• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.597-604
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• 2004

This work involves quantitatively investigating the correlation between reductions in strength and variations in pore structure under high temperature that can be utilized as estimation for predicting the inner temperature of member damaged by fire. The experimental results were remarkedly affected by micro-filling effect of silica fume and the different water-binder ratios. The increase of the exposure temperature caused the increase of porosity, which resulted from the reason that evaporable water in gel pore or capillary pores as well as chemically bound water was eliminated from hardened cement paste due to the dehydration of C-S-H and $Ca(OH)_2$. Thermal shrinkage of hardened cement paste gives rise to micro-crack, which cause the increase of porosity. Based on the experimental result that the increase of porosity is in charge of exposure temperature, how porosity is distributed can predict temperature-time history and assess the performance of concrete damaged by fire.

• Journal of the Korea Concrete Institute
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• v.16 no.6 s.84
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• pp.741-750
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• 2004

Air voids in hardened concrete have an important influence on concrete durability such as freeze-thaw resistance, surface scaling resistance, and water permeability, and they have been characterized by spacing factor Linear traverse and point count methods in ASTM standard have been used in estimating an air void system in hardened concrete. However, these methods require lots of time and efforts, further they are not repeatable. Image analysis method could be utilized In estimating an air void systems in hardened concrete with a developments of microscope, digital camera and computer program. The purpose of this study was to develope image analysis method and provide a guideline by comparing the results from ASTM method and image analysis method. The concerns were at air void content and diameter distribution, air voids system as well as spacing factors. The experimental variables included air content by air entrained agent (0, 0.01, $0.03\%$) and depth of specimen (top, middle, bottom). The result showed that it was possible to calculate spacing factor using image analysis technique, as well as air content, air diameter distribution, and air structure. This study also contributed in developing an reasonable and repeatable image analysis method.

• Journal of the Korean GEO-environmental Society
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• v.14 no.5
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• pp.41-47
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• 2013

Well-graded and dense soils have good engineering properties. Unsaturated soil properties such as shear strength, compressibility and permeability are closely related to the soil-water characteristic curve of the soil. Therefore it is important to study the effects of the coefficient of uniformity and the porosity on the soil-water characteristic curve of the sandy soils, which are also related to the grain size distribution and the density of the soil, respectively. In this study soil-water characteristic curves (SWCCs) for six sandy soil specimens were investigated using Tempe pressure cells. The test data were best-fitted to Fredlund and Xing equation. The obtained fitting parameters and the characteristic points of SWCCs were discussed and correlated with the porosity and the coefficient of uniformity of the specimens. The results show that the smaller the porosity of the specimen becomes, the larger the value of the residual matric suction becomes, whereas the larger the coefficient of uniformity of the specimen becomes, the larger the value of the residual matric suction becomes. Regardless of the coefficient of uniformity, the smaller the porosity of the specimen, the flatter the max. slope of SWCC.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1046-1054
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• 2006

The raw water DOC contained 39.3% of hydrophilics, 42.9% of hydriophobic, and 17.8% of transphilic. The hydrophobic fraction in this raw water was mostly fulvic acid. Fulvic acid comprised of 62% and the rest was humic acid(38%). There was more carboxylic acid functional group(64%) than phenolic group(36%). HPI-N and HPI-C comprised of 17% and 22% in the hydrophilic portion, respectively. The fouling mechanisms on the membrane surface and into its porous structure were analyzed in terms of several kinetic models. In order to analyze the fouling kinetics, the various kinetic models described in this paper were used to fit the experimental results. The kinetic models and kinetic constants obtained for each operation condition. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. Also, the permeate flux declined with decreasing internal pore size resulted from organic deposition into the membrane pore. The results of the membrane fouling test using UF membrane according to NOM fractions. HPI-N caused more fouling than HPI-C. Humic acid caused more fouling than fulvic acid probably due to higher adsorption capacity. Since humic acid has higher adsorption capacity than fulvic acid, it would be more adsorbed onto the membrane pores.

• Journal of Soil and Groundwater Environment
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• v.8 no.4
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• pp.21-26
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• 2003

Hwang and Powers (2003) developed a simple model for estimating water retention characteristic (WRC) directly from particle-size distribution (PSD) data, by applying a lognormal distribution law to both PSD and pore-size distribution. The objective of this work was to determine if the performance of the model developed by Hwang and Powers (2003) would be affected by soil texture. The results of this research proved that the performance of the model was indeed affected by soil texture. In particular, its performance diminished with increases in the fine particle fractions. Also, the nonlinear model, which assumes a nonlinear relation between particle-size and pore-size, performed better than the linear model, regardless of soil texture classes.

• Journal of the Korean Vacuum Society
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• v.2 no.3
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• pp.374-383
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• 1993

필라멘트와 Si 기판 사이의 기전력을 20, 80, 140, 200V로 증가시키면서 EACVD에 의하여 성장된 다이아몬드 박막에 대하여 다이아몬드/Si 계면분석 및 계면강도를 측정하였다. 주사형전자현미경(SEM), 고분해능투과형전자현미경(HRTEM), 오제이전자분석기(AES)에 의해 계면상태를 분석한 결과, 기전력 증가에 따라 활성탄화수소 이온(CmHn-)에너지가 증가되어져 CmHn-이 Siso로 침투(Impringement)가 증가되고 침투된 높은 에너지의 CmHn-이 Si과 화학결합하여 생성되는 SiC층 깊이 및 농도 분포도 증가된다. 풀 시험(Pull test)에 의한 계면강도 측정 결과, SiC층 깊이 및 농도분포가 증가할수록 계면강도가 증가하였다. 관찰된 파면과 파면의 X-선 메핑 결과 및 HRTEM과 AES에 의한 분석 결과, 기전력 증가에 따라 공극율이 적고 치밀한 다이아몬드 박막이 성장된다. 그리고 생성되는 SiC층 농도 및 깊이 분포가 증가함에 따라 다이아몬드/Si 계면이 강화되고, 상대적으로 파괴는 다이아몬드/Si 계면이 아닌 SiC층이나 Si 내부에서 발생된다. 결국, 기전력을 증가하여 활성탄화수소이온의 에너지를 증가함으로써 계면강도가 우수하며 공극율이 매우 적고 치밀한 다이아몬드 박막을 성장할 수 있다.

• Explosives and Blasting
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• v.23 no.2
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• pp.23-35
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• 2005

Excavation of an opening in a saturated porous rock may lead to the development of pore pressure around the opening due to the redistribution of initial rock stresses. The built-up of pore pressure, in turn, may affect the mechanical behavior of rock mass and give the different pattern of stress distribution around the opening from that of the case where the coupling is neglected. In this study, the short time response of an opening excavated in saturated ground under anisotropic initial stress conditions was investigated numerically. Not on the wall of opening but at a short distance from the wall, the tangential stresses were peak during the short period after excavation when the hydro-mechanical coupling is considered.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.25-31
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• 2019

This study was conducted to evaluate the penetration performance of the Silane Surface Protection Material (SSPM) penetrating the micro pore of concrete surface. The results was indicated microstructure, porosity and penetration depth of applied SSPM. Silica sand and conventional sand were used as fine aggregate in mortar. And liquid and cream types SSPM were used. The amounts of SPM were applied the 127, 255, 382, 510 g/m2 on the surface of mortar. The penetration depth specimens were made with $100{\times}30mm$ in according with KS F 4930. Penetration depth was evaluated according to KS F 4930, divide specimen and then spraying with water in cross section of specimens, and measure the depth of the non-wetted area. The microstructure result of mortar applied SSPM, it was obtained liquid and cream SSPM in mortar. The porosity results of SSPM application specimens were improved with than that of plain specimens. Test results indicated that the penetration depth of SPM were improved with increasing in amounts of SSPM. As a result of test, application of SSPM to concrete surface, it will improve durability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.67-74
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• 2015

In this study, effects of micropores on the freezing-thawing resistance of high volume slag concrete are reviewed. Concrete was made with slag which contains the ground granulated blast furnace slag(GGBS) and the pig iron preliminary treatment slag(PS) by replacing 0, 40, 70 %, then compressive strength, freezing-thawing resistance, micropores were reviewed. Also, specified design strength, target air contents were set. Deterioration was induced by using 14-day-age specimen which has low compressive strength for evaluating deterioration by freeze-thawing action. As results of the experiment, despite of specified design strength which has been set similarly and ensured target air contents, the pore size distribution of the concrete showed different results. Micropores in GGBS70 specimen have small amount of water which is likely to freeze because there is small amount of pore volume of 10~100 nm size at 0 cycle which has not been influenced by freezing-thawing. For these reasons, it was confirmed that the freezing-thawing resistance performance of GGBS70 is significantly superior than other specimens because relatively small expansion pressure is generated compared to the other specimens.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.115-122
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• 2004

When porous materials are dried, the particles flocculate into fish-net structure in gel phase. In order to exactly analyze the stress distribution of porous materials during drying process, the elastic tensor of microscopic gel structures has to be predicted considering pore shapes as well as porosities of porous materials. The elastic characteristics of porous materials associated with porosities were predicted analyzing microscopic gel structures with circular and cross pores via homogenization method and the drying processes of the electric porous ceramic insulator were simulated using finite element method (FEM). Comparing analysis results between consideration and negligence of pores, the deformed shape and distributions of temperature and moisture were similar but the residual stress was significantly different.