• 한국건축시공학회지
• /
• 제6권4호
• /
• pp.93-98
• /
• 2006

Admixture materials are used in mixing concrete or mortar to improve quality and performance of the concrete. This study examines the potential use of talc as a substitute for cement, the benefits of recycling waste resources for economical efficiency and quality improvement of concrete. The test was carried out by replacing the plain mix with fine grains of talc at the rate of 10%, 20%, and 30%. Talc was divided into three groups depending on the degree of pulverizing. For wet concrete, porosity, slump, bleeding per unit, and setting time by penetration resistance were measured; similarly, for dry concrete, strength and watertight Property were tested. Test results showed that the amount of bleeding and setting time could be shortened, but the strength and watertight proofing severely deteriorated. However, at the replacement rate of 10%, talc showed equal performance with the plain at all degrees of pulverization, which suggests its potential use as admixture material.

• Structural Engineering and Mechanics
• /
• 제81권6호
• /
• pp.729-736
• /
• 2022

Earth is facing a serious problem of pollution and scarcity of energy sources. The synthetic fibers used in automobile and Aerospace manufacturing sectors are non-renewable and harmful to environment. International Agency such as FAA and SAE is forcing for green fuel, green materials and structures. Further exploration is much needed to understand its potential in structural applications. In the current study, hemp and Jute fibre based composites were developed and tested for assessing their suitability for possible applications in automobile and aerospace sectors. Composites were undergone tensile test, water absorption test, and fatigue analysis to understand its behavior under various loading conditions. The finite element analysis has been carried out to understand the fatigue behaviour of composites. The results revealed that the usage of hemp and jute fibre reinforced composites can improve mechanical properties and have shown a viable alternative to replace synthetic fibres such as glass fibres for specific applications. Hemp reinforced bio-composites have shown better performance as compared to Jute reinforced bio-composites while water resistance characteristics for hemp is poorer to jute fibres.

• 한국방재학회 논문집
• /
• 제8권6호
• /
• pp.47-52
• /
• 2008

겨울철 도로의 결빙을 방지하기 위하여 염화물계 제설제가 많이 사용되고 있으며, 매년 사용량이 증가하고 있다. 이러한 제설제의 사용은 구조물의 부착강도 저하, 표면스케일링, 환경오염을 발생시킨다. 본 연구에서는 17년간 사용해 온 콘크리트 도로 시설물의 피해상황에 대하여 현장조사를 실시하였으며, 기존 제설제와 개발된 친환경 제설제의 부식 저항성에 대한 비교 실내실험을 수행하였다. 현장피해 조사결과에 따르면, 제한 염화물량의 침투 깊이는 평균 40 mm정도로 나타났고, 조사구간의 표면 염화물 농도는 $3.45kg/m^3$으로 조사되었으며, 이에 비해 탄산화 깊이는 매우 적었다. 한편, 친환경 제설제의 경우, 기존 염화물계 제설제에 비해 염화물 침투 깊이가 적었으며, 부식저항성도 높은 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제14권1호
• /
• pp.102-108
• /
• 2010

본 연구의 목적은 폐 PET병을 재활용하여 만든 섬유(RPET)를 콘크리트 부재에 적용시키기 위한 성능 평가에 있다. RPET 섬유보강 효과를 평가하기 위해서 압축강도, 탄성계수, 쪼갬인장강도와 같은 기초물성실험과 건조수축균열실험을 수행하였다. 기초물성실험에서 RPET의 혼입률이 증가할수록 RPET 보강 콘크리트의 압축강도와 탄성계수는 감소하였고, 쪼갬인장강도는 증가하였다. 건조수축 실험에서 자유건조수축은 증가하였다. 반면에 구속건조수축의 경우 RPET 섬유에 의한 인장 저항성의 증가로 인해 균열 발생을 지연시켰다. RPET 섬유와 PP 섬유를 혼입한 콘크리트 시편의 특성을 비교해보면 두 섬유가 유사하다는 것을 알 수 있다. 따라서 RPET 섬유는 PP 섬유의 대체 재료로서 충분할 뿐만 아니라 폐 PET병을 재활용하고 환경오염을 저감시킨다는 측면에서 친환경적으로 더 뛰어나다는 것을 알 수 있다.

• 한국동물위생학회지
• /
• 제40권2호
• /
• pp.101-105
• /
• 2017

The purpose of this study was to investigate prevalence and antimicrobial resistance patterns of Campylobacter spp. from duck feces in northern area of the Gyeongnam province, Korea. Samples of 121 duck feces were taken from April to December 2014 for this survey. Samples were examined by bacteria isolation and reverse transcriptase-polymerase chain reaction assay for detection of Campylobacter spp. Campylobacter were isolated in 37 samples (30.6%). Among these samples, C. jejuni and C. coli were isolated in 35 samples and 2 samples, respectively. Minimum inhibitory concentration (MIC) test is performed to investigate antimicrobial resistance patterns of Campylobacter spp. C. jejuni were resistant to ciprofloxacin (85.7%), nalidixic acid(82.9%), tetracycline (77.1%), gentamicin (57.1%), azithromycin (40.0%), clindamycin (34.3%), erythromycin (22.9%), and florfenicol (8.6%). These data support a database of pollution and antimicrobial resistance of Campylobacter spp. from duck feces and provide a basic information of reducing the secondary damage of antibiotic misuse.

• 한국표면공학회지
• /
• 제29권5호
• /
• pp.545-548
• /
• 1996

$CrN_x$ films were deposited on SKD61 and S45C by cathodic arc ion plating process. In this study, the microstructure, microhardness, a hesion, wear and corrosion properties of the CrNx films were studied for various nitrogen partial pressures and the results were compared with those from the electroplated hard Cr. The crystal structure of the films was characterized by X-ray diffraction. Wear tests were performed under no lubricant condition at atmosphere by ball-on-disc type tribotester. Corrosion resistance of the films were studied by electrochemical corrosion test, measuring current demsity-potential curves. The results indicated that the $CrN_x$ films formed using ion plation method showed higer hardness and lower current density, friction coefficient than electroplated hard Cr. Consequently, the application of the CrNx coationgs by ion plating which is free of environmental pollution, is expected to improve lifetime of components in industrial practice.

• 복합신소재구조학회 논문집
• /
• 제6권3호
• /
• pp.41-49
• /
• 2015

The repair of manhole raise has been caused much construction times and disruption of traffic flow, serious environmental pollution from crushed construction wastes, and budget waste due to the repeated repair construction works. In order to overcome such problems, we have developed the new manhole repairing composite structures by using a glass fiber-reinforced polymer (GFRP) pipe, which can raise manhole to the regular height of the overlayed road pavement with rapid construction and minimum traffic jams. This environmental-friendly technology is method completed by the methyl methacrylate monomer (MMA) double wide flanged GFRP pipe composite structures in order to raise manhole to the regular height. In this paper, two kinds of the compressive strength tests of MMA mortar composites were conducted and evaluated by a general compressive strength test, and compressive strength test after freezing-thawing resistance test. It was found that this MMA mortar composites will be used for the application of the double wide flanged GFRP pipe composite structures.

• 한국농공학회논문집
• /
• 제52권6호
• /
• pp.125-134
• /
• 2010

This study was performed to evaluate the workability, strengths and durability of polymer concrete using oyster shell that are reclaimed at public shore illegally or leaved on the surroundings of shore to prevent the environmental pollution. We investigated the effect of oyster shell powder (OSP) and $CaCO_3$. on the slump, compressive strength, flexural strength, acid sulfuric and freezing and thawing resistance as a filler of polymer concrete. Modified OSP obtained by crushing oyster shell (less than 0.15 mm size) consists of 60.47 wt% of $SiO_2$ and 39.5 wt% of $CaCO_3$. As a result of slump test by OSP and $CaCO_3$. contents, it is found that slump of specimen used OSP is lower than that used $CaCO_3$. and the more OSP contents are, its slump is increased. Compressive and flexural strength of polymer concrete using OSP are similar or slightly lower than that using $CaCO_3$. In acid sulfuric test for 5 % $H_2SO_4$ and freezing thawing test, regardless of kinds of fillers and contents are not found fatal defects in weight change, falling-off in surface and durability factor.

• 한국환경농학회지
• /
• 제41권4호
• /
• pp.344-354
• /
• 2022

BACKGROUND: Although antibiotics have contributed to treatment of bacterial infection, the antibiotic abuse can lead to antibiotic resistant bacteria. Impact of human activities on distribution of antibiotic resistance has been intensively issued and occurrence of antibiotic resistant bacteria in contaminated environments would not be a surprise. Nonetheless, anthropogenic contamination with the dissemination of antibiotic resistance along uncontaminated environments has been less considered. The aim of this study is to investigate antibiotic resistant bacteria across Ulleungdo, known as antibiotic resistance free and anthropogenic pollution free environment in Rep. of Korea. METHODS AND RESULTS: Antibiotic resistant bacteria in coastal seawater of Ulleungdo were investigated in July 2021. Antibiotic susceptibility test using the disk diffusion method was applied with six drugs according to the Clinical and Laboratory Standards Institute (CLSI) guideline. Total 43 bacterial isolates were tested and 20 isolates among of them showed multidrug resistance. Particularly, the number and ratio of resistant bacteria were relatively high in a densely populated area of Ulleungdo. The bacterial communities were investigated using 16S rRNA gene metabarcoding approach in the coastal seawater and soils of Ulleungdo. In the bacterial communities, Firmicutes were selectively distributed only in seawater, suggesting the possibility of anthropogenic contamination in coastal seawater of Ulleungdo. CONCLUSION(S): We found antibiotic resistant bacteria in a populated area of Ulleungdo. The occurrence of antibiotic resistant bacteria in Ulleungdo seems to result from the recent anthropogenic impact. Consistent monitoring of antibiotic resistant bacteria in the uncontaminated environment needs to considered for future risk assessment of antibiotics.

• 콘크리트학회논문집
• /
• 제20권3호
• /
• pp.283-290
• /
• 2008

표면 침투제를 이용한 보수기법은 열화된 콘크리트구조물에 대해서 효과적이므로, 최근들어 많은 연구가 수행되고 있다. 특히 무기계 표면 보호재를 제조할 경우나 현장에서 적용할 경우, 공기오염이 없으므로 환경친화적이며, 침투층과 구콘크리트간의 물리적 성능 차이에 의한 박리가 발생하지 않는다. 침투된 콘크리트의 내구성 평가를 위해서는 장기폭로실험에 의한 평가가 매우 중요하지만, 대부분의 내구성 실험이 일시적이고 정성적인 실내실험에 국한되어 있다. 본 연구에서는 무기계 및 유/무기계 침투제를 사용한 콘크리트 시편에 대하여 장기염해폭로실험을 수행하여 내구적 특성을 실험적으로 평가하였다. 21 MPa과 34MPa로 제조된 2가지의 콘크리트 배합에 대하여, 2년간 해수중, 조석대, 비말대에 노출하였으며, 압축강도, 염화물 침투깊이, 철근부식 자연전위 등을 평가하였다. 평가 결과, 침투제를 적용한 시편은 강도 증가에서는 성능 개선 효과가 거의 없었으나, 염화물 침투깊이와 자연전위에 대해서는 내구성능이 개선된 것으로 평가되었다. 유/무기계 침투제 보다 무기계 침투제에서 염해저항성이 크게 평가되었으며 수중부, 조석대에 노출된 시편보다는 비말대에 노출된 시편에서 염해저항성이 높게 평가되었다.