• Title/Summary/Keyword: aggregate properties

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Effect of Fine Particle Cement and Recycled Aggregates as Alkali Activator on the Engineering Properties and Micro-Structure of High Volume Blast Furnace Slag Concrete (알칼리 자극제로서 미분시멘트와 순환골재가 고로슬래그 다량치환 콘크리트의 공학적 특성 및 미세구조에 미치는 영향)

  • Han, Min-Cheol;Lee, Hyang-Jae;Han, Cheon-Goo
    • Journal of the Korea Institute of Building Construction
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    • v.13 no.6
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    • pp.602-608
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    • 2013
  • The aim of this study is to investigate experimentally the effect of the combination of fine particle cement with high Blaine fineness (FC) and recycled aggregates on the engineering properties and micro structure of high volume blast furnace slag (BS) concrete with 75% BS and 21 MPa. FC manufactured by particle classification at the plant with Blaine fineness of more than $7000cm^2/g$ was used as additional alkali activator for high volume blast furnace slag concrete made with recycled fine and coarse aggregates. FC was replaced by 15, 20 and 25% OPC. Test results showed that the incorporation of FC resulted in an increase in the compressive strength compared to BS concrete without FC by as much as 30% due to accelerated hydration and associated latent hydraulic reaction. It was found that the use of FC and recycled aggregates played an important role in activating BS for high volume BS concrete by offering sufficient alkali.

Field Applicability Evaluation of SB Latex-Modified Concrete for Concrete Bridge Deck Overlay (콘크리트 교면 덧씌우기를 위한 SB 라텍스개질 콘크리트의 현장적용성 평가)

  • Yun, Kyong-Ku;Lee, Joo-Hyung;Hong, Chang-Woo;Kim, Ki-Hyun;Kim, Tae-Kyong
    • International Journal of Highway Engineering
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    • v.3 no.4 s.10
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    • pp.93-103
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    • 2001
  • This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

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Engineering Performance and Applicability of Eco-Friendly Concrete for Artificial Reefs Using Electric Arc Furnace Slags (전기로 슬래그를 활용한 인공리프용 친환경콘크리트의 공학적 성능 및 적용성)

  • Jo, Young-Jin;Choi, Se-Hyu
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.3
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    • pp.533-544
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    • 2015
  • Unlike the concrete structure built on land, that exposed to the marine environment is greatly degraded in durability due to the exposure to not only the physical action caused by sea wind, tide, and wave, but also the harsh conditions, including the chemical erosion and freeze-thaw which result from $SO_4{^{2-}}$, $Cl^-$ and $Mg^{2+}$ ions in seawater. In the process of the large scaled construction of submerged concrete structures, of course environmental hazardous substance, such as alkaline (pH) and heavy metals, may be leached. Thus, this issue needs to be adequately reviewed and studied. Therefore, this study attempted to develop a CSA (Calcium Sulfo Aluminate) activator using electric arc furnace reducing slags, as well as the eco-friendly concrete for artificial reefs using electric arc furnace oxidizing slag as aggregate for concrete. The strength properties of the eco-friendly concrete exposed to the marine environment were lower than those of the normal concrete by curing 28 days. This suggest that additional studies are needed to improve the early strength of the eco-friendly concrete. With respect to seawater resistance of the eco-friendly concrete, the average strength loss against 1 year of curing days reached 8-9%. the eco-friendly concrete using high volume of ground granulated blast furnace slags and high specific gravity of electronic arc furnace oxidizing slag demonstrated the sufficient usability as a freeze-thaw resistant material. With respect to heavy metal leaching properties of the eco-friendly concrete, heavy metal substances were immobilized by chemical bonding in the curing process through the hydration of concrete. Thus, heavy metal substances were neither identified at or below environmental hazard criteria nor detected, suggesting that the eco-friendly concrete is safe in terms of leaching of hazardous substances.

Flowability and Strength Properties of Mortar and Self-Compacting Concrete Mixed with Waste Concrete Powder (폐콘크리트 분말을 혼합한 모르타르 및 자기충전 콘크리트의 유동 및 강도특성)

  • Choi, Yun-Wang;Jung, Moon-Young;Moon, Dae-Joong;Kim, Sung-Su
    • Journal of the Korea Concrete Institute
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    • v.18 no.4 s.94
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    • pp.517-526
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    • 2006
  • In this study, in order to utilize waste concrete powder(WCP) which is occurred in manufacturing high quality recycled aggregate as an admixture for self-compacting concrete(SCC), the properties of cement paste, mortar, and concrete that were mixed two types of WCP, 928 and 1,360 $cm^2/g$ of surface area, were analyzed. As a result of experiment, we have found that WCP was a porous material with angle. When WCP was utilized as an admixture for SCC, its flowability and viscosity increased in proportion to the increase of a replacement ratio, and that a replacement ratio of WCP was proper within 15%. The compressive strength at 28 days mixed respectively with WCP2, 15 and 30%, showed about 36 and 28 MPa, and it showed a similar trend with a function suggested in CEB-FIP for the relationship of compressive strength and elastic modulus. According to the results, it is judged that WCP2 can be utilized as an mineral admixture of normal strength SCC.

Stress-Strain Properties of Surlightweight Polymer Concrete (초경량(超輕量) 폴리머 콘크리트의 응력(應力)-변형특성(變形特性))

  • Sung, Chan Yong;Kim, Kyung Tae;Min, Jeong Ki;Kim, Young Ik;Youn, Joon No;Jung, Hyun Jung
    • Korean Journal of Agricultural Science
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    • v.25 no.2
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    • pp.271-277
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    • 1998
  • This study was performed to evaluate the stress-strain properties of surlightweight polymer concrete using synthetic lightweight aggregates. The following conclusions were drawn; 1. The dynamic modulus of elasticity was in the range of $1.514{\times}10^5{\sim}1.916{\times}10^5kgf/cm^2$, which was approximately 48~96% of that of the normal cement concrete. It was showed larger with the decrease of synthetic lightweight fine aggregate. 2. The static modulus of elasticity was in the range of $2.552{\times}10^4{\sim}4.386{\times}10^4kgf/cm^2$, which was showed lower compared to that of the normal cement concrete. The poisson's number of surlightweight polymer concrete was less than that of the normal cement concrete. 3. The stress-strain curves of surlightweight polymer concrete were showed smaller with the increase of expanded clay.

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Improvement on Textural Properties of Soybean Curd by Freeze Denaturation of Soybeans (대두의 동결처리에 의한 두부의 텍스쳐 특성의 증진)

  • Baik, Sang-Ho;Kim, Myung-Kon;Yun, Sei-Eok;Joo, Hyun-Kyu
    • Korean Journal of Food Science and Technology
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    • v.28 no.2
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    • pp.267-272
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    • 1996
  • Effect of freezing of soybeans on instrumental and sensory textures of soybean curd was investigated. The hardness, gumminess and chewiness of soybean curd prepared with frozen soybeans were about three times as high as those prepared with unfrozen soybeans, while cohesiveness and elasticity were affected little by freezing. Sensory evaluation showed that freezing improved the quality of soybean curd. Instrumental and sensory textures of soybean curd prepared with frozen soybeans were excellent and almost same regardless of the boiling time when the soy slurry was boiled for 2.5 min or 5 min. However, the textures of soybean curd prepared with unfrozen soybeans were deteriorated by reducing the boiling time to 2.5 min. It was postulated that freezing facilitate the heat-denaturation of soyprotein to enhance aggregation of soy proteins and formation of cross-linkage between aggregate and $Ca^{++}$. Frozen soybeans resulted in soybean curd which lower fat content, while protein content of soybean curd was almost he same. Frozen soybeans gave a lower yield of soybean curd, which is supposed to be caused by the more fat loss during whey-off.

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A Study on Setting Time and Early Strength of Tablet-Shaped Accelerators (타블렛 형태 급결제가 콘크리트의 응결시간 및 조기강도에 미치는 영향에 관한 연구)

  • Ryou, Jae-Suk;Lee, Yong-Soo
    • Journal of the Korea Concrete Institute
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    • v.23 no.3
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    • pp.347-352
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    • 2011
  • When concrete is worked in cold weather, the methods of using hot air, water and aggregate heating, accelerators are used to prevent early frosting and to improve early strength. But these methods raise problems such as implementation difficulty, high cost, and energy losses. Among the available cold weathering methods, accelerator method is the most economical but with the drawbacks of rapid setting and insufficient workability in the initial hydration stage. Therefore, the tablet method usually used for pharmaceutical field was applied to the accelerator method to compare the controlled reaction time of the new and old accelerator method. Based on the test results, physical and mechanical properties of concrete were tested and the possibility of delaying initial reactions to increase the total reaction time was evaluated. The results showed that when both accelerators and tablet were used, setting-time decreased. Physical properties of concrete were optimal for tablet 0.5% and 1.0%. Also, accelerator 0.5%, tablet 0.5% and 1.0% showed good early strengths.

A Study on the Fundamental Properties of Ultra Rapid Hardening Mortar using Coal-Ash (잔골재 대체재로서 석탄회를 이용한 초속경 보수모르타르의 기초적 특성에 관한 연구)

  • Lee, Gun-Cheol;Oh, Dong-Uk;Kim, Young-Geun;Cho, Chung-Ki
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.1
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    • pp.128-135
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    • 2011
  • In this study, in order to develop ultra rapid hardening mortar(URHM) for tunnel repairs using bottom ash of low recycle ratio and Admixture as Eco concept, fundamental properties of URHM on temperature condition of construction field were performed. Test result, URHM of three types for fluidity and setting time were as in the following : B > C > A. Those for low temperatures were later than the standard condition. Compressive, bending and bond strength were similar with three types as follow. In compressive strength, initial strength of the low were smaller than the standard but the low in the long-term were similar with the standard. On the contrary to this, bending strength were similar in initial strength but the low in the long-term were smaller than the standard. The low in bond strength was average 35% less than the standard. Length changes was as in the following : A > C > B. the low is two times much as the standard but the case using blast furnace slag particles noticeably reduced length changes. Water absorption coefficient and water vapor resistance were as in the following : C > A > B. In case of URHM added bottom ash, water absorption coefficient and water vapor resistance were increased because bottom ash is porous material.

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A study of Mechanical Properties of Hot Mix Asphalt for Developing of Quiet Pavement (저소음 포장체 개발을 위한 아스팔트 혼합물의 역학적 특성 연구)

  • Lee, Kwan-Ho;Jeong, Tae-Hyun
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.1
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    • pp.49-55
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    • 2009
  • Our domestic economy has been developed very rapidly after 1960's. Also, it is dramatically increasing traffic on road and surround environmental issues. Especially, rapid economic growth has been induced large construction of pavement, and bigger and higher traffic for transportation. These are making air pollution, traffic noise and vibration. The social requirement against the revealed road environment and traffic sound reduction is being demanded. Traffic noise of city zone is showed over the environmental specification more than 57%. In order to overcome these situations, the social attention is being increased. The quiet pavement is the same format of permeable pavement, but is not same for functional performance. In this research, it has been carried out to evaluate the fundamental-mechanical properties of hot mix asphalt for quiet pavement. Especially, couple of laboratory tests are conducted like marshall stability, resilient modulus, indirect tensile test, and compaction energy analysis with gyratory compaction curve. Also, two-layer pavement system has been adopted for developing of quiet pavement. The basic performance of hot mix asphalt of quiet pavement show a satisfaction of specification of hot mix asphalt.

Granulation of Fine Zeolite Powder by Adding Polyvinyl Alcohol (Polyvinyl Alcohol첨가(添加)에 의한 Zeolite미분(微粉)의 입상화(粒狀化))

  • Choi, Jyung;Choi, Choong Ryeol;Lee, Dong Hoon
    • Korean Journal of Soil Science and Fertilizer
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    • v.28 no.2
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    • pp.123-129
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    • 1995
  • For the propose of increasing the value added, zeolite powder was granulated by adding Polyvinyl Alcohol (PVA) as cementing material. The optimal concentration of PVA for granulation and the physical properties of the prepared granule were investigated. Four percent PVA stock solution was made by adding distilled water at $90^{\circ}C$ water bath and incorporated with zeolite. The contents of water stable granule above 2.0mm in diameter was 98.0% in the case of 0.3% PVA addition and almost 100% in the case of 0.6% PVA addition. Increasing PVA concentration of granules increased the hardness and decreased the infiltration rate and the maximum water holding capacity of granules, However, the drying method hardly affected the physical properties of granules. With the increase in the mixing ratios of kaolinite or bentonite to zeolite, the hardness of granules increased but high water contents of granules resulted in rapid decrease in the hardness of granules. However, when smectite or perlite was mixed with zeolite, the increase in mixing ratios to zeolite resulted in the decrease in hardness, the increase in the infilteration rate and maximum water holding capacity of granules.

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