• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.811-819
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• 1999

A theoretical model to predict the effective thermal conductivity of sands Is developed by considering the participating heat transfer mechanisms and their relationship to the model geometry. Comparison between the calculations and the measurements indicates that the assumptions to introduce two model constants (${\phi}_{af}$ and ${\delta}$) for model development were justified. As a results, the model was proved to predict the effective thermal conductivities of 2- and 3-component systems of two silica sands saturated with fluids or bonded with liquid binders in a reasonable accuracy.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.112-113
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• 2021

Since natural sand is being depleted, research is being conducted to use glass similar to sand as an aggregate. When non-reusable waste glass is crushed and used as fine aggregate, it is known that alkali of cement and silica of glass react to cause an alkali aggregate reaction. The purpose of this study is to provide basic data by studying the strength according to color to use waste glass as fine aggregate. When 10% was replaced, both flexural and compressive strength showed strength values similar to those of Plain. When replaced by 20% and 30%, the 7-day intensity was higher than that of Plain. In addition, colorless glass was found to have the highest strength among glass colors. More research is expected to be needed to become a fine aggregate of waste glass.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.205-215
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• 1999

Crushable sandy soil grounds are widely found along the coast throughout the world. The ground composed of lime sand, which is characterized by the material with high compressibility due to particle crushing contains carbonate calcium. In this study, in order to clarify the characteristics of the particle crushing as related to the strength and deformation properties of sands, isotropic compression test was carried out on three different types of carbonate sands and a silica sand. A crushability index, K, is proposed in connection with the yielding and particle crushing stress of sands at various relative densities under isotropic compression. It is concluded that the representative crushability index, K, associated with the soil particle strength, can be a key factor in preliminary parameters in evaluating soil crushability.

• Journal of Korea Foundry Society
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• v.4 no.4
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• pp.5-13
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• 1984

This paper is presented for showing the effect of cooling rate on dendrite arm spacing, correlated with the chilling power of molding materials (conventional plaster, foamed plaster, silica sand) and section thickness, and also showing relationship between dendrite arm spacing and mechanical properties for an aluminum - 8.6 percent silicon - 3.6 percent copper alloy. Local solidification time $(t_f)$ and secondary dendrite arm spacing (d) could be varied widely in accordance with the molding materials and casting thickness, and the following relationship is obtained: $d=9.4t_f\;^{0.31}$ A good correlation between dendrite arm spacing and mechanical properties such as ultimate tensile strength, yield strength, hardness was found, that is, mechanical properties decreased in a linear manner with increase in log of secondary dendrite arm spacing. Ultimate tensile strength in conventional plaster mold casting decreased by 15 percent comparing with the sand casting, where as in foamed plaster mold casting, it decreased by 30 percent comparing with the sand casting. From those results, it has been verified that DAS might be the most representative parameter for predicting mechanical properties varing with the different cooling condition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.25-28
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• 2007

In this study we measured the changes according to time respectively on the basis of 0, 30, 60 and 90 minutes, taking into consideration the decline in fluidity of concrete according to elapsed time to analyze manufacturing capability of batcher plant according to elapsed time of ready-mixed concrete manufactured in batcher plant, and offer basic data for mixture design of ultra-high strength concrete. The proportion of water-binder was 23.55, water content was 160kg/m3, proportion of replacement of crushed sand was 0, 20 and 40% at 3 level, and we applied to the same condition of triaxial component using blast furnace slag powder and silica fume as admixture. And to meet the demand of certain fluidity, we measured respectively on property before and after hardening of ultra-high strength concrete using superplasticizer. As a result of experiment, before hardening of ultra-high strength concrete showed the best fluidity in conditions of crushed sand replacement rates of 20% and superplasticizer composition of 1.95%, but it appeared that fluidity drops as time goes by in the same composition condition. And it appeared that when it comes to hardened, the changes of compression strength according to elapsed time by crushed sand replacement rates were within 1MPa. Therefore, it turned out that the difference of strength according to elapsed time was low and compression strength of 280dys in composition mentioned above appeared highly as 88MPa.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1997.05a
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• pp.53-56
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• 1997

오염된 토양의 복원기술 개발의 일환으로 폐수의 처리 등에 많이 이용되어온 Fenton-like oxidation을 petroleum으로 오염된 토양의 in-situ/ex-situ remediation을 위한 data 축적을 위해 실험실상에서 적용하여 보았다. 천연 토양속에 흔히 존재하는 철광석의 한 형태인 magnetite, goethite를 이용해 Fenton-like oxidation을 유도하여 silica sand에 오염된 kerosene의 분해를 잔존 TPH의 분석을 통하여 확인하였다. 초기 kerosene의 농도, 과수의 농도, 철광석의 양을 변수로 하여 최적 처리조건을 구하기 위한 실험을 진행하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.237-238
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• 2009

This study presents effect on replacement level of recycled fine aggregates(30% and 50%)instead of silica sand in SHCC with PYA fiber.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.1
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• pp.1-7
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• 1986

The GaAs bulk single crystals are grown by the Horizontal Bridgman method. During the growth, one of the problems in Bridgman method is the boat wetting between GaAs molten and silica boat. This boat wetting may result in another nucleation to form twin crystals. In this study, We find that the optimal size for sand blasting is 320 mesh. Backfilling the ampoule with argon gas during the vaccum bake-out decreaes the boat wetting. The reaction mechanism of Ga with quartz to produce suboxide, Ga2O, and sillion is discussed.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.2
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• pp.61-68
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• 1975

A laboratory study was conducted to determine the effect of nitrogen mineralization in accordance with addition of calcium silicate and wollastonite on the fresh soil condition. Results are summarized as follows. 1. Nitrogen mineralization due to application of silica materials was rapidly occured in Saweon sand soil than in Honam clay soil. Also wollastonite application more stimulated the nitrogen mineralization than calcium silicate. 2. Silica material application enhanced loss of applied nitrogen by denitrification due to accelerate the nitrification in Suweon sand soil. This tendency was more severe in calcium silicate applicated treatment than in wallasnonite applicated. 3. From these results, nitrogen should be applicated with organic matter to improve the supply of nitrogen nutrient to plant when silica materials were applied.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.527-535
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• 2001

The watertight property of concrete was examined, that is affected by the sort of self waterproofing admixture and the change of the addition ratio of admixture. Various self waterproofing admixtures were made by changing the mixing ratio of silica fume, zinc stearate and silica sand. The result showed as follows. As the adding ratio of self waterproofing admixture increases, the fluidity is increased and the setting time is delayed. While compressive strength of concrete with self waterproofing admixture A which is currently using is increased until the adding ratio of self waterproofing admixture reached 18kg/㎥ and decreased over 24 kg/㎥, that with self waterproofing admixture B, C and D which are developed are higher than that of A. Absorption is decreased as the adding ratio of self waterproofing admixture and the increasing of age in concrete. Especially, when self waterproofing admixture has a lot of zinc stearate, absorption is decreased manifestly. The property of permeability is similar to that of absorption; permeability is decreased as the adding ratio of self waterproofing admixture and the increasing of age in concrete. Consequently, when the ratio of silica fume, zinc stearate and silica sand in self waterproofing admixture is 1 : 2 : 1 and addition ratio of self waterproofing admixture is 6kg/㎥, the high quality concrete is obtained comparing to the concrete with existent self waterproofing admixture.