• Title/Summary/Keyword: setting time of concrete

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An Experimental Study on the Setting of Antiwashout Underwater concrete Using Fly Ash (플라이애쉬를 사용한 수중불분리성 콘크리트의 응결에 관한 실험적 연구)

  • 권중현;김봉익
    • Journal of Ocean Engineering and Technology
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    • v.15 no.4
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    • pp.120-125
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    • 2001
  • This paper describes the effect of fly ash replacement on the setting time of antiwashout underwater concrete, where cement was replaced by 0% to 50%. Experimental work was performed on the condition of sea water and in air to find out the characteristics of setting time between the concretes that were cast in air and cast in 15$^{\circ}C$ of sea water. The experimental results show that the setting time of underwater concrete with 50% replacement was delayed about 10 hours than normal concrete. And it can be concluded that, at the case of underseawater concrete addicted with fly ash, the delayed final setting times are shown as the function Tf=0.069F+7.69, where Tf is the delayed final setting time and F is quantity of fly ash, respectively. These results confirm that the setting time underseawater concrete could be prolonged.

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Super Retarding Agent Affecting Setting Time of Concrete Using Mineral Admixture (혼화재를 사용한 콘크리트의 응결 시간에 미치는 초지연제의 영향)

  • Jeon Chung Keun;Kim Jong;Han Min Cheol;Shin Dong An;Oh Sean Kyo;Han Chean Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.643-646
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    • 2005
  • This paper reports the influence of super retarding agent(SRA) on the setting time of concrete incorporating mineral admixture including fly ash(FA), expansive additive(EA), silica fume(SF), blast furnace slag(BS) and blast furnace slag along with fly ash(BS+FA). An increase in SRA resulted in retarding the setting time of control concrete, while the use of mineral admixture led to a delay of setting time markedly, compared with that of control concrete under no SRA content. Meanwhile, An increase in SRA in concrete with mineral admixture exhibited comparable setting delay with control concrete. Furthermore, in case of the use of BS and SF, acceleration of setting time was observed with increase of SRA content. It is considered that proper dosage of SRA of concrete with SF and BS to secure similar setting delay with control concrete require rather larger than that of control concrete. Accordingly, For concrete with mineral admixture, in order to decide the proper dosage of SRA, application of correction factors is needed.

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Relation of Concrete Setting Characteristic and Lateral Pressure in Mass Concrete Wall (매스콘크리트 벽체에서 콘크리트 응결 특성과 측압과의 관계)

  • 박찬규;유재현;백승준;정재홍;진용만
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.935-938
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    • 2001
  • This paper reports the relation of concrete setting characteristic and lateral pressure in mass concrete wall such as side wall of LNG underground storage tank. In order to estimate the lateral pressure, initial setting time of low heat cement concrete with type of mineral admixture was measured for three concrete mixtures(W/P=41.6%) containing limestone powder, fly ash, and slag powder. As a result, the lateral pressure of the concrete containing limestone powder was the smallest than those of other concretes as well as the initial setting time.

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Estimation of the Setting Time of the Super Retarding Concrete Combining Mineral Admixtures (혼화재를 조합 사용한 초지연 콘크리트의 응결시간 추정)

  • Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.8 no.3
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    • pp.111-117
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    • 2008
  • This study provides the setting time prediction method of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24{\sim}35KJ/mol$ with slightly difference along with mixture proportion. This value is smaller than existing value $30{\sim}50KJ/mol$. It is Indicated that equivalent age using setting time can be a proper method to predict setting time and it also exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided setting time prediction value with super retarding agent contents and mineral admixture combination. Setting time prediction equation provided herein is possibly valid for estimating precise setting time of the super retarding concrete at the job site.

Construction Considering the Difference of Setting Time of Super Retarding Agent for Reduction of Hydration Heat of Footing Mass Concrete (기초 매스콘크리트의 수화열 저감을 위한 초지연제 응결시간차 공법의 현장 적용)

  • 황인성;배정렬;윤석명;김기철;오선교;한천구
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.95-98
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    • 2003
  • This paper presents the results of field experiment to apply the difference of setting tine method using super retarding agent for reducing hydration heat of mass concrete of foundation. According to the results, as the properties of fresh concrete, base concrete satisfies aimed slump and air content, and there is no difference of slump and air content with mixture of super retarding agent. The mixing ratio of super retarding agent is determined for setting time to be retarded by 12 hours in comparison with base concrete, but because the temperature of the air and concrete is low, the difference of setting time is retarded to 24 hours. In man concrete of foundation to which the difference of setting time method is applied, crack by hydration heat is not seen because the lower concrete of super retarding agent generates heat after generation of hydration heat of the upper concrete.

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Study on the Setting time of Concrete Using Ultrasonic Test (초음파법에 의한 콘크리트 응결시간 측정에 관한 연구)

  • 구본창;강민호;이대근;김종우;하재담;박석균
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04b
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    • pp.707-711
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    • 1998
  • Ultrasonic test usually was used for defect detection, crack depth measurements and strength estimation of hardened concrete. The essence of the pulse velocity method is that the transition time of an ultrasonic longitudinal pulse is measured in concrete. Ultrasonic velocity was propagated to the age of concrete, made a radical change at that time when concrete was setted. This study which monitored the change in a concrete by ultrasonic test was performed to estimate initial setting and final setting.

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Setting Time Evaluation of Concrete Using Electrical Resistivity Measurement (전기비저항 측정을 이용한 콘크리트 응결시점 평가)

  • Lee, Han Ju;Yim, Hong Jae
    • Journal of the Korea Concrete Institute
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    • v.29 no.4
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    • pp.361-369
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    • 2017
  • Setting time of cement-based materials can represent a developing strength in early-age mixture, and it can be used a significant parameter of high-performance concrete having various mix-proportions. Generally, initial and final setting time of concrete is measured by penetration resistance method that used a wet-sieving mortar mixture, therefore, it hardly represents the setting time of sound concrete including coarse aggregate. Recently, several nondestructive methods, such as ultrasonic velocity and impendence measurement, are proposed to evaluate the setting time of fresh concrete. This study attempts to measure an electrical resistivity using four-electrode method for evaluation of setting time in early-age cement-based materials. For this purpose, total 10 mixtures are prepared as different mix-proportions including chemical admixture. Based on the experimental results, two electrical parameters, such as initial electrical resistivity and rising time, are proposed to reflect a microstructure development by hydration of cement-based materials. As a result, proposed parameter is also discussed with the measured setting time by penetration resistance method.

A Study on the Temperature Dependency Affecting Setting and Strength Development of Concrete Using Mineral Admixtures (혼화재 사용 콘크리트의 응결 및 강도발현에 미치는 온도의존성에 관한 연구)

  • Joo, Eun-Hi;Shon, Myeong-Soo;Jeon, Hyun-Kyu;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.707-710
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    • 2005
  • This experimental study investigate temperature dependency affecting setting and strength development of concrete using mineral admixtures such as CKD, FA and BS. For the properties of setting at $5^{\circ}C$, setting time of concrete with mineral admixture was delayed about $3\~14$ hour compared with that of plain concrete. Use of CKD had a desirable effect on reducing setting retard under $5^{\circ}C$ because of $CaCO_3$ of CKD while use of FA and BS retarded setting time greatly. For compressive strength under $5^{\circ}C$, concrete with CKD had the most compressive strength in early age compared with the other mineral admixtures but exhibited slight strength loss in $-5^{\circ}C$ at 28days. Especially, concrete with FA and BS was observed in early stage at low curing temperature because of strength loss remarkably in $-5^{\circ}C$.

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A Fundamental Test of Temperature Crack Reduction Method Application by Setting Time Control of Large-Scaled Mat Foundation Mass Concrete (초대형 매트기초 매스 콘크리트의 응결시간조정에 의한 온도균열저감 공법적용의 기초적 실험)

  • Han, Cheon-Goo;Lee, Jae-Sam;Noh, Sang-Kyun
    • Journal of the Korea Institute of Building Construction
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    • v.9 no.3
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    • pp.95-101
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    • 2009
  • Constructing large-scale mat foundation mass concrete is increasing for the stability of building structure, because a lot of high rise building are being built in order to make full use of limited space. However, It is of increasing concerns that because limited placing equipments, available job-site and systems for mass concete placement in construction field do not allow to place great quantity of concrete at the same time in large scale mat foundation, consistency between placement lift can not be secured. And also, it is likely to crack due to stress caused by the difference of hydration heat generation time. To find out the solution against above problems, this study is to reconfirm the performance of normal concrete designed by mix proportion and super retarding concrete. The Fundamental test shows what happens if low heat proportioning and control method of setting time are applied at the job-site of newly constructed high rise building. The test result show that slump flow of concrete has been somewhat increased as the target retarding time gets longer, while the air content has been slightly decreased but this is no great difference from normal concrete. The setting time shows to be retarded as target retarding time gets longer, the range of retarding time increases. It is necessary to increase the amount of mix of super retarding agent in the proportion ration by setting curing temperature high since outdoor curing is about 6 hours faster than standard curing, which means the temperature of the concrete will be higher than the temperature of the surrounding environment, due to its high hydration heat when applying in a construction site. The compressive strength of super retarding concrete appears to be lower than normal concrete due to the retarding action in the early stage. However, as the time goes by, the compressive strength gets higher, and by the 28th day the strength becomes the same or higher than normal concrete.

Setting Properties of Concrete with the Combination of Mineral and Chemical Admixture (광물질혼화재와 화학혼화제의 조합사용에 따른 콘크리트의 응결특성)

  • Kim Jong;Song Seung Heon;Jeon Chung Keun;Han Min Cheol;Oh Seon kyo;Han Cheon Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.505-508
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    • 2004
  • This paper investigated the setting and compressive strength of concrete with the combination of mineral and chemical admixture. According to test results, plain concrete with high early strength development type AE water reducing agent(HEAEWRA) and $10\%$ of CKD respectively had earlier setting time than concrete with AE water reducing agent by $0.5\~1.5$ hours. Setting time of concrete with retarding type AE water reducing agent(RAEWRA) and FA $30\%$, BS $60\%$ respectively retarded by as much as $4\~7.5$ hours compared with plain concrete. Plain concrete with HEA WRA, $10\%$ of CKD and RAEWRA had higher strength than that of AE water reducing agent by as much as 5MPa at 28days. From the result of the paper, it is found that the combination of mineral admixture and setting accelerating or retarding agent can reduce the hydration heat cracks by setting time difference and hydration heat reduction effects.

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