• Title/Summary/Keyword: high strength cement

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Effect of Microstructure on the Prooperties of High Strength Hardened Cement Paste (II) (고강도 시멘트 경화체의 특성에 미치는 미세구조의 영향 (II))

  • 김정환;최상흘;한기성
    • Journal of the Korean Ceramic Society
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    • v.27 no.8
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    • pp.1034-1042
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    • 1990
  • Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose(HPMC) with various admixtures was carried out. The cement paste was mixed with 0.1 of water cement ratio by twin roll mill and cured 60 days in humidity chamber. When the quartz powder or white cement was added to the paste, the flexural strength was 900∼1000kg/㎠ and the Young's modulus was 8∼9×105kg/㎠. When the silicafume was added, the flexural strength was 800kg/㎠ and the Young's modulus was 6×105kg/㎠.

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Studies on the High Strength Cement Hardened Body Blended by Industrial By-Products (산업 폐부산물을 혼합재로한 고강도 시멘트 경화체의 제조 및 특성분석)

  • 연영훈;최상흘
    • Journal of the Korean Ceramic Society
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    • v.31 no.12
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    • pp.1507-1512
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    • 1994
  • High strength cement hardened body was prepared by ordinary portland cement, silica-fume, super-plasticizer and the industrial by-product powder such as tailing, paper sludge ash and granulated slag. These raw materials were mixed and formed with w/c=0.18. The cement hardened body is cured in the autoclave at 18$0^{\circ}C$, 10atm. These admixtures made the compressive strength of all specimens develope by 170~230%. The highest compressive strength could be obtained by 236 MPa when mix composition was 14 wt% of silica-fume and 26 wt% of granulated slag. The compressive strength increased with decreasing the average pore size and the amount of the poe over the size of 50 nm by which the appearance of high compressive strength of the cement hardened body were mainly influenced. In the result, the hydration products were C-S-H, tobermorite and ettringite and it was realized that the reason why the cement hardened body became dense and revealed the higher strength was that those hydrates were formed inside of the pore and filled in it and the unhydrated materials played the role of an inner-filler.

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A Fundamental Study on the Hydration and micro Structure of high Strength Concrete Used by high Calcium Sulfate Cement (고황산염 시멘트를 이용한 고강도 콘크리트의 수화거동과 미세구조에 관한 기초적 연구)

  • 박승범;임창덕
    • Proceedings of the Korea Concrete Institute Conference
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    • 1993.04a
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    • pp.99-105
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    • 1993
  • The purpose of this fundamental study is to investigate the mechanism of high strength concrete using the high calcium sulfate cement from a point of view in cement hydration and micro structure. As a results, it was found that the internal pores of concrete are decreased by using the high calcium sulfate cement, because the hydrates of Ettringite which is densified in structure is much formed in early ages at steam curing. In addition to the ettringite needs the 32 times of free water formed mixing water for hydration. This effect are not only decreased the water to cement ratio and also increase to comp, strength of concrete. It was conclude that these above the two facts are the main mechanism of high strength concrete using high calcium sulfate cement.

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The Study on the Optimum Mix Design of the High-Strength Concrete in Site (고강도 콘크리트의 현장최적배합에 관한 연구)

  • Lee, Sang-Soo;Won, Cheol;Kim, Dong-Seok;Ahn, Jae-Hyun;Park, Chil-Lim
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.10a
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    • pp.232-238
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    • 1996
  • In this paper, the properties of high-strength concrete are described with respect to materials and mix conditions(water-cement ratio, chemical admixture, replacement of fly ash). As primary purposes of this study, the optimum mix design method of high-strength concrete to decrease unit cement contents is investigated, and the properties of fresh and hardened concretes are tested in terms of slump, air content and compressive strength. As results of this study, workability and strength development of the high-strength concrete depend on the water-cement ratio, replacement ratio of fly ash and dosage of the chemical admixture. The conditions which are proposed optimum mix design of the high-strength concrete show W/C 37%, S/A 42~45% and unit cement content 470~480kg/$\textrm{m}^3$. Based on the results, the applicability of high-strength concrete in site is clearly proved.

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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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Experimental Estimation of the Early Strength of Belite Cement Mortar Using Microwave (저열 포틀랜드(4종)시멘트 모르터의 마이크로파를 이용한 조기강도 추정에 관한 실험적 연구)

  • 김민석;박재한;정근호;이종균;이영도;정상진
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.1077-1082
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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, Belite cement is suitable for mass structure which is needed high strength, high fluidity and low heat property. This study is to examine the possibility of 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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A Study on the Optimum Cement Content of High Strength Concrete (고강도 콘크리트의 적정 단위시멘트량 선정 방안)

  • Lee, Jang Hwa;Kim, Sung Wook;Lee, Jong Suk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.7 no.1
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    • pp.173-179
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    • 2003
  • Currently, in the mix design of high strength concrete, cement content depend on the target slump which is fixed with tests. However this cause high content cement use because it is based on the mix design of normal strength concrete. Also, comparatively high content cement might decrease the durability of the concrete. Therefore, in this study, we investigated proper cement content satisfying durability, workability, compressive strength, and reviewed use of admixtures, proper sand-aggregate ratio to the cement content. The results indicate that cement content ranging $370{\sim}550kg/m^3$ did not affect the compressive strength. The field workers should consider durability, workability as well as compressive strength for determining the optimal cement content in the mix design of the high strength concrete.

A Study on the Bond Strength of Coated Rebar by Polymer Cement Slurry Made of EVA and Ultra High-Early Strength Cement (EVA와 초조강시멘트를 사용한 폴리머 시멘트 슬러리 도장철근의 부착강도에 관한 연구)

  • Hyung, Won-gil;Jo, Young-Kug
    • Journal of the Korea Concrete Institute
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    • v.27 no.6
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    • pp.633-640
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    • 2015
  • Polymer cement slurry (PCS) is made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the bond strength of coated rebar by polymer cement slurry made of EVA and ultra high-early strength cement. The test pieces are prepared with EVA polymer dispersion and ultra high-early strength cement having four types of polymer-cement ratios, four types of coating thicknesses and four curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day, and coating thicknesses of $75{\mu}m$ and $100{\mu}m$. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and EVA at polymer-cement ratio of 80%, and coating thickness of $100{\mu}m$ is about 1.32 and 1.38 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with polymer-cement ratio of 80% or 100% and coating thickness of $100{\mu}m$ at curing age of 1-day can replace epoxy-coated rebar.

Compressive Strength Properties of Steam-Cured Low Cement Mortar (증기양생한 저시멘트 모르타르의 압축강도 특성)

  • Yoon, Seong-Joe;Im, Geon-Woo;Lee, Gun-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.295-296
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    • 2023
  • This study evaluated the compressive strength after making mortar with low cement composition for carbon-neutral steam curing to respond to climate change. Blast furnace slag, fly ash, and ultra-high powder fly ash were used as substitutes for cement. The cement substitute was used at 40% of the mass of cement, and after steam curing, the compressive strength was measured on the 1st, 3rd, 7th and 28th days of age. As a result of the experiment, at the age of 1 day, the mixture using only cement showed the highest strength, but from the 3rd day, the specimen using ultra-high powder showed a high strength development rate, followed by blast furnace slag and fly ash.

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Strength Development of Low Heat Portland Cement Concrete in High Strength Range (저열 포틀랜드 시멘트 콘크리트의 고강도 영역에서의 강도발현 특성)

  • Ha Jae Dam;Um Tai Sun;Lee Jong Ryul;Kwon Young Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.353-356
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    • 2005
  • Strength development of low heat portland cement(Type IV) concrete in high strength range is tested. In this study strength development according to water-binder ratio, strength development according to age, effect of fly ash and super plasticizer are tested. This study tests effect of low heat portland cement in high strength range concrete and provide guide line concrete mix design for later study and/or construction.

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