• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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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.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.212-215
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• 2007

고분자전해질연료전지 시스템이 영하 조건에 노출될 경우, 셀의 성능 및 내구성에 미치는 영향을 실험적으로 확인해 보았다. -30 $^{\circ}C{\sim}70$ $^{\circ}C$ 조건을 반복 경험시키며, 성능저하 정도를 살펴보았다. 일반적인 운전조건과 동결/해동에 의한 성능저하 요인을 분리하여 확인하기 위해, 30 $^{\circ}C{\sim}70$ $^{\circ}C$ 범위의 사이클을 진행한 경우에 대해, 위와 통일한 분석을 통하여 성능 및 각종 물성 값의 변화를 비교하였다. 동결조건에서 셀의 성능저하는 형성된 얼음의 물리적 부피팽창으로 인한 계면저항의 증가가 주요 원인임을 밝힐 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.449-454
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• 1999

Pavement concrete subjected to severe environmental condition may be vulnerable to frost attack practically where de-icing chemicals are used. This study focused on the investigation of durability characteristics of pavement concrete incorporation polypropylene fibers and application feasibility of these into the pavements of local roads and highway. A series of labortory tests were performed with main experimental variable such as fiber types, fiber contents. and type of concrete mix. The test of compressive strength was executed as primary tests, before the durability tests such as a scaling resistance were performed. De-icing salt resistance test was progressed by recycling freeze and thaw in the presence of a 4% calcium chloride solution. The deteriorated surfaces were rated by visual inspection and the loss weight were measured at every 5 cycles.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.433-438
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• 2000

The purpose of this study is to examine the resistance of water-permeable concretes to freezing and thawing action. The water-permeable concretes with cement-aggregate ratio of 1:5.5(by weight) and two kinds of admixture content [SP : superplasticizer(0, 1.0%), HPAE : high performance air entraining agent(0.5, 1%)] used OPC(ordinary portland cement) as binder were prepared, and then tested for relative dynamic modulus of elasiticity, mass change, length change and durablity factor. It's been concluded from the test results that the superior relative dynamic modulus of elasiticity and durability factor of water-permeable concretes were obtained at superplaciticizer 1.0% after 300 cycles. The water-permeable concretes used superplasiticizer 1.0% having relative durability factor of 88% after 300 cycles.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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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 the Korean Society of Food Science and Nutrition
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• v.30 no.3
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.99-104
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• 1998

In this paper, the properties of inter-locking block using fly ash are investigated. The experimental parameters are the replacement ratio of fly ash, the amount of AE water-reducing agent and mixing porpotion of mortar. According to the experimental results, the improvement of quality in the side of strength, absorption ratio and freeze-thaw resistance for manufacturing inter-locking block and the curtailment of cost can be achieved in case of 15% of fly ash and 0.3% of AE water-reducing agent are mixed into mortar mixture of 1:6(C:S).

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.137-140
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• 1998

An entrained air is important in improving freeze/thaw resistance to the concrete structures. To achieve a proper degree of air entrainment, air entraining admixtures(AEA) are typically added to the concrete mixture, but it has been noted that an increase in the carbon content(LOI) of fly ash causes problems in proper air entrainment in concrete. In this study, the entrained air content of mortar with fly ash as an additive was considered according to the mix design as a type of AEA, adding amount of fly ash and AEA, and the elapsed time. Moreover, two different types of measurement were also tired for air content.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.285-291
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• 1998

During recent years, the durability of concrete structures has been considered in concret practice and material research. To preserve the brittleness of concrete as well as energy absorption and impact resistance, amount of fiber usage has greatly increased in the field of public works. Ultra fine powder, silica fume, mixed into concrete, it reduce void of concrete structure. Especially, there's a great effect for strength improvement of concrete by initial pozzolanic reactions. For these reasons, if silica fume mixed into concrete, it decrease the total void by microfilter effect . Pozzolan reaction, between cement particle and silica powder, can elaborate the micro structure of matrix. And so, in this paper, we deal SFRC for the purpose of efficiently using of industrial by-products(silica fume). Also we performed the test for durability such as freeze-thaw resistance and accelerated carbonation of SFRC using silica fume.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.201-202
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• 2010

In this Study, we manufactured the 70, 100MPa grade high strength concrete with the land sand by batcher plant in the field. In order to verify attainment of design compressive strength and the durability of the manufactured concretes we examined the tests such as compressive strength test, freeze-thaw test, carbonation test, test for concrete's ability to resist chloride ion penetration.