• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.29-29
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• 2007

본 연구에서는 분산강화 스테인리스강을 이용하여 케비테이션 발생 시 고체입자충격에 의한 재료의 침식메커니즘 및 침식저항성을 고찰하고자 하였다. 케비테이션 시간에 따른 침식저항성 측정결과, 기존재료에 비해 분산강화된 시편의 무게손실량이 낮았으며 침식잠복기가 짧고 침식속도가 낮아 전반적으로 우수한 저항성을 보였다. 이것은 침식표면의 손상메커니즘 관찰을 통해 확인할 수 있었다.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.23-30
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• 2011

In this study, deterioration degrees of concrete were investigated at laboratory under seawater attack and cycling freeze-thaw, which are major durability performance deterioration factors of concrete. Deteriorations of mixed concrete using Portland & blended cement were examined by instrumental analysis of changes in relative dynamic modulus of elasticity and compressive strength. After 520 cycles of freeze-thaw, relative dynamic modulus of elasticity and compressive strength of concrete mixed with normal Portland and LHC over 75% showed relatively low resistance of approximately 44% of those values of SRC. Concrete replaced with 50% fine powder of blast furnace slag showed the most excellent freeze-thaw resistance among the tested blended cement concrete.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1027-1034
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• 2016

In this research, experimental study about size effect of solid particles on erosion resistance is presented. A high-density polyethylene particle with a mm-sized diameter is accelerated using a two-stage light gas gun up to Mach number of approximately 3.0. An accelerated particle impacts aluminum alloy such as Al1050 and Al6061 T6, and infrared windows such as ZnS and sapphire specimens. For the aluminum alloy, craters that form on the surface of the specimens are measured to characterize the erosion resistance of the material. For the infrared windows, repetitive tests are conducted until a linear or circumferential crack is found to create damage threshold curves that define a material's erosive resistance. From the comparison of test data for various sizes of high-density polyethylene particles, it is found that erosion resistance of material is linearly dependent on the size of particles.

• Magazine of the Korea Concrete Institute
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• v.4 no.3
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• pp.157-166
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• 1992

해수환경하의 콘크리트 구조물은 동결융해의 반복에 의한 물리적인 침식과 해수중에 용존하는 각종의 이온들의 침투로 인한 화학적 침식에 의해 현저한 성능저하현상을 나타내는 것으로 알려져있다. 본 연구는 포졸란계 혼합재인 플라이 애쉬, 슬래그, 슬리카 흄과 폴리머계 혼합재인 Ethylene Vinyl Acetate(EVA), Styrene-Butadiene Rubber(SBR)를 사용하여 제조한 콘크리트 경화체의 해수환 경하에서 동결융해 저항성에 미치는 혼합재의 종류 및 첨가량의 영향, W/C의 영향을 비교 검토한 실험적 연구이다. 콘크리트의 동결융해 저항성을 위해서는 공기연행이 필수적이며, 공기연행시킨 경우 W/C가 낮을수록 동결융해 저항성이 우수하였다. 해수중에서의 동결융해 저항성은 슬래그분말을 첨가할 때 우수하였으며, 폴리머계 혼합재에서는 EVA가 우수한 결과를 나타내었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.427-435
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• 2012

In order to evaluate the effects of exposure conditions on the resistance to sulfate attack of normal and blended cement mortars, several mechanical characteristics of the mortars such as expansion, strength and bulk density were regularly monitored for 52 cycles under sodium sulfate attack. The mortar specimens were exposed to 3 different types of exposure conditions; 1) continuous full immersion(Exposure A), continuous half-immersion(Exposure B) and cyclic wetting-drying(Exposure C). Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens subjected to Exposure B, showing the wide cracks in the portions where attacking solution is adjacent to air. Additionally, the beneficial effect of ground granulated blast-furnace slag and silica fume was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability and densified structure. Thus, it is suggested that when concrete made with normal cement is exposed to sulfate environment, proper considerations on the exposure conditions should be taken.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.757-764
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• 2008

This paper was conducted to evaluate the durability of cement mortars exposed to varying concentrations of sodium sulfate for up to 540 days. Three types of cement mortars, namely OPC, SRC and SGC, were exposed to four sodium sulfate solutions with concentrations of 4225, 8450, 16900 and 33800 ppm of ${SO_4}^{2-}$ ions at ambient temperature. The sulfate deterioration was evaluated by measuring compressive strength and linear expansion of mortar specimens. Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens in highly concentrated sulfate solution. In particular, the $C_3A$ content in cements plays a critical role in resisting expansion due to sodium sulfate attack. Additionally, the beneficial effect of GGBS was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability. Another important observation was that the parameters for the evaluation of deterioration degree are greatly dependent on the products formed by sulfate attack.

• Resources Recycling
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• v.15 no.3 s.71
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• pp.74-80
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• 2006

In this article, we would like to investigate a durability characterization of cement mortar with inert filler, which is ground calcium carbonate(GCC). The kinds of techniques to evaluate cement mortar are chloride ion ingress, carbonation and sulfate attack. For the experimental result of the resistance of chloride ion ingress, carbonation and sulfate attack, as the addition of GCC makes decreasing the permeability by micro-filler effect, the specimens of $5{\sim}15%$ ratio of replacement are superior to the GCC0 mortar specimen with respect to durability of cement matrix in this scope.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.487-495
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• 2011

The sampling and measuring methods of root fiber quantity which greatly governs the stability evaluation of a vegetated levee revetment are proposed by this study and the erosion characteristics related to root fiber quantity are analysed by the experiments. The Phragmites Japonica Steud confirmed the dominant species in a vegetated levee revetment and the Zoysinagrass are selected as the experimental vegetations. The characteristics of erosion depth and erosion rate are analysed according to the root fiber quantity and their corresponding regression equations are suggested. The erosion depth and erosion rate highly decrease with root fiber quantity by experimental results which results in great increasing the erosion resistance of a vegetated levee revetment. The corresponding regression equations for both vegetations of the Phragmites Japonica Steud and the Zoysinagrass are suggested with high determination coefficients. The erosion resistance of the Zoysinagrass is better than that of the Phragmites Japonica Steud.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.121-128
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• 2007

The present study evaluates the resistance to sulfate attack of cement matrix with or without silica fume. The main variable was the replacement levels of silica fume. In order to introduce sulfate attack to cement matrix, mortars and pastes was exposed to sodium sulfate solution for 510 days. Visual examination, expansion and compressive strength loss of mortars in addition to characteristics of pore for the paste samples were regularly investigated. From the test results, it was clearly observed that the cement matrix with silica fume was very resistant to sulfate attack irrespective of the replacement levels of silica fume. However, the severe deterioration due to sulfate attack was found in cement matrix without silica fume.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2011.10a
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• pp.479-480
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• 2011