• 한국구조물진단유지관리공학회 논문집
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• 제4권3호
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• pp.177-184
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• 2000

The purpose of this study is to evaluate the performance of a new viscosity modifying admixture for concrete agent. For this purpose, selected test variables were the ratio of water to cement, the ratio of cement to fine aggregate, contents of superplasticizer, contents of viscosity modifying admixture. As a result of this study, it has been found that addition of viscosity modifying admixture to mortar modfies its fluidity and reduces its segregation by increasing the mortar viscosity. And it has been found that a new viscosity modifying admixture do not significantly affect the setting time, air content of mortar.

• 콘크리트학회논문집
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• 제11권6호
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• pp.69-78
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• 1999

Hydroxyethyl cellulose -based-viscosity modifying admixture and melamine-basd-superplasticizer were selected to be admixtures for self-compacting concrete based on the test results of fluidity and air content of mortar using 3 different viscosity modifying admixtures. The experimental results show that the initial and final set of self-compacting concrete and fly ash concrete with viscosity modifying admixture only have been delayed approximately 5 hours and 8~9 hours, respectively. It is found that the optimum dosage of viscosity modifying admixtures, coarse aggregate and cement content are 0.2% of water content, under 742 kg/$\textrm{m}^3$ and over 364 kg/$\textrm{m}^3$, respectively. Test results also show that the optimum fly ash in replacement of cement is 10% of cement weight for the enhancement of fluidity and long-term strength.

• 한국건설순환자원학회논문집
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• 제5권1호
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• pp.68-75
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• 2017

본 연구에서는 프리스트레스트 콘크리트용 고품질 그라우트를 개발하기 위한 기초 자료로 활용하기 위해 그라우트의 화학 혼화제로 고성능 감수제와 증점제의 양과 사용방법이 유동성, 블리딩률, 체적변화 및 압축강도에 미치는 영향에 대해 검토하였다. 증점제와 고성능 감수제가 유동성에 미치는 영향에 대해 검토한 결과, 증점제와 고성능 감수제를 조합사용한 경우에는 고성능 감수제의 사용량이 너무 적으면 응집현상이 발생하여 유동성이 저하되나, 고성능 감수제 사용량 0.1% 이상부터 유동성이 크게 향상되는 것으로 나타났다. 증점제의 사용량이 증가할수록 블리딩률이 감소하며, 고성능 감수제는 0.05%까지 블리딩률이 증가하나, 0.1%부터 블리딩률이 감소하는 것으로 나타났다. 또한 고성능 감수제와 증점제를 각각 0.15%를 조합한 그라우트의 배합이 유하시간, 플로우, 블리딩 및 체적변화 측면에서 가장 양호한 것으로 분석되었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.83-84
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Therefore, in this research, the proper use of VMA was suggested to prevent segregation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.52-53
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• 2018

In this study, viscosity analysis of the lightweight foamed mortar was conducted to evaluate the foam stability. According to a series of experiment, void volume related with density of the mixture and viscosity of the mixture were infleunced by water-to-binder ratio and addition of viscosity modifying admixture (VMA). Especially, the stability of the foam inside the mortar was confirmed with adding VMA.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.56-57
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Hence, in this research, VMA was used to prevent segregation.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권2호
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• pp.112-116
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• 2001

The production of extracellular polysaccharide, EPS WN9, from Paenibacillus sp. and its suitability as a viscosity modifying admixture for cement mortar mixing were investigated. After 48h culture in an optimized medium, cell growth and EPS production were 1.2g/L and 4.0g/L, respectively. By adding EPS WN9 to mortar, it was possible to prepare a homogeneous mortar without material segregation and excess air entrapment. The optimal amount of EPS addition to mortar found to be 0.02 to 0.05%(w/w) of the cement used. Increasing the dosage of EPS WN9 from 0 to 0.05%(w/w) resulted in a setting retardation of 0.14h to 0.8h and an increase in the compressive strength of mortar of 10 to 20%.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.142-143
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• 2021

The purpose of this study is to analyze the extent of the rheology parameters at the segregation boundary of mid-range workability concrete. In addition, it was intended to present the extent of the rheology parameters of the normal strength concrete with segregation resistance using the determination of segregation occurrence of concrete and the use of the rheology parameters. However, it was confirmed that segregation occurs even if the measured rheology parameters is in the range of the suggested rheology parameters. Therefore, it is determined that the conditions under which segregation occurs will provide fundamental data that can be rheological defined. Additional studies are also needed on the relationship between rheological parameters and segregation.

• Computers and Concrete
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• 제20권1호
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• pp.31-38
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• 2017

In the present study an Artificial Neural Network (ANN) was used to predict the compressive strength of self-compacting concrete. The data developed experimentally for self-compacting concrete and the data sets of a total of 99 concrete samples were used in this work. ANN's are considered as nonlinear statistical data modeling tools where complex relationships between inputs and outputs are modeled or patterns are found. In the present ANN model, eight input parameters are used to predict the compressive strength of self-compacting of concrete. These include varying amounts of cement, coarse aggregate, fine aggregate, fly ash, fiber, water, super plasticizer (SP), viscosity modifying admixture (VMA) while the single output parameter is the compressive strength of concrete. The importance of different input parameters for predicting the strengths at various ages using neural network was discussed in the study. There is a perfect correlation between the experimental and prediction of the compressive strength of SCC based on ANN with very low root mean square errors. Also, the efficiency of ANN model is better compared to the multivariable regression analysis (MRA). Hence it can be concluded that the ANN model has more potential compared to MRA model in developing an optimum mix proportion for predicting the compressive strength of concrete without much loss of material and time.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.541-562
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• 2006

This paper compares the performance of axially loaded concrete filled steel tube (CFST) columns cast using a conventionally vibrated normal concrete (NC) and a novel self-consolidating concrete (SCC) made with a new viscosity modifying admixture (VMA). A total of sixteen columns with a standard compressive strength of about 50 MPa for both SCC and NC were tested by applying concentric axial load through the concrete core. Columns were fabricated without and with longitudinal and hoop reinforcement (Series I and Series II, respectively) in addition to the tube confinement. The slenderness of the columns expressed as height to diameter ratio (H/D) ranged between 4.8 and 9.5 for Series CI and between 3.1 and 6.5 for Series CII. The strength and ductility of SCC columns were found comparable to those of their NC counterparts as the maximum strength enhancement in NC columns ranged between 1.1% and 7.5% only. No significant difference in strain development was found due to the presence of SCC or NC or due to the presence of longitudinal and hoop reinforcement. Biaxial stress development in the steel tube as per von Mises yield criterion showed similar characteristics for both SCC and NC columns. The confined strength ($f^{\prime}_{cc}$) of SCC was found to be lower than that of NC and $f^{\prime}_{cc}$ also decreased with the increase of slenderness of the columns. Analytical models for the prediction of confined concrete strength and axial strength of CFST columns were developed and their performance was validated through test results. The proposed models were found to predict the axial strength of CFST columns better than existing models and Code based design procedures.