• Resources Recycling
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• v.8 no.1
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• pp.44-51
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• 1999

Converter slag was reduced and modified by the simultaneous addition of carbon and waste foundry sand as a $SiO_2$ source. The basic properties such as phase distribution, composition, specific density, hardness. absorption of water and compressive strength of modified slags were measured. The Iron recovery was significantly affected by the basicity of slag. The properties of slow cooled-modified slags of basicity 1.34 arc very similar to the natural aggregates.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.1
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• pp.86-93
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• 2006

In the drinking water treatment, the aesthetic and color problem are caused by the manganese which is occurring and present in the surface, lake and ground water. The most common treatment processes for removing manganese are known for oxidation followed by filtration. In this study, the manganese sand process was used for removing manganese with river bank filtrate as a source. In the manganese sand process, the residual chlorine and pH are important factors on the continuous manganese oxidation. In addition, space velocity (SV) and alum dosage are play a role of manganese removal. Even though manganese removal increased with increasing chlorine concentration, the control of residual chlorine is actually difficult in this process As the results of tests, the residual chlorine concentration as well as manganese removal were effectively achieved at pH 7.5. The optimum attached manganese concentration on manganese sand was confirmed to 0.3mg/L by the experimental result of a typical sand converting to manganese sand.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.127-138
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• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1551-1558
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• 1994

An experiment was conducted to investigate whether an equation of heat transfer coefficient derived form energy equation of two-phase plug flow can be actually applied to the industrial field. The heat is constantly transfered to the sand beds from the wall of heat exchanger while the sand moves down through cylindrical heat exchanger by gravity from feed hooper. To increase heat transfer, turbulators such as glass ball and steel pipe packings were used. In addition, the experiment in the case of fluidizing the sand beds was also carried out. The temperatures of the sand beds and the wall were measured along the heat exchanger axis. The density and porosity of the sand beds were also measured. The deviations of the mean velocity of sands from the velocity on the wall surface because of the slip conditions on the wall were negligible (within 3%). The heat transfer coefficients when the turbulators were used and when the sand beds were fluidized were found to be much greater than those of the plain plug flow.

• Advances in concrete construction
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• v.11 no.1
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• pp.19-32
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• 2021

In the present experimental study, the high performance hybrid fiber reinforced concrete (HPHFRC) is prepared using the Modified Andreasen and Andersen (A&A) particle packing model. Total of 16 trial mixes of HPHFRC with Indian standard sand (SS) and natural river sand (NS) are prepared to achieve the selection criteria (flow percent>150 and compressive strength>80 MPa). Based on the flow percent and compressive strength criteria, the selected mixes evaluated to study the effect of usage of natural river sand (NS) and the expensive Indian standard sand (SS) on the mechanical, durability, and microstructure property of designed HPHFRC. It has been found that the Modified A&A model is reliable to design the mix for HPHFRC with excellent mechanical, durability, and microstructure properties. In addition to that, a moderate difference in the mechanical and durability properties of NS contained HPHFRC and SS contained HPHFRC is found. Based on the obtained results of NS contained HPHFRC, it can be concluded that the use of natural river sand (NS) can be successfully adopted for the production of HPHFRC, resulted in a reduction of the production cost without compromising the excellent performance of HPHFRC.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.207-214
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• 1997

Strength experimental on mortar which use Quenched Blast-Furnace Slag as aggregate was carried our for a fundamental study of application possibility of Quenched Blast-Furnace Slag as aggregate. It gives the following results. The strength of mortar use Quenched Blast-Furnace Slag is decrease as substitution rate is higher. As W/C rate increase, the strength decrease, but the strength decrease of fine aggregate rate 1:3 is lower than 1:2. The relation with fine aggregate is that the amount of fine aggregate is inversely proportional to strength. Th relation with age is proportional to strength and strength rate of going is lower than general mortar in 28 age the change of strength proportionately with W/C rate is that as W/C rate increases, th strength is drop ; it shows that it has same tendency as general mortar sand or crushed sand, but while W/C rate increase the strength is as high as general mortar. The reason can be assumed that water content per unit needed to Quenched Blast-Furance Slag is more than in case of sand. In addition, the relation with substitution rate is that the strength is the strongest at substitution rate 25% and 50% ; that is , sometimes it is higher than mortar which use sand 100%. In addition, long age strength of mortar which use Quenched Blast-Furnace Slag as aggregate is about to be studied in the last.

• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.212-217
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• 2011

The effects of alloying element and grain refinement on the tensile properties of magnesium alloy poured into sand mold were investigated. The strength of magnesium alloy was greatly increased by the addition of aluminium and that was increased with the increased aluminum content added up to 8.10 wt% and decreased beyond that. Even though the strength of Mg-8.10 wt%Al alloy was rather decreased by the addition of zinc, that was increased with increased zinc content added up to 0.50 wt% and decreased with the increased one beyond that. The maximum tensile strength was obtained with 0.50 wt%Mn added. The strength and elongation were simultaneously increased with grain refinement and the optimum amount of strontium addition for this was 0.30 wt%. The optimum chemical composition was obtained and the yield strength, tensile strength and elongation of the alloy with this composition were 90.2, 176.3MPa and 4.43%, respectively.

• Geomechanics and Engineering
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• v.25 no.3
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• pp.207-219
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• 2021

Several additives are used to enhance the geotechnical properties (e.g., shear wave velocity, shear modulus) of soils to provide sustainable, economical and eco-friendly solutions in geotechnical and geo-environmental engineering. In this study, piezoelectric ring actuators are used to measure the shear wave velocity of unreinforced, fiber, cemented, and fiber reinforced cemented Toyoura sand. One dimensional oedometer tests are performed on medium dense specimens of Toyoura sand-cement-fiber-silica flour mixtures with different percentages of silica flour (0-42%), fiber and cement (e.g., 0-3%) additives. The experimental results indicate that behavior of the mixtures is significantly affected by the concentration of silica flour, fiber and cement additives. Results show that with the addition of 1-3% of PVA fibers, the shear wave velocity increases by only 1-3%. However, the addition of 1-4% of cement increases the shear wave velocity by 8-35%. 10.5-21% increase of silica flour reduces the shear wave velocity by 2-5% but adding 28-42% silica flour significantly reduces the shear wave velocity by 12-31%. In addition, the combined effect of cement and fibers was also found and with only 2% cement and 1% fiber, the shear wave velocity increase was found to be approximately 24% and with only 3% cement and 3% fibers this increased to 35%. The results from this study for the normalized shear modulus and normalized mean effective stress agree well with previous findings on pure Toyoura sand, Toyoura silty sand, fiber reinforced, fiber reinforced cemented Toyoura sand. Any variations are likely due to the difference in stress history (i.e., isotropic versus anisotropic consolidation) and the measurement method. In addition, these small discrepancies could be attributed to several other factors. The potential factors include the difference in specimen sizes, test devices, methods of analysis for the measurement of arrival time, the use of an appropriate Ko to convert the vertical stresses into mean effective stress, and sample preparation techniques. Lastly, it was investigated that there is a robust inverse relationship between α factor and 𝞫₀ exponent. It was found that less compressible soils exhibit higher 𝜶 factors and lower 𝞫₀ exponents.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.141-147
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• 2005

The development of automobile, vessel, rail road, and machine industry leads an increase of foundry production used as their components, which cause a by-product, waste foundry sand (WFS). The amount of the WFS produced in Korea is over 700,000 tons a year, but most WFS has been buried itself and only $5{\~}6\%$ WFS is recycled as construction materials. Therefore, it is necessary for most WFS to research other ways which can be used in a higher value added product. The study on recycling it as a fine aggregate for concrete or green sand has been in progress in America and Japan since 1970s and 1980s respaectively. In this study, two types of WFS were used as a fine aggregate for concrete. Nine types of concrete aimed at the specified strength of 30 MPa were mixed with washed seashore coarse sand in which salt was removed, and WFS and then appropriate mixture proportion of concrete was determined. Moreover, basic properties such as air contents, setting time, bleeding, workability and slump loss of the fresh concrete with WFS were tested and compared with those of the concrete mixed without WFS. In addition, both compressive strength of hardened concrete at each ages and tensile strength of it at the age of 28 days were measured and discussed.

• Geomechanics and Engineering
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• v.23 no.1
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• pp.31-38
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• 2020

Soil-cement stabilization is a type of ground improvement method which has been used to improve the engineering properties of soil. The unconfined compression test is the commonly used method to evaluate the quality of the stabilized soil due to its simplicity, reliability, rapidity and cost-effectiveness. The main objective of this study was to evaluate the effect of recovered carbon black (rCB) on the strength characteristic of cement-stabilized sand. Various rCB contents and water to cement ratios (w/c) were examined. The unconfined compression test on stabilized sand with different curing times was also conducted for a reconstituted specimen. From the test result, it was found that the compressive strength of cement-stabilized sand increased with the increase of the rCB content up to 3% and the curing time and with the decrease of the w/c ratio, showing that the optimum rCB concentration of the tested stabilized sand was around 3%. In addition, a prediction equation was suggested in this study for cement-stabilized sand with rCB as a function of the w/c ratio and rCB concentration at 14 and 28 days of curing.