• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.112-115
• /
• 2003

Aggregate may limit the strength of concrete, and aggregate with undesirable properties cannot produces strong concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, in 2002, the using ration of crushed stone occupies about 97% of whole coarse aggregate, and ratio of crushed sand occupies about 18.3% of whole fine aggregate. This is a study to compare and analyze the properties of crushed aggregate for concrete to do mix proportion and improve the concrete quality. According to results, it was found that nearly all the properties of crushed aggregate satisfied with the value recommended by KS.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2006년도 춘계 학술발표회 논문집
• /
• pp.1054-1059
• /
• 2006

For reclamaing fill materials, hydraulic fill is needed in domestic parts of the reclamation sites every year. Engineering properties of soils after reclamation is calculated by laboratory. But before or after reclamation, reclamation quatities depend on the depth from the ground surface when hydraulic fill is dumped. In this paper, the engineering properties on the depth from ground surface are assumed by cone penetration test where fine grained soft soil is formed is proposed through several sites.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.1400-1407
• /
• 2005

There are a number of approaches to in situ remediation that are used at contaminated sites for removing contaminants from the contaminated zone without excavating the soil. These include soil flushing, dual phase extraction, and soil vapor extraction. Of these techniques, soil flushing is the focus of the investigation in this paper. The concept of using prefabricated vertical drains(PVDs) for remediation of contaminated sites with fine-grained soils is examined. The PVD system is used to shorten the drainage path or the groundwater flow and promote subsurface liquid movement expediting the soil flushing process. The use of PVDs in the current state of practice has been limited to soil improvement. The use of PVDs under vacuum conditions is investigated using sample soil consisting of silty sand.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
• /
• pp.388-393
• /
• 1996

This study evaluated characteristics and performance of recycled concrete as a pavement which was constructed on a low volume road. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Natural sand from a source was used as fine aggregate together with admixtures such as plasticizer and fly ash (0.8% and 5% by wt. of cement, respectively). The length, thickness and width of the pavement were 100mm, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were approximately 45Kg/$\textrm{cm}^2$, 250Kg/$\textrm{cm}^2$, and 240,000 Kg/$\textrm{cm}^2$, respectively. The pavement could be constructed by hand without much difficulty. The surface was finished smoothy by wet fabric and only minor cracks were found on the surface.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2016년도 추계 학술논문 발표대회
• /
• pp.58-59
• /
• 2016

Oyster shell is produced by shucking process in oyster farming in southern coast of Korea. In average, about 6.7kg of oyster shell is produced as an industrial waste for 1kg of oyster flesh, and even only in last year, it is estimated that about 150,000 ton of oyster shell is produced. Oyster shell is light weighted and its strength characteristic is similar to sand. So we produced mortar test piece using grounded oyster shell powder under 0.6mm, 0.6~1.2mm, 1.2~2.5mm, 2.5~5.0mm of its particle size according to fine aggregate standard and reviewed strength Properties.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2016년도 추계 학술논문 발표대회
• /
• pp.156-157
• /
• 2016

Oyster shell is produced by shucking process in oyster farming in southern coast of Korea. In average, about 6.7kg of oyster shell is produced as an industrial waste for 1kg of oyster flesh, and even only in last year, it is estimated that about 150,000 ton of oyster shell is produced. Oyster shell is light weighted and the strength characteristic of it is similar to sand. So we produced mortar test using different law of multiple proportions of grounded oyster shell powder of its particle size according to fine aggregate standard and reviewed strength Properties.

• 한국정밀공학회지
• /
• 제18권10호
• /
• pp.178-183
• /
• 2001

Abrasive jet machining(AJM) process is similar to the sand blasting and effectively removes hard and brittle materials. AJM has applied to rough working such as debarring and rough finishing. As the need for machining of ceramics, semiconductor, electronic devices and LCD are increasing, micro AJM is developed, and has become the inevitable technique to micromachining. This paper describes the performance of the micro AJM in micro grooving of glass. Diameter of hole and width of line in grooving is 80${\mu}{\textrm}{m}$. Experimental results showed good performance in micro grooving of glass, but the size of machined groove increased about 2~4${\mu}{\textrm}{m}$. With the fine tuning of masking process and compensation of film wear. this micro AJM could be effectively applied to the micro machining of semiconductor, electronic devices and LCD.

• 태양에너지
• /
• 제6권1호
• /
• pp.3-11
• /
• 1986

Minimum fludizing velocities and voidages were investigated for closely sized sand and magnesia particles with mean diameters in the range of $297-841\;{\mu}m$ over the temperature between 15 and $1.000^{\circ}C$. Boundaries between changing behaviour at $Re_{mf}=14$ and Ar=17,000 were observed. In beds of fine particles in Geldart's group "B", the minimum fluidizing velocity ($U_{mf}$) decreased as temperature increased, but not as much as expected on account of the gas viscosity increase, furthermore the increase in the minimum fluidizing voidage (${\in}_{mf}$). With larger particles in group "D", $U_{mf}$ increased, first, with temperature increase because of reduced gas density, and depending on the particle size, $U_{mf}$ reduced as flow conditions moved from turbulent to laminar. Among the correlations predicting $U_{mf}$, Ergun equation agreed best with the experimental data providing that the change in ${\in}_{mf}$ according to temperature is allowed for.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
• /
• pp.513-516
• /
• 2005

Previous study on recycled aggregate(RA) has largely been limited to the manufacture of nonstructural-grade concrete due to undesirable physical properties of them such as, high water absorption leading to high water demand of concrete. The restriction seriously limits its market and consequently diminishes the use of RA as a construction material. This paper presents the mechanical properties of recycled concrete substituted by both waste foundry sand(WFS) and recycled coarse aggregate replaced with fine and coarse aggregate concurrently. The result shows that the compressive and tensile strength decrease with the increment of substitution ratio of RA and WFS while bending strength of RA concrete increase.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 가을 학술발표회 논문집
• /
• pp.459-466
• /
• 2002

This study reviews the engineering properties of vegetation as one of all factors to select vegetation species for slope protection. The vegetation species mainly applied in domestic soil slope protection were inspected, and the root properties such as root pattern, root length, root weight, were analyzed. And then direct shear tests on undisturbed fine sand including roots were performed to review the effect of root reinforcement. From these analyses, it was concluded that the engineering properties of vegetation should be considered to select vegetation species for slope protection.