• 제목/요약/키워드: high flow concrete

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The Effect of Fly Ash Replacement on Alkali - Silica Reaction (플라이 애쉬 치환에 따른 알칼리-실리카 반응의 팽창저감 효과)

  • Kim Jung Eun;Jun Ssang Sun;Seo Ki Young;Jin Chi Sub
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.185-188
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    • 2004
  • The effect of fly ash to prevent detrimental expansion due to alkali -silica reaction was investigated through the ASTM C 1260 method that is one of the most commonly used method because results can be obtained within about 16 days. Reactive aggregate used is a netamorphic rock and sedimentary rock. The replacement proportions of portland cement by fly ash were respectively 0, 5, 10, 15, 25 and 35 percent. Expansion of mortar bars due to alkali-silica reaction decreased with the increase of fly ash content. The results show that the expansion due to alkali-silica reaction is dramatically reduced in the presence of high volume fly ash. When the fly ash content examine from all angles (strength and a flow), the replacement proportions of fly ash is about $25\%$ in order to control on expansion.

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The Relationship between Rheology Properties and Particle size distribution in Cement paste (시멘트 페이스트에서 유동성과 입도분포와의 관계)

  • Hwang, Hae-Jeong;Lee, Seung-Heun;Lee, Won-Jun;Kim, Won-Ki
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.721-724
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    • 2006
  • In this study, particle size distribution of cement powder system were adjusted using the blast furnace slag powder, Blaine $2250cm^2/g\;and\;8300cm^2/g$, which easy to adjust particle size distribution to examine how particle size distribution of the binder has an effect on rheological properties of the cement paste. In addition, the relationship between n-value of Rosin-Rammler function and plastic viscosity were discussed. All measured flow curves represented thixotropy behavior and the hysteresis area was smaller for the more added coarse particle. When the combination was based on a ratio of $20{\sim}25vol%$ fine particles, $30{\sim}40vol%$ OPC and $40{\sim}45vol%$ coarse particles of the total volume, a high fluidity and low yield strength was achieved.

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A Fundamental Research on Determining Segregation Boundary using Rheological Parameters for 21 and 24MPa grade of Normal Strength Concrete (레올로지 정수를 이용하여 21, 24MPa급 일반강도 콘크리트의 재료분리 경계를 판단하기 위한 기초연구)

  • Lee, You-Jung;Lee, Young-Jun;Han, Dongyeop
    • Journal of the Korea Institute of Building Construction
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    • v.20 no.5
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    • pp.399-407
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    • 2020
  • The aim of the research is to provide the boundary conditions for segregation of normal strength grade and high fluidity concrete mixture (so called mid-fluidity concrete) with rheology parameters. Since the normal strength grade concrete mixture has a relatively high water-to-cement ratio and no SCMs, it is easy to be segregated when superplasticizer is added. Hence, to achieve the mid-fluidity concrete of normal strength grade and high fluidity, preventing segregation of the mixture is inevitable. In this research, using two superplasticizers with different solid concentrations, the flow behaviors and rheological behaviors were assessed by increasing fluidity until the segregation happened. According to the experiment in this research, an unusual behavior in rheology parameters was observed when the concrete mixture started to be segregated. From this results and report, it is expected to contribute on the definition of segregation with rheological test methods.

A Fluidity Experiment of Pre-Mix Cement for Dispersibility Improvement of Mineral Admixture (광물질 혼화재의 분산성 향상을 위한 프리믹스 시멘트의 유동성 실험)

  • Han, Cheon-Goo;Lee, Hai-Ill;Noh, Sang-Kyun;Kim, Ki-Hoon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.2
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    • pp.90-96
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    • 2009
  • The high rising building construction makes increasing the requirement of high strength concrete. Especially, the workability analysis is related with dispersion of admixture such as SF for improving strength and FA, BS for reducing construction cost and improving durability of Ultra High Strength Concrete which has over 100 MPa of compressive strength is very important. Precisely, decreases dispersion because of lumping situation of each admixture and it causes the workability of admixture is decreased. Therefore, the workability of cement paste is tested for analyze effects of pre-mixed cement for solving those problems with it to this research. The summary of the results are like below. First of all, OBS is increasing workability more than OFS. This result causes that the glassy surface of BS in the OBS is increasing workability and the absorption of admixture of FA in the OFS is decreasing workability. In the case of mixing methods, pre-mixing method is increasing workability more than normal one. This result shows that the normal mixing method is bad dispersion of binders. The other side, the pre-mixing method is good. Furthermore, depending on the mixing time, according to the increasing mixing time such as 30, 60, and 120 seconds, the dispersion of binders and workability turns better.

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Effect Analysis of Mix Designing Factors on Workability and Rheological Parameters of Self-Compacting Concrete (배합요인이 자기충전 콘크리트의 워커빌리티 및 레올로지 파라미터에 미치는 영향 분석)

  • Yoon, Seob;Han, Min-Cheol
    • Journal of the Korea Institute of Building Construction
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    • v.18 no.3
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    • pp.235-242
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    • 2018
  • The objective of the paper is to investigate the effect of mix designing factors on the workability and rheological parameters of self compacting concrete in order to facilitate the difficulties of quality control of high sensitivity of SCC. Mix proportions of SCC were prepared with various conditions of coarse, and fine aggregate, and unit water content, and the SCC mixtures were tested on workability, rheological properties to provide basic data for quantitative evaluation. Test results indicated that the yield stress of SCC decreased with increasing the coarse aggregate volume ratio, and increased with increasing the amount of VMA. However, unit water content, fine aggregate type, and air content didn't affect the yield stress value. The plastic viscosity according to the mixing factors showed a similar tendency to the yield stress. In addition, there was no correlation between yield stress and workability (flow, T50, V-lot). However, there was closely correlation among plastic viscosity and T50 and V-lot. Especially, T50 and V-lot time decreased with decreasing plastic viscosity.

Seismic performances of RC columns reinforced with screw ribbed reinforcements connected by mechanical splice

  • Lee, Se-Jung;Lee, Deuck Hang;Kim, Kang Su;Oh, Jae-Yuel;Park, Min-Kook;Yang, Il-Seung
    • Computers and Concrete
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    • v.12 no.2
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    • pp.131-149
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    • 2013
  • Various types of reinforcement splicing methods have been developed and implemented in reinforced concrete construction projects for achieving the continuity of reinforcements. Due to the complicated reinforcement arrangements and the difficulties in securing bar spacing, the traditional lap splicing method, which has been widely used in reinforced concrete constructions, often shows low constructability and difficulties in quality control. Also, lap spliced regions are likely to be over-reinforced, which may not be desirable in seismic design. On the other hand, mechanical splicing methods can offer simple and clear arrangements of reinforcement. In order to utilize the couplers for the ribbed-deformed bars, however, additional screw processing at the ends of reinforcing bars is typically required, which often lead to performance degradations of reinforced concrete members due to the lack of workmanship in screw processing or in adjusting the length of reinforcing bars. On the contrary, the use of screw-ribbed reinforcements can easily solve these issues on the mechanical splicing methods, because it does not require the screw process on the bar. In this study, the mechanical coupler suitable for the screw-ribbed reinforcements has been developed, in which any gap between the reinforcements and sleeve device can be removed by grouting high-flow inorganic mortar. This study presents the uniaxial tension tests on the screw-ribbed reinforcement with the mechanical sleeve devices and the cyclic loading tests on RC columns with the developed coupler. The test results show that the mechanical sleeve connection developed in this study has an excellent splicing performance, and that it is applicable to reinforced concrete columns with a proper confinement by hoop reinforcement.

Physical Properties of Foamed Concrete up In the Manufacturing Waste Expanded Poly-Styrene (폐스티로폼의 가공 형태에 따른 기포콘크리트의 물리적 특성 변화)

  • 오세출;서치호;신상태;지석원;김봉주
    • Journal of the Korea Concrete Institute
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    • v.14 no.2
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    • pp.207-215
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    • 2002
  • This study is focusing on mixing the foamed concrete incorporated by waste expanded polystyrene(W-EPS), investigating the physical properties and offering a proper quality control method to the field engineers. Two types of W-EPS (type A and type B) were studied. Type A (B) had globular (crushed) shape and diameter of 3-5 (1-2) mm. The results show that the flow was suddenly reduced with increasing mixing quantity of two types, but it satisfies KS F 4039 until 60 % of mixing rate. In general, the absorption rate was suddenly reduced with increased mixing quantity of two types especially, in type A. Apparent specific gravity was 0.36∼0.53 and reduced with increasing mixing quantify of type A. But it increased in case of type B. Compressive strength and heat conduction rate increased with mixing with W-EPS than non-mixing W-EPS but reduced with mixing too much W-EPS. Based ong the results, it is believed that mixing with W-EPS can improve the recycle of industrial wastes and produce the high quality foamed concrete.

Effect of the Various Admixtures to Improvement of Concrete Using Over-added Blast Furnace Slag at Early Age (고로슬래그 미분말을 다량 사용한 콘크리트의 초기품질 향상에 미치는 각종 혼합재료의 영향)

  • Lee, Ju-Sun;Pei, Chang-Chun;Ryu, Gum-Sung;Koh, Kyung-Taek;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.733-736
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    • 2008
  • This study, with the purpose for early quality improvement of concrete which used large quantity of fly ash, changed various admixture material type and reviewed the basic characteristics. First off, the flow overall was highest when polycarb onic Acid high early strength AE water reducing agent was displaced, while air amount satisfied target level only in the case of plain, and setting time was shown best by getting 30 more minutes than plain and about 3 more hours than conventional when KOH is displaced. Compressive strength was shown best at age 1 day and 3 days when KOH was displaced, and at age 28 days when fine particle cement was displaced. By and large, this study concludes that concrete quality improvement admixture material that used large amount of fly ash showed worse effects than plain, therefore it is determined that there need be more study for development of concrete early quality improvement admixture material that used large amount of fly ash.

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Modeling of heated concrete-filled steel tubes with steel fiber and tire rubber under axial compression

  • Sabetifar, Hassan;Nematzadeh, Mahdi;Gholampour, Aliakbar
    • Computers and Concrete
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    • v.29 no.1
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    • pp.15-29
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    • 2022
  • Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

Patent Investigations and Analysis for the Curtain Wall System based on the Autoclaved Lightweight Concrete(ALC) (경량기포콘크리트 재료를 활용한 커튼월 구법에 관한 일본 특허기술의 분석 연구)

  • Kim, Young-Ho
    • Journal of The Korean Digital Architecture Interior Association
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    • v.12 no.1
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    • pp.81-88
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    • 2012
  • According to the survey results of the Ministry of Land, Transport and Maritime Affairs in the end of December 2011, the residential buildings was reported as 67.3% of 4,529,464 buildings. Reflected in the national energy policy, the residential building is expected that greater energy savings. To have realized the Passive House Project used the Autoclaved Lightweight Concrete(ALC) material on exterior wall, we take advantage of a very large energy savings. Therefore, this study investigate the patent documents of three major companies, SUMITOMO, CLION, ASAHI KASEI, in Japan. and analyze technical flow and benchmarking patent. As a result, the Sliding method or the Rocking method of ALC panels how to install is to be superior to high-performance drift and safety by a earthquake. And the embedded anchor in panel needs to improve the shape and the strength of bearing. Thus installation technology of the ALC exterior wall investigated in japanese patent documents is expected to the fastening units and anchors.