• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.993-998
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• 2009

This study was conducted to propose the model that is able to predict long-term settlement of sands containing carbonates. We can observe that in addition to the initial elastic compression, a considerable additional compression occurs with long-term period in some sands. The compressibility of sands is significantly dependent on particle characteristics. Some sands have many pores and particularly has an angular shape. To predict of long-term settlement of these sands which contain carbonates, first of all a variety of tests which are to assess chemical, physical and compression characteristics of these sands were conducted. Second, in order to know settlement with time, the time parameter was determined by analyzing the measured data obtained from $\bigcirc\bigcirc$ area. The measured settlement of this area shows that in addition to the initial elastic compression, a considerable additional compression occurring with time. It was caused by the crushing, shattering, and rearrangement of particles, which were real phenomena in sandy soils under loading condition. Based on this case study, we proposed that a simple method is able to predict settlement with time of sandy soil containing carbonates.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.112-116
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• 2005

In the present study, the focus is on the analysis of carbothermal reduction of oxide powder prepared from waste WC/Co hardmetal by solid carbon under a stream of argon for the recycling of the WC/Co hard-metal. The oxide powder was prepared by the combination of the oxidation and crushing processes using the waste $WC-8 wt.\%Co$ hardmetal as the raw material. This oxide powder was mixed with carbon black, and then this mixture was carbothermally reduced under a flowing argon atmosphere. The changes in the phase structure and gases discharge of the mixture during carbothermal reduction was analysed using XRD and gas analyzer. The oxide powder prepared from waste $WC-8wt.\%Co$ hardmetal has a mixture of $WO_{3} and CoWO_{4}$. This oxide powder reduced at about $850^{\circ}C$, formed tungsten carbides at about $950^{\circ}C$, and then fully transformed to a mixed state of tungsten carbide (WC) and cobalt at about $1100^{\circ}C$ by solid carbon under a stream of argon. The WC/Co composite powder synthesized at $1000^{\circ}C$ for 6 hours from oxide powder of waste $WC-8wt.\%Co$ hardmetal has an average particle size of $0.3 {\mu}m$.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.99-107
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• 2004

This research is to determine the level of environmental pollution at a blasting construction area which is the origin of noise, vibration, and suspended particle, and to compare the results with other domestic and international standard data. This experiment is also to find out the effects resulting from blasting construction and to propose a plan that can decrease environmental pollution. The blasting construction area is a factory site which is about one and half million square meter and sewage disposal plant is about ninety thousand square meter. Both were selected as the areas for the tests to be conducted in determination test. The test to determine the level of noise, vibration, and total suspended particle was conducted thirty times around the blasting construction area by comparing measurement results and numerical analysis. However, as the test was not conducted in the laboratory but in the actual blasting construction area, it was not possible to do the test with the same exact conditions each true. Therefore, the test was not ideal as conditions could change from test to test. For the most part, the level of noise was below the standard level of 70dB. Every vibration test was under the standard limitation. For example, a house, 200m away was tested for noise and vibration and the level was found to be under the 0.2 cm/sec which is the standard for specialty designed cultural sites., i.e very low level. Also a buried oil pipeline that was 30m away also marked under 2.0cm/sec which is the norm for an industrial area. However, if there were an oil pipeline under the house, the amount of charging gunpowder per hole should be decreased compared to the amount used in the test. The test result for suspended particles under the standard limitation which is 24hour average 300$\mu\textrm{g}$/㎥ at a distance from blasting wavelength, but at detonator, total suspended particle from the blast origin exceeded the standard limitation. If explosion occurs when it detonates in the hole, most of the energy would be absorbed in the crushing of rocks, but some remaining energy would make noises and vibration inevitable. So the important thing is how to minimize the environmental pollution from the blasting. There should be regulations in order that the standard limitation is not exceeded, and to decrease the environmental pollution from the blasting.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.2
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• pp.184-193
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• 2015

Objectives: This study focused on three aspects: characterizing concentrations of airborne particles by size distributions and asbestos fibers generated by various building materials; analyzing the characteristics of fibers produced by each simulation and asbestos fibers released from ACBMs; and investigating correlations of airborne asbestos fibers and particles generated and association of particle and asbestos concentrations. Methods: We selected three ACBMs including an insulation board, cement asbestos slate and wallboard. We constructed 4 scenarios; a) crushing with a hammer; b) cutting with a industrial knife; c) brushing with a metal brush; and d) tightening & loosening with a hand drill. We implemented one simulation for 30 seconds followed by 30 seconds resting period. We repeated a total of 5 cycles for 5 minutes. Results: The highest concentration of particulate & fibrous matters was from crushing with a hammer in each scenario followed by brushing with a metal brush, cutting with a industrial knife, and tightening & loosening with a hand drill. For ACBMs studied, asbestos concentrations were highest from an insulation board followed by cement asbestos slate, and wallboard. No difference in terms of concentration was found between an insulation board and asbestos slate. Fibers with $5{\sim}20{\mu}m$ in length were included in 76~90% of total fibrous matters. The distribution of the straight form fibers was greater than that of the curl form. About 90% of $PM_{Total}$ released from ACBMs was consisted of $PM_{10}$ while only 10% of $PM_{Total}$ was $PM_{2.5}$. Particulate matters like $PM_{2.5}$ was significantly correlated with fibrous matters($R^2=0.81$). Conclusions: We found ACBMs can significantly release asbestos fibers as well as $PM_{2.5}$. Concentrations of asbestos generated by ACBMs were well correlated with $PM_{2.5}$.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.29-37
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• 2024

In this study, recycled concrete aggregates (RCA) were treated in a 5-kg-scale prototype reactor with carbon dioxide (CO₂) to enhance their material quality and geotechnical performance. The aggregate crushing value (ACV) and California bearing ratio (CBR) were measured on untreated RCAs and CO₂-treated RCAs. After CO₂ treatment, the ACV decreased from 35.6% to 33.2%, and the CBR increased from 97.5% to 102.4%. The CO₂ treatment caused a reduction of fine particle generation and an increase in bearing capacity through carbonation. When CO₂ treatment was performed with mechanical agitation, which provided additional enhancement in mechanical quality, the ACV was reduced further to 30.3%, and the CBR increased to 137.7%. If upscaled effectively, the proposed CO₂ treatment technique would be an effective method to reduce carbon emissions in construction industries.

• Geotechnical Engineering
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• v.12 no.6
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• pp.115-126
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• 1996

The purpose of 1,his study is to analyze the compression and strength charactefistics of the decomposed -weathered soil originating from biotite gneiss or fine grained gneiss sampled from Poidong, Seoul : to figure out the behavioural characteristics of the decomposed -weathered soil in accordance with mineral composition and origin by comparing experimental results of residual soils. originating from granites and sampled from Bulam, Andong and Kimchun area. A series of CIU, CID CKoV, CKoD tests were car lied out. Although weathered soils have different origin and mineral composition, the slope of the NCL A was similar. It was also shown that plastic strain ratio was about 85% mainly due to the particle crushing effect during compression. The Poidong soil showed strain softening phenomenon unlike the Kimchun and Andong soils. this implies that the behavioural characteristics are affected by the origin and the mineral composition of the soil particles. Moreover, it was found that the angle of the shear resistance$(\phi')$ was dependent on the mineral composition. On the oher hand, measured Af values of decomposed weathered soils were more than one regardless of the origin and the mineral composition.

• Resources Recycling
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• v.28 no.6
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• pp.64-72
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• 2019

Fly ash has different chemical composition depending on the type and quality of flaming coal. Fly ash is classified according to carbon content and particle size. Waste glass powder is manufactured by crushing glass. Exterior Insulation Finish System (EIFS) is generally applied by using poly-styrene foam which is economical and has excellent thermal insulation performance. However, poly-styrene foam has excellent insulation performance, but it is vulnerable to fire, which is becoming a serious problem. In this study, using a fly ash and waste glass powder to produce a finishing mortar at high temperatures. Also, High temperature strength and flame retardant properties were tested according to the cover thickness. From the test result, finishing mortar prepared using fly ash and waste glass powder is due to the improved heat resistance by alkali-activated bonding. However, since the strength decreases at high temperatures, it is necessary to select an appropriate mixing proportion.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.1
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• pp.55-59
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• 1984

An organic compound fertilizer was manufactured using wet oxidation human waste as principal source of phosphorus and organic matter. The waste was treated with sulfuric and glutamic acids to increase the available and water-soluble $P_2O_5$ contents. The treatment of 0.1 N sulfuric acid with 24 hours curing was best way in recovering the maximum percentage of $P_2O_5$ originally in the waste. The particle size distribution of trial product varied considerably in the amount of glutamic acid used for granulation. The number of relatively large fertilizer particles was increased as the amount of glutamic acid was increased. The granule crushing strength was generally high in large granules in which 12.5 weight percent of glutamic acid were used for granulation. The trial product showed high moisture absorption due to its porous structure and chemical makeup.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.6
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• pp.357-366
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• 2003

This study was conducted to develop n convenient and efficient granular type absorbent with high CEC from powdery zeolite, which is a waste produced while crushing the natural zeolite of Korea to get a particular particle size. The change of mineralogical characteristics during hydrothermal alternation of natural zeolite to Na-P zeolite in alkaline solution at various reaction times was determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and total elemental analysis. The columnar aggregate of Na-P Zeolite was produced by calcinating the natural zeolite-charcoal extrudates of about 3 mm diameter. In 24 hours reaction, clinoptillonite, mordenite and feldspar in natural zeolite were disappeared by 3 N NaOH treatment, while Na-P Zeolite with spherical granular structure was newly detected by XRD. As increasing reaction time, Si/Al ratio in remaining solution was deceased. The CEC of the synthesized material increased more than 2 times compared with that of natural zeolite, although the diameter of Na-P zeolite were rather increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3102-3107
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• 2013

Inorganic pigments were prepared from $Al_2O_3$, CoO, $Cr_2O_3$, ZnO, $SrO_2$ and Kaolin. The pigment was prepared through the processes of mixing and crushing of the raw materials, sintering, milling and drying. The color of the pigments was changed from blue to green as $Cr_2O_3$ contents in the pigment increased. The color became brighter irrespective of the pigment composition as pigment particle size became smaller. Maximum sintering temperature was the most suitable at around $1,250^{\circ}C$. In the test of compatability between the pigment and glaze, the color became close to green as $Cr_2O_3$ contents in the pigment increased, and became close to blue as CoO contents increased.