• Title/Summary/Keyword: 타설 온도

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Temperature Patterns in Concrete Pavements at Very Early Ages (콘크리트 도로 포장의 초기 온도 분포 분석)

  • Kim, Seong-Min;Nam, Jeong-Hee
    • International Journal of Highway Engineering
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    • v.7 no.3 s.25
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    • pp.79-91
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    • 2005
  • The temperature patterns in Portland cement concrete (PCC) pavements were measured and comprehensively analyzed from the beginning of the concrete placement based on the temperature measurement technique developed using innovative and inexpensive temperature measurement sensors. The temperature measurements in PCC pavements were taken at several different locations forvarious slab thicknesses. The concrete temperature patterns in the vertical and longitudinal directions of the pavement were analyzed and the effects of the pavement surface reflectivity, shading, and covering on the concrete temperatures were evaluated. The results of this study showed that the significant differences in the maximum concrete temperatures on the placement day were observed according to the concrete placement time. Since the zero-stress temperature is a function of the maximum concrete temperature on the placement day, the placement time would be an important factor that affects the behavior and performance of concrete pavements. The surface conditions of the pavement, such as the surface color, shading, and covering also affected the temperature patterns in PCC pavements significantly.

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Hydration Heat Analysis of Coping With Ambient and Placing Concrete Temperature (교각 코핑부의 외기온도와 타설온도에 따른 수화열 해석)

  • Yang, Joo-Kyoung
    • Journal of the Korea Computer Industry Society
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    • v.9 no.3
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    • pp.99-104
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    • 2008
  • The thermal stresses due to hydration heat in massive concrete structures are affected by ambient temperature and placing concrete temperature. It is needed to predict the thermal stresses considering ambient temperature and placing concrete temperature. In this study, hydration heat analyses of coping were carried out. After the maximum tensile stress was occurred at 2,75 days the crack index was increased. Therefore the possibility of crack occurrence was rare. The possibility of crack occurrence can be reduced by placing concrete temperature drop. Therefore some method to drop the placing concrete temperature may be effective to reduce the possibility of crack occurrence.

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Numerical Experiment on Environmental Conditions of Mass Concrete (매스콘크리트의 주변환경조건에 대한 수치실험)

  • 이장화;변근주
    • Magazine of the Korea Concrete Institute
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    • v.9 no.5
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    • pp.217-224
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    • 1997
  • 매스콘크리트의 타설시 온도이력을 정확히 예측하기 위해서는 재령별로 민감하게 변하는 시공 및 주변 환경요인을 엄밀히 반영하여 온도이력을 합리적으로 해석하는 것이 필요하다. 본 연구에서는 시공시에 발생되는 주변환경조건을 고려한 상태에서 온도이력을 해석할 수 있도록 개발된 해석프로그램을 이용하여 주변환경조건에 대한 수치실험을 수행하고자 한다. 수치실험의 목적은 매스콘크리트 타설시 각종 인자가 매스콘크리트의 온도이력에 미치는 영향정도를 정량적으로 파악하여 실제 매스콘크리트의 설계 및 시공시 사전에 콘크리트의 온도이력을 예측하여 효율적으로 관리하는데 있다. 수치실험을 수행한 결과주어진 구조물의 설계조건에 부가하여 타설시기, 타설온도,거푸집조건 및 제거시기, 양생 및 개기온도 등의 시공시 주변환경조건의 영향이 대단히 민감하게 작용하는 것으로 나타났다.

An Effect on Early Temperature of Placing Concrete Affecting Compressive Strength of Concrete (콘크리트 타설 초기온도가 압축강도에 미치는 영향)

  • Park, Dae-Oh;Park, Young-Shin;Park, Jae-Myung;Gang, Yeon-Woo;Jun, Byung-Chea
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.641-644
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    • 2008
  • The strength of concrete is developed by cement hydration reaction influenced by the circumferential temperatures. In this study, therefore, the experiments are conducted and evaluated about the characteristics as changes of early concrete placing temperature and curing temperature to understand the effects of the temperature which influences concrete properties. The results of the experiments changing the early concrete placing temperature in 5$^{\circ}C$ and 10$^{\circ}C$ are followed. In case of conducting standard concrete curing, early compressive strength development rate of the concrete which had low placing temperature was low, but it was shown that early compressive strength development rate was not affected by low placing temperature in age 28 days of concrete. In case of conducting outdoor curing in winter, early compressive strength development rate of the concrete which had high placing temperature was high in all test specimens. As a results, early compressive strength development of concrete was influenced by temperature of early concrete, but after aging 28 days of concrete, it was influenced by curing temperature rather than temperature of early concrete.

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A Study of the Thermal Analysis for the Crack Control of Underground Pier Footing (지하 교각 기초의 온도균열 제어를 위한 수화열 해석 연구)

  • Park, Weon-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.2
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    • pp.91-101
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    • 2006
  • Lately, massive concrete structures are increasingly built. In such massive structures, the heat of hydration of mass concrete causes thermal cracks. To avoid thermal crack, methods widely acceptable for practical use are pre-cooling, pipe cooling and control of placing height. Thermal stress analysis is performed to find the way of controlling the thermal crack of pier footing mat in this paper. The footing mat model for the analysis is $12m{\times}14m$area and 3m height. The analysis results are compared with method of control of lift height and method of pipe cooling. The analysis results show that thermal crack can be removed by method of placing control and pipe cooling at footing mat placed on the ground.

Hydration Heat Analysis of Mass Concrete considering Heat Transfer Coefficient and Hydration Heat Difference (수화발열량차 및 열전달계수 변화를 고려한 매스콘크리트의 수화열 해석)

  • Han, Seung-Baek;Lee, Seong-Su;Shin, Hyo-Bum;Kim, Ho-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.249-252
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    • 2008
  • In recent large-scale structures, as mass concrete type structure is frequently applied to the building, temperature crack due to hydration heat needs to be considered. Since a volume change is internally or externally restricted in a mold after placing concrete, temperature crack of mass concrete takes place. By this reason, the reduction method to control this crack is required. In this study, low heat mixture and hydration heat difference is used to execute the analysis of hydration heat, considering the changes of heat transfer coefficient according to curing conditions and block placement of mass concrete. For the analytical modelling, original portland cement and concrete of low heat mixture are placed in the upper and lower payer, respectively. A convection boundary condition is fixed because mass concrete of block placement is characterized by the difference of mold form and curing condition. Through the analysis results considering the changes of low heat mixture, block placement, and heat transfer coefficient, we check out the temperature and stress distribution and analyze the temperature crack reduction effect.

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Thermal analysis of concrete dam considering placing interval (타설 간격을 고려한 콘크리트 댐의 수화열 해석특성)

  • Chu, In-Yeop;Jang, Bong-Seok;Kim, Jin-Keun;Park, Byung-Kook
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.385-386
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    • 2009
  • The temperature crack of concrete structure is caused by the phenomenon which the concrete volume is restricted in the inside or outside part due th the temperature variations induced by the hydration heat of cement. And mass concrete structures are weak in temperature crack. This study performed the hydration heat analysis of Seongdeok dam to analyze the hydration heat according to different interval of placement.

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Development of Temperature Control Technology for Massive Machine Foundations (기계기초 매스콘크리트의 균열제어를 위한 온도관리기법의 개발)

  • Huh, Taik-Nyung;Son, Young-Hyun;Lee, Suck-Hong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.4
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    • pp.227-233
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    • 2001
  • 최근 비약적인 경제발전에 힘입어 장대교량, 항만, 댐, 도로, 원자력 발전소 등과 같은 대규모 기간구조물의 건설이 증가하고 있으며, 구조물은 대형화 혹은 고강도화되는 추세에 있다. 특히, 전술한 구조물을 매스콘크리트로 가설하게 되면 초기재령시에 수화열로 인한 균열이 발생할 가능성이 매우 높기 때문에 효율적인 매스콘크리트의 개발과 매스콘크리트 구조물의 설계기술 및 시공방법이 중요한 연구대상으로 등장하게 된다. 본 논문에서는 가로 52.6m, 세로 14.4m, 높이 8.5m의 기계기초 매스콘크리트의 시공에 적합한 온도관리기법을 다음과 같은 단계로 제안하고자 한다. 먼저 온도상승요인을 최소화하는 콘크리트의 배합비를 산정한다. 산정된 콘크리트의 열특성을 측정하기 위해 단열온도실험을 수행하여 각종 열특성상수와 단열온도 상승곡선식을 도출한다. 이와 같은 열특성치를 콘크리트 구조체에 적용하여 열응력해석을 수행한다. 이와 같은 열응력해석을 통하여 구조물의 분할타설높이에 따라 온도균열이 발생하지 않는 콘크리트 내외부의 온도차를 결정한다. 이때 열응력해석에 범용 유한요소 프로그램인 Diana을 사용한다. 콘크리트의 타설은 현장조건과 타설시점을 최대로 고려하고 양생방법으로 콘크리트 내외부의 온도차를 최소화하기 위해 이중단열효과가 있는 거푸집과 가열장비을 사용한다. 또한 콘크리트의 온도관리를 위하여 구조물 내외부에 온도게이지를 매립하고 30분마다 계측을 수행하면서 콘크리트 내외부 온도차가 허용 해석범위를 유지하도록 한다. 양생기간은 7-10일 정도를 유지한다. 전술한 온도관리기법을 통하여 완공후 수평정밀도가 기초의 허용침하량으로 환산하여 $1{\mu}m$ 인 고정밀도의 기계기초는 완벽하게 시공되었다. 따라서 매스콘크리트의 온도균열을 제어할 수 있는 시공방법으로 제안한다. 또한 매스콘크리트의 내외부 온도차를 단열온도실험과 온도해석으로부터 정한 값이내로 제어하고 충분한 양생관리를 병행하면 수화열에 의한 콘크리트의 온도균열을 최소화할 수 있을 것으로 기대한다.

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Design of a Concrete Mix Considering Curing Temperature and Delay Time in Concrete Placement (현장 콘크리트 타설시 양생온도와 대기시간을 고려한 배합설계 결정)

  • Moon, Sungwoo;Lee, Seong-Haeng;Choi, Hyun-Uk
    • Korean Journal of Construction Engineering and Management
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    • v.20 no.1
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    • pp.133-140
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    • 2019
  • The concrete mix should be designed and produced to reflect the specific site conditions during concrete placement. That is, the concrete mix design should be planned considering temperatures, work environments, pouring methods, etc. The objective of this research is to understand the external factors of curing temperature and delay time that influence concrete strengths during pouring work, and provide concrete mix design that can be most robust to the effects of external factors. The Taguchi's robust method is used in preparing the concrete mix design to achieve the research objective. In a case study, an indoor concrete test was performed to find the optimal combination of concrete mixes with external factors of curing temperature and delay time. Concrete test cylinders were made to test concrete strengths given different external factors. The study results showed that the optimal performance of concrete strength can be achieved by applying the robust method when preparing a concrete mix design.

Hydration Heat Analysis of Seongdeok Cofferdam (성덕 다목적댐 가물막이댐의 수화열 해석)

  • Kim, Jin-Keun;Chu, In-Yeop;Jang, Bong-Seok;Ha, Jae-Dam;Park, Byung-Kook;Kim, Jeong-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.481-484
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    • 2008
  • The temperature crack of concrete structure is caused by the phenomenon which the concrete volume is restricted in the inside or outside part due th the temperature variations induced by the hydration heat of cement. And mass concrete structures are weak in temperature crack. Seongdeok multi-purpose dam is gravity dam which is being constructed in Cheongsong-gun, Gyeonsangbuk-do. Upstream cofferdam was constructed to examine the temperature crack due to hydration heat and to decide the height of placement. Therefore this study performed the hydration heat analysis of Seongdeok upstream coffer dam to analyze the hydration heat according to different height of placement and to compare with measured results.

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