• Title/Summary/Keyword: Concrete Mixing

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Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Material Property of Sprayed FRP - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - Sprayed FRP를 구성하는 재료특성에 관한 연구 -)

  • Lee, Li-Hyung;Lee, Kang-Seok;Son, Young-Sun;Byeon, In-Hee;Lim, Byung-Ho;Na, Jung-Min
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.141-144
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    • 2006
  • The main purpose of this study is to develop a Sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing carbon or glass shot fibers and the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the Sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of Sprayed FRP, this study carried out tensile tests of the material specimens which are changed with the combinations of various variables such as the length of shot fiber and mixture ratio of shot fiber and resin. These variables are set to have the material strength equal to one layer of the FRP sheet. As a result, the optimal length of glass and carbon shot fibers were derived into 3.8cm, and the optimal mixture ratio was also deriver into 1:2 from each variable. And also, the thickness of Sprayed FRP to have the strength equal to one layer of FRP sheet was finally calculated.

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The Material Properties on the Crushing Effect of Recycled Aggregates (파쇄횟수가 순환골재의 품질특성에 미치는 영향)

  • Won, Chul;Park, Sang-Joon
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.125-130
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    • 2010
  • It is necessary to re-establish the code and to control the quality of the recycled aggregate itself for ensuring the useability of the recycled aggregate using waste concrete. Generally, adhering mortar cause of the water absorption ratio increment and strength decreased at the surface of the aggregate of the recycled aggregate using waste concrete, thus removing the adhering mortar could increase the useability of the recycled aggregate in the concrete industry. In this study, as a quality control method of the recycled aggregate using waste concrete, the quality characteristic of the recycled aggregate according to the mixing proportion between the recycled and the natural aggregate is obtained Therefore, a system is established to reuse the recycled aggregate in the construction industry.

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An Experimental Study on the Early Compressive Strength Improvement of Cement Mortar Mixed with Blast Furnace Slag using Powdered Stimulants (분말형 자극제를 이용한 고로슬래그미분말 혼입 시멘트 모르타르의 조기 압축강도 향상에 관한 실험적 연구)

  • Lee, Kang Jin;Kim, Jin Hyoung;Park, Ki Bong;Lee, Han Seung
    • KIEAE Journal
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    • v.12 no.3
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    • pp.115-122
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    • 2012
  • Based on previous research and existing literature, this study examines the development of admixture, which increases the early concrete strength (1 and 3 day) by mixing blast furnace slag cement and concrete stimulant. The research on early strength development of concrete is necessary in dealing with the drawbacks of slow early strength concrete on site and to shorten the construction time. The study confirmed that when a high alkaline mortar mixture is mixed with blast furnace slag, the early strength of admixture exceeds that of ordinary portland cement (OPC). The use of calcium chloride ($CaCl_2$) promotes hydration of cement at low temperature and show similar strength as the blast furnace slag admixture. Although calcium chloride seems economically advantageous, it causes steel corrosion and its use in concrete should be further studied in-depth.

Temperature and Compressive Strength of the Concrete According to the Types of Rapid Hardening Cements (조강성 시멘트 종류에 따른 콘크리트의 온도이력 및 압축강도 특성)

  • Kim, Sang-Min;Choi, Yoon-Ho;Hyun, Seung Yong;Kim, Jong;Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.100-101
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    • 2020
  • In this study, the temperature history and compressive strength of the concretes according to the type of cement were measured and analyzed in comparison as part of the experiment on the material mixing side to reduce the hydration heat crack of the mat foundation constructed with mass concrete. As a result, the peak temperature and maximum temperature reach time of concrete using high rapid cement were shown to be similar to that of semi rapid cement. In particular, in compressive strength after three days, semi rapid cement was measured higher than that of concrete using high rapid cement. Therefore, if semi rapid cement is used in accordance with the site conditions, it is deemed possible to shorten the air due to reduction of temperature cracks and improvement of initial strength.

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Quantitative Analysis of Hydrate products of the Cement Paste Mixed with Admixtures (혼화재 혼입 시멘트 페이스트의 수화생성물 정량 분석)

  • Park, Dong-Cheon
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.176-177
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    • 2021
  • In order to compensate for the defects of concrete made using only Portland cement, three-component powder mixed with blast slag and fly ash, and four-component powder concrete mixed with silica fume are being produced. When each of the admixtures is used alone, the above-described excellent performance is expressed and up to 70% of the powder is used. These technologies are also contributing to the reduction of greenhouse gases under Act on Low Carbon. Green Growth. However, calcium hydroxide is consumed as a stimulator or reaction in the case of silica fume, which causes latent hydroponicity of slag, pozzolane reaction, and silica mixtures represented by fly ash. It is known that the consumption of calcium hydroxide affects the alkalinity of concrete. As a result, the carbonation resistance is significantly lower among the durability of concrete. Research on quantification of such effects is insufficient. In this study, an experiment was conducted to quantify calcium hydroxide of the three-component and four-component powder paste using thermal analysis equipment (DTG), and the effect of the mixing amount was discussed.

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Properties of Fresh State and Characteristics of Shrinkage in Concrete Containing Low Fineness GGBFS (저분말도 고로슬래그 미분말을 혼입한 콘크리트의 굳지 않은 상태의 특성 및 수축 특성)

  • Kim, Tae-Hoon;Yoon, Yong-Sik;Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.1
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    • pp.1-7
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    • 2020
  • GGBFS(Ground Granulated Blast Furnace Slag) is one of the most actively used mineral admixtures with excellent long-aged strength and chloride diffusion resistance. Unlike Standard covering GGBFS in Japan and the U.K., the domestic standard for GGBFS does not contain low fineness of GGBFS under 4000 grade. In this paper, several basic tests are carried out for the concrete with 3,000 grade GGBFS concrete and ternary blended concrete for reducing hydration heat by mixing 4,000 grade GGBFS and fly ash, such as fresh concrete properties, compressive strength, and shrinkage properties. The air content and slump between the ternary blended concrete and the concrete with low-fineness GGBFS showed the similar level, and the results of difference in setting time from them were less than 20 minutes, showing no significant difference. In the evaluation of compressive strength and shrinkage characteristics, the ternary blended concrete showed lower long-aged strength and higher shrinkage than the low-fineness GGBFS concrete.

Durability and Strength Characteristics of Concrete Using Sludge Water above Specification (규정 이상의 회수수를 사용한 콘크리트의 내구성 및 강도 특성)

  • Yang, Eun-Ik;Park, Jin-Ho;Kim, Kang-Rea;Jo, Gyou-Jea
    • Journal of the Korea Concrete Institute
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    • v.18 no.2 s.92
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    • pp.199-204
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    • 2006
  • Recently, The sludge water of ready mixed concrete has been investigated because of environmental pollution and disposal cost. So, sludge water is partially reused as mixing water. However, if sludge water is reused too much that would influence the qualify of concrete. KS specification limits the amount of sludge content up to 3% of cement weight. In this study, the effect of ready mixed concrete sludge on the characteristics of concrete is compared to raise the reuse ratio of sludge of ready mixed concrete. According to this experiment results, as blending ratio of re-mi-con sludge increases, workability is decreases. However, the sludge of ready mixed concrete water have a positive effect on the strength development. The drying shrinkage and the resistance of freezing and thawing have a minor effect.

A Study on Fire-proof Characteristics of Ultra High Strength Concrete Using Polyamide Fiber (폴리아미드섬유를 사용한 초고강도 콘크리트의 내화성능에 관한 연구)

  • Lee, Soo-Choul;Jeon, Joong-Kyu;Jeon, Chan-Ki
    • Journal of the Society of Disaster Information
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    • v.7 no.4
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    • pp.286-293
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    • 2011
  • Accordingly architectural structure is getting high-rise and bigger, a use of high strength and high performance concrete has been increased. High performance concrete has cons of explosion in a fire. This explosion in the fire can cause the loss of the sheath on a concrete surface, therefore it effects that increasing a rate of heat transmission between the steel bar and inner concrete. Preventing this explosion of high performance concrete in the fire, many kinds of researches are now in progressing. Typically, researches with using polypropylene-fiber and steel-fiber can prove controling the explosion, but the reduction of mobility was posed as a problem of workability. Consequently, to solve the problem as mentioned above, concrete cans secure fire resisting capacity through the using of coating liquid, including Ester-lubricant and non-ionic characteristic surfactant. This research has been drawn a ideal condition in compressive strength areas of concrete by an experiment. When applying 13mm of polyamide fiber, proper fiber mixing volume by compressive strength areas of concrete more than 2.5kg in 160MPa. These amount of a compound can control the explosion.

Fundamental Properties of Mortar and Concrete Using High Calcium Fly Ash (고칼슘 플라이애시를 활용한 모르타르 및 콘크리트의 기초적 물성)

  • Lee, Min-Hi
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.3
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    • pp.284-291
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    • 2016
  • To evaluate the properties of inorganic composites using a great quantity of high-calcium fly ash generated in combined heat and power plants, high-calcium fly ash and F-class fly ash commonly used as concrete admixtures were substituted with binding materials to examine changes of fluidity and compressive strength depending on the substitution ratio for each curing temperature. According to the experimental result, CFA-mixed mortar showed a tendency to reduce its flow unlike FFA-mixed mortar as the substitution ratio was increased, but its flow loss showed smaller than FFA as time passed. As a result of examining compressive strength depending on mixing FA, FFA-mixed mortar had an optimum range within 50% when curing at ambient temperature, but it was found that the compressive strength is reduced when mixing CFA. When curing at high temperature, FFA did not relatively have a great effect on the substitution ratio, but CFA could expect a strength enhancement effect compared with 100% of OPC when using within 25% of binding materials.

Characteristics of Environment-Friendly Porous Polymer Concrete for Permeable Pavement

  • Kim, Young-Ik;Sung-Chan, Yong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.7
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    • pp.25-33
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    • 2005
  • This study was performed to develop environment-friendly porous polymer concrete utilizing recycled aggregates [RPPC] for permeable pavement of uniform quality with high permeability and flexural strength as well as excellent freezing and thawing resistance. The void ratios of RPPC are in the range of 15$\sim$$24\%$, showing the tendency that it is reduced to a great extent as the mixing ratio of the binder increases. The compressive and flexural strength of RPPC are in the range of 19$\sim$26 MPa and 6.2$\sim$7.4 MPa, respectively. Also, it shows a tendency to increase as the mixing ratio of the binder and filler increases. The permeability coefficients of RPPC are in the range of $6.3\times$$10_{-1}$$\sim$$1.5\times$$10_{-2}$cm/s. The flexural loads of RPPC are in the range of 18$\sim$32 KN. The weight reduction ratios obtained from the test for freezing and thawing resistance are in the range of 1.1$\sim$$2.4\%$ after 300 cycles of repeated freezing and thawing of the specimen for all mixes. The relative compressive strengths of RPPC after 300 cycles of freezing and thawing against the compressive strength before freezing and thawing test are in the range of 89$\sim$$96\%$.