• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.55-60
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• 2001

Influencing factors on flexural toughness of ring-type fiber reinforced concrete(RSFRC) are investigated. An experiment proceeding ASTM C 78 is peformed to make a comparison between ring-type fibers and double-hook type fibers. Most specimen with ring type fibers have failed by the cone type failure, while discrete hook type fibers have failed by fiber pullout. For the hook-type fiber reinforced concrete(SFRC), the first crack load increases, as the fiber mixing volume increases. Aspect ratio(fiber length/fiber diameter) is critical for hook type fibers, so the flexural toughness increases significantly, as the length of fiber increases. However, for the ring type, the toughness indices Increase as the number of fibers in the specimen increases. Since there is no bond problem between the ring fiber and the concrete matrix, the aspect ratio does not affect the performance of the composite material with the newly developed steel fibers. Influencing factors with respect to flexural toughness RSFRC were observed to be ring diameter, diameter of steel fiber and fiber content.

• 대한토목학회논문집
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• 제3권4호
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• pp.33-45
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• 1983

레디믹스트콘크리트가 배치 플랜트에서 출하되어 현장에서 타설을 완료 할 때까지의 운반시간이 지연되는 경우가 있으며, 이로 인하여 워커빌리티가 저하되어 적절한 조치를 취하지 않고서는 시공이 어려운 문제점이 종종 야기되고 있다. 그래서 레디믹스트콘크리트의 운반시간에 따른 품질변화를 알아보며, 저하된 워커빌리티의 개선과 아울러 소요의 품질을 유지하기 위한 수단으로 시멘트와 물 및 유동화제를 추가로 첨가하는 방법과 유동화제의 적정 첨가량을 구하기 위한 실험을 실시하였다. 그 결과 레디믹스트콘크리트에 유동화제를 첨가하여 재믹싱함으로써 품질개선에 얼마간 유효한 결과를 얻었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.360-365
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• 1995

The purpose of this study is to identify the various characteristics of the 53-years old railway tunnel linning concrete. The nondestructive technique such as the surface hardness method and the ultrasonic method, the extent of carbonation by the phenolphthalein indicator, and the chemical analysis due to XRD/XRF are considered Also the concrete core was cut in two pieces per tunnel for the exact evaluation of strength. On the basis of the experimental result, it is concluded that the durability and the serviceability of old tunnel linning concrete are affected by the initial mixing condition and the environmental effect.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.65-74
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• 2016

During concrete pumping, the migration and redistribution of particles occur in a pipe and the lubrication layer that forms between the bulk concrete and the pipe wall is the governing factor determining the flow behavior. In order to identify flow behavior of pumping, in this study, the viscoelastic properties related to the microstructural behavior of a flocculated suspension were examined by using dynamic oscillatory measurements. Cement paste is assumed to be a constituent material of the lubrication layer and ten cases of mixing design are employed by changing the proportions of mineral admixtures. The relationship between the yield stress obtained from the steady shear test and the dynamic modulus resulted from the oscillatory shear measurement was derived and the implications of the correlation are discussed. Moreover, based on the investigation of the viscoelastic properties with oscillatory measurements, the initial behavior of pumped concrete was analyzed systematically.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.319-324
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• 1999

This study is to investigate the properties on the load-deflection and fracture behaviors of the steel fiber reinforced concrete(SFRC) slab model specimens, Steel fibers of indent, crimp, and end hook shape were considered to reinforce the matrix under various mixing conditions and proportions. Initial cracking load, maximum load, and energy absorption capacity(load carrying capacity) of SFRC panel specimen increased with increase of steel fiber contents. And the plain concrete slab was fractured abruptly after maximum load but SRFC slabs were fractured smoothly by steel fibers in concrete matrix operated as cracking resistance force after maximum load. Indent, crimp and end hook shape steel fibers were effective in reinforcing the matrices but end hook type fiber were superior to indent and crimp type fibers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.37-40
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• 2006

In these days, as building structures are getting taller, larger, and more diversified, structural systems with more economy and more efficiency are being required and so are more efficient building materials. this study conducted a basic experiment to conclude an adequate selection of materials and to calculate an optimal mixing proportion of those materials to produce High-strength concrete in a 130MPa of specified concrete strength. And also we conducted an experiment to find out basic properties of this concrete such as slump-flow, strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.219-220
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• 2009

본 연구는 순환잔골재가 갖는 미분말이 자기충전 콘크리트(SCC)특성인 고강도와 높은 유동성을 발현하기에 적당하여 폐콘크리트에서 발생하는 순환잔골재를 천연잔골재 대비 혼입률을 25% 씩 증가시켜, 총 5수준으로 자기충전 콘크리트(SCC)에 적용하였으며, 이에 따라 굳지 않은 콘크리트의 물리적특성, 경화한 콘크리트의 역학적 및 내구특성을 검토하여 순환잔골재를 자기충전 콘크리트(SCC)로서의 활용 가능성을 검토하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.431-432
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• 2009

본 연구는 콘크리트용 골재 대체재로서 석탄재의 혼입률을 변화시켜 제작한 콘크리트 공시체의 충격저항성(내충격성, 내마모성 등)을 분석한 결과, 석탄재 혼입률이 증가함에 따라 내마모성과 내충격성이 감소하는 경향을 보였으며, 이를 보완하기 위하여 섬유신소재(GF, HPSF)를 혼입한 경우 내충격성이 증진된 결과를 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.369-374
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• 1997

This study is the experimental results on the flowing properties of the super flowing concrete (SFC) using limestone (LS), which is to develop the SFC in level of ordinary strength. And this study is described with respect to basic concept, confined water ratio ($\beta_p$) of binder (cement+limestone) in paste, relationship between volume ratio of water-binder (w/b) and addition ratio of superplasticizer in mortar, flowing velocity and funneling time and compressive strength in concrete to replacement ratio of LS. The results of this study is improved to flowing properties in fleshly concrete with increasing replacement ratio of LS. The optimal mixing condition of the SFC using LS in level of ordinary strength is proved W/C 55%, LS 40% and W/C 60%, LS 50%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.799-804
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• 2003

The purpose of this study was to investigate the effects of re-vibration and curing temperature onto the physical properties of latex-modified concrete with ordinary cement and rapid-setting cement, and thus to provide a guide line of re-vibration and curing conditions for good quality controls. The main experimental variables included two cement types(ordinary portland cement, rapid-setting cement), curing Temperature($10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$), re-vibration methods(continued, intermittent), and re-vibration times(initial setting, one day after mixing). The experimental results showed that the re-vibration affected little to the mechanical properties of LMC and RSLMC, while, the curing temperature a quite some. The early strength development was the highest at $20^{\circ}C$ curing temperature, and decreased at higher temperature. The permeability of concrete generally decreased with curing time. The rapid chloride permeability was a function of time and temperature. The chloride permeability of RSLMC was so small and negligible.