• 한국세라믹학회지
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• 제14권2호
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• pp.88-94
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• 1977

Zircon sand of two different particle distribution with 2 percent of ground pyrophyllite were adoted to prepare the dense specimens of the stopper nozzle for the tundish. The molding pressure of $600kg/cm^2$ brought about the superior properties to those obtained t the pressure of $300kg/cm^2$, and as the firing temperatures were increased from $1, 350^{\circ}C$ to $1, 600^{\circ}C$, the better characteristics resulted. The addition of 2 percent $MgCr_2O_4$ to zircon pyrophyllite batch was more effective in corrosion-resistance to the blast furnace-slag.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 춘계학술논문 발표대회
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• pp.25-28
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• 2007

In this study we measured the changes according to time respectively on the basis of 0, 30, 60 and 90 minutes, taking into consideration the decline in fluidity of concrete according to elapsed time to analyze manufacturing capability of batcher plant according to elapsed time of ready-mixed concrete manufactured in batcher plant, and offer basic data for mixture design of ultra-high strength concrete. The proportion of water-binder was 23.55, water content was 160kg/m3, proportion of replacement of crushed sand was 0, 20 and 40% at 3 level, and we applied to the same condition of triaxial component using blast furnace slag powder and silica fume as admixture. And to meet the demand of certain fluidity, we measured respectively on property before and after hardening of ultra-high strength concrete using superplasticizer. As a result of experiment, before hardening of ultra-high strength concrete showed the best fluidity in conditions of crushed sand replacement rates of 20% and superplasticizer composition of 1.95%, but it appeared that fluidity drops as time goes by in the same composition condition. And it appeared that when it comes to hardened, the changes of compression strength according to elapsed time by crushed sand replacement rates were within 1MPa. Therefore, it turned out that the difference of strength according to elapsed time was low and compression strength of 280dys in composition mentioned above appeared highly as 88MPa.

• 한국세라믹학회지
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• 제18권1호
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• pp.3-12
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• 1981

A glass-ceramics based on blast-furnace slag, with some additives to the theoretical composition in order to control properties of mother glass and the heat treatment conditions, has been investigated. The raw materials in this study were blast-furnace slag, serpentine, feldspar and quartz as mother glass ingredients. Titanium dioxide and chromite were used as the nucleating agents. Batch compositions of the prepared glasses and ceraming conditions were found by trial and error method. The optimum conditions were confirmed by analyzing several measured physical properties such as density change during heat treatment, microhardness of slag-ceramics prepared, viscosity change of glass at heat treatment temperatures, nucleation density change, dilatometric properties, differential thermal analysis, identification of the grown crystal and crystal sizes. The batch composition feasible to prepare slag-ceramics was 40% of blast-furnace slag, 25% of serpentine, 18% of feldspar and 17% of silica sand. Three percent titanium dioxide and 1% chromite of the mother glass were added as nucleating agents. The ceraming conditions under which the slag-ceramics having considerably good properties can be developed found as: "The glass was heated at 75$0^{\circ}C$ for 2 hours for nucleation, and the temperature was raised up to 1, 00$0^{\circ}C$ with a rate of 0.75$^{\circ}C$/min for crystal growth.owth.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.453-458
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• 2001

This study was performed to reuse the dyeing wastewater sludge treated by Fenton process through the solidification/stabilization technique. To solidify the dyeing sludge the industrial by-products such as blast furnace slag, fly ash and waste sand with cement were used. The laboratory scale and pilot scale test were conducted at room temperature to make construction brick which has high compressive strength and low leaching of heavy metals. The experimental results showed that blast furnace slag and fly ash could be used instead of cement and the products satisfied the regulation of Korean Standards. The blast furnace slag increased the compressive strength and the optimum ratio of slag/dyeing sludge on dry basis was found 0.4. The solidifying agent of SB series could increase rapidly the compressive strength and the optimum ratio of solidifying agent/sludge on dry basis was 0.26 at which the strength was two times compared with non-added condition. The portion of waste and industrial by-products in matrix was over 80%. From the pilot test the optimum pressure in molding was 100kg/$\textrm{cm}^2$ at which the compressive strength was over 100kg/$\textrm{cm}^2$. And the strength increased continuously to 160kg/$\textrm{cm}^2$ until 120 days curing time due to pozzolanic reaction. When SB-20 as a solidifying agent was used, the unconfined compressive strength of dyeing sludge could be obtained 110kg/$\textrm{cm}^2$ which satisfied the regulation of cement brick in Korea Standard(KS).

• Journal of Korean Dental Science
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• 제9권1호
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• pp.19-27
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• 2016

Purpose: Laser treatment has become a popular method in implant dentistry, and lasers have been used for the decontamination of implant surfaces when treating peri-implantitis. This study was performed to evaluate the effects of an Erbium-doped:Yttrium-Aluminum-Garnet (Er:YAG) laser with different settings on machined (MA), sand-blasted and acid-etched (SA), and resorbable blast media (RBM) titanium surfaces using scanning electron microscopy and confocal microscopy. Materials and Methods: Four MA, four SA, and four RBM discs were either irradiated at 40 mJ/20 Hz, 90 mJ/20 Hz, or 40 mJ/25 Hz for 2 minutes. The specimens were evaluated with scanning electron microscopy and confocal microscopy. Result: The untreated MA surface demonstrated uniform roughness with circumferential machining marks, and depressions were observed after laser treatment. The untreated SA surface demonstrated a rough surface with sharp spikes and deep pits, and the laser produced noticeable changes on the SA titanium surfaces with melting and fusion. The untreated RBM surface demonstrated a rough surface with irregular indentation, and treatment with the laser produced changes on the RBM titanium surfaces. The Er:YAG laser produced significant changes on the roughness parameters, including arithmetic mean height of the surface (Sa) and maximum height of the surface (Sz), of the MA and SA surfaces. However, the Er:YAG laser did not produce notable changes on the roughness parameters, such as Sa and Sz, of the RBM surfaces. Conclusion: This study evaluated the effects of an Er:YAG laser on MA, SA, and RBM titanium discs using confocal microscopy and scanning electron microscopy. Treatment with the laser produced significant changes in the roughness of MA and SA surfaces, but the roughness parameters of the RBM discs were not significantly changed. Further research is needed to evaluate the efficiency of the Er:YAG laser in removing the contaminants, adhering bacteria, and the effects of treatment on cellular attachment, proliferation, and differentiation.

• 콘크리트학회논문집
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• 제26권5호
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• pp.607-614
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• 2014

본 논문에서는 품질확보를 위하여 혼합골재 입도분포를 적용한 부순모래 숏크리트에 플라이애시, 고로슬래그 미분말, 메타카올린, 실리카퓸을 종류 및 혼입률에 변동을 주어 혼입하여 숏크리트의 기초특성과 내구특성에 미치는 영향을 고찰하였다. 또한 각 혼화재료의 주요 혼입률을 선정하고 실제 숏팅을 실시 하여 숏팅 전 후의 기초특성과 내구특성을 분석하였다. 실내실험 결과 광물성 혼화재료 혼입률이 증가할수록 압축강도가 증가하는 경향을 보였다. 특히 메타카올린을 혼입한 경우 가장 우수한 강도 증진효과를 보였으며, 숏팅 후 압축강도 역시 코어링에 의한 강도감소 현상을 감안하여도 강도 발현이 우수한 혼화재료로 판단된다. 염소이온 침투저항성 시험과 황산저항성 시험 결과 광물성 혼화재료 혼입은 염소이온과 황산에 대한 저항성이 증진되는 경향을 보인다. 화상분석을 통한 공극구조 분석 결과 공기연행제를 사용하지 않아 소요의 간격계수와 비표면적을 얻는데 실패하였으며, 향후 공기연행제의 도입 후 실험이 진행될 필요성을 보이고 있다.

• 한국구조물진단유지관리공학회 논문집
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• 제11권5호
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• pp.114-122
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• 2007

강구조물의 고력볼트 마찰접합부에 있어서 마찰면의 부식은 장기적으로 마찰력 감소와 접합부 내력저하를 초래한다. 본 연구는 고력볼트 접합부의 부식을 방지하고 소요 역학적 성질을 만족시키기 위해 접합부의 마찰면에 Zn/Al 금속용사 방청처리 한 고력볼트 접합부를 대상으로 마찰면의 표면처리방법과 피막두께를 주요 변수로 하여 인장시험을 실시하였고, 실험으로 부터 마찰면 표면거칠기와 미끄럼계수를 측정하였다. 무도장 샌드블라스트 처리한 접합부 및 샌드블라스트 처리 후 금속용사를 실시한 볼트 접합부의 미끄럼 계수는 국내 규준의 규정 값과 비교하여 동등 이상의 우수한 미끄럼계수 값을 나타냈다.

• 한국지반신소재학회논문집
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• 제18권1호
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• pp.67-77
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• 2019

그라우팅 공법은 연약지반의 보강과 방수 및 지하수위저하 또는 상승과 진동으로 인한 침하 및 부등침하로 손상된 구조물의 지지력을 높이고 차수를 목적으로 하는데 사용된다. 본 연구는 아라미드 섬유를 이용하여 그라우트재료의 압축강도를 향상시키고, 고로슬래그 미분말을 이용하여 높은 강도의 지반개량공법을 개발하는데 있다. 따라서 본 연구에서는 시멘트와 고로슬래그미 분말의 비는 100:0, 70:30, 40:60%로 고치환(50%이상)까지 확인하고, 아라미드 혼입률은 시멘트와 고로슬래그 중량의 0, 0.5, 1.0%로 증가시켜 첨가하였으며, 표면의 유제처리 비율을 0.7과 1.2%로 샌드겔을 성형하여 일축압축시험을 수행하였다. 환경성 평가는 중금속용출시험과 pH 측정을 수행하였다. 실험결과 아라미드 섬유 1%첨가 시 일축압축강도는 약 1.3배 정도 강도가 증가하였고, 6가크롬은 고로슬래그 미분말이 30% 증가할수록 중금속 용출은 약 50% 감소하였으나, pH용출시험결과, 고로슬래그 미분말이 30% 증가할수록 pH는 약 0.5 증가하는 경향을 나타났다. 향후 pH에 대한 부분은 보완이 필요할 것으로 판단된다.

• Computers and Concrete
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• 제21권2호
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• pp.139-147
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• 2018

Due to enhanced construction requirement, ready mixed concrete are being popular day by day. The current study aimed to develop ready mixed concrete using GBFS contained cement and determine its properties of fresh and hardened states. A real scale experiment was set up in a ready mixed plant for measuring workability and compressive strength. The workability was tested after mixing (within 5 minutes), 30, 60, 90, 120 and 150 minutes of the running of bulk carrier. The ready mixed carrier employed spinning motion i.e., rotating around its axis with 20 RPM and running on road with 1km/h speed. The mixing ratio of cement: sand:gravel, water to cement ratio, super plasticizer were, 1:1.73:2.47, 0.40 and 6% of cement, respectively. The chemical composition of raw material was determined using XRF and the properties of cements were measured according to ASTM standards. The experimental results confirm that the cement with composition of 6.89% of GBFS, 4% of Gypsum and 89.11% of clinker showed the good compressive strength and workability of concrete after 150 minutes of the spinning motion in bulk carrier.

• Advances in concrete construction
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• 제13권3호
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• pp.233-242
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• 2022

An attempt is made to develop an eco-friendly concrete with ground granulated blast furnace slag (GGBS) and pond ash as partial replacement materials for cement and fine aggregate, respectively without compromising the strength and durability. Sixteen concrete mixes were developed by replacing cement and fine aggregate by GGBS and pond ash, respectively in stages of 10%. The maximum replacement levels of cement and fine aggregates were 50% and 30% respectively. Experimental results revealed that the optimum percentage of GGBS and pond ash replacement levels were 30% and 20% respectively. The optimized mix was used further to study the flexural behavior and durability properties. Reinforced Concrete (RC) beams were cast and tested under a four-point bending configuration. Also, the specimens prepared from the optimized mix were subjected to alternate wet and dry cycles of acid (3.5% HCl and H₂SO₄) and sulphate (10% MgSO₄) solutions. Results show that the optimized concrete mix with GGBS and pond ash had a negligible weight loss and strength reduction.