• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.61-62
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• 2022

Carbon nanotubes were used to secure high strength, high durability, and fracture toughness of cementitous composites.In this study, carbon nanotube dispersion solutions were prepared using commercial superplasticizers, such as polycarboxylate-ester and sodium naphthalene sulfonate with tip sonication. The solutions were used to prepare cement paste with MWCNT and The mechanical properties of the cement paste composite with MWCNT solutions were evaluated.

• 한국건설순환자원학회논문집
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• 제8권1호
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• pp.33-40
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• 2013

최근 시멘트 생산 시에 발생하는 다량의 $CO_2$로 인한 환경문제가 심각한 실정이며, 이러한 환경문제를 해결하기 위해 고로슬래그 미분말과 같은 산업부산물을 시멘트 대체 재료로 사용한 알칼리 활성 슬래그 콘크리트에 대한 연구가 활발히 진행되고 있다. AAS 콘크리트는 상온에서 고강도 발현이 가능하지만 알칼리 반응으로 인한 빠른 응결시간과 유동성 손실로 인해 작업시간 확보에 어려움이 있는 것으로 알려져 있다. 본 연구에서는 알칼리 활성 콘크리트의 구조 부재 적용을 위한 기초 자료 확보를 위해 AAS 모르타르의 압축강도 및 유동 특성에 시멘트용 유동화제가 미치는 영향을 분석하였다. 물-결합재비(W/B)는 0.35로 고정하고 알칼리 활성화제로 수산화나트륨과 물유리를 사용하여 AAS 모르타르를 제조하였으며, 유동성 확보를 위해 4종의 유동화제인 나프탈렌(N), 리그닌(L), 멜라민(M), PC(P) 계를 각각 슬래그 질량대비 최대 2%까지 첨가하여 압축강도, 플로우, 초음파 속도를 측정하였다. 실험결과, 멜라민계 유동화제를 첨가한 경우 AAS 모르타르의 압축 강도 저하 현상 없이 유동성이 증진되는 것으로 나타났으며, 나프탈렌계와 PC계의 경우에는 유동성 개선효과가 미미한 것으로 나타났다.

• 한국세라믹학회지
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• 제41권5호
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• pp.417-424
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• 2004

메톡시폴리에틸렌글리콜모노메타크릴레이트(MPEGMAA)와 메타크릴산(MAA)을 공중합시킨 폴리카복실레이트계 고유동화제(PCA)의 그라프트 사슬인 폴리에틸렌옥사이드(PEO)의 길이가 다를 경우, 보통포틀랜드시멘트(OPC)의 수화 반응에 미치는 영향을 Fourier Transform Infrared Spectroscopy(FT-IR), X-Ray Diffraction(XRD)과 Differential Scanning Calorimetry (DSC)를 이용하여 조사하였다. PCA의 그라프트 사슬의 길이에 따라 초기 재령에서 수화 반응에 미치는 영향은 달라지나, 장기 재령에서는 큰 차이가 없었다. 또한 PCA가 첨가된 경우의 Ca(OH)$_2$의 상대 피크 강도의 비(I[001］/I［101］)는 OPC에 비해 감소하였다.

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.69-88
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• 2015

Self-consolidating concrete (SCC) is a stable and cohesive high consistency concrete mix with enhanced filling ability properties that reduce the need for mechanical compaction. Limited standards and specifications have been reported in the literature on the structural behavior of reinforced self-compacting concrete elements. The significance of the research presented in this paper stems from the need to investigate the effect of enhanced fluidity of SCC on the structural behavior of high strength self-consolidating reinforced concrete beams. To meet the objectives of this research, twelve reinforced concrete beams were prepared with two different generations of superplasticizers and designed to exhibit flexure, shear, or bond splitting failure. The compared beams were identical except for the type of superplasticizer being used (second generation sulphonated-based superplasticizer or third generation polycarboxylate-based superplasticizer). The outcomes of the experimental work revealed comparable resistance of beam specimens made with self-compacting (SCC) and conventional vibrated concrete (VC). The dissimilarities in the experimental values between the SCC and the control VC beams were not major, leading to the conclusion that the high flowability of SCC has little effect on the flexural, shear and bond strengths of concrete members.

• Computers and Concrete
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• 제6권4호
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• pp.343-356
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• 2009

Experiments were designed to investigate the flow behavior of portland cement paste and concrete incorporating superplasticizers. The paste and concrete mixtures were subjected to prolonged mixing for up to 110 min at high temperature. The yield stress values of concrete and that of the corresponding cement paste were measured using a rotating rheometer and viscometer, respectively. The results reveal a weak linear correlation between the yield stress of concrete mixtures and that of the corresponding cement pastes. Results also indicate that the yield stress of concrete varies in a linear fashion with the elapsed time, while its variations with the temperature and superplasticizer dosage follow power and inverse power functions, respectively. In this study, the genetic algorithms (GA) technique was used to predict the yield stress of concrete considering various parameters, such as the mixing time, ambient temperature, and superplasticizer dosage. A sensitivity study was conducted to evaluate the ability of the GA equations thus developed to capture the effects of test parameters on the yield stress of concrete. It was found that the GA equations were sensitive to the effects of test parameters and provided yield stress predictions that compared well with corresponding experimental data.

• 한국세라믹학회지
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• 제37권8호
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• pp.751-759
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• 2000

Effects of the dosage change, from 0 to 2.0 wt% based on cement weight, of naphthalenic (NSF) and polycarboxylic(NT-2) superplasticizers, on the fluidity of cement paste substituted by 10 wt% II-anhydrite and fly ash respectively as well as II-anhydrite and fly ash itself were investigated. Dispersion properties between particles in suspension were investigated by zeta potential test. Initial fluidity and slump loss in the paste system were observed through mini-slump and apparent viscosity changes with elapsed time. Zeta potential on the particle surface was a tendency to increase according to increasing of NSF dosage. Especially, zeta potential of fly ash has the highest value among all particles equivalent to NSF dosage. In the fluidity of cement paste substituted by inorganic particles, the specimen with substitution of 10 wt% II-anhydrite and fly ash for cement was more effective than cement itself to improve initial fluidity and retain stable fluidity of cement paste. In addition, effect of NT-2 and NSF to improve the fluidity of cement paste, addition of 1.0 wt% NT-2 was more effective than 1.5wt% NSF.

• Computers and Concrete
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• 제8권3호
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• pp.279-292
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• 2011

The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.

• Advances in materials Research
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• 제7권1호
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• pp.45-72
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• 2018

In the present study, a special attention has been paid to the effects regarding the use of different superplasticizers in different dosages. To do so, 36 mixes of normal and self-compacting concrete with two water/binder ratios of 0.35 and 0.45, four different types of superplasticizer including melamine-formaldehyde, naphthalene-formaldehyde, carboxylic-ether and poly-carboxylate, four different superplasticizer/cement ratios of 0.4%, 0.8%, 1.2% and 1.6% and two silica fume/cement ratios of 0% and 10% have been cast. Moreover, the initial and final setting time of the pastes have been tested. For self-compacting mixes, flow time, slump flow, V-funnel, J-ring and L-box tests have been carried out as well as testing the compressive strength and rupture modulus. For normal concrete mixes,slump test has been conducted to assess the workability of the mix and then for each mix, the compressive strength and rupture modulus have been determined. The results indicate that in addition to the important role of superplasticizer type and dosage on fresh state properties of concrete, these parameters as well as the use of silica fume could affect the hardened state properties of the mixes. For instance, the mixes whose superplasticizer were poly-carboxylic-ether based showed better compressive and tensile strength than other mixes. Besides, the air contents showed robust dependency to the type of the superplasticizer. However, the use of silica fume decreased the air contents of the mixes.

• 한국건설순환자원학회논문집
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• 제9권2호
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• pp.200-207
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• 2021

이 연구의 목적은 고성능 감수제의 종류가 알칼리활성 슬래그 기반 무시멘트 복합재료의 인장거동과 균열패턴에 미치는 영향을 실험적으로 조사하는 것이다. 이를 위하여 고성능 감수제 종류에 따라 3종류의 배합을 준비하였고, 압축강도 및 인장실험을 수행하였다. 실험결과 혼합 후 굳기 전에 섬유뭉침이나 섬유의 쏠림이 없었지만 고성능 감수제의 종류에 따라 복합재료의 인장강도, 인장변형성능, 그리고 인성은 최대 28.1%, 39.1%, 66.2% 차이가 나는 것으로 나타났다. 또한 고성능 감수제는 균열개수와 최대 섬유 가교 응력에 영향을 주는 것으로 나타났다.

• 공업화학
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• 제9권3호
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• pp.336-341
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• 1998

II형 무수석고의 평균 입경과 치환율이 시멘트페이스트의 유동성에 미치는 영향에 대해 비교하였다. 나프탈렌계(NSF)와 폴리카르본산계(NT-2) 등 2가지 고유동화제의 첨가량을 0~2.0wt%으로 변화시켰을 때 3종으로 구분한 II형 무수석고의 평균입경(4, 14, $35{\mu}m$)과 치환율(3, 5, 10, 15wt%)의 변화에 따른 영향을 측정하였다. 이들 변수들에 따른 영향을 측정하기 위하여 시멘트페이스트의 초기 유동성 및 경과시간별로 겉보기 점도를 관찰하였다. 시멘페이스트의 초기유동성은 II형 무수석고의 평균입경에 의한 영향보다는 II형 무수석고의 치환율 증가에 의한 영향이 더욱 큰 것으로 나타났다. II형 무수석고의 치환율을 10wt%로 고정시 NT-2, 1.0wt% 첨가로 시멘트페이스트의 유동성은 동일 첨가량의 NSF보다 크게 향상되었다. 이는 측정된 변수들의 범위 중에서 가장 우수한 시멘트 페이스트의 유동성을 보여주는 경우이다. NT-2, 1.0wt% 첨가에서 II형 무수석고의 치환율 증가에 따라 시멘트 페이스트의 겉보기 점도가 현저하게 감소되었다. 이로부터 시멘트 페이스트의 유동성 향상을 위해서는 NT-2의 첨가와 더불어 시멘트를 II형 무수석고로 일정비율 치환하는 것이 더욱 효과적임을 알 수 있었다.