of coal ashes are generated from coal-fired thermal power plants every year in Korea. Excluding the recycled portion (Current recycling rate: approximately 70%), all of the generated coal ashes end up in coastal landfills. Currently, the difficulties faced in establishing new ash treatment fields are attributed to the concerns raised over the environmental impacts caused by the landfills at individual plant facilities. Given the number of coal-fired thermal power plants to be built in the future (reflected in the 7th Basic Plan for Long-term Electricity Supply and Demand), building new ash treatment fields or seeking a new treatment plan seems unavoidable. Based upon a review of coal ash and its management, this study concluded that the most effective and fundamental strategy to minimize the environmental impacts resulting from coal ash landfills is to avoid constructing new coal-fired powerplants and furthermore, suggests that the practice of beneficial use and recycling the produced coal wastes should be encouraged.

• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.61-66
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• 2014

The various recycling methods of mixed coal ash have been developed considerably and it's recycling quantity has been increased. However, the more relatively finer grain content of coal ash in ash pond is increased the more it's quantity is increased in recycling as products for drainage in soft ground etc. Accordingly, the geotechnical properties of mixed coal ash in ash pond would be inferior and it's recycling rate should reach the limitations in increase. In this study, to recycle mixed coal ash contained fine grain in considerably amount as products for strength, etc. By adding binder to it and manifesting, it's compressive strength is stronger than the criteria, these are suggested; 1) the variety of compressive strength test performed on mixed coal ash of various grain distributions as main material, 2) the kind of binder, it's mixing quantity and the optimum content rate range of fine grain coal ash that the compressive strength stronger than a certain compressive strength is manifested. Cement is more excellent than quicklime as binder in manifesting stronger compressive strength and the sieve type to sort it is #40 sieve in order to recycle all mixed coal ash in ash pond efficiently as products for drainage as well as products for strength, etc. And, it could increase insufficient compressive strength remarkably that content of pure sand is more in the rate as pure sand and the part of mixed coal ash in ash pond to pass through #40 sieve is mixed in the ratio of 2 to 8.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.121-125
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• 2015

Distribution of rare earth metals (REMs) and rare valuable metals (RVMs) contents in coal ashes (fly ash, bottom ash, and pond ash) and leachate from 11 coal-fired power plants in Korea were investigated. Coal ashes and leachates were found to contain important REMs and RVMs such as Yttrium (Y) and Neodymium (Nd), which was in the range of 23~75 mg/kg. However, it still requires developing effective recovery and separation methods in order to utilize REMs and RVMs in ash and leachate. Recovery of valuable elements (Y and Nd) from various and extensive ash sources (8.21 million tons/year in 2013) can provide the existing power plants with additional profit; therefore, it can significantly improve economics of the power plants.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.125-128
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• 2005

Coal ash, which is generated as a byproduct at a coal thermal power plant, can be classified into fly ash and bottom ash. Most of fly ash is recycled as an admixture for concrete, while bottom ash is not recycled but dumped into an ash landfill disposal site. So, if a technology for recycling bottom ash efficiently, which is increasingly generated year by year, is not developed, environmental problems will take place as a matter course and further an enormous economical cost will be required for construction of additional ash landfill disposal sites. In this study an optimum mix proportion design and a quality control method for utilizing the reclamation coal ash as an aggregate for secondary concrete products such as an artificial reef was successfully developed.