• 한국농공학회지
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• 제24권2호
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• pp.67-75
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• 1982

A study on the effect of water reducing agent on the various characteristics of concrete has been conducted. The experimental results of the study are summarized as follows. 1. Slump test for the concrete added water reducing setretarding agent in proper quantity have been conducted. According to the test results, the decreasing rate of slump value become bigger than plain concrete with increase of the unit weight of cement and elapse of time 2. In case the proper quantity content of maximum compressive strength in Fig. 5 of water reducing set retarding agent is added, unit weight of water is decreased about 15% or so as compared with plain concrete. with the increase of water reducing set accelerating agent content unit weight of water is decreased much more, And other hand, amount of air entraining shows the increasing tendency with the increase of water reducing agent content. 3. The adding rate of water reducing agent which produce maximum strength shows that WR-CH and WR-SA which is water reducing set-starding agent is 0.2% and WR-CO is 0.5% and that WS-PO which is water reducing set accelerating agent is 0.5 4. compressive strength jof the concrete made of sulfate resistant cement shows less than the strength of normal portland cement at initial strength but the strength of both cement shows almost same at curing age of 28 days. 5. when proper quantity of water reducing set retarding agent is used, boned strength is increased about 15% at curing age of 28days. 6. According to the result of durability test, dynamic young's mudulus of elasticity at plain concrete is decreased about 50% as compared with initial step at 300 cycle of freezing and thawing after curing age of days. on the contarary the concrete used water reducing agent is decreased less than 7%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.157-160
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• 2006

Recently, trouble of sand supply is occurred according to exhaustion of natural sand resources. To solve this problem, sea sand and crushed sand are used. But, necessity of water reducing agent because quality of concrete that use sea sand and crushed sand is deteriorated. Therefore in this study was examined on the engineering properties of concrete with kind of fine aggregate and addition ratio of water reducing agents. As a result, compressive strength appeared similar standard regardless of kind of fine aggregate. Compressive strength, durability was similar in decrease of the unit water content by increase of addition ratio of the water reducing agent. Also, drying shrinkage resistivity was improved because the unit water content decreased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.232-328
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• 2001

This paper investigates the influences of water content and viscosity agent on the bleeding of concrete. According to test results, fluidity shows decline tendency as water content decreases, and dosage of viscosity agent increases. PEO viscosity agent does not affect the air contents while, MC viscosity agent causes air loss. As for bleeding, bleeding decreases with decrease of water content. As dosage of viscosity agent increase, bleeding decreases, regardless of viscosity kinds. It is thought that viscosity agents have the favorable effect of reducing bleeding, if fluidity and air loss are improved.

• 콘크리트학회지
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• 제6권6호
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• pp.135-142
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• 1994

본 연구는 고유동성, 고강도 및 고내구성을 가진 고성능 콘크리트를 실용화시키기 위하여 국내에서 시판되고 있는 9종류의 고성능 감수제를 사용한 콘크리트의 품질 특성을 평가하였다. 이를 위하여 혼화제 첨가량에 따라서 굳지 않은 콘크리트의 슬럼프, 공기걍, 단위중량 및 감수율과 경화콘크리트의 압축강도비를 비교분석하였다. 본 시험결과, 국내 시판되는 고성능 감수제를 사용한 콘크리트의 공기연행 효과는 거의 없었으며 또한, 보통강도 및 고성능 콘크리트 각각에 대하여 최적혼화제 첨가량이 존재함을 알아냈다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.132-137
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• 1993

The purpose of this study is to evaluate the quality characteristics of concrete using super plasticizer which is on the market within the country. For this purpose, nine kinds of super plasticizer are compared and analyzed for the slump , air content, unit weight, water-reducing percent and ratios of compressive strength with admixture content. As a result, the optimum quantity of admixture content were obtaining for ordinary and high strength concrete using super plasticizer.

• 한국건축시공학회지
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• 제17권5호
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• pp.429-435
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• 2017

본 연구의 목적은 일반강도 콘크리트 배합에 있어서 다양한 감수제에 따른 유동성과 품질 안정성을 평가하는 데에 있다. 감수제의 사용은 골재 품질이 저하되는 최근의 상황에서 피할 수 없지만 적절한 성능의 감수제 사용이 중요하다. 이에 본 연구에서는 일반강도 수준의 모르타르에 대하여 세 가지 종류의 감수제에 대하여 유동성 증진성능과 더불어 품질안정성을 레올로지적으로 평가하였다. 또한 콘크리트 배합에 있어서 단위수량 변화에 따른 유동성 변화를 측정하였으며 단위수량 저감효과와 그에 따른 제조원가를 산정하고 비교하였다. 본 연구를 통해 실제 현장에서 적절한 성능의 감수제를 선택할 수 있는 사례를 제공하고 이를 통해 경제적이고 효과적으로 유동성을 발휘하며 안정적인 품질을 확보할 수 있는 환경 마련에 기여하고자 한다.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.185-206
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• 2015

This paper presents statistical models developed to study the influence of key mix design parameters on the properties of lightweight self-consolidating concrete (LWSCC) with expanded shale (ESH) aggregates. Twenty LWSCC mixtures are designed and tested, where responses (properties) are evaluated to analyze influence of mix design parameters and develop the models. Such responses included slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, sieve segregation, unit weight and compressive strength. The developed models are valid for mixes with 0.30-0.40 water-to-binder ratio, high range water reducing admixture of 0.3-1.2 % (by total content of binder) and total binder content of $410-550kg/m^3$. The models are able to identify the influential mix design parameters and their interactions which can be useful to reduce the test protocol needed for proportioning of LWSCCs. Three industrial class ESH-LWSCC mixtures are developed using statistical models and their performance is validated through test results with good agreement. The developed ESH-LWSCC mixtures are able to satisfy the European EFNARC criteria for self-consolidating concrete.

• 한국약용작물학회지
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• 제19권6호
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• pp.501-507
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• 2011

This experiment was carried out in order to collect the basic data on the standardization of the manufacturing process of Rehmannia glutinosa Libosch. var. purpurea Makino drying. By the drying methods of R. glutinosa, the content of water, inorganic components, reducing sugar, catalpol and benzo[${\alpha}$]pyrene were investigated. The water content was 15.6~17.2% when R. glutinosa was dried by cold-warm air moisture absorption drying method (CAMAD) at $60^{\circ}C$ during 6 days. Among of the inorganic components of R. glutinosa the K content was the most followed by P, Na, Ca and Mg. The reducing sugar content of R. glutinosa by the hot air drying method (HAD) was much more than that by the CAMAD. The catalpol content of R. glutinosa was not different by the drying temperature when it was dried by the CAMAD. The catalpol content of the large size tuber (about 50.0 g/unit) showed a tendency to increase from $60^{\circ}C$ until $70^{\circ}C$ drying temperature, but that of the small size tuber(about 4.0 g/unit) was decreased as being a trend as the drying temperature high when R. glutinosa was dried by the HAD, But the catalpol content R. glutinosa had a tendency to drop significantly at drying temperature above $80^{\circ}C$. The benzo[${\alpha}$]pyrene content was little detected when R. glutinosa was dried by both the SLD and the CAMAD, and the sampling by the HAD indicated within the scope of 5 ${\mu}g/kg$ which was the scope to regulate by Korean food and drug administration. In conclusion, it seemed that an appropriate drying temperature of R. glutinosa by the CAMAD and the HAD was about $60^{\circ}C$ and about $70^{\circ}C$, respectively, when we consider the catalpol content and benzo[${\alpha}$]pyrene detection in the manufacturing process of drying R. glutinosa.

• Steel and Composite Structures
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• 재36권6호
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• pp.657-669
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• 2020

This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.

• 한국건축시공학회지
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• 제9권2호
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• pp.85-91
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• 2009

W/C and unit volume, which significantly affect quality of concrete related to strength and durability, are regulated at below $185kg/m^3$ for regular concrete generally used in standard specification for constructions. The aim of this research is to develop chemical admixture and find out its potential use by identifying characteristics of admixtures added to soft concrete and hardening concrete, of which content ratio of component for each type of admixtures is subject to change in accordance with unit volume within KS' allowable range. Sodium gluconate, polyoxyethylene nonylphenyl ether, poly carboxylic copolymer in slump, which is characteristic of soft concrete, are deemed highly sensitive while there is no air entrainment except for $10\sim70%$ in WE, WR component content ratio and NP. In hardening concrete, strength in general showed higher action in compressive strength and tensile strength than in plain strength. Use of proper AE agent and AE water reducing agent at the same time is deemed to be used as chemical admixtures capable of manufacturing high-quality, high-quantity concrete.