• Resources Recycling
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• v.11 no.2
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• pp.20-27
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• 2002

This study was to develop the triboelectrostatic separation technique to recycle the coal from about 20% of mill reject products remained by grinding process in the coal thermoelectric power plant. In this study, we get a test results that can product the cleaned coal of 15% ash content and 66.23% recovery from mill reject of 47% ash content. And then, from the result of the releases analysis, we proved the excellence of treatment method, after showing the treament processing which is able to get 80% of recovery of coal from 20% of ash content demanded in the power plant.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.234-240
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• 2016

Energetically-modified material using reject fly ash (RFA), generated from thermal power plants, was manufactured to investigate the effect of the material on the physical and chemical characteristics of cement mortar. In order to modify reject fly ash, a vibration mill was used. Particle size, grain shape, and crystal structure of the ash were analyzed. Then, the compressive strength of the mortar using energetically-modified reject fly ash (ERFA) was measured. Microstructure and X-ray diffraction (XRD) patterns were also used in the analysis. As the replacement rate of ERFA increased, the value of the compressive strength tended to decrease. However, it was found that the compressive strength values of 7 and 28 days-cured specimens were higher than those of conventional ordinary Portland cement (OPC) mortar with 10 % replacement rate condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.301-302
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• 2010

The purpose of this study was to get basic information of using high blaine reject ash as a mineral admixtures in cement or concrete system. Compressive strength of mortar and rheological properties of slag cement with fly ash or high blaine reject ash($6,400cm^2/g$) were investigated.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.158-163
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• 2012

The purpose of this study is to improve recycling rate of the coal reject ash by investigating bloating mechanism for artificial lightweight aggregate of reject ash. In this study, we use reject ash (R/A) and dredged soil (D/S) as raw materials. The artificial lightweight aggregates were formed by plastic forming (${\phi}$ = 10 mm) and sintered by temperature raising method at different temperatures (between 1200 and $1275^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of R/A-D/S contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of R/A 80 wt.%. From the microstructure images, we considered the artificial lightweight aggregates content of R/A over 80 wt.% are distributed numerous uniform micro-pores by vitrification without Black Core and the artificial lightweight aggregates of R/A below 80wt.% are distributed macro-pores with Black Core.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.44-49
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• 2019

The purpose of this study is to analyze the fundamental characteristics of concrete with the change of reject ash(Reject ash=Rj) in the mixed aggregate where single grain aggregate of different grain size and aggregate of opposite grain size are mixed together, to analyze the possibility of a mixed aggregate system that premixes at an aggregate manufacturing plant and delivers it as one aggregate. As a result of the experimental study, it was found that the grain size regulation is satisfied if the mixed aggregate(CSb+SS) is substituted for about 5% of Rj. In the case of the fluidity slump, slump flow and air volume, it was found that they decrease as the substitution ratio of Rj increases, while the compressive strength increases as the substitution ratio of Rj increases. Therefore, it is analyzed that it would contribute greatly to an improvement of quality such as improvement of compressive strength if adequate fluidity and air quantity are secured by the water reducing agent and AE agent while premixing the Rj, which is disposed of by landfill, with about 5% of the mixed aggregate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.185-191
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• 2010

To effectively utilize resources of reject ash and dredged soil, globular shape-formed artificial lightweight aggregate were manufactured in 8~10 mm size. Starting materials were changed various grading and composition, sintered at $1050{\sim}1250^{\circ}C$. The specific gravity, water absorptance of artificial lightweight aggregates were measured on the basis of the KS. In this study could make a prediction about application of bloating mechanism by ferrous materials and alkali/alkali-earth oxide at high temperature.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.11-21
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• 2013

PURPOSES: As pavement generally provides service shorter than an expected life cycle, maintenance cost increases gradually. In order to help extending the service life and reduce maintenance cost, a new multi-functional composite pavement system is being developed in Korea. METHODS: This study is a part to develop the multi-functional composite pavement and is to investigate the mechanical performances of fiber-reinforced lean concrete for pavement subbase. The inherent problem of fiber reinforced concrete is dispersion of fibers in concrete mix. This study additionally evaluated fiber dispersion characteristics with respect to different fiber types. RESULTS: From the test results, the compressive strengths of the concretes satisfied the required limit of 5MPa at 7days. The standard deviation of the measured number of fibers were lower in the order of nylon, steel fiber and polypropylene. CONCLUSIONS: Reject ash was shown to be satisfactory as a replacement material to Portland cement in lean concrete base. The fiber volume fraction is suggested to be 0.4% even though the fracture toughness did not vary significantly with respect to fiber types. However, fracture energy absorbed up to complete failure increased with the increased fiber volume fraction increment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.77-83
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• 2014

The purpose of this study was to figure out the impacts of iron oxide types and dosages to bloating when producing artificial lightweight aggregates by utilization of recycled resources such as bottom-ash, reject-ash and dredgedsoil. In order to figure out chemical characteristics of raw materials, XRD and XRF analyses were performed. 50 wt% of dredged-soil, 15 wt% of bottom-ash and 35wt.% of reject-ash were mixed, then the amount of iron oxide was varied at 5 to 30 wt% with intervals of 5 wt% with $Fe_2O_3$ and $Fe_3O_4$ respectively. As molded aggregates were sintered by rapid sintering in intervals of $40^{\circ}C$ from $1060^{\circ}C$ to $1180^{\circ}C$, specific gravity and water absorption were measured. As a result, the artificial lightweight aggregate with iron oxide of 10~15 vol% showed the lowest specific gravity, and it was identified that the more iron oxide vol% increases, the more specific gravity increases because of liquid phase sintering.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.5
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• pp.199-204
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• 2015

In this study, prevention methods of radial cracks generated inside of artificial lightweight aggregate made of reject ash and dredged soil were investigated. The reject ash and dredged soil had mixed with weight ratio of 7 : 3 and formed to spheric shape of 5~20 mm diameter, then, the aggregates were manufactured using flash sintering method at $1200^{\circ}C$ for 10 min. The formation of radial cracks in the aggregates were suppressed as the size of specimen decreased. Also, the addition of silica to aggregates had prevented generation of the radial cracks. As the size and the amount of silica powder added increased, the development of radial cracks was constrained. Therefore the artificial lightweight aggregate manufactured in this study expected to be applicable to many fields such as construction and environmental usages. Also it is expected to contribute greatly to increase the recycling rate of reject ash and dredged soil.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.543-551
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• 2012

Road pavements in Korea generally show shorter service life than the predicted one. There are many reasons for this phenomenon including increased traffic load and other attacks from exposure conditions. In order to extend a service life and upgrade the pavement, a new multi-functional composite pavement system is being developed in Korea. This study is to investigate the performances of fiber-reinforced lean concrete for pavement base. This study considered mineral admixtures of fly ash and reject ash. The reject ash is defined as ash that does not meet the specifications for fly ash so that it cannot be used as a supplemental material for cement replacement. Due to the inherent property of lean concrete, compaction during the fabrication of specimens is a key factor. Therefore, this study suggests an appropriate compaction method. From the test results, the compressive strengths of the concrete satisfied the required limit of 5 MPa at 7 days. When a compaction roller was used to mimic actual field conditions, the strength development seemed to be influenced by the compaction energy rather than hydration of cement itself.