• 한국정밀공학회지
• /
• 제2권3호
• /
• pp.41-46
• /
• 1985

The behavior of the burn-on in sand mold has been investigated by varying the pouring metal, bonding materials, additive materials and molding sand. The results obtained from thease experiments are as follows; 1) The burn-on layer of silica sand decreased in order of carbon steel, gray cast iron and stainless steel, and thease burn layer proceeded mostly by producing FeO. 2) The burning reaction of silica sand mold in carbon steel castings declined with increasingly bentonite content, but water-glass scarcely took part in the burn-on reaction. 3) The addition of feldspar and seacoal to silica sand promoted the inhibiting burn-on. 4) The burn-on layer of sand mold decreased of silica sand, chromite sand and olivine sand.

• 자원리싸이클링
• /
• 제5권1호
• /
• pp.9-13
• /
• 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.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.1029-1034
• /
• 2001

The effects of binder content and silica sand content on the freezing and thawing resistance of lightweight polymer concrete are examined. As a result, the mass loss and pulse velocity of lightweight polymer concrete decrease with increasing binder content and silica sand content. The relative dynamic modulus and durability factor of lightweight polymer concrete reaches minimum at a silica sand content of 50% and a binder content of 28%, and is inclined to increase with increasing binder content and silica sand content.

• Advances in concrete construction
• /
• 제10권5호
• /
• pp.431-441
• /
• 2020

For the purpose of improving the properties of UHPC as well as the economic efficiency in production of the material, Availability of river sands as fine aggregate instead of micro silica sand were investigated. Four different sizes of river sands were considered. Using river sand instead of micro silica sand increased the flowability, and decreased the yield stress and plastic viscosity in rheological properties, and the effect was higher with larger particle size of river sand. It was demonstrated by analyses based on the packing density. In the results of compressive strength and elastic modulus, even though river sand was not as good as micro silica sand, it could provide high strength of over 170 MPa and elastic modulus greater than 40 GPa. The difference in compressive strength depending on the size of river sand was explained with the concept of maximum paste thickness based on the packing density of aggregate. The flexural performance with river sand also presented relatively lower resistance than micro silica sand, and the reduction was greater with larger particle size of river sand. The flexural performance was proven to be also influenced by the difference in the fiber orientation distribution due to the size of river sand.

• 공업화학
• /
• 제19권6호
• /
• pp.680-684
• /
• 2008

Silica sand 내에서의 메탄 하이드레이트($CH_4$ hydrate)의 형성과 분해는 $7.0^{\circ}C$의 온도에서 실험되었다. Silica sand 내에서 형성되는 메탄 하이드레이트의 형성 및 분해 특성을 연구하기 위해 새로운 반응기를 제작하였다. Silica sand bed 내에서 메탄하이드레이트의 형성과 분해되는 동안의 온도변화에 대한 연구를 위해 반응기 내의 주입한 silica sand 높이에 따라 열전대의 위치를 다르게 설치하여 실험하였다. 반응기 내에 가해지는 압력과 온도는 메탄 하이드레이트의 형성과 분해를 발생시키는 요인이다. 메탄 하이드레이트 형성을 위한 가스 흡착곡선과 분해실험을 위한 가스 발생곡선은 실험데이터로부터 결정되었다. 8 MPa의 압력에서 $7.0^{\circ}C$의 온도에서 메탄 하이드레이트 형성 실험을 수행한 결과 70%의 메탄이 하이드레이트로 전환됨을 알 수 있었다. 형성된 메탄 하이드레이트의 분해에 의한 메탄의 회수율은 82%였다.

• 상하수도학회지
• /
• 제31권6호
• /
• pp.521-527
• /
• 2017

Phosphorus is one of the limiting nutrients for the growth of phytoplankton and algae and is therefore one of leading causes of eutrophication. Most phosphorous in water is present in the form of phosphates. Different technologies have been applied for phosphate removal from wastewater, such as physical, chemical precipitation by using ferric, calcium or aluminum salts, biological, and adsorption. Adsorption is one of efficient method to remove phosphates in wastewater. To find the optimal media for phosphate removal, physical characteristics of media was analysed, and the phosphate removal efficiency of media (silica sand, slag, zeolite, activated carbon) was also investigated in this study. Silica sand showed highest relative density and wear rate, and phosphate removal efficiency. Silica sand removed about 36% of phosphate. To improve the phosphate removal efficiency of silica sand, Fe coating was conducted. Fe coated silica sand showed 3 times higher removal efficiency than non-coated one.

• 산업기술연구
• /
• 제22권A호
• /
• pp.119-125
• /
• 2002

In Kwangjin industrial company, mill is operating for the foundry sand production at the rate of 25t/hr from quartzite. Foundry sands fall into four distinct categories: silica sand, lake sand, bank sand, and natural molding sand. Silica sand is a general term used to describe crushed, washed, graded, dried, and cooled clay-free sands. This study was conducted for the investigation of the foundry sand productivity and the life span of the hammer according to the material quality. The life time of hammer from several manufacturer were compared in order to find out the grinding efficiency of the various hammer material. In the result of tests, the life time of high-Mn hammer was 10.5 hours while that of high-Cr was 19.5 hours. The life time in case of typical worn shape hammers was about 12 hours and the average time of a blowhole hammer was about 6.5 hours.

• 한국주조공학회지
• /
• 제22권3호
• /
• pp.137-143
• /
• 2002

Silica sand, zircon sand, and steel shots were used as mold packing materials in lost foam casting of the aluminum alloy bar. Vibration acceleration in three directions and temperatures in the casting and mold were measured, and packing and cooling characteristics of these materials were investigated. Packing densities increased with increase in vibration magnitude and time, and were $1.41{\sim}1.49g/cm^2$ for silica sand, $2.54{\sim}2.86g/cm^2$ for zircon sand, and $3.92{\sim}4.52g/cm^2$ for steel shots. Sound castings were obtained only without evacuation of the flask during pouring. Solidification time became faster in order of silica sand, zircon sand and steel shot packing because steel shot has the highest cooling capacity of them. Solidification time of steel shot packing was shortened to about 1/2 of silica sand packing. Cooling capacity of sand mold was generally evaluated by heat diffusivity of the mold, however could be simply evaluated with specific heat per unit volume of the packing material in lost foam casting.

• Geomechanics and Engineering
• /
• 제12권1호
• /
• pp.127-138
• /
• 2017

A series of high-pressure isotropic compression tests were performed on four types of poorly graded silica sand that were artificially prepared based on representative grading curves and similar mineralogy composition of seabed sediment containing different fines contents existing in the Nankai Trough. The addition of fines steepens the initial compression path and increases the decrement of the void ratio after loading. The transitional behaviour of the poorly graded sand with a larger amount of fines content was identified. The slope of the normal compression line shows a slight decreasing tendency with the level of fines content. The bulk modulus of silica sand with fines was lower when compared with the published results of silica sand without fines. A small amount of particle crushing of the four types of poorly graded sand with variable fines content levels was noticed, and the results indicated that the degree of particle crushing tended to decrease as the fines content increased.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
• /
• pp.48-49
• /
• 2017

In order to examine the effect of voids on the ultrasonic wave velocity, specimens made of Silica-Sand with voids were prepared for the measurements. The volume fraction of 0, 15, and 30% of voids were used to compare the differences. Because of its more homogeneous distribution of materials properties, the Silica-Sand specimens were used, as compared to mortar specimens. The results showed clear change in ultrasonic wave velocity with different volume fraction of voids. This result is to be used for the estimation of the integrity of concrete structures using ultrasonic wave velocity method as nondestructive testing.