• Title, Summary, Keyword: Porosity

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Prediction for Pore Structure of Cement Mortar Exposed to Freezing-Thawing Action by Ultrasonic Pulse Velocity Measurement (초음파 속도 측정을 통한 동결·융해 작용을 받는 시멘트 모르타르의 공극 구조 예측)

  • Pang, Gi-Sung;Lee, Kwang-Myong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.4
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    • pp.421-426
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    • 2017
  • In this paper, the effect of freezing-thawing action on the dynamic modulus and porosity was examined by ultrasonic pulse velocity (UPV) measurement. UPV was measured every 30 cycles during the freezing-thawing test, and dynamic modulus and porosity of cement mortar were calculated by relationship among UPV, porosity and dynamic modulus. Porosity analysis was also performed to compare with calculated porosity by mercury intrusion porosimetry (MIP). From the test, it was found that dynamic modulus of cement mortar was decreased 13% after 300 cycles. The calculated porosity was increased about 30% compared with the initial porosity before freezing-thawing action. The calculated porosity showed similar increase tendency with the porosity measured by MIP. So, it can be concluded that the porosity change of cementitious materials by freezing-thawing action can be predicted by UPV measurement.

Physical Properties of Rocks according to Heating Treatment (열충격 시험에 의한 암석의 물성변화)

  • Kim, Jae-Hwan;Lee, Myeong-Seong;Lee, Jae-Man;Lee, Mi-Hye;Park, Sung-Mi
    • 보존과학연구
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    • pp.31-42
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    • 2010
  • This study were performed thermal shock test for four kind of different rocks (Iksan granite, Namsan granite, Jeongseon marble, Yeongyang sandstone), and according to heating temperature($400^{\circ}C$, $600^{\circ}C$) on samples were investigated physical properties such as specify gravity, porosity, p-wave velocity. As a result, the tendency was appeared that porosity increased, and specific gravity and p-wave velocity decreased at a more higher temperature. But, the situation of change appeared characteristic according to temperature and rock types. In the case of Yeongyang sandstone, it appeared in especially porosity increasing at $400^{\circ}C$. The specific gravity was little change in the all the rock at $400^{\circ}C$ but the decreased at $600^{\circ}C$. Therefore the specific gravity in the temperature range is due to the relatively small impact on the change is expected. Porosity of the granite at $400^{\circ}C$ changes little. but marble in the rate of change is large. Conversely, the sandstone porosity decreased. At $600^{\circ}C$ increased porosity in all of rocks. particularly sandstone the smallest increase in porosity. Experiments showed that p-wave velocity measured through dry rocks was sensitive to quantify the thermal damage. The p-wave velocity of all rocks decreased with increasing temperature. In the relation between porosity and p-wave velocity, p-wave velocity decreased with increasing porosity. On the other hand, in case of Yeongyang sandstone p-wave velocity decreased with decreasing porosity. thus, development of microcracks more affects p-wave velocity than porosity. In this study, damage intensity was well explained with porosity and p-wave velocity values depending on temperature increase.

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The Change of Porosity During the Fabrication of Vitreous Bonded CBN Tools (유리질 결합 CBN공구 제조시 기공량 변화)

  • Yang, Jin
    • Journal of the Korean Ceramic Society
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    • v.35 no.9
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    • pp.988-994
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    • 1998
  • In the manufacturing of vitreous bonded CBN tool the porosity change associated with various processing conditions, I. e. the sintering temperature and the size and the amount of abrasive grits was observed. In the case of sintering of vitreous bond material only the specimen density reached the maximum at 950$^{\circ}C$ and then the total porosity was increased slightly with the temperature above 950$^{\circ}C$. In the sintering of a-brasive grits and the vitreous bond material together a marked increase in the total porosity was found with the temperature above 950$^{\circ}C$ Reducing the grit size at the constant volume fraction of abrasive grits showed an increase in the total porosity at whole sintering temperature. On the contrary. it was observed that increasing the volume fraction of abrasive grits with a same size showed the increased open porosity simultaneously with decreased closed porosity at whole sintering temperature.

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The Influence of Porosity on the Characteristics of Porous Concrete (공극률 변화에 따른 포러스콘크리트의 특성)

  • Jung, Yong-Wook;Lee, Seung-Han;Jang, Suk-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.691-694
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    • 2005
  • The present study was to examine the influence of porosity and moisture content on the water permeability, strength and plant-growth characteristics of porous concrete. The result of the experiment verified that the coefficient of permeability of porous concrete with porosity between $30\%\;and\;36\%$ increased by 2cm/sec and the compressive strength decreased 1MPa at every $3\%$ increase of porosity. In addition, the plant growth of porous concrete showed 5cm at $36\%$ porosity and 2.5cm at $30\%$ porosity respectively. Thus, the higher the porosity, the more the plant grew. When $2\%$ moisture content was used in porous concrete with the same porosity, the plant growth was accelerated two times faster than the case without it.

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Effect of Fatigue Strength in Fillet Weldments with Different Groove Angle and Porosity (필렛 용접 시 그루브 각도와 미세기공에 따른 피로강도의 영향)

  • Koo, Bon-Cheol
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.6 no.2
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    • pp.9-16
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    • 2007
  • The fatigue test of the fillet weldments were executed with different groove angles and porosity. The groove angles of $90^{\circ}$, $45^{\circ}$ and $55^{\circ}$ were compared with fatigue lives. After the fillet weldment failure, the porosity which found at the fractured surface were observed to account the effect on fatigue life. Finite element analysis were performed to correlate the fatigue strength and the size & the location of porosity. The stress-strain field were severely affected by the length of notch and the size & location of porosity. Based on the quantitative analysis of porosity effect, the total volume of porosity was key factor for fatigue strength of the fillet weldment.

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The Effect of Casting Conditions on Shrinkage and Porosity of A356.2 Alloys (A356.2 합금의 수축과 기공에 미치는 주조 조건의 영향)

  • Jeon, Gyu-Tae;Kim, Ki-Young;Kim, Suk-Jun
    • Journal of Korea Foundry Society
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    • v.37 no.6
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    • pp.193-198
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    • 2017
  • In this study, volumes of shrinkage and porosity of A356.2 alloys during casting were analyzed as a function of melt temperature, pouring diameter, mold temperature, and Sr content. The temperature of the melt barely affected the shrinkage and porosity formation. The pouring diameter determined the pouring rate, and it was proportional to the shrinkage, yet no relationships with the density of porosity were observed. When the mold was heated at $400^{\circ}C$, shrinkage and porosity in the alloy increased above the one in the mold without heating. However, the mold without heating experienced interior shrinkage and the porosity was mainly distributed near interior shrinkage. The addition of Sr to the melt resulted in more shrinkage and less porosity.

Effect of distribution shape of the porosity on the interfacial stresses of the FGM beam strengthened with FRP plate

  • Rabia, Benferhat;Daouadji, Tahar Hassaine;Abderezak, Rabahi
    • Earthquakes and Structures
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    • v.16 no.5
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    • pp.601-609
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    • 2019
  • The effect of the porosity and its distribution shape on the normal and shear interfacial stresses of the FGM beam strengthened with FRP plate subjected to a uniformly distributed load are investigated analytically in the present paper. Basically, the governing equations of FGM beams with porosity strengthened with composite plates are identical to the ones without porosity. Nonetheless, when the effect of the porosity and its distribution shape are taken into account, the rule of mixture was reformulated to assess the material characteristics with the porosity phases and its distribution shape. This work discusses the influence of the gradient index, the porosity and its distribution shape on the interfacial stresses.

A Study on the Estimation of Physical Parameters of Unsaturated Porous Media in the Laboratory (불포화 다공질매질의 물성치 측정을 위한 실험적 연구)

  • 김만일
    • The Journal of Engineering Geology
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    • v.14 no.2
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    • pp.169-177
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    • 2004
  • The permeation movements of groundwater recharge and contaminate materials receive a eat effect due to porosity and effective porosity of porous media which is composing underground consisted of saturation and unsaturated states. This study developed Frequency Domain Reflectometry(FDR) system and measurement sensor, and then carried out the laboratory experiments to measure effective porosity for unsaturated porous media. Also, I suggested dielectric mixing models(DMMs) which can calculate the effective porosity from relation of measured dielectric constants. In the experimental results the extent range of effective porosity of standard sand and river sand which are unsaturated soil sample were measured in about 65∼85 % for porosity. In relation of effective porosity and porosity, especially, effective porosity confirmed that displays decreasing a little tendency as porosity increases. This is because unsaturated soil did not reach in saturation enough by air of very small amount that exist in pore between soil particles.

A study on measurement of physical parameters using electromagnetic wave of the compacted saturated soil (고주파수 전자기파를 이용한 압밀 포화토 물성치 측정을 위한 연구)

  • Kim, Man-Il;Kim, Hyoung-Soo;Suk, Hee-Jun
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.354-361
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    • 2005
  • Physical parameters such as porosity and effective porosity are important physical parameters that determine the transfer and movement of water and solutes in porous media. Various methods of determining these parameters have been developed, with varying degrees of accuracy and applicability. Most of the existing methods produce static results. They do not produce instantaneous and real time of porosity and effective porosity in a porous media. In this study, a new permittivity method called Frequency Domain Reflectometry with Vector analyzer (FDR-V) is proposed to determine the porosity and effective porosity of some sand samples in the laboratory. The advantage of the FDR-V method is that it instantaneously determines the temporal variation of dielectric constants of porous media. Then, the porosity and the effective porosity of porous media are computed using well established empirical equations. Results obtained from the FDR-V method compared favorably with results from other permittivity methods such as gravimetric, injection and replacement tests. The ratio of effective porosity to porosity was $85{\sim}92%$, when FDR-V was used. This value compared favourably with 90%, which has been usually quoted in previous studies. Considering the convenience and its applicability, the measurement system of FDR-V permittivity holds a great potential in porous media and contaminant transport studies.

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Determination of porosity and effective porosity of saturated porous media using a permittivity method in the laboratory (유전율법을 이용한 다공질 매질의 공극률 및 유효공극률의 측정에 관한 연구)

  • 김만일;니시가끼마코토
    • The Journal of Engineering Geology
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    • v.13 no.4
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    • pp.419-428
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    • 2003
  • In order to evaluate groundwater movement and the infiltration of contaminants, such as petroleum products, the determination of porosity and effective porosity is very important. Porosity and effective porosity are important physical parameters that determine the transfer and movement of water and solutes in porous media. Various methods of determining these parameters have been developed, with varying degrees of accuracy and applicability. Most of the existing methods produce static results. They do not produce instantaneous and real time of porosity and effective porosity in a porous media. In this study, we used a new permittivity method called Frequency Domain Reflectometry with Vector analyzer (FDR-V) to determine the porosity and effective porosity of some sand samples in the laboratory. The advantage of the FDR-V method is that it instantaneously determines the temporal variation of dielectric constants of porous media. Then, the porosity and the effective porosity of porous media are computed using well established empirical equations. Results obtained from the FDR-V method compared favorably with results from other permittivity methods such as gravimetric, injection and replacement tests. The ratio of effective porosity to porosity was 85 - 92 %, when FDR-V was used. This value compared favourably with 90 %, which has been usually quoted in previous studies. Considering the convenience and its applicability, the EDR-V permittivity holds a great potential in porous media and contaminant transport studies.