• 한국구조물진단유지관리공학회 논문집
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• 제19권3호
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• pp.83-91
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• 2015

포러스 콘크리트는 시멘트, 물 그리고 굵은골재로 구성되어 있으며, 공기 및 물의 투과 그리고 흡음 등 지구 환경부하를 저감시키기 위해 사용되어 왔다. 그러나 포러스 콘크리트의 물리적, 역학적 성상은 시공시 이루어지는 다짐하중에 의해 변한다. 따라서 본 연구에서는 결합재 종류, 물-결합재비, 목표공극율에 따른 포러스 콘크리트의 물리적, 역학적 성상을 파악하였으며 특히, 다짐하중에 따른 포러스 콘크리트의 공극율, 강도, 투수계수의 물성변화를 파악하였다. 본 연구에서 사용한 골재는 부순자갈 생산과정에서 발생되는 부산물로서 최대크기는 13mm이다. 연구결과, 포러스 콘크리트의 목표 공극율, 투수계수, 압축강도는 공극율과 밀접한 상관성을 지니고 있으며, 공극율은 포러스 콘크리트의 배합설계로 제시할 수 있는 가능성이 있는 것으로 판단되다. 포러스 콘크리트의 압축강도는 팽창재 치환율 5%에서 가장 높게 나타났으며, 실리카 흄 치환율 10%에서 치환하지 않은 콘크리트보다 32% 높게 나타났다. 그리고 다짐하중을 변화시킨 본 연구결과 압축강도는 하중 15kN부터 증가하였고, 공극율은 하중 0.8kN부터, 투수계수는 하중 35kN부터 각각 감소하는 것으로 나타났다.

• The Korean Journal of Ceramics
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• 제5권2호
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• pp.162-164
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• 1999

Microsotructure designed porous ceramics of calcium hydroxyapatite $(Ca_{10}(PO_4)_6(OH)_2)$ were prepared by hydrothermal method. The particle size, shape, and the micro-pore size of the porous hydroxyapatite ceramics could becontrolled. The hydroxyapatite was non-stoichiometric apatite with calcium deficient compositions (Ca/P ratio < 1.67). The composition of non-stoichiometric hydroxyapatite ceramics could be controlled from 1.50 to 1.63 in Ca/P ratio. The hydroxyapatite ceramics preparedc at $105^{\circ}C$ under the saturated vapor pressure for 20h were composed of rod-shaped crystals with about 10$\mu\textrm{m}$ in length with the mean aspect ratio of 40. The porous ceramics of calcium deficient hydroxyapatite had about 45% porosity with the inter-connecting pore structure. Porous hydroxyapatite ceramics prepared hydrothermally had the compressive strength of about 10 to 30 MPa. In addition, porous ceramics of $\beta$-tricalcium phosphate ($\beta-Ca_3(PO_4)_2$) were prepared from the calcium deficient hydroxyapatite.

• Steel and Composite Structures
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• 제42권3호
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• pp.375-388
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• 2022

In this work, limit elastic speed analysis of functionally graded porous rotating disks has been reported. The work proposes an effective approach for modeling the mechanical properties of a porous functionally graded rotating disk. Four different types of porosity models namely: uniform, symmetric, inner maximum, and outer maximum distribution are considered. The approach used is the variational principle, and the solution has been achieved using Galerkin's error minimization theory. The study aims to investigate the effect of grading indices, aspect ratio, porosity volume fraction, and porosity types on limit angular speed for uniform and variable disk geometries of constant mass. To validate the current study, finite element analysis has been used, and there is good agreement between the two methods. The study yielded a decrease in limit speed as grading indices and aspect ratio increase. The porosity volume fraction is found to be more significant than the aspect ratio effect. The research demonstrates a range of operable speeds for porous and non-porous disk profiles that can be used in industries as design data. The results show a significant increase in limit speed for an exponential disk when compared to other disk profiles, and thus, the study demonstrates a range of FG-based structures for applications in industries that will not only save material (lightweight structures) but also improve overall performance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.677-682
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• 2000

Porous concrete is defined as d type of concrete for which the fine aggregate component the matrix is entirely omitted. Although it had been used as a building material in Europe for over 60 years, low strength and high void ratio limited its application in the past. In recent years, however high void ratio of concrete has been recognized again and can be used as an environmental conscious material, for example, parking lots, draining light-traffic-volume pavements and as sea water purifying material. The result of an experiment on the void ratio of fiber reinforced porous concrete and its influence on the compressive strength and permeability relationship of concrete are reported in this paper. One-sized coarse aggregate of 5-10mm, and three absolute content of fiber(steel fiber, polyprophylen fiber) were used. The result of measured void ratio, permeability coefficient and compressive strength show a small variation. Void ratio, permeability coefficient and compressive strength of fiber reinforced porous concrete depend on contents of fiber and absolute volume ratios of paste to aggregate.

• 콘크리트학회논문집
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• 제16권4호
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• pp.541-548
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• 2004

본 연구는 도로, 철도, 주택가 및 도심지역의 소음저감과 건설부산물로 발생하는 폐콘크리트 재생골재의 유효이용을 위하여 포러스콘크리트의 목표공극률과 재생골재 혼입률에 따른 물리 역학적 특성 및 흡음특성을 평가하였다. 시험결과, 목표공극률과 실측공극률과의 차이는 1.7% 이내로 나타났고 압축강도는 목표공극률이 25%, 재생골재의 혼입률이 50%를 초과하는 경우에는 급격한 강도저하 경향을 나타냈다. 또한, 폐콘크리트 재생골재를 사용한 포러스콘크리트의 흡음 특성은 NRC의 경우 목표 공극률이 25%에서 가장 우수한 흡음특성을 나타냈으며, 재생골재의 혼입률에 따른 영향은 작은 것으로 나타났다. 따라서, 포러스콘크리트의 강도 및 흡음특성을 고려하였을 때 적정 목표공극률은 25%, 폐콘크리트 재생골재의 혼입률은 50% 정도가 유효한 것으로 판단된다.

• 대한기계학회논문집
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• 제17권5호
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• pp.1115-1122
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• 1993

Several yield criteria for porous materials are compared with each other, defining the apparent yield stress as the yield stress of the porous material in simple compression. It was found that the plastic Poisson's ratio is the parameter needed to define the yield criterion, rather than the relative density. The plastic Poisson's ratio is regarded as a material characteristic that is obtained from a simple compression test. A new form of yield criterion was suggested, and it was applied to hydrostatic compression as well as uniaxial strain compression of sintered Al-2024 powder. The crossover point in the mean stress vs volume change curves of the processes was predicted. It is presented that the flow stress of the fully densed material can be obtained from that of the porous material using relations obtained from the yield criterion.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 제2회 단조심포지엄 단조기술의 진보
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• pp.64-73
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• 1995

The forging limit curves of sintered porous metals have been calculated, in terms of the two principal strains, by the Lee-Kuhn initial imperfection model. The various yield functions for porous metal have been applied to the initial imperfection model. When the value of initial imperfection ratio equals the value of initial relative density of the sintered porous metals, the calculation values are in good agreement with the measured data. The slopes of the forging limit curves are about 0.5 as in the case of non-porous metals.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.685-688
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• 2008

콘크리트는 압축에 강한 특성을 지닌 재료이지만, 인장 및 휨강도가 낮고 균열에 대한 저항성이 약한취성재료라는 단점을 가지고 있어 이에 대한 보완책으로서 철근이 사용되어 왔다. 하지만, 포러스콘크리트는 내부에 존재하는 다량의 연속공극으로 인하여 철근보강시 철근이 공기에 노출되어 부식되는 문제점을 보이고 있다. 따라서, 본 연구에서는 강섬유를 혼입과 목표공극률에 따른 공극률, 압축강도,휨강도 및 휨인성 특성을 검토하였다. 실험결과, 강섬유의 혼입에 따른 실측공극률은 증가하는 것으로 나타났으며, 강도특성에서는 강섬유의 혼입률이 증가 함에 따라 증가하는 것으로 나타났으나 일정량 이상의 섬유가 혼입되었을 경우에는 강도가 오히려 감소되는 것으로 나타났다. 또한, 휨인성평가에서는 강섬유를 혼입하지 않은 포러스콘 크리트에 비하여 처짐변형 성능이 현저히 개선되는 것으로 나타났다. 따라서 강섬유를 포러스콘크리트에 활용한 2차제품 및 포장재료 등에 적용하기 위한 강도 및 휨저항성능 향상재료로 사용가능성을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.568-571
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• 2004

This research estimated the physical. mechanical characteristic and the character of sound absorption according to target void ratio of porous concrete and the mixing ratio of recycled aggregate for the valid utilization of recycled aggregate using waste concrete and sound reduction out of a road, a railway, a residential street, and a downtown area. As a result of the test, compressive strength tended to be a radical strength fall when target void ratio was $25\%$ and contents of recycled aggregate exceeded over $50\%$. Also, the character of sound absorption of porous concrete which used recycled aggregate using waste concrete was the most excellent when target void ratio was $25\%$, and the influence by contents of recycled aggregate was trivial. Therefore, when the strength and the character of sound absorption of porous concrete are considered, it is proved valid that proper target void ratio was $25\%$ and contents of recycled aggregate using waste concrete was $50\%$ or so.

• 한국세라믹학회지
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• 제45권5호
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• pp.285-289
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• 2008

Porous self-bonded silicon carbide (SiC) ceramics were fabricated at temperatures ranging from 1750 to $1850^{\circ}C$ using SiC, silicon (Si), and carbon (C) powders as starting materials. The effect of the Si:C ratio on porosity and strength was investigated as a function of sintering temperature. It was possible to produce self-bonded SiC ceramics with porosities ranging from 36% to 43%. The porous ceramics showed a maximal porosity when the Si:C ratio was 2:1 regardless of the sintering temperature. In contrast, the maximum strength was obtained when the ratio was 5:1.