• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.638-644
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• 1999

Workability time of superplasticized concrete is maintained generally for 30-60 minutes only. Therefore it is of great advantage for the concrete producer to use a high range water reducer which provides an extended slump life. Recently slump retentive srperplasticizer has been developed. Concrete mixing tests were done to know slump, setting, air content, bleeding and hardening characteristics of concrete using slump retentive superplasticizer. With slump retentive superplasticizer, high quality concrete was produced and slump loss of concrete was reduced in big way, making long transportation time possible as a practical alternative to on-site addition.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.247-250
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• 2000

As construction technology advances, most of concrete structures are becoming larger and taller. Therefore, high strength and high quality concrete is necessary for them. Nowadays, the proposal of using type IV(belite cement) is investigated to satisfy high flowing, low heat, and ho호 strength. In this study, the flow value and compressive strength of mortar were investigated according to usage of AE high range water reducer. And the slump flow value, falling time and heigth difference of concrete with beilte cement and ordinary cement were examined depending on water cement ratio, sand ratio and unit water weigth, and compressive strength to checked depending on age.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.35-36
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• 2016

Recently, with the increasing demand of high performance of concrete, the mix design of concrete mixture has became low water-to-binder ratio with high binder content. To compensate these trend of mix design, high range water reducer, or superplascizier has been invented to achieve high flowable concrete. Although this superplasticizer provides favorable workability based on its dispersing action on the components of concrete mixture, it has an limitation of decreasing viscosity of the mixture, and thus it is difficult to secure sufficient workability for high performance concrete mixtures with high binder content. To improve the workability of concrete with high viscosity, recently, low-viscosity type superplasticizer was introduced, and in this research, a fundamental properties of low-viscosity type superplasticizer is evaluated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.79-88
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• 1993

The purpose of this study is to provide a firm base for the quality improvement of high strength concrete and the development of ultra high strength concrete as well as enviromental con-servation and utilization of byproducts from industrial processing such as Fly ash and Silica fume. A comprehensive experimental study was performed to investigate the effects on the quality improvement of high strength concrete using mineral admixtures. As results, 400~500kg/$\textrm{cm}^2$ compressive strength and excellent flowability can be obtained if fly ash is replaced with cement in the range of 305. In case of using powder type silica fume, 600~700 kg/$\textrm{cm}^2$ compressive strength is showed and 600~800kg/$\textrm{cm}^2$ compressive strength cam be obtained with liquid type silica fume. But it is necessary to increase dosage of high range water reducer for flowability using powder type silica fume. Especially, higher strength concrete cam be obtained when maximum size of coarse aggregate is lower than 25mm.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.235-240
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• 1995

A 36 stories high multi-use building was designed with the specified concrete strength range of 300~400kg/$\textrm{cm}^2$ On the ground of the concept of compressive strength, adequate mix designing for the concrete, which has the target strength range of 390-520kg/$\textrm{cm}^2$, was carried out to provide enough strength margin. And with due regard to the workability and transportation time, the slump and slump flow ranged 16~21cm and 30~45cm respectively, maintaining these properties up to 2-hours from the beginning of the mix. The high-range water reducer is incorporated into the mix as a admixture. The building construction is controlled satisfactorily, so far. The actual average 28-day compressive strength is 370kg/$\textrm{cm}^2$, the standard deviation is 28kg/$\textrm{cm}^2$ and the coefficient of variation is 7.6% for concrete of 300kg/$\textrm{cm}^2$ specified strength.

• 콘크리트학회논문집
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• 제12권5호
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• pp.111-120
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• 2000

In case of constructing concrete structure under water, generally concrete mixed with antiwashout admixture, high range water reducer, or AE-water reducing agent etc has been manufactured to ensure the quality of antiwashout underwater concrete because of being difficulty in ascertaining construction situation by the naked eye. The properties of high quality antiwashout underwater concrete that were aimed at affluent fluidity, workability and the compressive strength of 450 kgf/$\textrm{cm}^2$ at 28 ages using two types of blended cements are following as;(1) Setting time of antiwashout underwater concretes using blended cements was more greatly delayed than that of control concrete, however, was satisfied with criteria value of "Quality standard specification of antiwashout admixture for concrete".(2) As a test results of slump flow, efflux time and box elevation of head, it was found that workability of high quality antiwashout underwater concrete was improved. (3) Heat evolution amount of OPC was 1.5 times as high as that of two types of bended cements in 72 hours. (4) Suspended solids of antiwashout underwater concrete using blended cements was more than that of control concrete, also compressive strength of high quality antiwashout underwater concrete was very low in early age, but was better than that of control concrete as to increasing ages.

• 콘크리트학회지
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• 제8권4호
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• pp.161-169
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• 1996

화학조성이 다른 스티렌-무수말레인산 공중합체(1:1SMA, 5:1SMA)를 합성하고 이들을 황산화하여 수용성의 공중합체(1:1SSMA, 5:1SSMA)를 제조하였다. 이들 공중합체를 첨가한 시멘트 모르타르의 유동특성을 조사한 결과, 5:1SSMA는 1:1SSMA보다 우수한 플로우를 나타내었다. 또한 5:1SSMA를 1%첨가한 시멘트 모르타르는 60분 후에도 95% 이상의 플로우를 유지하였다. 한편 합성고분자를 0.5% 첨가한 경화시멘트 모르타르의 압축강도도 조사하였다. 그 결과 5:1SSMA를 첨가한 시험체의 28일 압축강도는 첨가하지 않은 시험체보다 41%증가한 반면 1:1SSMA는 29%의 증가를 나타내었다. 본 연구에서 제조한 5:1SSMA는 새로운 카르본산계 고성능감수제로서 그 활용이 크게 기대되어 진다.

• 콘크리트학회지
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• 제5권1호
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• pp.165-173
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• 1993

본 연구는 고강도 콘크리트 실용화의 일환으로 국내에서 시판되고 있는 고성능 감수제의 품질성능을 평가하기 위한 것이다. 이러한 연구를 위하여 8종류의 고성능 감수제를 대상으로 첨가량에 따른 특성을 비교하였다. 또한 경시변화에 따른 특성을 비교, 분석하기 위하여 슬럼프, 공기량 그리고 압축강도비를 측정하였다. 이 때 고성능 감수제의 품질성능 평가 규준는 JASS 5T-402 규준에 따라 실시하였다. 실험결과 국내에서 시판되는 고성능 감수제는 공기량, 앞축강도비에 대해서는 모두 만족하였지만 슬럼프 경시 저하량은 DA를 제외한 모든 고성능 감수제가 규준치를 초과하였다. 따라서 현장에서 고강도콘크리트를 생산할 경우 배합방법이나 첨가방법을 개선하여 시공성을 확보하는 방안이 필요할 것이다.

• 한국건설순환자원학회논문집
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• 제5권4호
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• pp.353-358
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• 2017

본 연구의 목적은 고성능 시멘트계열 재료의 점성을 감소시키는 것에 대한 기초적인 정보를 제공하는 것이다. 레올로지적 측면에서 시멘트 계열 재료의 유동성을 결정하는 것은 항복응력과 소성점도이다. 물결합재비가 낮고 분체비율이 높은 고성능 시멘트계열 재료의 경우, 고성능 감수제로는 항복응력을 줄일 수는 있으나 점성을 낮추는 것이 어렵다. 따라서 이 연구에서는 시멘트계열 재료의 소성점도를 줄이기 위한 목적으로 두가지 방법, 즉, 분말상태의 적절한 조합 및 저점도형 고성능 감수제의 사용을 제시하였다. 첫째, 다양한 산업부산물을 치환하여 석탄재 원분과 폐석회석 분말이 점성저하에 효과가 있음을 밝혔으며 저점도형 고성능 감수제가 일반형 고성능 감수제에 비해 시멘트 페이스트의 점도를 낮추는 것을 확인하였다. 따라서 본 연구의 결과를 바탕으로 다양한 방법의 시멘트계열 재료의 점도를 낮추는 기초적인 방법을 제공할 것으로 기대한다.

• Advances in concrete construction
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• 제10권3호
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• pp.257-269
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• 2020

The aim of this study is to investigate the flexural performance of hybrid fiber reinforced self-compacting concrete (HFRSCC) having different ratio of micro and macro steel fiber. A total of five mixtures are prepared. In all mixtures, the sum of the steel fiber content is 1% and also water/binder ratio is kept constant. The amount of high range water reducer admixture (HRWRA) is arranged to satisfy the workability criteria of self-compacting concrete. Four-point bending test is carried out to analyze the flexural performance of the mixtures at 28 and 56 curing days. From the obtained load-deflection curves, the load carrying capacity, deflection and toughness values are investigated according to ASTM C1609, ASTM C1018 and JSCE standards. The mixtures containing higher ratio of macro steel fiber exhibit numerous micro-cracks and, thus, deflection-hardening response is observed. The mixture containing 1% micro steel fiber shows worst performance in the view of all flexural parameters. An improvement is observed in the aspect of toughness and load carrying capacity as the macro steel fiber content increases. The test results based on the standards are also compared taking account of abovementioned standards.