• Title/Summary/Keyword: early strength

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Early Estimation of Compressive Strength of Concrete Using Mineral Admixture by Refrigeration Curing Method (냉동양생에 의한 광물질 혼합 콘크리트의 압축강도 추정)

  • Sung , Chan-Yong;Cho , Il-Ho
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.5
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    • pp.55-60
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    • 2004
  • This study was performed to evaluate the early estimation of compressive strength of concrete using mineral admixture by refrigeration curing method. It was a method of early decision for the property of concrete after the curing age 28days through the refrigeration curing at $-18{\pm}3^{\circ}$ for five hours. The test result was fixed connection between the curing age 28days and 31hours by the compressive strength test through the standard curing and refrigeration curing. Accordingly, it can be reduced the mistake of construction work by forecasting the property of concrete through the refrigeration curing.

Study on the field application according to the early strength of the concrete admixed with polycarboxylate superplasticizer (폴리카본산계 고성능감수제를 이용한 콘크리트의 초기강도에 따른 현장적용성 연구)

  • Lee Jin Woo;Kim Kyung Min;Bae Yeoun Ki;Lee Jae Sam
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.200-203
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    • 2004
  • In this study, it is examined the properties of flow and early strength of concrete according to superplasticizer. For this experiment, it is analyzed that the flow and strength properties according to the mixture factors, compared with naphthalene superplasticizer(normal & delay type) focused on polycarboxylate superplasticizer. (1) The slump loss of concrete used polycarboxylate superplasticizer showed $4\~8cm$, it is judged that slump loss according to the time lapse can be minimized. (2) The performance of polycarboxylate superplasticizer is about $70\%$ level of the normal naphthalene type, it is superior to the delay type, but the performance showed so lowly. The 28days, early strength didn't differ according to the kind of superplasticizer.

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An Experimental Study on the Early Frost Resistance Properties of High-Strength Concrete in Winter Concreting (동절기 고강도콘크리트의 시공에 있어서 초기동해 방지에 관한 실험적 연구)

  • 권영진
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2001.11a
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    • pp.76-81
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    • 2001
  • Recently, the structure is higher and larger, so that the application of high-strength concrete is increased, And as the development of construction skills, it is possible to place during the winter. Concrete work during winter is indispensible to shorten time of completion and cut costs. When concrete work during winter is placed, it has anxiety that concrete freeze at low temperature. As repetition of concrete's freezing cause reduction of durability, it is necessary for mixing to pay attention to air content and W/C ratios. Accordingly, in this study, we estimate the frost resistance by air content and W/C ratios, and development of strength after early-frost damage in the high-strength concrete during the cold weather. In this study, it could be confirmed that factors which were air content, W/C ratios and early curing period, affected on the frost resistance.

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A Study on the Cold Weather Concrete using High Early Strength Concrete (조강시멘트를 이용한 한중콘크리트의 특성평가 연구)

  • 임채용;엄태선;유재상;이종열;이순기;이동호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.261-264
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    • 2003
  • Cold weather can lead to many problems in mixing, placing, setting time, and curing of concrete that can have harmful effects on its properties and service life. Korean Concrete Institute (KCI) defines cold weather as a period when the average daily air temperature is less $4^{\circ}C$ and recommends to cast concrete with special care such as shielding, heating and so on. The use of high early strength cements may improve the rate of hardening characteristics of concrete in cold weather by making it possible to achieve faster setting time and evolving more hydration heat than ordinary Portland cement. Higher early strength can be achieved using Type III cement especially during the first 7 days. The strength increase property of Type III cement at low temperature was studied. As a conclusion the heat or heat insulation curing period can be reduced to 50~75%. So, it can be used for cold weather concreting to reduce construction cost and extend the construction season.

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A Study on Securing Early Strength of Concrete in a Low Temperature Time (저온기 콘크리트의 조기압축강도 확보방안에 관한 연구)

  • Lee, Do-Bum;Choi, Il-Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.273-276
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    • 2004
  • Recently. cold weather constructions were popularized because of the importance of construction term. The special method about mix design and curing of concrete was being planned to conduct cold weather constructions, but these method were not considered in a low temperature time. A Strength revelation of concrete is delayed in a curing condition of low temperature. If a construction was loaded in this case, cracks or remaining deformations are generated in a construction. So, a strength revelation characteristic in early age was investigated to secure early strength of concrete in curing condition of a low temperature. In this study, the method about concrete mix design was presented to secure construction safety in a low temperature time.

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Concrete strength monitoring based on the variation of ultrasonic waveform acquired by piezoelectric aggregates

  • Wei, Li;Wang, Zijian;Cao, Maosen;Fu, Ronghua
    • Structural Engineering and Mechanics
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    • v.76 no.5
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    • pp.591-598
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    • 2020
  • Ultrasonic waves provide a non-destructive and sensitive way to monitor the concrete hydration. However, limited works are reported to monitor the evolution of the mechanical parameter at early ages. In this study, modified piezoelectric aggregates are embedded inside a concrete beam to excite and receive primary waves. A hydration index, namely, the variation of ultrasonic waveform (VUW) is developed to characterize the variation of the transmitted waves during the hydration process. The recorded hydration indices are compared with the compressive strength measured by destructive test at different ages. The results show that the VUW is closer to the compressive strength than the other two traditional hydration indices, ultrasonic velocity and wave packet energy. The proposed VUW provides a simple and accurate way to monitor the concrete hydration at early ages.

A Study on the Adhesive Performance of High-early Strengthening Polymer Cement Composites for Crack Repair of RC Structures (RC 구조물의 균열보수용 조강성 폴리머 시멘트 복합체의 접착성능에 관한 연구)

  • Park, Dong-Yeop;Kim, Sang-Hyeon;Jo, Young-Kug
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.11a
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    • pp.179-180
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    • 2023
  • The adhesion performance of PCCs for crack repair of RC structures was greater in the case of using ultra high-early strength cement than in the case of using ordinary Portland cement, and the effect of mixing silica fume was higher in the case of ordinary Portland cement than that of ultra high-early strength cement. On the other hand, 130% of W/C was more fluid than 80% of W/C in the same P/C 80%, which increased the fillability and improved the strength, but the strength improvement effect was the greatest in adhesion in flexure. Through this study, the basic characteristics of the adhesion performance of PCCs were identified, and based on this, it is necessary to induce an optimal mixing design that can increase adhesion performance through various mixing designs.

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Suggestion for Non-Destructive Testing Equation to Estimate Compressive Strength of Early Strength Concrete (조기강도 콘크리트의 압축강도 추정을 위한 비파괴검사 실험식의 제안)

  • Lee, Tae-Gyu;Kang, Yeon-Woo;Choi, Hyeong-Gil;Choe, Gyeong-Choel;Kim, Gyu-Yong
    • Journal of the Korea Institute of Building Construction
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    • v.16 no.3
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    • pp.229-235
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    • 2016
  • In construction field, it used various technique for concrete formwork. Part of them, non-destructive test has been conducted to estimate a compressive strength of concrete easily such as rebound method and ultrasonic pulse velocity method etc. Former research has recommend proposed equation based on experimental data to investigate strength of concrete but it was sometimes deferent actual value of that from in field because of the few of data in case of early strength concrete. In this study, an experiment was conducted to analyze strength properties for early strength concrete using cylinder mold and $1,000mm{\times}1,000mm{\times}200mm$ rectangular specimen. And compressive strength of concrete was tested by non-destructive test, and calculated by the equation proposed former research. As a result, the non-destructive test results showed approximately 70 percent of the failure test value for all conditions, and worse reliability was obtained for high strength concrete samples when the ultrasonic pulse velocity method was used. Based on the scope of this study, the experimental equation for estimating compressive strength of early strength concrete from 24MPa to 60MPa was proposed.

A study on the Practical Application of High Early Strength Type Concrete Using Fine Particle Classifying Cement (입도분급 미분 시멘트를 이용한 조강형 콘크리트의 현장실용화에 관한 연구)

  • Choi, Sung-Yong;No, Dong-Hyun;Kim, Ki-Hoon;Kim, Kyung-Min;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2008.05a
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    • pp.117-121
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    • 2008
  • This study investigates practical application of high early strength type concrete using fine particle classifying cement, and the results are summarized as following. The replacement use of FC 30% did not great influence on concrete mix, therefore mixing without additional SP and AE was available using equal mix with OPC. The ratio of increasing temperature by heat of hydration was similar with OPC, and the compressive strength was over then 5MPa at -28℃ outside temperature on 2nd day. Therefore, it is considering that the first purpose, the effect of shortening terms of work by early demolding, will be available. The rebound rate of type "P" schumidt hammer was relative with compressive strength, and the rebound rate for verifying 5MPa of compressive strength was estimated about 55 considering rate of safety. Therefore, assuming demolding date is available efficiently.

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An Experimental Study on the Strength Estimation of Belite Cement Mortar by Microwave Heating (마이크로파를 이용한 저열 포틀랜드(4종)시멘트 모르터의 조기강도 추정에 관한 실험적 연구)

  • 김민석;정근호;이영도;정재영;정상진
    • Journal of the Korea Institute of Building Construction
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    • v.1 no.2
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    • pp.179-184
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    • 2001
  • The most recent building trend is going large, high rise, high strength as overlarge project is developing in domestic construction business. Belite cement has properties like low heat, excellent long term strength, and durability without admixture(fly ash, silica fume). so, Beilte cement is suitable for mass structure which is needed high strength, high fluidity and low heat property. This study is to examine the possibility if site adoption microwave-use early strength estimation method. Based on the existed study related the portland cement, the interrelation between Belite cement and microwave-use early strength estimation method is required. In this study, interrelation between mortar and Evaluating strength estimation method is investigated before the concrete experiment.

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