• Title/Summary/Keyword: low-heat concrete

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Temperature Crack Control in Slab Type구s Mass Concrete Structures (슬래브형 매스콘크리트 구조물의 온도균열제어)

  • 김동석;구본창;하재담;진형하;오승제;변근주
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.333-336
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    • 1999
  • The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The Aim of this paper is to verify the effect of low heat blended cement in reducing thermal stress in slab type's mass concrete such as container harbor structures.

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An Experimental Study on the Physical Properties of Concrete Using all kinds of Cements (시멘트특성에 따른 콘크리트의 물리적 성질에 관한 실험적 연구)

  • 김상철;노재호;강승희;최수홍
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.04a
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    • pp.36-41
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    • 1996
  • The selection of Cement types is greatly dependent on the structural requirement and consturction location associated with control of hydration heat, acquisition of early strength, existence of sulfate attacks and so on. Based on this, this study adresses the comparison of physical properties of concrete according to the use of different cement types. As a result of testing with OPC, blast furnace slag and low heat cement, it is found that concrete made with low heat cement is much better in term of hydration heat and permeability. It is also recommended to select a preper cement type depending on structural characteristics.

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Property Evaluation of Low-Heat Concrete with Phosphate-PCM Composite (Phosphate-PCM계 복합물질 기반 저발열 콘크리트의 특성 평가)

  • Ki, Jun-Do;Lee, Sang-Hyun;Cho, Hong-Bum;Kim, Young-Sun;Seok, Won-Kyun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.06a
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    • pp.175-176
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    • 2020
  • This study aims to develop the hydration heat reducing material (powder type) to lower the heat of hydration of mass members in the extremely hot weather condition. In this study, we applied the developed material to the concrete that used two kinds of binders with cement and evaluate the concrete properties with it.

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The Resistance of Penetrability and Diffusion of Chloride Ion in Blended Low Heat Type Cement Concrete (저발열형 시멘트 콘크리트의 염소이온 침투$\cdot$확산에 대한 저항성)

  • 문한영;신화철
    • Journal of the Korea Concrete Institute
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    • v.11 no.4
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    • pp.31-41
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    • 1999
  • Blended Low Heat type cement is ground granulated blast furnace slag and fly ash mixed ternary with ordinary portland cement. From the viewpoint of X-ray patterns of domestic LHC, the main components of cement such as $C_2$S, $C_3$A, $C_3$S are considerably reduced. Therefore the heat evolution of LHC paste is 42cal/g lower than of OPC paste. At early age, the compressive strength development of LHC concrete is delayed, but the slump loss ratio of fresh concrete is reduced more than 20% with elapsed time. The penetrability of LHC is lower than that of OPC by 1/7.8 with the penetrability of chloride ion into the concrete until the age of 120 days. And the PD Index value of LHC is 0.44$\times$10-6 $\textrm{cm}^2$/s, which indicates only 39.3% of OPC. From the Mercury Intrusion Porosimetry test of cement past, we know that the pore size of LHC is more dense than that of OPC by production of C-S-H.

Field Application of the Mass Concrete Utilizing Combined Method for Temperature Crack Reduction (온도균열 저감공법을 복합사용한 매스콘크리트의 현장적용)

  • Han, Sang-Yoon;Lee, Chung-Sub;Baek, Dae-Hyun;Jang, Duk-Bae;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2010.05a
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    • pp.37-39
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    • 2010
  • In this study, with new office construction site of S Construction company as subject, to solve all the problems according to reduced hydration heat and temperature crack of mass concrete used mat foundation and placing time difference, low heat combination of coarse particle cement and fly-ash and setting time difference applied AE water reducing agent, and to prevent the early frost damage caused by low outdoor temperature, a heat insulation method using double bubble sheet was conducted. As a result, it was found that hydration heat and setting time difference was reduced by applying a low heat combination and setting time difference construction method, and that the high insulation capability of the double bubble sheet was able to not only prevent the early frost damage but also reduce temperature difference between the central part and the upper part of mass concrete.

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Field Application of a Technique for Reducing Hydration Heat-induced Cracks in Mass Concrete (수화발열량차 공법을 이용한 매트기초 매스콘크리트 균열저감 및 현장적용)

  • Jo, Man-Ki;Kim, Jun-Ho;Heo, Young-Sun;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2012.11a
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    • pp.55-57
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    • 2012
  • In this study, the field applicability on reducing the heat of hydration of mass concrete by using the hydration heat difference method is analyzed with the following summary. As a result of applying the hydration heat difference method by using low heating combination, the temperature difference between the central part and the surface part of mass material was reduced, and as a result of visual observation, there was no showing of cracks by the hydration heat on the upper surface part. Therefore, the cracking index of the field to apply this method was shown to be approximately 1.57 with very little crack occurrence probability of less than 3%.

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Zero-Crack Construction on the Fundamental Mass Concrete Using Double Bubble Sheets and Applying Low Heat Mixture (저발열 배합 및 이중버블시트에 의한 기초 매트 매스 콘크리트의 무균열 시공)

  • Park, Yong-Kyu;Song, Sung-Bin;Baek, Byung-Hoon;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2006.11a
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    • pp.5-8
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    • 2006
  • This study investigates the field application, Songdo the # 1st WORLD, on zero-crack construction of the fundamental mass concrete using double bubble sheets and applying low heat mixture. Experimental results of hydration heat analysis showed that crack modulus of concrete incorporating 20% of blast furnace slag cement was 1.0 in 120 hours, representing 50% probability of crack occurrence, thus requiring additional measures. As for a curing method, a specimen insulating two layers of vinyl chloride+double bubble sheets exhibited only $16.5^{\circ}C$ difference between upper and lower sections, and it also showed favorable workability as well as competitive economic side. Therefore it was determined to use it for curing method in this field. For the curing results of practical field, using 2 layers of vinyl chloride+double bubble sheets and applying low heat mixture on the fundamental mass concrete in 3A residential building exhibited less than only $15^{\circ}C$ difference between surface and center section of that in 5 days elapse and less than $20^{\circ}C$ in 9 days. This means that the crack by hydration heat was prevented, and other fields structures also resisted the plastic shrinkage by insulating the vinyl, sinking crack by second temping, even drying shrinkage by the mixture of low unit water. Therefore the crack on the placement has not been found so far, since the construction was started before 6 month.

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Thermal Crack Control about of LNG in Inchon (인천 LNG 지하탱크 Bottom 의 온도균열제어)

  • Koo, Bon-Chang;Ha, Sang-Wook;Kim, Dong-Seuk;Ha, Jae-Dam;Lee, Jong-Ryul;Kwon, Young-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.291-296
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    • 2000
  • The crack of concrete induced by the heat of hydration is s serious problem, particularly in concrete structures such as bridge piers. thick walls, box type walls, mat-slab of nuclear reactor building, dams of foundations of high rise buildings, etc. As a result of the temperature rise and restriction condition of foundation, the thermal stress which way induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which consider steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis, Secondly it shows the application of the cracks control technique like the bottom of No.15,16 Underground LNG Tank in Inchon.

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Thermal Crack Control of Massive Foundation Mat of Office-tel Using Thermal Analysis (오피스텔 대형 기초매트의 온도해석을 통한 온도균열제어)

  • 김태홍;하재담;김동석;이종열
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10b
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    • pp.1181-1186
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    • 2000
  • The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as biers, thick walls, box type walls, mat-slab of nuclear reactor buildings, dams or foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which considers steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis considering season. Secondly it shows the application of the cracks control technique like block placement.

Construction and Evaluation of Thermal Crack Stability about Bottom Slab of the #219 LNG Underground Tank in Incheon (인천 LNG 지하탱크 #219 Bottom Slab시공 및 온도균열 안정성 평가)

  • Son, Young-Jun;Ha, Jae-Dam;Um, Tai-Sun;Lee, Jong-Ryul;Park, Jong-Sik
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.689-692
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    • 2006
  • The crack of concrete induced by the heat of hydration is a serious problem, particularly in massive concrete structures. In order to control the temperature crack of massive concrete, the selection of appropriate materials like low heat cement, mixture materials, etc. is essential. In tills study, mix proportion using low heat portland cement and lime stone powder was designed and the best mix proportion, B-1, was selected. When bottom slab of the #219 LNG tank in Incheon was constructed, concrete temperature was measured. And thermal stress was analyzed about bottom slab of the LNG tank. As results of the thermal analysis, crack index was 1.60 in bottom slab and satisfied with construction specifications(over 1.0).

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