• Geomechanics and Engineering
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• 제10권1호
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• pp.77-94
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• 2016

Cyclic triaxial and resonant column tests were conducted to understand the beneficial effects of various grouted sands on liquefaction resistance and dynamic properties. The test procedures were performed on a variety of grouted sands, such as silicate-grouted sand, silicate-cement grouted sand and cement-grouted sand. For each type of grout, sand specimen was mixed with a 3.5% and 5% grout by volume. The specimens were tested at a curing age of 3, 7, 28 and 91 days, and the results of the cyclic stress ratio, the maximum shear modulus and the damping ratio were obtained during the testing program. The influence of important parameters, including the type of grout, grout content, shear strain, confining pressure, and curing age, were investigated. Results indicated that sodium silicate grout does not improve the liquefaction resistance and shear modulus; however, silicate-cement and cement grout remarkably increased the liquefaction resistance and shear modulus. Shear modulus decreased and damping ratio increased with an increase in the amplitude of shear strain. The effect of confining pressure on clean sand and sodium silicate grouted sand was found to be insignificant. Furthermore, a nonlinear regression analysis was used to prove the agreement of the shear modulus-shear strain relation presented by the hyperbolic law for different grouted sands, and the coefficients of determination, $R^2$, were nearly greater than 0.984.

• 한국주조공학회지
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• 제23권5호
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• pp.235-243
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• 2003

The collapsibility of sodium silicate-bonded sands mixed with the L.D converter slag powder to form a hardener were investigated. Five to six percent sodium silicate on the basis of silica sand and 30-40% L.D converter slag powder on the basis of sodium silicate, were mixed and the compressive strength, surface stability index(SSI), bench time, retained strength of the standard sand specimens were measured. The properties were similar to those of general inorganic bonded self-setting molds. The compressive strength and surface stability index were increased and the retained strength and bench time were decreased with increased amount of the L.D converter slag powder. The retained strength of sodium silicate-bonded self-setting molds with the L.D converter slag powder were decreased than $CO_2$ sand molds. The collapsibility of sodium silicate-bonded self-setting molds with the L.D converter slag powder were superior in comparison with $CO_2$ sand molds. The L.D converter slag powder could be used as hardener and collapse agent for the sodium silicate-bonded self-setting molds.

• 자원리싸이클링
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• 제5권1호
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• pp.9-13
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• 1996

Once-used $CO_2$-silicate bonded sand from domestic foundry is mostly discarded in a reclaimed land because of its bad collapsibility and reproduction properties. So this causes serious environmental problem. We can get 82% recovery of silica from used sand by scrubbing reclamation process in this research. When we repeat the reclamation-recycling of the foundry sand, artificial silica sand is broken down below 2-cycles, but natural silica sand does not destroyed when used repeatedly more than 10-cycles and have a good property of recycling with little change of its size.

• 한국세라믹학회지
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• 제13권1호
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• pp.20-24
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• 1976

These are many kinds of self-hardening methods for sand mold using sodium silicate. When sodium silicate solution is mixed with calcium-orthosilicate powder hardening reaction occurs, which is based for self-hardening method at high temperature. The high temperature strength and resicual strength of mold are related to the mole ratio of sodium silicate and the contents of calcium-orthosilicate powder. The results obtained in this study were as follows: 1) The high temperature strength of mold was maximum at about $600^{\circ}C$, and at higher temperature showed lower value on the contrary. 2) The high temperature strength of mold was increased by increasing the amount of sodium silicate having lower mole ratio and high concentration. 3) The residual strength of mold was reduced by increasing the mole ratio of sodium silicate and increasing the concentration of calcium-orthosilicate.

• 한국지반공학회논문집
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• 제23권6호
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• pp.103-114
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• 2007

제주도 해안지역에 분포하고 있는 모래는 화산암류가 풍화되어 형성된 모래와 조개 등의 어패류가 풍화되어 탄산염 $(CaCO_3)$ 함유량이 많은 모래, 그리고 이들 두 가지 특징이 혼재한 모래로 분류할 수 있었다. 분류된 모래들 중 삼양, 김녕, 제주외항 지역의 모래에 압축 특성을 알고자 압축시험을 수행한 결과, 삼양인 경우 초기압축이 다른 모래에 비해 큰 것으로 나타났으며 김녕, 제주외항 모래인 경우 초기압축외의 추가적인 압축도 상당히 발생하였으며, 이는 압축시험 전·후의 모래의 입도분포 분석 결과 입자의 파쇄와 재배열에 의한 것으로 나타났다. 또한 현재 제주외항 항만시설 축조공사에 따른 지반의 침하특성을 분석한 결과 초기 압축 외에도 모래의 파쇄성과 재배열에 의해 상당시간동안 압축이 일어난 것을 알 수 있으며, 파쇄성과 재배열이 고려되지 않은 기존 탄성침하량 산정법을 이용한 침하량과 기존의 침하시간 산정 시 과소평가 될 우려가 있는 것으로 나타났다.

• 한국주조공학회지
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• 제3권3호
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• pp.181-187
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• 1983

Effects of retained compression strength on the collapsibility of $CO_2$ mold sand using sodium silicate were studied. The results obtained from the experiment are summurized as follows; 1) The sand mixtures increased their compression strength and retained compression strength when content of sodium silicate is high or mole ratio of sodium silicate is high. 2) Increase of retained strength has a maximum value at temperatures about $200^{\circ}C$. When the sample reached $800^{\circ}C$, the binder bridge are homogeneous. The retained strength is increased. 3) Decrease of retained strength at temperatures over $200^{\circ}C$ is caused by pore formation and additives of seacoal markedly accelerated pore formations.

• 한국주조공학회지
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• 제22권3호
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• pp.121-129
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• 2002

According to the investigation of waste $CO_2$ molding sand in the 15 steel foundries in Busan and Gyeong area, about 1 ton of waste $CO_2$ molding sand per ton of steel castings production was produced In order to reduce amount of $Na_2O$, Loss of Boiling (L.O.B), Loss of Ignition (L.O.I), Conductivity and PH which are present in the waste $CO_2$ molding sand below the reclamation effect, more than 50% of elimination for reclamation was required. It was found that the waste $CO_2$ molding sand does not contain a harmful component designated by industrial waste materials. Reclamation of the waste $CO_2$ molding sand was practically achieved by an abrasive-dry reclamation process. According to bench time of the sodium silicate-bonded $CO_2$ molding sand, reduction of compressive strength and surface stability index(S.S.I) become slowdown. Therefore, the reclaimed sand could be allowed the reuse of molding sand in $CO_2$ molding process including core sand.

• 한국세라믹학회지
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• 제15권4호
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• pp.193-198
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• 1978

Test-bricks were prepared from an artifically graded Ham Kang sand and a commercial CaO and autoclaved for 6 hours at $16 kg/cm^2$ pressure $(203^{\circ}C)$. Bricks were tested for compressive strength, free lime, saluble silica and amount of water absorption. Physical properties of bricks were very much depended on the size distribution of sand particle and the amount of soluble silica in bricks.

• 한국지반신소재학회논문집
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• 제13권4호
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• pp.57-68
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• 2014

본 연구에서는 화산섬 제주의 해안지역에 산발적으로 분포하고 있는 모래들을 성인에 따라 세 개의 그룹으로 분류(규산염모래, 탄산염모래, 혼재된 모래)하여 그 특성을 정리하였다. 기본물성은 일반적인 모래의 비중에 비해 규산염모래는 다소 높고 탄산염모래는 낮은 값들을 포함하여 넓게 분포하며 전체적으로 비교적 입경이 큰 탄산염광물이 혼재되어 있어 분급이 불량하고 균등계수가 낮다. 구성성분에 따른 압축강도와의 관계는 규산염성분은 압축강도와 양의 상관을 보이고 탄산염성분은 음의 상관을 보여 서로 상반되는 경향을 보인다. 두성분의 비가 1:1을 기준으로 탄산염성분비가 작아지는 지역의 모래는 건설용 잔골재로 활용이 가능할 것으로 추정된다. 탄성계수 산정 시 압축강도의 2제곱근(ACI 308)과 3제곱근(KCI 2012)을 비교하기 위해 탄성계수를 무차원하여 검토하였다.

• 한국주조공학회지
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• 제7권4호
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• pp.366-379
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• 1987

The influences of some factors on the variation of compression strength of $CO_2$ process were investigated with an attention given to use of high $SiO_2\;/Na_2O$ silicate, addition of organics and gassing operation. 1) Higher ratio binder offers faster rates of hardening with lower $CO_2$ consumption requiring more concentration for a good strength development. A mixture containing 4 percent of 2.7:1 ratio silicate produces the strength above $8kg\;/\;cm^2$ after 80 seconds gassing, but 5% and 6% respectively of 3.0:1 and3.3:1 ratio silicate are necessary to achieve equivalent levels of strength. 2) The correct water content in sand mixtures containing higher ratio silicates is necessary for the better strength properties to be obtained. The addition of 1% water to the sand mixtures bonded with 5%,3:1 ratio and 6%,3.3:1 ratio silicates maintains near-maximum strength on extended gassing. 3) When higher ratio silicates with 3:1 and 3.3:1 ratios are used,the addition of organic additives such as oil, sucrose and polyol results in considerable changes in strength. The presence of 1.0 to 1.5 percent of polyol produces a noticiable improvement 4) Gas diluted with air raises the efficiency of gas utilization. When gas contains 50 percent $CO_2$, the efficience is significantly increased with the best strength in the silicates having high ratios of 3:1 and 3.3:1. 5) The strength of molds is liable to change on storage with the reduction in water content. The magnitude of the strength change is determinded with the mole ratio. The presence of polyol in the mixture with 3.3:1 ratio silicate has a pronounced effect on maintaining the gassed strength.