• 한국재료학회지
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• 제22권9호
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• pp.494-498
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• 2012

Geopolymer cements and geopolymer resins are newly advanced mineral binders that are used in order to reduce the carbon dioxide generation that accompanies cement production. The effect of additives on the compressive strength of geopolymerized class-F fly ash was investigated. Blast furnace slag, calcium hydroxide($Ca(OH)_2$), and silica fume powders were added to fly ash. A geopolymeric reaction was initiated by adding a solution of water glass and sodium hydroxide(NaOH) to the powder mixtures. The compressive strength of pure fly ash cured at room temperature for 28 days was found to be as low as 291 $kgf/cm^{-2}$, which was not a suitable value for use in engineering materials. On the contrary, addition of 20 wt% and 40 wt% of blast furnace slag powders to fly ash increased the compressive strength to 458 $kgf/cm^{-2}$ and 750 $kgf/cm^{-2}$, respectively. 5 wt% addition of $Ca(OH)_2$ increased the compressive strength up to 640 $kgf/cm^{-2}$; further addition of $Ca(OH)_2$ further increased the compressive strength. When 2 wt% of silica fume was added, the compressive strength increased to 577 $kgf/cm^{-2}$; the maximum strength was obtained at 6 wt% addition of silica fume. It was confirmed that the addition of CaO and $SiO_2$ to the fly ash powders was effective at increasing the compressive strength of geopolymerized fly ash.

• 콘크리트학회지
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• 제6권1호
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• pp.142-151
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• 1994

본 연구는 강섬유보강 콘크리트의 시공성 및 공학적 특성에 미치는 강섬유 길이의 영향과 실리카흄 및 플라이애시와 같은 콘크리트용 혼화재의 첨가에 의한 영향을 실험적으로 고찰한 것으로서 본 연구결과 낮은 물결함재비를 채용하고 고성능감수제를 사용함으로써 슬럼프 10(cm)의 유동성과 $600(kgf/\textrm{m}^2)$ 이상의 28일 압축강도를 갖는 강섬유보강콘크리트의 제조가 가능하였으며, 실리카흄의 사용은 강섬유보강콘크리트의 시공성 및 공학적 특성 개선에 유효한 인자로 나타났으며, 또한 강섬유보강콘크리트의 인장강도는 보통콘크리트에 비하여 높게 나타나 강섬유가 콘크리트의 인성증진에 기여 하는 것으로 나타났다.

• International Journal of Concrete Structures and Materials
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• 제7권3호
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• pp.239-249
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• 2013

In the present scenario to fulfill the demands of sustainable construction, concrete made with multi-blended cement system of OPC and different mineral admixtures, is the judicious choice for the construction industry. Silica fume (SF) and fly ash (FA) are the most commonly used mineral admixtures in ternary blend cement systems. Synergy between the contributions of both on the mechanical properties of the concrete is an important factor. This study reports the effect of replacement of OPC by fly ash (20, 30, 40 and 50 % replacement of OPC) and/or silica fume (7 and 10 %) on the mechanical properties of concrete like compressive strength and split tensile strength, with three different w/b ratio of 0.3, 0.4 and 0.45. The results indicate that, as the total replacement level of OPC in concrete using ternary blend of OPC + FA + SF increases, the strength with respect to control mix increases up to certain replacement level and thereafter decreases. If the cement content of control mixes at each w/b ratio is kept constant, then as w/b ratio decreases, higher percentage of OPC can be replaced with FA + SF to get 28 days strength comparable to the control mix. A new method was proposed to find the efficiency factor of SF and FA individually in ternary blend cement system, based on principle of modified Bolomey's equation for predicting compressive strength of concrete using binary blend cement system. Efficiency factor for SF and FA were always higher in ternary blend cement system than their respective binary blend cement system. Split tensile strength of concrete using binary and ternary cement system were higher than OPC for a given compressive strength level.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.97-108
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• 2016

When the energy performance of concrete is substantially higher than that of normal type concrete, such concrete is regarded as energy efficient concrete (WBSCSD 2009). An experimental study was conducted to investigate mechanical properties of energy efficient concrete with binary, ternary and quaternary admixture at different curing ages. Slump test for workability and air content test were performed on fresh concretes. Compressive strength, splitting tensile strength were made on hardened concrete specimens. The mechanical properties of concrete were compared with predicted values by ACI 363R-84 Code, NZS 3101-95 Code, CSA A23.3-94 Code, CEB-FIP Model, EN 1991, EC 2-02, AIJ Code, JSCE Code, and KCI Code. The use of silica fume increased the compressive strengths, splitting tensile strengths, modulus of elasticities and Poisson's ratios. On the other hand, the compressive strength and splitting tensile strength decreased with increasing fly ash.

• 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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.605-608
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• 2008

본 연구는 고강도 혼합재 사용에 따른 고강도 콘크리트의 기초물성 및 내화특성을 검토한 것으로, 그 결과를 요약하면 다음과 같다. 유동특성으로 고강도 혼합재를 사용할 경우, 실리카흄을 사용한 경우보다 목표 슬럼프플로우를 만족키 위한 고성능 감수제의 사용량이 감소하는 것으로 나타나, 유동성 확보 차원에서 고강도 혼합재를 사용할 때 실리카흄과 비교할시 우수한 것으로 나타났다. 강도특성으로는 고강도 혼합재 사용 시 재령 7일 초기압축강도가 실리카흄을 사용한 경우보다 증가하는 것으로 나타나, 초기 강도 확보에서 유리함을 확인할 수 있었고, 재령 28일에서는 모두 비슷하게 압축강도를 발현하는 것으로 나타났다. 섬유 혼입율 변화에 따른 압축강도는 미소한 차이만 있을 뿐 큰 차이는 없는 것으로 나타났다. 섬유 무혼입에서 고강도 혼합재 및 실리카흄 모두 폭열이 발생하였지만, 섬유 혼입량 0.05% 이상에서는 폭열이 방지되는 것으로 나타났다.

• 콘크리트학회논문집
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• 제25권5호
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• pp.565-572
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• 2013

CBPC(chemically-bonded phosphate ceramic) 바인더는 사소 MgO와 인산의 강력한 산-염기 반응을 이용한 초속경 보수재료로서, 시멘트와는 달리 CaO의 함량을 10% 이하로 줄인 재료이다. 이번 실험에서는 CBPC 바인더에 천연광물 및 산업부산물로 이뤄진 6가지 충전재들을 첨가하고 물리적 성능 및 수화 반응을 관찰하였다. 실리카퓸을 첨가한시편이 압축강도 및 동탄성계수가 상대적으로 높았고, 특히 장기강도 면에서 뚜렷한 증가율을 보였다. 또한 XRD 분석을 통해 실리카퓸을 첨가한 시편에서 마그네슘의 수화물인 M-S-H gel and $MgCO_3$ 피크를 관찰 할 수 있었다. 칼슘 성분이 다량 포함된 충전재를 넣은 시편의 경우 강도 및 내구성 면에서 좋지 않은 결과를 낳은 것으로 보아, 칼슘과 마그네슘 수화물은 서로 화학적으로 결합하지 않으므로 섞지 않는 것이 좋다는 결론을 도출했다. 결과적으로 MgO를 기반으로 하는 모르타르에는 순수하게 실리카 성분으로만 이루어진 실리카 흄과 같은 충전재가 알맞은 것으로 나타났다.

• 한국산학기술학회논문지
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• 제19권6호
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• pp.98-103
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• 2018

산업의 발전에 따라 설비 및 재료 등 따라서 재료 표면의 특성을 내식성 및 고강도, 내마모성 등을 향상 시키기 위하여 지금까지 많은 코팅 기술들이 발전해 왔다. 그 중 CCO(CaCoO, 이후 CCO) 박막 형성은 전자재료 영역에서 연구, 사용이 되어오고 있는데, 이 CCO 박막의 특징 중 하나가 고온의 열에 강하다는 것이 있다. 특히 CCO 박막을 형성 시키는 방법 또한 비교적 간단하여 고온의 산화 분위기에 도입이 가능 할 것으로 판단되었다. 따라서 본 연구에서는 이 CCO 박막의 코팅이 용융 아연 도금 설비에 적용을 하기 전에, 고온 및 Zn fume에 대한 부식성을 파악하여 용융 아연 도금 설비에 적용이 가능한지를 파악하기 위한 실험 및 분석을 실시 하였다. 우선 기본 소재 STS304 표면에 CCO 박막을 형성 시키고, 650도의 대기로에서 Zn fume의 분위기 내에서 산화 시킨 후 CCO 박막의 부식 정도를 확인 및 측정 하였다. 산화는 30일간 진행되었고, 30일 후 SEM을 이용하여 CCO박막의 형상을 확인 하였으며 동전위분극 실험을 통하여 부식성을 분석하였다.

• 한국산업보건학회지
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• 제9권1호
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• pp.14-22
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• 1999

This study was conducted to evaluate workplace protection factors(WPF) for two half-facepiece respirators (HR-1, HR-2) in welding workplace and to provide data on the workplace performance of negative-pressure, half-facepiece respirators against airborne particulate contaminants. The outside iron oxide(Fe2O3) concentration of welding fume for the respirator HR-1 ranged from 0.177 to $12.508mg/m^3$ with a geometric mean of $1.118mg/m^3$ and the HR-2 respirator showed a iron oxide range of 0.500 to $3.494mg/m^3$ with a geometric mean of $1.082mg/m^3$. But the inside oxide concentration of welding fume for the respirator HR-1 ranged from 0.002 to $0.364mg/m^3$ with a geometric mean of $0.019mg/m^3$ and the HR-2 respirator showed a iron oxide range of 0.012 to $0.639mg/m^3$ with a geometric mean of $0.041mg/m^3$. The iron oxide inside concentrations were significantly less than $5mg/m^3$(TLV) for both of respirators. The WPF were ranged from 3 to 3744 with a geometric mean of 60 for HR-1 and range from 2 to 129 a geometric mean of 26 for HR-2. And, in this study, the 5th percentile of the workplace protection factors for half-facepiece aspirators (HR-1, HR-2) were 11.2 and 7.1, respectively. The correlation relationship between the Quantative Fit Factors(QNFT) and the WPF for half-mask negative pressure respirators were 0.099 and 0.460.

• 한국세라믹학회지
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• 제44권9호
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• pp.502-509
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• 2007

This paper investigated how Fine Fly Ash (FFA) with $14,000\;cm^2/g$ of Fineness affects the micro structure and material properties of High-Performance Concrete (HPC) before and after hardening from Material Test of HPC and Cement Paste. FFA is applied as a substitute of Silica Fume which is used necessarily in producing HPC. As a Material Test results, 5% FFA series specimen shows the lower fluidity than SF series specimen. When, however, the Fluidity of 10% FFA series specimen is increased reversely to the similar value of SF series specimen. The Porosity of FFA series specimen of 3 day age is displayed to $21{\sim}24%$, which is higher than $19{\sim}20%$ porosity of SF series specimen, while that of 28 day age is reached to $8{\sim}9%$, which is improved compared with 10% fo SF series specimen. It can be thought that FFA has better influence on the porosity of HPC in case of long term age. The Compressive strength of FFA series specimen shows the similar result with the property of porosity. The compressive strength of 28 day age FFA series specimen is $98{\sim}106%$ of SF series specimen and 107% of plain specimen to reveal better strength development.