• Resources Recycling
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• v.18 no.2
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• pp.39-50
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• 2009

Portland cement production is under critical review due to high amount of $CO_2$ gas released to the atmosphere. Attempts to increase the utilization of fly ash, a by-products from thermal power plant to partially replace the cement in concrete are gathering momentum. But most of fly ash is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. Instead, the source of material such as fly ash, that are rich in Silicon(Si) and Aluminium(Al), are activated by alkaline liquids to produce the binder. Hence concrete with no cement is effective in the reduction of $CO_2$ gas. In this study, we investigated the influence of the compressive strength of mortar on alkaline activator and curing condition in order to develop cementless fly ash based alkali-activated concrete. In view of the results, we found out that it was possible for us to make alkali-activated mortar with 70MPa at the age of 28days by using alkaline activator manufactured as 1:1 the mass ratio of 9M NaOH and sodium silicate and applying the atmospheric curing after high temperature at $60^{\circ}C$ for 48hours.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.4
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• pp.315-323
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• 1998

Soil aggregate distribution and its relation to wind erosion were examined for the surface soil of the experimental plots for grasses in the New Incheon International Airport, of which soil was reclaimed with sea sands in the Youngjong Island. The soil aggregate with the size between 0.10 and 0.84mm was 74 percents. The 6 percents of the soil aggregates were non-erodible. With this aggregate distribution the wind erodiblity of the soil, I. was $380Mg\;ha^{-1}\;yr^{-1}$ with I value and climatic factor calculated for the dry period from November to May, $45.2Mg\;ha^{-1}\;yr^{-1}$ of the surface soil were estimated to be eroded. The erodible particles with 0.37mm diameter could fly to 17.8, 29.9 and 49.8 meters by saltation at wind speed of 7, 9 and $15m\;s^{-1}$, respectively. The wind erosion could be reduced by increasing vegetation coverage and applying hydrophyllic soil conditioner.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.569-569
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• 2016

본 연구에서는 소유역 내 오염원 현황에 따른 발생부하와 배출부하를 분석하고자 하였다. 대상유역은 경상북도 영천시 북안천 일대이며, 소유역을 6개의 세유역으로 구분하여 발생부하와 배출부하를 산정하였다. 오염원 현황자료는 2013년 전국오염원 조사자료를 기초로 하였으며, 행정구역 단위의 오염원 조사 및 행정구역과 유역의 경계가 일치 하지 않는 경우의 오염원별 점유율은 토지종합정보망(Land Management Information System, LMIS)의 연속지적도 자료를 이용하여 면적비로 산정하였다. 대상유역의 전체 인구는 총 5,140명이며, 이 중 시가 인구가 2명, 비시가 인구가 5,138명으로 나타났다. 생활계 오염원은 소유역 별 인구를 분석한 결과, FW-'1은 3,113명, FW-'2는 298 명, FW-'3은 604 명, FW-'4는 836 명, FW-'5는 283 명, 그리고 FW-'6은 6 명으로 분석되었다. FW-'1의 인구는 총 3,113명으로 대상유역에서 가장 많은 인구가 분포하고 있는 것으로 나타났다. 축산계 오염원은 FW-'1 지점에 총 115 가구의 농가가 위치하여 소유역 중 가장 많은 축산 농가가 위치하고 있으며. 가축 사육 두수는 돼지 8,040두, 젖소 394두, 한우 1,587두, 사슴 10두 그리고 가금(기타) 수가 292,158두로 다른 지점들과 비교하여 사육 두수가 가장 많은 것으로 나타났다. FW-'2 지점은 돼지 1,350두가 있는 돼지 농가가 1가구 위치하고 있는 것으로 나타났다. FW-'3 지점은 돼지 14,692두, 한우 1,287두, 가금(기타) 100두가 있으며, 축산 농가는 총 42가구가 위치하고 있는 것으로 나타났다. 다른 지점들과 비교하여 돼지 사육 두수가 가장 많은 것으로 나타났다. FW-'4 지점의 가축현황은 돼지가 900마리, 한우 1,222 마리이며, 총 57개의 농가가 위치하고 있고, 이 중 돼지 농가는 1가구이며, 그 외 56개의 농가는 모두 한우 농가이다. FW-'5 지점은 한우 407마리 가금(기타) 150마리가 있는 것으로 나타났으며, FW-'6 지점은 축산 농가가 존재하지 않는다. 또한 대상유역 내에는 총 14개의 산업체가 있으며, $800.33m^3/day$만큼의 폐수를 발생시키고 있다. 이중 FW-'1 지점 산업체 개수는 12개이며, 폐수 발생량은 $730.59m^3/day$로 가장 많은 양의 폐수가 발생하고 있다. 대상유역 내에는 산업계, 양식계, 매립계의 오염원은 없는 것으로 나타났다. 오염원 자료를 바탕으로 발생부하량과 배출부하량 산정결과 생활계와 축산계, 토지계 중축산계의 BOD, T-N, T-P 모두 가장 높은 것으로 분석되었다. 배출부하량 비교 결과에서도 BOD, T-N, T-P 모두 축산계 배출부하량의 비율이 높게 나타났으며, 이 중 BOD는 토지계 배출부하량이 차지하는 비율이 축산계 배출부하량보다 약간 높게 나타났다. T-N과 T-P는 축산계 배출부하량 비율이 가장 높은 것으로 분석되었다. 그러나 오염원의 정량적인 발생원 규명을 위해서는 오염원 그룹이 포함되어있는 지역에 대하여 장기적인 실측 모니터링을 통해 얻은 오염부하를 산정하여 비교?분석하는 연구가 필요할 것으로 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.28-36
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• 2021

It is known that buried rebars inside concrete structures are protected from corrosion due to passive layer. It is very important to delay the timing of corrosion or evaluate a detection of corrosion initiation for the purpose of cost-beneficiary service life of a structure. In this study, corrosion monitoring was performed on concrete specimens considering 3 levels of cover depth(60 mm, 45 mm, and 30 mm), W/C(water to cement) ratio(40.0%, 50.0%, and 60.0%) and chloride concentration(0.0%, 3.5%, and 7.0%). OCP(Open Circuit Potential) was measured using agar-based socket type sensors. The OCP measurement showed the consistent behavior where the potential was reduced in wet conditions and it was partially recovered in dry conditions. In the case of 30 mm of cover depth for most W/C ratio cases, the lowest OCP value was measured and rapid OCP recovery was evaluated in increasing cover depth from 30 mm to 45 mm, since cover depth was an effective protection against chloride ion ingress. As the chloride concentration increased, the effect on the cover depth tended to be more dominant than the that of W/C ratio. After additional monitoring and physical evaluation of chloride concentration after specimen dismantling, the proposed system can be improved with increasing reliability of the corrosion monitoring.

• Journal of Environmental Impact Assessment
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• v.28 no.3
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• pp.312-331
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• 2019

An offshore waste disposal facility refers to a landfill site for final landfilling of stabilized inorganic solid waste such as land and marine waste incineration materials, and the aim of such a facility is to solve the problem of insufficient waste disposal space on land and create and develop environmentally friendly marine spaces. The purpose of this study is to prepare guidelines for the construction of offshore waste disposal facilities, which reflect the need and importance of paying sufficient heed to environmental considerations from the initial stage of the project, in order to investigate, predict, and assess how such guidelines will affect the marine environment in relation to the construction of offshore waste disposal facilities, with the goal of minimizing the impact on and damage to the environment. For the purpose of this research, guidelines focusing on the construction of offshore waste disposal facilities were derived through an analysis of domestic cases and similar foreign cases and an assessment of their level of compliance with existing EIA guidelines through the operation of a discussion forum. In order to review the EIA report on similar cases in Korea, 17 EIA documents (2005~2016) for dredged soil dumping areas and ash ponds of thermal power plants were analyzed to investigate the status of marine organisms, marine physics, marine water quality, and marine sediment and to understand what types of problems can occur and what improvement measures can be taken. The purpose of these guidelines were to minimize damage to the marine environment by promoting EIA protocols in accordance with scientific and systematic procedures, to reduce the consultation period related to projects, to resolve social conflicts, and to reduce economic costs.

• Journal of the Korean GEO-environmental Society
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• v.20 no.5
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• pp.23-29
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• 2019

In general, pipe laying works are performed by constructing underground facilities such as pipes and then refilling the rest of the area with sand or soil. However, there are many problems in the compaction process such as difficulties in tampering around the underground facility and low compaction efficiency. Such problems cause deformation and damage to the underground pipes during refilling work and ultimately cause road sinks. Construction methods using CLSM are one of the typical methods to solve these issues, and recently, studies on CLSM using coal ash, which has similar engineering properties as sand, have been actively performed to protect environment and recycle resources. While many studies have been conducted to recycle fly ash in many ways, the demand for recycling bottom ash is increasing as most of the bottom ash is not recycled and reclaimed at ash disposal sites. Therefore, in order to find bottom ash applications using eco-friendly soil binders that are environmentally beneficial and conform with CLSM standards, this study investigated flow characteristics and strength change characteristics of eco-friendly soil binders, weathered granite soil, a typical site-generated soil, bottom ash, and fly ash mixed soil and evaluated the soil pollution to present CLSM application methods using bottom ash.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.256-262
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• 2018

A great amount of fly ash, which is a waste from a thermal power plant, has not been appropriately recycled until now. Landfill of flay ash causes environmental pollution and enormous economic costs. In this study, manufacturing of architectural ceramic tile was investigated replacing fly ash with clay raw material. The properties of porcelain tile was analyzed after manufacturing porcelain tile with mineral based glaze and fast firing process. In particular, the effect of the fly ash addition on the properties of ceramic tile was investigated by increasing the amount of limestone addition. Porcelain tile with fly ash showed excellent bending strength, water absorption, warping and abrasion resistance. However, a significant decrease in durability was observed through the autoclave test. Addition of limestone increased the water absorption, twisting and hydration expansion of the ceramic tile, but it was confirmed that the durability of the ceramic tile with fly ash was greatly improved. In conclusion, recycled architectural ceramic tiles, which can meet domestic construction standards, could be manufactured with the addition of fly ash and limestone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.113-119
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• 2019

Many researches on alternative materials as construction materials is continuing by recycling industrial byproducts due to shortage of sitereclamation and natural aggregates. In this paper, engineering properties in early-aged OPC (Ordinary Portland Cement) and GGBFS (Ground Granulated Blast Furnace Slag) concrete are evaluated with EOS aggregate replacement. The related experiments were carried out with 0.6 of water to binder ratio, three levels of EOS replacement ratios (0%, 30% and 50%) for fine aggregate, and two levels of cement replacement with GGBFS (0% and 40%). Several tests such as slump air content, and unit mass measurement are performed for fresh concrete, and compressive strength and diffusion coefficient referred to NT BUILD 492 method are measured for hardened concrete. Through the tests, it was evaluated that the compressive strength in concrete with EOS aggregate increased to 3 days and 7 days but slightly decreased at the age of 28 days. In the accelerated chloride penetration test, GGBFS concrete showed reduced diffusion coefficients by 60 - 67% compared with OPC concrete. The lowest chloride diffusion coefficient was evaluated in the 50% replacement with EOS aggregate, which showed an applicability of EOS aggregate to concrete production.

• Resources Recycling
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• v.28 no.4
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• pp.44-50
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• 2019

In the electric arc furnace process, the chemical energy such as the heat of oxidation reaction and the heat of carbon combustion etc. is consumed as 30% of the total input energy. In order to reduce $CO_2$ emission in EAF, it is necessary to decrease the use of electric power energy during scrap melting stage and increase the use of chemical energy. In general, when the carbon materials is individually charged into the molten steel, the carbon materials floated to the slag layer due to low density before it is dissolved in molten steel. When the concentration of carbon in the molten steel is high, the combustion energy of carbon by oxygen injection can lower the electric power energy and improve the chemical energy consumption. Therefore, an efficient charging methods of carbon material is required to increase the efficiency of carbon combustion heat. On the other hand, Al-dross, which is known as a by-product after Al smelting, includes over 25 mass% of metallic Al, and the oxidation heats of Al is lager than that of carbon. However, the recycling ratio fo Al-dross was very low and is almost landfilled. In order to effectively utilize the heats of oxidation of Al in Al-dross, it is necessary to study the application of Al-dross in the steel process. In this study, the dissolution efficiency of carbon and aluminum in molten steel was investigated by varying the reaction temperature and the mixing ratios of coke and Al-dross.

• Korean Journal of Heritage: History & Science
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• v.49 no.4
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• pp.64-79
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• 2016

The purpose of the present study is to clarify the process of change to the pond at the Jongmyo Shrine(宗廟), from the Joseon Dynasty period to the modern and contemporary era. The consequent research results can be summarized as follows. The first record of the Jongmyo pond is confirmed in the "Annals of King Sejong(世宗實錄)". The pond, which was being constructed at the time, refers to the current upper pond(上池). A pair of islets(雙島) were constructed during the Sukjong(肅宗) period, with several trees planted on the middle islet(中池). The middle pond is thick with lotuses. In particular, the middle island on the middle pond subsequently changed into a single island(單島), which is likely to be related to the pond expansion during the reign of Youngjo(英祖). When the lower pond(下池), involving dualistic arrangement, was constructed in the modern and contemporary era, the pond of the Jongmyo Shrine underwent a drastic transformation phase. The lower pond was constructed before 1947 at the latest, and when the right side of the lower pond was filled in the mid 1980s, the dualistically arranged lower pond became a unified type of lower pond. On the other hand, the bank protections of the upper and middle ponds were constructed with earth, but was subsequently modified into its current form using stone.