• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.705-710
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• 2002

Recently, there has been for a number of reasons growing interest in the use of porous concrete, and it is used as an ecological material. But, because the valuation methods of the quality on the fresh porous concrete aren't established up till now, it is difficult that the harden porous concrete is made sure of its required quality. This study is to present the measurement method of the void ratio on the fresh porous concrete and to analyze the influence of water-cement ratio and vibrating time on the binder content covered a coarse aggregate. Results of this study were shown as follows; The measurement methods of the void ratio and aggregate-binder weight ratio on the fresh porous concrete can be useful as data for the quality control of fresh porous concrete.

• Advances in concrete construction
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• 제5권2호
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• pp.87-99
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• 2017

After passing through a magnetic field, the physical quality of water improves, and magnetic water (MW) is produced. There are many investigations on the effects of magnetic field on water that shows MW properties like saturation and memory effect. This study investigates the fresh and hardened properties of concrete mixed with MW, which contains silica fume (SF) and superplasticizer (SP). The test variables included the magnetic field intensity for producing MW (three kinds of water), SF content replaced cement (0 and 10 percent), water-to-cementitious materials ratio (W/CM=0.25, 0.35 and 0.45) and curing time (7, 28 and 90 days). The results of this study show that MW had a positive impact on the workability and compressive strength of concrete. By rising the intensity of the magnetic field which was used for producing MW, its positive influence on both workability and compressive strength improved. MW had greater positive impacts on samples containing SP that did not have SF. Moreover, the best compressive strength improvements of concrete achieved as W/CM ratio decreased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.341-346
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• 2002

This study is intended to check the possibility to estimate water content by heat-drying method with variation of W/C and slump. According to the results, in case of electric range method, when water content is less than 165kg/m$^3$ in mixture, it is estimated more and in more than 165kg/m$^3$, it is estimated less. It shows that water content in gas burner method is estimated less by about 2kg/m$^3$. Also, estimated water content shows difference by less than 12kg/m$^3$ in electric range method and by less than 12kg/m$^3$ in gas burner method. Therefore, it is thinked that if tested without error from preparing a sample to calculating amount of water, water content will be estimated exactly in the construction field.

• KCI Concrete Journal
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• 제11권3호
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• pp.29-43
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• 1999

The effects of superplasticizers on fresh and hardened concrete were investigated. The experimental program included tests on the workability and slump loss, bleeding, setting time, air content, compressive, tensile and flexural strength, permeability, shrinkage, freeze-thaw durability and creep deformation. Properties of superplasticized concrete were compared with those of conventional and base concretes. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete. They permitted a significant water reduction while maintaining the same workability. Bleeding of superplasticized concrete was much lower than that of conventional concrete of the same consistency. This indicates that the use of superplasticizers did not affect the tendency of segregation of fresh concrete. The compressive, tensile, and flexural strengths of superplasticized concrete were significantly higher than those of conventional concrete. The permeability and drying shrinkage and creep of superplasticized concrete were less than those of conventional concrete, but there were no significant differences between base and superplasticized concrete. Compared with base concrete, non-air-entrained superplasticized concrete had slightly higher freeze-thaw durability. and superplasticized concrete with an appropriate amount of entrained air Eave even better resistance to freezing and thawing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.161-166
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• 1994

Production of high strength concrete requires a low water-cement ratio and this leads to the high cement content. Mineral admixture like fly ash(FA) is often cheaper than ordinary portland cement(OPC) and this factor in combination with possible improvement in workability and moderation of the heat evolution of the cement-rich mixes tends to encourage its use. The other mineral admixture that its use has been widly advocated is silica fume that increases compressive strength due to its pozzolanic reaction. The objective of this study is to assess the contribution of mineral admixtures(FA, SF) to the workability and the strength of concrete with low water-binder ratios. In this experimental study that investigates and analyzes the properties of fresh concrete, it is presented that using admixtures like flysh and silica fume as binding material increases properties of high strength flowing concrete having very low water cementitious ratios of 0.25 and 0.30.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1989년도 가을 학술발표회 논문집
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• pp.15-20
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• 1989

The effect of superplasticizing agents on the sorkability performance in fresh concrete have been analyzed and investigated under various mix proportions of water cement ratio of 0.40, 0.50, 0.60 and 0.70, superplasticizing agents of NL-4000 and Rheobuild-716, and addition rate of sp. agents of 0.0, 0.5, 1.0, 1.5 and 2.0 in the practical range. It is the aim of this study to provide the fundamental data on the fluidity performance and workability improvement of superplasticized concrete such as time-dependent change of slump, flow value and compacting factor, air content, bleeding, mixing temperature and setting rate of fresh concrete comparing with base concrete and conventional concrete for the practical use and research data accumulation of superplasticized concrete in the side of development of concrete construction technology and management.

• 콘크리트학회논문집
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• 제22권4호
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• pp.559-566
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• 2010

굳지 않은 경량골재 콘크리트의 다양한 특성에 대한 경량굵은골재 최대크기와 천연모래 치환율의 영향을 평가하기 위해 15배합의 경량골재 콘크리트가 배합되었다. 또한 굳지 않은 경량골재 콘크리트의 유동특성에 영향을 줄 수 있는 경량골재의 내부구조와 공극의 분포 및 시간에 따른 흡수 특성 등이 측정되었다. 실험 결과 경량골재 콘크리트의 초기 슬럼프는 천연 모래 치환율이 증가할수록 감소하였으며, 전경량 콘크리트의 슬럼프는 배합 후 30~60분 사이에 초기 슬럼프의 80%가 감소하였다. 경량골재 콘크리트의 공기량과 블리딩 량은 경량굵은골재 최대크기와 천연 모래 치환율에 중요한 영향을 받았다. 경험식인 ACI 211과 콘크리트표준시방서는 경량골재 콘크리트의 공기량을 과소평가 하였으며, 천연 모래 치환율의 감소할수록 그 과소평가 정도는 증가하였다. 이 연구에 의해 제안된 경량골재 콘크리트의 공기량과 블리딩율에 대한 예측모델은 실험 결과와 잘 일치하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.191-196
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• 1994

This study is designed for analyzing the mechanical properties of cement mortar with kind of water, sludge content for the water, mixing proportion and open time of recycling water. And this study is aimed for presenting the reference data in practical use. For the results of this study, the flow properties of fresh mortar and the strength of compresive of hardened mortar is increased until the sludge content 4.5~6.0, but is decreased after the sludge content of that.

• 한국농공학회지
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• 제26권3호
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• pp.68-80
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• 1984

This study was attempted in order to investigate the effects of superplasticizers on fresh and hardened concrete. The experimental program included tests on the slump and slump loss, bleeding, time of set, air content, the compacting, factor Vee Dee, compressive strength, tensile and flexural strength, permeability, shrinkage and freege-thaw durability. The major conclusions that can be drawn on the study are as follows. 1. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete so that tinder appropriate conditions, they either considerably improved its workability or permitted a water reduction of at least 8-12% to be made while maintaining normal workability. 2. The bleeding ratios of base and S,P. Concrete were much lower than those of the conventional concrete. Differences between the base and S.P. Concrete were insignifician. 3. The setting time was the longest for conventionla concrete, followed by S.P. concrete and base concrete in thatorder. And AE water reduction admixtures showed an appreciable influence on the setting and hardening characteristics of concrete and prolonged the stiffening times. 4. The high initial slump values of S.P. concrete generally decreased rapidly with increased standing time. CF values showed increasing tendencies with the increase of S.P. content, and excessive addition of S.P. caused the segregation of fresh concrete, resulting in its rejection. 5. Though there was a slight increase in strength, no significant differences are observed between base and S.P. concrete in terms of the compressive, tensile and flexural strength. 6. The permeability of S.P. concrete was significantly less than that of the conventional concrete, and the shrinkage of S.P. concrete was considerably smaller than that of the conventional concrete, but there were no significant differences between base and S.P. concrete. 7. Compared to base concrete, S.P. concrete without entrained air tended to slightly increase freeze-thaw durability, and S.P. concrete with an appropriate entrained air gave satisfactory resistance to freezing and thawing.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.232-233
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• 2013

The unit-water content in fresh concrete determines consistency, and play an important role in condensing the structure of concrete and enhancing the durability of concrete. The capacitance measurement method measure quickly unit-water content and is the best way to apply to construction site. In this study, the unit-water content of capacitance measurement method is estimated according to types and replacemment ratio of admixture. and the field application of capacitance measurement method is reviewed.