• Title/Summary/Keyword: cement production

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Theoretical Proposal for the Mix Design of Recycled Cement Utilizing Inorganic Construction Wastes (무기계 건설폐기물을 이용한 재생시멘트 배합설계에 관한 이론적 제안)

  • Kim, Ji-Hoon;Tae, Sung-Ho;Song, Hun;Shin, Hyeon-Uk
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.3
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    • pp.250-258
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    • 2016
  • Until now, the construction material industry has been recognized as a typical environmental destruction industry. However, recently, in order to reduce $CO_2$ emission, the main cause of environmental problems, lots of studies have been done about recycling industrial by-products and construction wastes. Therefore, the purpose of this study is to confirm whether it is possible to use as an alternative material in cement production process as a part of the development of recycled cement using an inorganic construction waste. For this study, the inorganic construction wastes was collected and analyzed each chemical component by XRF(X-ray Fluorescene). Also, the inorganic construction wastes were combined based on the chemical component of the cement, to perform this analysis. As a result, when the inorganic construction wastes was properly combined, it is possible to consider the development of the recycled cement used the inorganic construction wastes.

Evaluation of Applicability of CMD-SOIL Recycled Resources as Ground Improvement Material for Deep Mixing Method (심층혼합공법용 지반개량재로서 순환자원을 재활용한 CMD-SOIL의 적용성 평가)

  • Ham, Tae-Gew;Seo, Se-Gwan;Cho, Dae-Sung
    • Journal of the Korean Geosynthetics Society
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    • v.20 no.4
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    • pp.43-52
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    • 2021
  • As port development in soft ground is actively promoted for international logistics and transportation, the Deep Mixing Method (DMM) is continuously applied to form an improved column body directly in the ground by mixing cement with soil to secure the stability of the structure. However, in the case of cement, there is a problem of emitting a lot of greenhouse gases during the production process, so the development and use of new alternative materials are socially required to achieve the national goal of carbon neutrality. Accordingly, in this study, CMD-SOIL, developed to induce a hardening reaction similar to cement by recycling recycled resources, was used as a ground improvement material for the DMM. In addition, it was attempted to determine the possibility of replacing cement by conducting on-site test construction and evaluating applicability. As a result of the study, the compressive strength of CMD-SOIL compared to the design reference strength was 1.46 to 2.64 times higher in the field mixing test and 1.2 to 5.03 times higher than in the confirmed boring. In addition, the ratio (λ) of the compressive strength in the field to the design reference strength was 0.63 to 1.14, which was similar to the previous research results. Therefore, in the case of CMD-SOIL, it is possible to express the compressive strength necessary to secure stability, and there is no difference in applicability compared to existing materials such as ordinary portland cement and blast furnace slag cement, so it was analyzed that it could be used as a ground improvement material for the DMM.

A High Viscosity of Curdlan at Alkaline pH Increases Segregational Resistance of Concrete (염기성 pH에서의 고점도 커들란에 의한 콘크리트의 재료분리 억제 효과 증진)

  • 이인영;김선원;이중헌;김미경;조인성;박영훈
    • KSBB Journal
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    • v.14 no.1
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    • pp.114-118
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    • 1999
  • In order to use a polysaccharide, curdlan, as a concrete admixture, we first developed a pilot-scale fermentation process for the mass production of curdlan. We also examined the rheological properties of curdlan, and tested how well the curdlan obtained in this work increased the segregational resistance of the cement slurry. Fermentation was performed in a 300-liter fermenter equipped with 3 disk-turbine impellers. Since curdlan production is stimulated under nitrogen-limiting conditions, the culture pH was shifted from the optimal pH for cell growth (pH 7.0) to the optimal pH for curdlan production (pH 5.5) at the onset of ammonium exhaustion. We obtained a curdlan production of 65 g/L in 120 hr batch cultivation of Agrobacterium species. The insoluble curdlan at the final stage of fermentation was readily harvested by centrifugation together with the cells. The freeze-dried sample contained 78% (w/w) of curdlan. The solubility and viscosity of the curdlan increased with the increase of the solution pH, which enhances the viscosity of concrete since the pH of concrete is extremely high (pH 13.0). Test results of the curdlan as a concrete admixture with cement slurry demonstrated that it prohibits the leakage of water. In conclusion, this work certifies and enlarges curdlan's industrial potential as a concrete admixture.

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Optimal Electric Energy Subscription Policy for Multiple Plants with Uncertain Demand

  • Nilrangsee, Puvarin;Bohez, Erik L.J.
    • Industrial Engineering and Management Systems
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    • v.6 no.2
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    • pp.106-118
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    • 2007
  • This paper present a new optimization model to generate aggregate production planning by considering electric cost. The new Time Of Switching (TOS) electric type is introduced by switching over Time Of Day (TOD) and Time Of Use (TOU) electric types to minimize the electric cost. The fuzzy demand and Dynamic inventory tracking with multiple plant capacity are modeled to cover the uncertain demand of customer. The constraint for minimum hour limitation of plant running per one start up event is introduced to minimize plants idle time. Furthermore; the Optimal Weight Moving Average Factor for customer demand forecasting is introduced by monthly factors to reduce forecasting error. Application is illustrated for multiple cement mill plants. The mathematical model was formulated in spreadsheet format. Then the spreadsheet-solver technique was used as a tool to solve the model. A simulation running on part of the system in a test for six months shows the optimal solution could save 60% of the actual cost.

Corrosion initiation time models in RC coastal structures based on reliability approach

  • Djeddi, Lamine;Amirat, Abdelaziz
    • Advances in concrete construction
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    • v.9 no.2
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    • pp.149-159
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    • 2020
  • The present work proposes new engineering models for determining corrosion initiation time in concrete reinforcing steels in marine environment. The models are based on Fick's second law that is commonly used for chloride diffusion. The latter is based on deterministic analyses involving the most influencing parameters such as distance of the concrete structure from the seaside, depth of steel concrete cover, ambient temperature, relative humidity and the water-cement ratio. However, a realistic corrosion initiation time cannot be estimated because of the uncertainties associated to the different parameters of the models. Therefore a reliability approach using FORM/SORM method has been applied to develop the proposed engineering models integrating a limit state function and a reliability index β. As a result, the corrosion initiation time is expressed by new exponential engineering models where the uncertainties are associated to the model parameters. The main emerging result is a realistic decision tool for corrosion planning inspection.

An Experimental Study on the Production and Mechanical Properties of Super-Workable Concrete (초유동 콘크리트의 제조 및 역학적 특성에 관한 실험적 연구)

  • Bae, Su-Ho;Youn, Sang-Dai;Lee, Dae-Hyoung
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.40 no.6
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    • pp.104-113
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    • 1998
  • The purpose of this experimental research is to produce the super-workable concrete using ordinary portland cement, blast-furnace slag lowder, and fly ash respectively, and investigate mechanical properties of super-workable concrete. For this purpose, after production of super-workable concrete for different unit weights of binder and percentages of fine aggregate, optimum mixing proportion of them was determined, and then mechanical properties of super-workable concrete such as static modulud of elasticity as well as compressive, tensile and flexural strength were tested and analyzed. Also, the mechanical performances of super-workable concrete were compared with those of high-strength concrete has an excellent mobility, compactability and segregation-resistance, but the strength of super-workable concrete is somewhat lower than that of high-strength concrete with equal mixing proportions of concrete.

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The Changing Patterns of Demand-Supply and Role of Mineral Resources in Economic Growth during Industrialization of the Republic of Korea (한국공업화과정(韓國工業化過程)에서의 광물자원(鑛物資源)의 수급구조변화(需給構造變化)와 경제성장(經濟成長)에 있어서의 역할(役割))

  • Yun, Suckew
    • Economic and Environmental Geology
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    • v.18 no.1
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    • pp.65-92
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    • 1985
  • A total of 12 mineral commodities significant in domestic output, economy and/or strategy of the Republic of Korea are chosen to examine the structural changes in production and demand-supply of these minerals during the last two decades of her industrialization. These include iron and manganese ores as the raw materials for iron and steel making, copper, zinc and tungsten ores among other non-ferrous metallic minerals, limestone (cement), kaolin, talc, pyrophyllite and graphite among other non-metallic minerals, and anthracite coal as the only domestic source of fossil energy. These are reviewed historically in time-series based on the statistical data which are tabulated and graphed in terms of domestic output, export, import, apparent demand-supply, its increasing rate, and self-sufficiency rate of each commodity. The increasing rates of demand-supply (IRDS) of some more important commodities are compared with those of Gross Domestic Production (GDP) and Economic Growth Rate (EGR) to evaluate how the IRDS contributed to the GDP and EGR. The major results revealed are as follows: Among the 12 commodities, the domestic output of 8 commodities appeared to have grown with steady upward trends: they are ores of lead, zinc and tungsten, limestone (cement), kaolin, talc, pyrophyllite and anthracite coal. Two commodities, ores of iron and copper, continued with unchanging or slightly declining trends and varied fluctuations, in spite of their cardinal importance to the heavy industry and strategy of Korea. The remaining two, graphite and manganese ore, have gradualy declined in domestic output in which the former has still enough resource potential but the latter has not and virtually ceased its domestic output. Trade patterns for mineral commodities in the Republic of Korea during the last two decades have changed greatly, being marked by a shift from mineral-exporting to mineral importing, mainly because of increasing consumption of mineral raw materials for industrialization rather than beceuse of decreasing output of domestic mineral commodities in quantity. In terms of trade patterns, the 12 commodities concerned in this study can be classified into the following four groups. The 1st group - ores of lead and tungsten have only been exported without imports. The 2nd group - amorphous graphite, and pyrophyllite have mainly been exported but partly been imported. The 3rd group - kaolin, talc and crystalline graphite have equally been exported and imported, but quantity of imports have rapidly been increased with time. The 4th group - ores of iron, manganese and zinc have shifted from exports to imports during the industrialization, particularly owing to the initiation of iron and steel making by the Pohang Iron and Steel Company in the middle 1970' s and the new establishment of the Onsan Zinc Refinery in the late 1970' s. All of the 12 commodities under considerations were far above 100% in self-sufficiency rate before or in the early 1960' s. Recently, however, most of them have been declined to below 100% except for those of limestone (cement) and pyrophyllite. It is particularly serious to identify that the self-sufficiency rates of the three important metallic minerals, iron, copper and manganese ores in 1982 appeared to be 5.1%, 0.5%, and 0.01%, respectively. The average self-sufficiency rate of the total domestic minerals produced in 1982 was 14.4% (in value) for that year. Mining industry appeared to be extremely high in its intermediate demand rate whereas its intermediate input rate to be quite low indicating that mineral raw materials have been exerted strong forward linkage effects upon the other industries rather than backward linkage effects. In comparing the curves of increasing rates of demand-supply of several major minerals - iron ore, manganese ore, copper ore, limestone (cement), kaolin, and anthracite coal - with those of Gross Domestic Production and Economic Growth Rate drawn on every graph, it is clearly shown that the curves of increasing rates of demand-supply comprise around 6 to 7 periods of cycles which roughly harmonious with those of the curves of GDP and EGR, except for the curve of anthracite coal of which the configuration seems to have resulted from the (artificial) government's mineral policy rather than from economic free market mechanism. The harmonic feature of these curves well suggests that the increasing rates of demand-supply of major minerals have been significantly contributed to the GDP and EGR. In addition, the wider amplitudes of the iron, manganese and copper curves than those of the limestone (cement) and kaolin curves indicate that the contribution of the former, metallic commodities, has been greater than that of the latter, non-metallic commodities.

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An Experimental Study on The Development of fly-ash Cement Mortal Permanent (플라이애쉬 시멘트 모르터를 사용한 비탈형 영구거푸집 개발에 관한 실험적연구)

  • 김형남;김우재;김성식;김영희;정상진
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.481-486
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    • 1999
  • According to results of this research Fly-ash Cement permanent-form production was found to be possible by fly-ash mortal. The compress strength 350kg/$\textrm{cm}^2$, banding strength 120kg/$\textrm{cm}^2$ were possible material separting and bleeding by excessive W/C rate was decreased permanent-form made by polymer solved high price of polymer by fly-ash. Model material was made by result of first research. There were no minute-crack on beam form and out surface of form was very smooth, So filling degree seemed desirable length of form after steaming curing was maintained as expected. with these results production of form seemed possible. In the banding load test, fly-ash showed increase of maxim load 12% than RC. in the case of minute-crack, comparing with RC, fly-ash showed no crack at connect. at the first stage under continuing loading size of crack increased. These phenomena seemed to be based on contribution of stress of inner bars in permanent-form. in the test of defection, fly-ash shower about 10% beam load increase than RC. in the case of beam defection, RC showed sudden decrease of tolerance at maxim load and total breaking, but permanent-form showed breaking of bending maintaining defection with contribution of steel stress ($\Phi$6 wire-mash). There phenomenic seemed to be attributed to increase of surface and steel tolerance of form. According to construction explacemaion, it was guessed that each panel was constructed by conner-steels in form edge. so cohesiveness was small. on these bases. keeping width of horizontal band 30cm, form-panel of 20mm width was found to be of use. Permanent-form was found to be efficient in compressibleness, defection, safety and use of Fly-ash mortal.

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Effect of Acidic Leachate on the Cement-based Landfill Soil Liner System (고화토차수층에 대한 산성침출수의 영향과 대책방안 - 산업부산물(고로슬래그, 플라이애쉬) 재활용 방안 중심으로 -)

  • Cho, Jae-Beom;Hyun, Jae-Hyuk;Lee, Jong-Deuk;Park, Joung-Ku
    • Journal of Korean Society of Environmental Engineers
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    • v.28 no.3
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    • pp.265-269
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    • 2006
  • This study was to investigate the effect of acidic leachate on the landfill liner system and healing of cracks by using industrial by-products; BFS(Blast Furnace Slag) and FA(Fly Ash). From the results of pH measurement, for OPC(Ordinary Portland Cement) and DM(Dredged Mud) mixtures immersed acidic leachate, the initial pH($4.5{\sim}5.5$) was heavily increased to approximately 10 after 60 days experiment due to the production of 2 mole $OH^-$ which was occurred by hydrolysis of CaO and MgO etc.. Meanwhile, the initial pH of acidic leachate immersed DM mixtures with BFS and FA respectively was lasted for longer period as compared to the comparison. The reason was that production of low Ca C-S-H hydrates which stabilized in acidic liquid. The physical properties(compressive strength, hydraulic conductivity) of DM mixtures added BFS and FA was improved. It was concluded that the dissolution of hydrates was disturbed by high alkalinity of BFS and FA.

Carbonation Behavior of Lightweight Foamed Concrete Using Coal Fly Ash

  • Lee, Jae Hoon;Lee, Ki Gang
    • Journal of the Korean Ceramic Society
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    • v.53 no.3
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    • pp.354-361
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    • 2016
  • The purpose of this study was to prepare lightweight foamed concrete by mixing coal fly ash of circulating fluidized bed combustion(CFBC) with cement, and to develop uses for recycling by analyzing carbonation behavior resulting from a change in conditions for pressurized carbonation. For concrete, CFBC coal fly ash was mixed with Portland cement to the water-binder ratio of 0.5, and aging was applied at room temperature after 3 days of curing at $20^{\circ}C$, RH 60%. For carbonation, temperature was fixed at $60^{\circ}C$ and time at 1 h in the use of autoclave. Pressures were controlled to be $5kgf/cm^2$ and the supercritical condition of $80kgf/cm^2$, and gas compositions were employed as $CO_2$ 100% and $CO_2$ 15%+N2 85%. In the characteristics of produced lightweight concrete, the characteristics of lightweight foamed concrete resulting from carbonation reaction were affirmed through rate of weight change, carbonation depth test, air permeability, and processing analysis for the day 28 specimen. Based on these results, it is concluded that the present approach could provide a viable method for mass production of eco-friendly lightweight foamed concrete from CFBC coal fly ash stabilized by carbonation.