• Title/Summary/Keyword: low-heat concrete

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The Effect of Heat Curing Methods on the Temperature History of the Fly Ash Concrete Subjected to Extremely Low Temperature (복합보온양생 방법이 극저온 조건하 플라이애시 치환 콘크리트의 온도이력에 미치는 영향)

  • Han, Min-Cheol;Son, Ho-Jung
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.3
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    • pp.85-90
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    • 2012
  • In this study, temperature profile of the fly ash concrete were studied in accordance with the change of heating curing method combination for the slab concrete in order to develop efficient protection method of the concrete subjected to $-20^{\circ}C$. The slab concretes with the size of $1200mm{\times}600mm{\times}200mm$ were fabricated with W/B of 50% and exposed to $-20^{\circ}C$ for 7 days. Five different combinations of heat curing methods were applied to the slab concrete specimen; two combinations of heat supplying by electrical heater and surface heat insulation material such as polyethylene film and quadrupled layer bubble sheet based on heat enclosure installment; three combinations of heating coil embedment and surface heat insulation materials such as polyethylene film, sawdust and quadrupled layer bubble sheet based on heat enclosure installment. Test results showed that by applying both heating coil and bubble sheet and heat enclosure, the concrete exposed to $-20^{\circ}C$ can be effectively protected from early-age frost damage.

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Reducing Hydration Heat of Mass Concrete by Applying Combination of Powdered Materials and CGS as Fine Aggregate (분체계 재료조합 및 석탄 가스화 용융 슬래그를 잔골재로 활용한 매스 콘크리트 수화열 저감)

  • Park, Sang-Won;Han, Jun-Hiu;Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.24 no.2
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    • pp.169-180
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    • 2024
  • In this study, to suggest an efficient method of using coal gasification slag(CGS), a byproduct from integrated gasification combined cycle(IGCC), as a combined fine aggregate for concrete mixture, the diverse performances of concrete mixtures with combined fine aggregates of CGS, river sand, and crushed sand were evaluated. Additionally, using CGS, the reduction of the hydration heat and the strength developing performance were analyzed to provide a method for reducing the heat of hydration of mass concrete by using combined fine aggregate with CGS and replacing fly ash with cement. The results of the study can be summarized as follows: as a method of recycling CGS from IGCC as concrete fine aggregate, a combination of CGS with crushed sand offers advantages for the concrete mixture. Additionally, when the CGS combined aggregate is used with low-heat-mix designed concrete with fly ash, it has the synergistic effect of reducing the hydration heat of mass concrete compared to the low-heat-designed concrete mixture currently in wide use.

Prevention of Early Frost Damage of the Concrete under Severely Low Temperature according to Heat Curingmethods (극저온 조건에서 보온양생 방법 변화에 따른 콘크리트의 초기동해 방지)

  • Han, min-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.16 no.1
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    • pp.67-76
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    • 2016
  • Concrete exposed to severely low temperature below $-20^{\circ}C$ should be provided with proper heat supplying curing to protect the concrete from early frost damage at the time of pouring.meanwhile, so far, effective heat curingmethods of the concrete under severely low temperature are not well established in Korea. For this reason, the objective of this paper is to provide effective heat curingmethod of concrete exposed to severely low temperature to protect early frost damage by varying the combination of heat curingmaterial combinations. Temperature history,maturity development and core strength results are investigated. Fourmock-up specimens simulating slab, wall and column were prepared and heat insulation, heat supplying and both were applied. Test results indicate that the combination of quadruple layer bubble sheet(4BS) and embedding of heating cable has desirable performance for a slab, and heat supplying curing inside heat enclosure and heat generationmat also shows desirable performance for a wall, and for a column, use of EPS heat insulation has proper performance against early frost damage, which reaches $45^{\circ}D{\cdot}D$ and helps the concretemaintain above $0^{\circ}C$ within 3 days. Themethodsmentioned above are believed to be optimum protection from early frost damage of the concrete under $-20^{\circ}C$.

A Study on the Effect of Pipe Cooling in Mass-Concrete (매스콘크리트의 파이프 쿨링 효과)

  • 윤승권;김은경;김래현;신치범
    • Proceedings of the Korea Concrete Institute Conference
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    • 1995.10a
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    • pp.329-333
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    • 1995
  • The usual methods for the temperature control of mass-concrete structures include the use of low-heat cement, pre-cooling, or pipe-cooling. In order to control the heat of hydration of mass-concrete structures such as massive pier or anchor block, and mat foundation, the pipe cooling method is widely acceptable for pratical use. In this paper, method of analysis using the Finite Element Method was applied to analyze the heat exchange on the field of three dimensional thermal conduction. The result of analysis Well agreed with experimentally measurement data by "KUMATANI". The method of this analysis will be used widely to control the heat of hydration by the pipe cooling in mass-concrete.-concrete.

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Chemical Resistance of Low Heat Cement Concrete Used in Wastewater Treatment Structures Built on Reclaimed Land (해안매립지 하수처리시설물에 적용한 저발열시멘트 콘크리트의 내화학성 평가)

  • Chung, Yongtaek;Lee, Byungjae;Kim, Yunyong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.7
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    • pp.113-119
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    • 2019
  • Concrete structures built on reclaimed land are combined with chemical erosion such as chlorine and sulfate ions from seawater. Chloride attack deteriorates the performance of the structure by corroding reinforcing bars. In addition, the waste water treatment structure has a problem that the concrete is deteriorated by the sulfate generated inside. Therefore, in this study, the characteristics and chemical resistance of low heat cement concrete used in wastewater treatment structures constructed on reclaimed land were evaluated. As a result of the experiment, the target slump and air content were satisfied under all the mixing conditions. The slump of low heat cement (LHC) concrete was higher than that of ordinary portland cement (OPC) concrete, while the air content of LHC concrete was smaller than that of OPC concrete with the same mix proportion. As a result of compressive strength test, OPC concrete showed higher strength at younger age compared to 28 days. In contrast, LHC concrete exhibited higher strength than OPC concrete at the age of 56 days. As a result of chlorine ion penetration tests, LHC-B concrete showed chlorine ion penetration resistance performance of the "very low" level at the age of 56 days. As a result of chemical resistance evaluation, when the LHC concrete is applied without epoxy treatment, chemical resistance is improved by about 18% compared to OPC concrete. In testing chemical resistance, the epoxy coated concrete exhibited less than 5% strength reduction when compared to sound concrete.

An Application of the Mass Concrete Using Ternary Blended Cement (3성분계 시멘트를 사용한 매스콘크리트의 시공사례)

  • 권영호;하재담;전성근;김무한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.1229-1234
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    • 2001
  • The bottom slab of Inchon LNG in-ground #213 tank is designed as a massive structure witch has a large depth and section. The purpose of this study is to determine the optimum mix design having good workability and low hydration heat for bottom slab concrete and to control the actual concrete quality in site. For this purpose, we select the optimum mix design used ternary blended cement(furnace slag cement+fly ash) and design factors. As test results of actual application, we have finish placing the bottom slab concrete of 23,180㎥ during 68hours with good success and obtain the good quality of fresh and hardened concrete including slump, air contents, no-segregation, compressive strength and low hydration heat in actual data. All test results are satisfied with our specifications for bottom slab concrete and we cut costs as the use of ternary blended cement and the reduction of placing hours.

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The characteristics of Low Blaine Cement (저 분말도 포틀랜드 시멘트의 특성)

  • 김재영;전준영;송종택
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.10c
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    • pp.13-18
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    • 1998
  • This experiments carried out in order to investigate decreasing of the hydration heat and physical characteristics of the low blaine OPC. The experiments results indicated hydration heat was reduced by about 15% in th low blaine OPC(2300$\textrm{cm}^2$/g). The Mini-slump value of the cement paste was significantly increased and viscosity of one was decreased as blaine value in OPC decrease.

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The Characteristics of Blastfurnace Slag Blended Cement with Low Blaine Slag Powder (저 분말도 슬래그를 사용한 슬래그 시멘트의 특성)

  • 변승호;최현국;김재영;송종택
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.10c
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    • pp.19-24
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    • 1998
  • In this study, blended cement with low blaine(2000, 3000$\textrm{cm}^2$/g) blast-furnace slag power by 10-70wt.% was investigated through the measurement hydration heat, physical properties. The experiment results indicated compressive strength was decreased as low blaine slag blended, but hydration heat was reduced significantly and flow of the cement paste was increased.

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Evaluation of Shrinkage and Creep Behavior of Low-Heat Cement Concrete (저열 시멘트 콘크리트의 건조수축 및 크리프 거동 평가)

  • Mun, Jae-Sung;Yang, Keun-Hyeok;Kim, Si-Jun
    • Journal of the Korea Institute of Building Construction
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    • v.16 no.4
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    • pp.305-311
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    • 2016
  • This study examined the long-term inelastic characteristics, including unrestrained shrinkage and creep, of low-heat cement concrete under different ambient curing temperatures. To achieve the designed compressive strength of 42MPa, water-to-binder ratios were selected to be 27.5, 30, and 32.5% for curing temperatures of 5, 20, and $40^{\circ}C$, respectively. Test results showed that the shrinkage strains of concrete mixtures tended to decrease with the decrease in curing temperature because of the delayed evaporation of internal capillary and gel waters. Meanwhile, creep strains were higher in concrete specimens under lower curing temperature due to the occurrence of the transition temperature creep. The design models of KCI provision gave better accuracy in comparison with test results than those of ACI 209, although a correction factor for low-heat cement needs to be established in the KCI provision.

Evaluation of Thermal Characteristics in Association with Cement Types in Massive Concrete Structure (매스콘크리트 구조물에서의 시멘트 종류별 수화발열 특성 평가)

  • 김상철;강석화;김진근
    • Journal of the Korea Concrete Institute
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    • v.11 no.6
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    • pp.3-12
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    • 1999
  • The larger, loftier and more highly strengthened the recent structures become, the greater attention is paid to the problem of thermal crack occurrence associate with hydration heat. As one of methods to solve the problem, a care has been taken to the improvement of construction such as the application of pre-cooling or pipe-cooling, adjustment of concrete block size, concrete placement timing, joint arrangement and so on. But it is expected that a proper selection of cement shall additionally contribute to the control of thermal cracks. In this study, thus, we selected 4 types of cements such as Type V for anti-sulphate, blast furnace cements (slag content of 45% and 65% respectively)and ternary blended low heat cement, and carried out mock-up tests. In every assigned time, temperatures and thermal stresses were measured and calculated from raw data. As a result of measurement, it was found that the magnitude of hydration heat is in order of blast furnace slag cement. Type V and ternary blended low heat cement. Results of thermal stresses were same as the order of temperature. In addition, thermal stresses calculated from the data of strain gauges showed almost similar to those measured from effective stress gauges only when strain values were adjusted properly in accordance with initial time of stress appearance. Theoretical results agreed well with the measured values comparatively, but showed slight differences. It is inferred that these differences shall be reduced if more tests capable of evaluating thermal characteristics of concrete are carried out.