• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.457-460
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• 2008

CFRP plates has been established as an effective method for rehabilitation and strengthening of concrete structures. The CFRP reinforcements are bonded to beams and slabs using structural adhesives. Adhesive strength can be affected by environmental exposure. During freezing-and-thawing cycling, temperature-induced stresses in the adhesive layer, due to differential thermal expansion between the CFRP and the substrate concrete, may lead to bond damage and contribute to or cause premature CFRP composite separation. This paper presents the results of experimental program undertaken to investigate the effects of freeze-thaw cycling (from -18 to $4^{\circ}C$) on the behavior and failure characteristics of RC beams strengthened in shear with CFRP plate using acoustic emission (AE) technique.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.841-846
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• 2002

As growing of industrialization and increasing of population. the quantities of waste are rapidly growing in the earth. It cause some problems such as the waste of natural resources and environmental pollution. In this context, recycling waste glass as a material of concrete has a great advantage environmentally and economically. On that score, other contries have start recycling waste glass widely and accoumulatig the technology of manufacturing equipment and construction. However, few studies have been done in this country. Therefore, this study was conducted freeze-thaw resistance test and neutralization reaction test to analyze the durability properties of steel fiber reinforced concrete containing waste glass as fine aggregate and containing industrial by-products(Fly ash).

• 한국식품영양과학회지
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• 제30권3호
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• pp.565-568
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• 2001

A study was conducted to investigate cryoprotectant effect of commercially produced oligosaccharides (IMO: isomalto-oligosaccharides, FO: fructo-oligosaccharides and GO: galacto-oligosaccharides) on beef protein and to compare their effectiveness to sucrose or a mixture of sucrose and sorbitol on freezing. The optimal addition level of cryoprotectants was determined by measuring $Ca^{2+}$-ATPase activity of sample treated with different concentration (0 to 12%) after freeze-thaw cycle. Since the stabilization effect was not dramatically increased above 8% sugar concentrations, the 8% was determined as an usage level. During frozen storage (at -18$^{\circ}C$ for 12 week), commercially produced oligosaccharides showed lower cryoprotection ability than sucrose but higher than sucrose+sorbitol as measured by protein solubilities and $Ca^{2+}$-ATPase activities.

• 동아시아식생활학회지
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• 제3권2호
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• pp.139-145
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• 1993

Retrogradation characteristics of the acetylated and raw starch were investigated with the chucheongbyeo and Samkangbyeo. The freeze-thaw stability and syneresis on starch gel were more stable and lower in acetylated rice starch, suggested that the rice starch acetylated with acetyl group is more stable in the various conditions. The retrogradation time constant of acetylated rice starch gel from the Chucheongbyeo and Samkangbyeo which were measured at 5$^{\circ}C$ storage were 11.7 days and 10.2 days, respectively. In addition, the retrogradation time constant in 21$^{\circ}C$ were 50.5 days and 49.8 days, indicating that retrogradation was noticiably retarded in this occation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.339-344
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• 1997

During recent years the durability of concrete structures has attracted considerable interest in concrete practice, material research and long-term deformation. To preserve the brittleness of concrete as well as energy absorption and impact resistance, amount of fiber usage has greatly increased year to year in the field of public works. When fly ash, fine powder, mixed into concrete, it condensed the void of concrete structure. Expecially, there's a great effect for strength improvement of concrete by initial pozzolanic reactions. Pozzolan reaction, between cement particle and fly ash, can elaborate the micro structure of matrix. So it was able to improve the effect of fiber reinforced by increased adhesion between cement paste and steel fiber. And so, in this paper, we dealt SFRC for the purpose of efficiently using of industrial by-products and its economical manufacturing. Also we performed the test for durability such as chemical resistance, freeze-thaw resistance and accelerated carbonation of SFRC using fly ash.

• 한국안전학회지
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• 제18권3호
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• pp.109-113
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• 2003

Concrete and shotcrete should withstand the conditions for which they have been designed, without deterioration, over a period of years. But connote and shotcrete are being deteriorated according to aging by internal and external causes. Recently, many studies on the durability of concrete have been conducted But the durability of shotcrete is rarely studied. So, in this study, chloride ion penetration test freeze and thaw test neutralization test were conducted to examine the durability characteristics of shotcrete with several accelerator and chemical admixture types. These results indicate that shotcrete with allah free accelerator and with superplasticizer are durable. Therefore, the present study provides a fm base to make high performance shotcrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.810-813
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• 2004

Air void systems in hardened concrete has an important influence on concrete durability such as freeze-thaw resistance, water permeability, surface scaling resistance, and etc. Linear traverse method and point count method described at ASTM have been widely used to estimate the air void system in hardened concrete. These methods, however, are rarely used at present, because they require many efforts, are time consuming works, depend on each person's decision, and are not repeatable. Thus, new image analysis method using microscope and computer processes has been approached for analyzing air void system in hardened concrete. However, it is just in initial step. The purposes of this study were to develope an effective and reliable image analysis technique for estimating air void system in hardened concrete. The developed technique was proved to be accurate, reasonable and repeatable.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.78-81
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• 2003

Recently, physical properties of concrete containing ternary blended cement were actively researching to develop durability, mobility, and atc. as well as strength increase of concrete. In this study, durability of concrete such as the resistance against chloride ion penetration, rebar corrosion, freeze and thaw, and sulfate were researched for concrete containing ordinary portland cement(OPC) and ternary blended cement(TBC), respectively. For this purpose, concrete specimens containing OPC and TBC, respectively, were made for 37.5% of W/C, and then various durability experiments described above were carried out. As a result, it was observed from the test that concrete containing TBC showed excellent durability than concrete containing OPC.

• Journal of Microbiology
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• 제35권4호
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• pp.354-359
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• 1997

Methods for the extraction of DNA from water sample were approximated. Four different procedures of DNA extraction were carried out with pellets obtained from centrifugation of 4 liter water samples. The recovery efficiency and purity of DNA extracted by each method from different sources were compared. DNA yield varied with extraction methods, Method I, which involves enzymatic and freeze-thaw lysis steps and phenol and phenol-chloroform purification of extracted nucleic acid, showed a significantly higher yield and purity than the other methods. The use of glass beads in the DNA extraction methods improved the purity of DNA suitable for PCR. Bovine serum albumin in the PCR reaction mixture was useful in reducing inhibitory effects of contaminants. The efficiency of an extraction method was determined by the detection of the aer of Aeromonas hydrophila with PCR. The lower limit of detection of A. hydrophila from seeded tap water was 2 CFU/ml in PCR when method I was used for DNA preparation.

• 한국안전학회지
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• 제19권2호
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• pp.98-103
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• 2004

Shotcrete needs the enough durability without deterioration for life time. But shotcrete is being deteriorated according to aging like concrete by internal causes whithin itself and by external causes which can be physical, chemical, or mechanical. Durable shotcrete can be made by incresing the cement content, adding chemical and mineral admixtures and so on. So, in this study, chloride ion penetration test, freeze and thaw test, neutralization test were conducted to examine the durability characteristice of shotcrete with mineral admixtures such as silica fume, blast-furnace slag and fly ash. These results indicate that shotcrete with silica fume is durable. Therefore, the present study provides a firm base to make high performance shtcrete.