• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.145-150
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• 1990

In order to discuss the freeze-thaw durability of FRC and mechanical properties by the fiber types of FRC, experimental studies of FRC were carried out. The kinds of fiber used which are in CFRC are PAN-based and Pitch-based carbon fiber and in GFRC are alkali-resistance glass fiber. To examine the effects of the kinds, types (continuous fiber and Tow, Belt, Cloth) and contents of fiber and matrices, the following three methods CFRC and GFRC, Air cured, Water cured and Autoclaved CFRC and GFRC were tested. According to the test results, the flexural, tensile strength and toughness of FRC were remarkably influenced by types of fiber and addition of condensed silica fume. Also, freeze-thaw resistance of FRC was considerably improved in comparision to conventional mortar.

• KCI Concrete Journal
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• 제11권3호
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• pp.29-43
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• 1999

The effects of superplasticizers on fresh and hardened concrete were investigated. The experimental program included tests on the workability and slump loss, bleeding, setting time, air content, compressive, tensile and flexural strength, permeability, shrinkage, freeze-thaw durability and creep deformation. Properties of superplasticized concrete were compared with those of conventional and base concretes. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete. They permitted a significant water reduction while maintaining the same workability. Bleeding of superplasticized concrete was much lower than that of conventional concrete of the same consistency. This indicates that the use of superplasticizers did not affect the tendency of segregation of fresh concrete. The compressive, tensile, and flexural strengths of superplasticized concrete were significantly higher than those of conventional concrete. The permeability and drying shrinkage and creep of superplasticized concrete were less than those of conventional concrete, but there were no significant differences between base and superplasticized concrete. Compared with base concrete, non-air-entrained superplasticized concrete had slightly higher freeze-thaw durability. and superplasticized concrete with an appropriate amount of entrained air Eave even better resistance to freezing and thawing.

• KCI Concrete Journal
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• 제11권3호
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• pp.65-77
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• 1999

A portland cement was reinforced by incorporating carbon fiber(CF), silica powder, and impregnating the pores with styrene monomers which were polymerized in situ. The effects of type, length, and volume loading of CF, mixing conditions, curing time and, curing conditions on mechanical behavior as well as freeze-thaw resistance and longer term stability of the carbon-fiber reinforced cement composites (CFRC) were investigated. The composite Paste exhibited a decrease in flow values linearly as the CF volume loadings increased. Tensile, compressive, and flexural strengths all generally increased as the CF loadings in the composite increased. Compressive strength decreased at CF loadings above approx. 3% in CFRC having no impregnated polymers due to the increase in porosity caused by the fibers. However, the polymer impregnation of CFRC improved all the strength values as compared with CFRC having no Polymer impregnation. Tensile stress-strain curves showed that polymer impregnation decreased the fracture energy of CFRC. Polymer impregnation clearly showed improvements in freeze-thaw resistance and drying shrinkage when compared with CFRC having no impregnated polymers.

• Geomechanics and Engineering
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• 제29권3호
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• pp.349-357
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• 2022

Abnormal climate events are occurring frequently around the world. In particular, cold waves and heavy snow lead to damage and deterioration of facilities, which can cause loss of life or property damage, such as shortening the lifespan of facilities. Therefore, it is very important to prepare an appropriate maintenance system and to establish a strategy to cope with abnormal weather conditions. In this study, laboratory freezing experiments were performed to analyze the freeze-thaw characteristics affecting the tunnel concrete lining, and heat flow analysis was carried out based on the test results. Based on these experimental and theoretical analysis results, quantitative freeze-thaw evaluation criteria for tunnel concrete linings were proposed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.217-218
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• 2023

In modern architecture, tiles are used as a decorative material to enhance the appearance of buildings. However, defects occurring during tile installation affect not only the appearance of the building, but also its maintenance. This study aims to investigate stable tile installation by producing tile modules using the floating mortar method and conducting freeze-thaw tests to measure their adhesion strength. Test results showed that the adhesion strength increased as the mesh size decreased, except for S3 mesh. This study highlights the importance of research on tile installation to solve problems related to building appearance and maintenance.

• Reproductive and Developmental Biology
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• 제35권1호
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• pp.55-60
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• 2011

The objective of this study was carried out to evaluate the efficiency of sperm collection methods on the post-thaw viability of cat semen. The cat semen was collected by artificial virginal (AV) and electronic ejaculate (EE) methods. The composition of semen extender was consisted of Tris-buffer supplemented with 20% egg yolk and 1% P/S antibiotics in Ext I, and more added 8% glycerol, 1.0% Equex STM paste of total volume in Ext II. The collected semen was adjusted the concentration and then diluted in Ext I for optimal concentration. The diluted semen was cooling to $5^{\circ}C$ temperature in refrigerator for at least 2 hrs and then diluted stepwise with Ext II for at least 1 hrs. After an equilibration for 1 hrs, the cooled semen was packaged in 0.5 ml straw and then freezing on the $LN_2$ vapor over 5 cm above from $LN_2$ and then immersed directly in $LN_2$ for cryopreservation. The frozen semen was thawed in $38^{\circ}C$ water for 15 sec and then evaluated the motility, viability, and morphology. Post-thaw semen were calculated the motility by SMI (sperm motility index). The live-dead sperm was evaluated by Eosin-B and morphological evaluation was by Diff-quik kit staining. The post-thaw concentration ($89{\times}10^6$ /ml vs. $128{\times}10^6$ /ml), viability ($22.6{\pm}10.6%$ vs. $37.1{\pm}26.1%$), morphological normality ($27.0{\pm}50.2%$ vs. $45.6{\pm}123.0%$) of EE and AV groups were not significant different, but the post-thaw motility was significant lower in EE than that in AV group ($53.1{\pm}3.6$ vs. $73.6{\pm}5.7$) (p<0.05). In conclusion, semen collection methods did not significant different between EE and AV groups except of post-thaw motility and so both semen collection methods could be applied in feline semen collection methods.

• 콘크리트학회논문집
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• 제13권5호
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• pp.484-490
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• 2001

본 연구는 라텍스 혼입률을 5, 10, 15, 20%로 변화함에 따른 염소이온 투수성과 동결융해저항성 관점에서 라텍스 개질 콘크리트의 내구특성을 고찰하고자 한다 콘크리트에 라텍스가 혼입되고 양생되었을 때 콘크리트는 라텍스 입자의 필름막에 의해 서로 연결된 시멘트수화물과 골재가 구성된다. 이때 라텍스의 양이 증가함에 따라 콘크리트의 휨강도는 증진되나, 압축강도는 다소 저하된다. 이와 같은 휨강도의 증가는 시멘트수화물과 골재사이의 라텍스 필름막에 기인한 것이며 압축강도의 감소는 라텍스의 성분 중 부타디엔의 유연성 때문에 발생되는 것으로 판단된다. 라텍스 개질 콘크리트와 보통콘크리트의 상대 투수성을 측정하기 위하여 염소이온투과시험법을 사용하였다. 실험 결과 라텍스 개질 콘크리트의 투수성은 보통콘크리트의 투수성보다 매우 낮음을 알 수 있었다. 이것은 라텍스 미립자가 미세공극을 충전하고 라텍스 입자의 필름막에 의해 골재와 시멘트수화물이 연결되었기 때문이다. 그리고 라텍스 개질 콘크리트의 동결융해저항성은 보통콘크리트에 비해 매우 높으며, 보통콘크리트에서는 동결융해저항성을 증가시키기 위해 공기연행제를 필요로 하지만, 라텍스 개질 콘크리트에서는 적절한 양생이 이루어지면 추가적인 공기연행제는 요구되지 않는다.

• 한국터널지하공간학회 논문집
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• 제22권1호
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• pp.121-133
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• 2020

전 세계적으로 이상기후 현상의 빈도와 강도는 높아지고 있는 추세이다. 이는 인명과 재산에 직접적인 피해를 줄 수 있으므로 이상기후에 대응하여 적정한 유지관리 전략을 수립하고 실천하는 것이 중요하다. 한파 또는 폭설이 빈번하게 발생하는 한랭지역에 건설되는 시설물의 경우에는 다른 지역에 위치하고 있는 시설물에 비하여 동결-융해에 의한 피해를 많이 받을 수 있으며, 해를 거듭할수록 그 피해 정도는 증가할 가능성이 매우 높다. 그러나 동결-융해의 피해를 정량적으로 확인할 수 있는 명확한 기준과 이에 대한 대응방안은 아직 제시되고 있지 않은 실정이다. 따라서 실내 동결시험 결과를 기반으로 지역별 기후특성을 고려한 동결조건을 -14℃에서 1일, -7℃에서 2일 또는 -5℃에서 3일 지속될 경우로 선정하였으며, 그 결과, 강원지역의 대관령(8.3회), 철원(5.3회), 태백(4.9회)의 순으로 동결-융해 환경에 노출되어 있는 것으로 판단되었다. 이러한 연구결과를 기반으로 도로터널의 동결-융해 평가기준을 새롭게 제시하였다. 본 연구에서 제시된 도로터널의 동결-융해 평가기준은 추후 한랭지역 터널의 정량적 평가와 유지관리 전략의 수립 시 활용될 수 있을 것으로 판단된다.

• 한국식품과학회지
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• 제46권5호
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• pp.593-600
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• 2014

찹쌀 전분과 검(XAT, LBG, 및 XAT:LBG) 혼합물의 페이스팅 특성과 이들 페이스트의 점탄특성 및 냉해동 안정성을 조사하여 일반 쌀 전분(20% 수준의 아밀로오스 함유)의 물성을 대체할 수 있으며 낮은 냉해동 안정성을 개선할 수 있는 찹쌀 전분-검 혼합물의 조성을 제시하고자 하였다. 찹쌀 전분은 검(XAT 및 LBG) 및 검 혼합물(XAT:LBG)에 의해 건조중량 대비 19:1의 비율로 대체하여(총 고형분 함량 5%, w/w) 페이스팅 점도 특성을 조사하였을 때 찹쌀 전분-검 혼합물 내의 XAT 농도가 낮아질수록 찹쌀 전분의 페이스팅 온도에 근접하였다. 최고점도는 찹쌀 전분-XAT 혼합물에서 가장 낮았으며 XAT와 LBG를 75:25의 비율의 검 혼합물로 찹쌀 전분을 대체하였을 때(X075L025)가 가장 높았다. 또한 찹쌀 전분-XAT:LBG의 최고점도에서 최종점도 사이의 온도 프로파일 범위에서 찹쌀 전분만을 이용하였을 때보다 높은 수준의 페이스팅 점도를 나타내었다. 찹쌀 전분-검 혼합물 페이스트의 점탄특성은 찹쌀 전분-XAT:LBG (X050L050 및 X025L050) 페이스트들에 한해 5 rad/s의 높은 진동수에서 일반 쌀 전분 페이스트의 저장탄성률과 유사해졌다. 손실탄성률은 모든 찹쌀 전분-검 혼합물 페이스틀이 찹쌀 전분과 일반 쌀 전분들 보다 높은 수준을 나타내었다. 냉해동 안정성과 관련하여 일반 쌀 전분 페이스트에 비해 찹쌀 전분 및 찹쌀 전분-검 혼합물들이 높은 냉해동 안정성을 나타내었다. 이 중 찹쌀 전분-XAT와 찹쌀 전분-XAT:LBG (X075L025)가 7회의 냉해동 순환처리에도 syneresis 현상이 관찰되지 않았다. 모든 결과들을 고려할 때 일반 쌀 전분을 대체할 수 있는 찹쌀 전분-검 혼합물은 XAT와 LBG를 건조중량 비율로 50:50으로 혼합한 검 혼합물을 찹쌀 전분의 건조중량의 5% 수준으로 대체하는 것으로 판단되었다.

• 한국해양공학회지
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• 제26권3호
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• pp.26-32
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• 2012

Recently, concrete using multicomponent blended cement has been required to increase the freeze-thaw and sulfate resistances of concrete structures exposed to a marine environment. Thus, the purpose of this study was to propose the use of concrete containing multicomponent blended cement as one of the alternatives for concrete structures exposed to a marine environment. For this purpose, batches of concrete containing ordinary portland cement (OPC), binary blended cement (OPC-G, G: ground granulated blast slag), ternary blended cement (OPC-GF, F: fly ash), and quaternary blended cement (OPC-GFM, M: mata-kaolin) were made using a water-binder ratio of 50%. Then, the durability levels, including thesulfate and freeze-thaw resistances, were estimated for concrete samples containing OPC, OPC-G, OPC-GF, and OPC-GFM. It was observed from the tests that the durability levels of the concrete samples containing OPC-G and OPC-GF were found to be much better than that of the concrete containing OPC. The optimum mixing proportions were a40% replacement ratio of ground granulated blast slag for the binary blended cement and a30% replacement ratio of ground granulated blast slag and 10% fly ash for the ternary blended cement.