• Title/Summary/Keyword: Recycling

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Fundamental Properties of Lightweight Concrete with Dry Bottom Ash as Fine Aggregate and Burned Artificial Lightweight Aggregate as Coarse Aggregate (건식 바텀애시 경량 잔골재와 소성 인공경량 굵은골재를 사용한 콘크리트의 기초 특성)

  • Choi, Hong-Beom;Kim, Jin-Man
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.4
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    • pp.267-274
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    • 2018
  • Though the wet bottom ash has been used as a type of lightweight aggregate, dry bottom ash, new type bottom ash from coal combustion power plant, has scarcely researched. It is excellent lightweight aggregate in the view point of construction material. This study is performed to check the applicability of dry bottom ash as a fine aggregate in lightweight aggregate concrete, by analyzing various properties of fresh and hardened concrete. We get results that the slump of concrete is within the target range at less than 75% replacement rate of dry bottom ash, the air content is not affected by the replacement rate of dry bottom ash, the bleeding capacity is less than $0.025cm^3/cm^2$ at 75% under of the replacement rate of dry bottom ash, and the compressive strength of concrete show 90% or more comparing the base mix while initial strength development is a little low. Oven dry unit weight of concrete is reduced by 8.9% when replaced 100% dry bottom ash, and dry shrinkage tends to decrease depending on increase of replacement rate of dry bottom ash. Modulus of elasticity of concrete shows no decease at 50% over of the replacement rate of dry bottom ash, while modulus of elasticity of concrete decreases when the replacement rate increases further. The dry bottom ash, when used as a fine aggregate in lightweight concrete, can be used effectively without any deterioration in quality.

Foundation Properties of Cement Mortar in the Use of Fine Aggregate of Coal Gasification Slag (석탄가스화 용융슬래그를 잔골재로 활용하는 시멘트 모르타르의 기초적 특성)

  • Park, Kyung-Taek;Han, Min-Cheol;Hyun, Seung-Yong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.2
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    • pp.116-122
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    • 2019
  • This study evaluated the properties of Coal gasification slag(CGS) according to the CGS contents of cement mortar condition as a basic step to examine the applicability of CGS as concrete fine aggregate. Flow increased with increasing CGS contents for both Crushed sand a(CSa) and Crushed sand b+Sea sand(CSb+SS), but the amount of air contents decreased to the opposite tendency. Based on 28 days is maximum compressive strength was obtained at CGS 50% when CSa was used and CGS 75% when CSb+SS. The flexural strength were the maximum at 25% and 50% of CGS, but the tendency was similar to the compressive strength. Compared with CSa, the compressive strength and flexural strength 5% higher than those of CSb+SS, in CGS using of were about 5% higher than those of unused CGS. As a result of comprehensive study on the quality of mortar according to the CGS contents, it can be concluded that when CGS is mixed with fine aggregate at about 50%, it can contribute to securing workability and strength development positively so that resource recycling and quality improvement can be achieved at the same time.

A Study on Performance Evaluation of Early-age Concrete with EOS Fine Aggregate and GGBFS (EOS 잔골재 및 GGBFS를 혼입한 초기재령 콘크리트의 성능 평가에 관한 연구)

  • Kwon, Seung Jun;Cho, Sung Jun;Lim, Hee Seob
    • 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.

Recycling of useful Materials from Fly Ash of Coal-fired Power Plant (석탄화력발전소에서 발생되는 비회로부터 유용성분의 회수)

  • Kim, Dul-Sun;Han, Gwang Su;Lee, Dong-Keun
    • Clean Technology
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    • v.25 no.3
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    • pp.179-188
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    • 2019
  • Upon the combustion of coal particles in a coal-fired power plant, fly ash (80%) and bottom ash (20%) are unavoidably produced. Most of the ashes are, however, just dumped onto a landfill site. When the landfill site that takes the fly ash and bottom ash is saturated, further operation of the coal-fired power plant might be discontinued unless a new alternative landfill site is prepared. In this study, wet flotation separation system (floating process) was employed in order to recover unburned carbon (UC), ceramic microsphere (CM) and cleaned ash (CA), all of which serving as useful components within fly ash. The average recovered fractions of UC, CM, and CA from fly ash were 92.10, 75.75, and 69.71, respectively, while the recovered fractions of UC were higher than those of CM and CA by 16% and 22%, respectively. The combustible component (CC) within the recovered UC possessed a weight percentage as high as 52.54wt%, whereas the burning heat of UC was estimated to be $4,232kcal\;kg^{-1}$. As more carbon-containing UC is recovered from fly ash, UC is expected to be used successfully as an industrial fuel. Owing to the effects of pH, more efficient chemical separations of CM and CA, rather than UC, were obtained. The average $SiO_2$ contents within the separated CM and CA had a value of 53.55wt% and 78.66wt%, respectively, which is indicative of their plausible future application as industrial materials in many fields.

The Effects of Project Learning of Pre-service Teachers on Self Directed Learning Ability and Creative Personality (초등예비교사의 프로젝트 학습이 자기주도적 학습능력 및 창의적 인성에 미치는 효과)

  • Lee, Yong-seob
    • Journal of the Korean Society of Earth Science Education
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    • v.12 no.2
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    • pp.141-150
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    • 2019
  • The purpose of this study is to investigate the effect of the pre-service teacher's maker project learning on self -directed learning ability and creative personality. This study established an eight-week period of experimental treatment from March to April 2019, and the students who participated in the study formed a research group of 75 students in three of their advanced classes who are attending the second semester of B University of Education and taking courses in 'Teaching Research 1'. The experimental treatment of research groups was conducted by the process of producing creative outputs through training of manufacturers. The experimental group of the study group was a process of producing creative output through maker education. The theme was set up to create creative output by group, worked with the main tool, 3D pen, and utilized the recycling material. When the creative output is completed, it is announced by presenting the actual product in each group. The results of the study are as follows. First, project learning by pre-service teachers had an effect on self-directed learning ability. Second, project learning by pre-service teachers had an effect on creative personality. Third, pre-service teachers was interested in learning about the project and responded positively to the students' perception.

Properties of Low Carbon Type Hydraulic Cement Binder Using Waste Recycle Powder (무기계 재생원료를 사용한 저탄소형 수경성 시멘트 결합재의 특성)

  • Song, Hun;Shin, Hyeon-Uk;Tae, Sung-Ho
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.1
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    • pp.22-28
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    • 2019
  • Cement is a basic material for the construction industry and it requires high temperature sintering when manufacturing cement. $CO_2$ emissions from raw materials and fuels are recognized as new environmental problems and efforts are underway to reduce them. Techniques for reducing $CO_2$ in concrete are also recommended to use blended cement such as blast furnace slag or fly ash. In addition, the construction waste generated in the dismantling of concrete structures is recognized as another environmental problem. Thus, various methods are being implemented to increase the recycling rate. The purpose of this study is to utilize the inorganic raw materials generated during the dismantling of the structure as a raw material for the low carbon type cement binder. Such as, waste concrete powder, waste cement block, waste clay brick and waste textile as raw materials for low carbon type cement binder. From the research results, low carbon type cement binder was manufactured from the raw material composition of waste concrete powder, waste cement block, waste clay brick and waste textile.

Comparative Evaluation on Collision and Particle Separation Efficiency between CO2 Bubbles and Air Bubbles Using Contact Zone Model of Flotation Process (부상분리 공정의 접촉영역 모델을 이용한 이산화탄소와 공기 기포의 충돌 및 입자 분리효율 비교 평가)

  • Yang, Jong-Won;Choi, Yong-Ho;Chae, In-Seok;Kim, Mi-Sug;Jeong, Yong-Hoon;Kim, Tae-Geum;Kwak, Dong-Heui
    • Journal of Korean Society on Water Environment
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    • v.35 no.1
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    • pp.64-71
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    • 2019
  • In recent years, carbon dioxide ($CO_2$) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using $CO_2$ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized $CO_2$ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between $CO_2$ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of $CO_2$ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that $CO_2$ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.

A Study on the Recognition and Needs Analysis of Community Residents to Reuse Closed Schools as Library (폐교 시설의 효과적인 도서관 활용을 위한 폐교 발생 지역 주민의 인식 및 요구 분석에 관한 연구)

  • Noh, Younghee;Ro, Ji-Yoon
    • Journal of the Korean Society for Library and Information Science
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    • v.53 no.2
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    • pp.91-116
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    • 2019
  • This study conducted a demand analysis for the operation and management of closed schools, the direction of future use of closed schools, and the utilization of closed schools, among local residents expected to play a key role in the successful use of closed libraries. According to the study, residents in areas where schools actually occur may actively consider the use of closed schools when they are lacking in the number of libraries in the region or when they hope to remodel their schools as libraries, given that they are positive about future use of closed schools and that remodeling them is more economical in terms of cost than building new libraries. The current awareness of the use and operation of closed schools remains at a normal level, so it is deemed necessary to improve the direction of the promotion, operation and recycling of closed schools in the order of promotion, operation and physical aspects by grouping obstacles to the operation and management of closed schools. In addition, the current status of cultural facilities and the demands of local residents are met in terms of the types of use of closed school facilities, and it means that closed schools can be used in a relatively easy-to-access location based on their location, while libraries can be used as a space for cultural facilities that are different from the existing public libraries, exhibition halls, and eco-friendly libraries.

A discourse on The Japanese Empire's destruction of official records : Focusing on the persistence of the records of Government-General of Chosen held by the National Archives of Korea (일제의 공문서 폐기 시론 -국가기록원 소장 조선총독부 기록의 잔존성을 중심으로-)

  • Yi, Kyoung Yong
    • The Korean Journal of Archival Studies
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    • no.67
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    • pp.205-236
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    • 2021
  • This study examined the record destruction problem systematically implemented by the Japanese colonial rule during the wartime period, centering on the persistence of the remaining records of Government-General of Chosen. It became clearer to recognize the historical probabilities that the decisions made by the Japanese cabinet were carried out on official documents in the same way throughout the empire, including mainland Japan and colonies. It was also confirmed that a system for disposing of records, such as reduction and organization of public documents, and recycling of paper resources, has already been established against the backdrop of the situation where the war spread and the war situation worsened after the late 1930s. In addition, it was attempted to extract the types and characteristics of documents discarded by the Japanese colonial rule through a review of the regulations on handling secret documents of the Government-General of Chosen and the regulations on the police department. At the same time, it was found that various chiefs (subsidiaries) that could know the status of documents to be retained or the status of preservation according to the governmental regulations revealed that there was no single book, and this was directly related to the massive destruction of official documents by the Joseon Governor-General immediately after defeat.

Environmental Effect of the Reduced Slag in the Electric Furnace (전기로 제강 환원슬래그 혼합토의 환경적 영향)

  • Na, Hyunsu;Yoon, Yeowon;Yoon, Gillim
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.7
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    • pp.23-29
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    • 2011
  • The oxidation slag has been widely used in civil engineering project, whereas the reduced slag from electric furnace has yet to be applied. Consequently in order to find out the recycling method in civil engineering field, the mineral compositions of the reduced slag were analyzed and some tests on water quality were performed to estimate the potential release of toxic compounds. Slag-soil mixtures of 0, 10, 20 and 30%(dry weight) soil were prepared in lysimeter columns and the effluents were collected with the period of one, two and four week options in closed system, respectively. The result from qualitative and quantitative analysis using X-ray Diffraction(XRD) and X-ray Fluorescence(XRF) indicates that the main mineral of the reduced slag is $Ca_2(SiO_4)$, a kind of calcium silicate. Also, the leaching medium analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy(ICP-OES) showed that main heavy metals such as Al, Fe and Mn are included in the reduced slag due to the effect of steel production process. It can be seen that the leachate does not violate the regulation guide line of waste material of heavy metal. Also the pH levels were increased from pH 6.9 for 0% soil to pH 10 for 30% soil. However the influence on leachate circulation period of one through four weeks was negligible.