• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.665-672
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• 2002

In this paper, the utilization of waste foundry sand produced in the molding process is studied as a backfill material for underground electric utility systems such as concrete box structures and pipe lines for power supply. The physical, chemical and thermal properties for waste foundry sand are investigated for mechanical stability, environmental hazard and power transmission capacity. Also its properties are compared with the natural river sand. The test results show that waste foundry sand can be utilized for underground concrete box structures as a backfill material; however, it can not be applied to underground pipe lines due to high thermal resistivity or low power transmission capacity.

• Computers and Concrete
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• 제21권3호
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• pp.311-319
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• 2018

This study used a volumetric method for design. The control group used waste Liquid Crystal Displayplay (LCD) glass powder to replace cement (0%, 10%, 20%, 30%), and the PZT group used Pd-Zr-Ti piezoelectric (PZT) powder to replace 5% of the fine aggregate to make cement mortar. The engineering and the mechanical and electricity properties were tested; flow, compressive strength, ultrasonic pulse velocity (UPV), water absorption and resistivity (SSD and OD electricity at 50 V and 100 V) were determined; and the correlations were determined by linear regression. The compressive strength of the control group (29.5-31.8 MPa) was higher than that of the PZT group (25.1-29 MPa) by 2.8-4.4 MPa at the curing age of 28 days. A 20% waste LCD glass powder replacement (31.8 MPa) can fill up finer pores and accelerate hydration. The control group had a higher 50 V-SSD resistivity ($1870-3244{\Omega}.cm$), and the PZT group had a lower resistivity ($1419-3013{\Omega}.cm$), meaning that the resistivity increases with the replacement of waste LCD glass powder. This is because the waste LCD glass powder contains 62% $SiO_2$, which is a low dielectric material that is an insulator. Therefore, the resistivity increases with the $SiO_2$ content.

• 한국구조물진단유지관리공학회지
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• 제17권2호
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• pp.24-28
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• 2013

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.210-219
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• 1997

This research which lays emphasis on ready mixed concrete standard 25-210~240kgf/$\textrm{cm}^2$ shows the influence caused by the ratio of ingredients of superplasticized concrete, and the flowing and strength development of mortar and concrete according to the ratio of ingredients. This research shows that flowability, compactability, and segregation resistivity are the best condition under the following ratio of ingredients: fly ash 30%, unit binders 490~510kg/$\textrm{m}^3$, unit weight of water 184~194kg/$\textrm{m}^3$, fine aggregate ratio 49~51%, and superplasticizer 1.1~1.5%. Following this ratio of ingredients, the reinforced concrete structures to need design strength 25-210~240kgf/$\textrm{cm}^2$ can apply to complicated constructions.

• Computers and Concrete
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• 제10권1호
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• pp.35-47
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• 2012

The ideal gradating curve is used in this study to estimate densified aggregate blended ratio and total surface area of aggregate, there by under assigned paste amount of concrete, and coating paste thickness can then be deduced. Four groups of concrete mixtures were prepared and the corresponding concrete properties, such as workability, compression strength, ultrasonic velocity, surface resistivity and chloride ion penetration, were measured and finally the results are interpreted in terms of "coating thickness". The result shows as the coating thickness of the concrete is higher than critical one, the coating thickness on aggregate does affect the workability, and whatever workability is required the superplasticizer can be adjusted to achieve the demand workability. Under a fixed paste quality at the same age, coating paste thickness is inversely proportional to the concrete properties, especially as the coating thickness gets thinner.

• 조명전기설비학회논문지
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• 제20권1호
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• pp.71-76
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• 2006

본 논문에서는 철관이 들어있는 건축물의 기초를 대용접지극으로 활용하기 위해 콘크리트의 전기적 특성에 관해서 기초적 검토를 하였다. 철근이 들어있는 몰탈블록 모형과 콘크리트블록 모형을 제작 후 접지저항 측정 결과에 따르면, 철근의 수량에 의한 접지 저항값과 대지저항률 보다 블록의 저항율에 의한 접지 저항값이 크게 영향을 받는 것을 알 수 있었다.

• 한국지반공학회논문집
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• 제31권10호
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• pp.17-28
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• 2015

최근 친환경 건설에 대한 엄격한 규제와 가용한 천연골재 자원의 고갈에 따른 대안으로 전력구 되메움재로서 순환골재에 대한 관심이 급증하고 있다. 본 논문에서는 일반적인 되메움재인 강모래와 콘크리트 재생 순환골재를 대상으로 다짐에너지가 가해질 때, 발생하는 골재의 입자파쇄를 실내다짐시험을 통해 규명하였다. 적용된 다짐에너지 수준에서 일반 강모래는 입자파쇄가 미미하여 다짐 전후 골재의 다짐특성과 열저항의 변화가 매우 적었다. 반면에 일반 강모래에 비하여 순환골재는 재생과정에서 이미 입자에 큰 응력이 가해진 상태이므로 추가 다짐에너지에 의한 입자파쇄가 발생했다. 다짐에 의한 순환골재 입자파쇄는 세립분 양을 증가시켜 전반적으로 되메움재의 열저항을 감소시키고 입도곡선의 모양을 변화시켰다. 특히, 순환골재의 입자파쇄는 다짐에너지의 댐핑이 상대적으로 적은 저함수비 구간에서 더 뚜렷하게 발생하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.787-790
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• 1999

To estimate durability of reinforced concrete structures located in or nearby seawater, many different kinds of accelerated tests for evaluation of chloride ion permeation in concrete were proposed. At present the only standardized test is the ASTM C 1202(RCP test). This test method is used to estimate the concrete's resistivity of the chloride penetration in concrete by using the total charges passed and sometimes used to calculate the chloride diffusion coefficients. However, this test may lead to an erroneous chloride diffusion coefficient. So this test method was compared with the modified Dhir's test and the traditional concentration diffusion test. Experimental results showed that the diffusion coefficients determined the RCP test and the PD Index gave wrongous values, but the diffusion coefficient acquired by considering a migration term was nearly the same to the CD Test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.118-123
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• 1995

Evaluating the moisture content for sand is useful for quality cotnrol of concrete. If water content of evaluate instantly and apply for mix proportion sand of concrete, in mixing propertion of concrete, it can makes to improve of concrete quality. In this study, the evaluating method for moisture content of sand, using the electric velocity and dielectric constant was proposed as a study of quality control of concrete. The obtained results are summarized as follow. The resistance ratio was decreased as the increase of moisture content The dielectric constant was decreased as the sand of the moisture content increase.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.519-522
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• 2005

Ka-Hwa highway bridge, located in a corrosive marine environment, had been examined the current condition of reinforcement corrosion in concrete throughout half-cell potentials, electrical resistivity, chloride contamination of concrete, and visual observation. According to the test, the chloride corrosion reinforced concrete structure is not only the protecting film around the reinforcement is deteriorated but also corrosion activity develops, for example, delamination areas of concrete. The purpose of this paper is to report the effects of Ka-Hwa highway bridge damaged by chlodide attack and to present the results of repair of Ka-Hwa highway concrete bridge in domestic marine environment.