• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.52-56
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• 1996

In this study, when natural mineral with Silica components(Zeolite & Mudstone) abundant in Korea used as an admixture for concrete, it is investigated that the properties of strength increase and economic effect compared with Silica Fume, the general admixture of high strength concrete.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.321-323
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• 2005

• 한국구조물진단유지관리공학회 논문집
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• 제10권5호
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• pp.171-178
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• 2006

고온에 노출된 고강도 콘크리트의 폭렬저감대책으로서 폴리프로필렌 섬유를 콘크리트에 혼입함으로써 취성적 파괴를 방지할 수 있는 것으로 보고 되었다. 그러나 초고강도 콘크리트 배합시 다량으로 혼입되는 PP섬유는 시공성을 저하시키는 원인이 된다. 또한 초고강도 콘크리트의 강도발현을 위하여 필수적으로 사용되는 실리카흄은 콘크리트의 수밀성을 높여 폭렬현상이 더욱 심하게 발생할 것으로 판단된다. 본 연구에서는 고강도 콘크리트에서 실리카흄이 폭렬에 미치는 영향과 초고강도 콘크리트의 시공성을 확보하기 위하여 PP섬유를 대신하여 PP분말 및 PVA의 내화성능을 실험을 통하여 관찰함으로써 초고강도 콘크리트의 내화성능확보를 위한 기초 자료를 제시하였다.

• International Journal of Concrete Structures and Materials
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• 제2권1호
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• pp.41-48
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• 2008

This study investigates the spalling properties of high strength concrete designed with various types of mineral admixture and diverse content ratios of polypropylene (PP) fiber. Experimental factors considered in series I are four pozzolan types of mineral admixture and series II consists of three shrinkage reducing types of mineral admixture. PP fiber was added 0.05, 0.10 and 0.15vol. % in each mixture of series I and series II, so that totally 27 specimens including control concretes in each series were prepared. Test results showed that the increase of fiber content decreased the slump flow of fresh concrete and increased or decreased the air content depending on the declining ratio of slump flow. For the properties of compressive strength, all specimens were indicated at around 50 MPa, which is high strength range; especially all specimens in series II were 60 MPa. Fire test was conducted in standard heating curve of ISO 834 with ${\phi}100{\times}200\;mm$ size of cylinder moulds for 1 hour. The specimens incorporating silica fume exhibited severe spalling and most specimens without the silica fume could be protected from the spalling occurrence in only 0.05vol % of PP fiber content. This fire test results demonstrated that the spalling occurrence in high strength concrete was not only affected by concrete strength related to the porosity of microstructure but also, even more influenced by micro pore structure induced by the mineral admixtures.

• Computers and Concrete
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• 제12권3호
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• pp.285-301
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• 2013

This paper concentrates on the results of experimental work on tensile strength of self-compacting concrete (SCC) caused by flexure, which is called rupture modulus. The work focused on concrete mixes having water/binder ratios of 0.35 and 0.45, which contained constant total binder contents of 500 $kg/m^3$ and 400 $kg/m^3$, respectively. The concrete mixes had four different dosages of a superplasticizer based on polycarboxylic with and without silica fume. The percentage of silica fume that replaced cement in this research was 10%. Based upon the experimental results, the existing equations for anticipating the rupture modulus of SCC according to its compressive strength were not exact enough. Therefore, it is decided to use artificial neural networks (ANN) for anticipating the rupture modulus of SCC from its compressive strength and workability. The conclusion was that the multi layer perceptron (MLP) networks could predict the tensile strength in all conditions, but radial basis (RB) networks were not exact enough in some circumstances. On the other hand, RB networks were more users friendly and they converged to the final networks quicker.

• 한국산업보건학회지
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• 제20권4호
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• pp.248-255
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• 2010

Airborne nanoparticle concentrations in three metrics (particle surface area concentration, particle number concentration, and particle mass concentrations) were measured by task in a laboratory making carbon nanotubes (CNTs) films using three direct reading instruments. Because of the conducted other researcher's experiment before the tasks, airborne nanoparticle surface area and number concentrations are the highest at the first time conducted weighing and mixing by sonication task, respectively. Because of the mist generated during mixing by sonication, the highest airborne nanoparticle surface area and PM1 concentrations were measured in the task among the total. Nanoparticle surface area concentrations at the researchers' breathing zones had high correlation (r=0.93, p<0.01) with those measured at an area in the laboratory. This result indicates that nanoparticles generated during the experiment contaminated the whole room air. When the experiment performed all the fume hoods weren't operated and making CNTs films task were conducted in the out of the fume hoods. In conclusion, researchers performing making CNTs film experiments were exposed to airborne nanoparticles generated during the experiment without adequate controls. We recommend that adequate controls should be implemented so that workers' exposures to airborne nanoparticle are limited to minimum levels.

• Computers and Concrete
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• 제15권6호
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• pp.935-950
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• 2015

The aim of this study is to provide experimental data regarding the compressive, shear and torsional strength of self-compacting concrete (SCC) used in rectangular beams, and then comparing the results with the equations presented by the CSA A23.3-04 and ACI 318-11. In fact, the gathered information in this field is quite useful for calibrating the computer models of other researchers. The other goal of this study was to investigate the effects of silica fume and superplasticizer dosages on the mechanical properties of SCC. In this research, SCC is made based on 16 different type mixing layout. Also two normal concrete (NC) or vibrating concrete are constructed to compare the results of SCC and NC. This work concentrated on concrete mixes having water/binder ratios of 0.45 and 0.35, which contained constant total binder contents of $400kg/m^3$ and $500kg/m^3$, respectively. The percentages of silica fume that replaced cement were 0% and 10%. The superplasticizer dosages utilized in the mixtures were 0.4%, 0.8%, 1.2% and 1.6% of the weight of cement. Beam dimensions used in this test were $30{\times}30{\times}120cm^3$. The results of this research indicated that shear and torsional strength of SCC beams to be used in computer models can be calculated utilizing the equations presented in CSA A23.3-04 and ACI 318-11.

• Computers and Concrete
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• 제21권2호
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• pp.149-156
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• 2018

This paper investigated the influence of binary and ternary blends of mineral admixtures in self-compacted mortar (SCM) on the fresh, mechanical and durability properties. For this purpose, 25 mortar mixtures were prepared having a total binder content of $640kg/cm^3$ and water/binder ratio between 0.41 and 0.50. All the mixtures consisted of Portland cement (PC), fly ash (FA) and silica fume (SF) as binary and ternary blends and air-entrained admixture wasn't used while control mixture contained only PC. The compressive and tensile strength tests were conducted for 28 and 91 days as well as slump-flow and V-funnel time tests whilst freeze-thaw (F-T) resistance and capillary water absorption tests were made for 91-day. Finally, in general, the use of SF with FA as ternary blends improved the tensile strength of mortars at 28- and 91-day while the use of SF15 with FA increased the compressive strength of the mortars compared to binary blends of FA. SCM mixtures with ternary blends had lower the sorptivity values than that of the mortars with binary blends of FA and the control mixture due to the beneficial properties of SF while the use of FA with SF as ternary blends induced the F-T resistance enhancement.

• 콘크리트학회지
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• 제11권2호
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• pp.115-125
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• 1999

콘크리트의 품질확보와 문제점 해결방안으로서 20세기 전반까지는 주로 시멘트의 종류를 달리하는 경우가 많았으나, 그 후반기부터는 각종 혼화재료를 사용하여 콘크리트의 결점을 보완하고 각종 요구성능에 부응하는 다양한 품질의 콘크리트를 제조하고 있다. 따라서 이같은 다양한 요구에 부응키 위해서는 혼화재료의 사용이 필수적이므로 본 연구에서는 강도증진 및 수화열 저감목적으로 많이 사용되고 있는 실리카흄, 플라이애쉬, 고로슬래그 미분말 및 농업부산물인 왕겨재의 특성을 규명키 위하여 이들을 혼입한 콘크리트에 대해서 단위결합재량별(300~600kg/$m^3$)로 이들 각각의 혼입률에 따라서 시공성 및 강도특성을 분석한 후 각 혼화재의 성능을 발휘할 수 있는 최소 결합재량과 시공성 및 강도특성이 가장 우수한 최적 혼입률 등을 도출하였다.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1452-1457
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• 2011

실리카흄과 이산화티타늄을 건식 및 습식방식에 의해 나노화하여 시멘트 모르타르의 강도특성실험을 수행하였다. 실험변수는 건식 및 습식 방식으로 제조된 혼화재를 각각 5,10,15,20%의 첨가율로 하였다. 그 결과 실리카흄과 이산화티타늄을 사용했을 때의 시멘트 모르타르 강도 특성이 유사하게 나타났으며 건식과 습식 혼화재의 비교에서는 습식 혼화재를 사용했을 때가 더 큰 강도 특성을 보였다.