• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.342-348
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• 2001

This study was conducted to obtain granular crystalline gypsum that can be used as raw material for plaster boards or cements from waste Plaster board. We could disintegrate preferentially gypsum to gypsum needle in 10${\mu}{\textrm}{m}$ or less size among the contents of waste plaster board (gypsum, paper, fiber, and inorganic material .etc.) by hydration afterwards the dehydration of crushed waste plaster board. In this case, the optimum conditions for minimizing the size of gypsum were dehydration rate of 75%~ 85%, hydration concentration of 10~20%, agitation speed of 250~400rpm, crushing size of 2cm or less. Gypsum of 98.21% grade was recovered with 99.0% yield from under screenings of 325mesh wet screening which followed by the dehydration-hydration process performed in the conditions of dehydration rate of 80%, hydration concentration of 15%, agitation speed of 300rpm, crushing size of 2cm or less. Subsequently, Plate-like Crystalline gypsum of is 151${\mu}{\textrm}{m}$ size and the grade of 99.49% with the Yield of 98.0% from the upper screenings of 270mesh wet screening carried out after the re-crystallization of the recovered gypsum needle slurry.

• Resources Recycling
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• v.10 no.6
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• pp.43-52
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• 2001

This study was conducted to obtain granular crystalline gypsum that can be used as raw material for Plaster boards or cements from waste Plaster board. Gypsum could be Preferentially disintegrated to gypsum needle in $10\mu\textrm{m}$ or less size by hydration after the dehydration of crushed waste Plaster board. The finer the gypsum needle, it is easier to remove coarse impurities and to recover the gypsum needle. The optimum conditions for obtain the finer gypsum size were dehydration rate of 75~85%, solid concentration at hydration of 10~15%, agitation speed of 250~400 rpm, crushing size before dehydration of 2 cm or less. Gypsum of 98.21% grade was recovered with 99.0% yield as the undersize of 325 mesh wet screening followed by the dehydration-hydration process performed at the conditions of dehydration rate of 80%, solid concentration at hydration of 15%, agitation speed of 300 rpm, crushing size before dehydration of 2 cm or less. After the recrystallization of recovered gypsum, Plate-like gypsum of $151\mu\textrm{m}$ size with 99.49% grade was obtained as the oversize of 270 mesh in a wet screening.

• Resources Recycling
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• v.17 no.2
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• pp.16-29
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• 2008

According to the statistical data of the Ministry of Environment, 47million tons of construction waste were generated, and 96.7% of them was recycled in 2005. However, the recycled products seem to be remained under low quality. Because mixed demolition and construction waste, so called DC Waste, including concrete, brick, plaster, lumber, plastics building materials, paper and some dirt and stone, is very variable and difficult to estimate its exact composition, it is regarded as having little or no value to the construction industry. 'The Research group on recycling of construction waste' was started by the Housing & Urban Research Institute(KNHC), which is sponsored as a large scale national project by the Ministry of Construction and Transportation. This research group intends to establish recycling system through planing, processing, developing practical technology, and eventually contribute to save natural resource and to vitalize the industry. In this paper an overview of DC waste management and recycling technology is given in some detail. Particularly, "recycling law of construction waste" and recent research trends on recycling of construction waste are discussed.

• KIEAE Journal
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• v.7 no.1
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• pp.33-40
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• 2007

0.4 Million tons of shell powder have been disused as waste in KOREA and caused severe environmental pollution though shell powder can be utilized in real life for many ways. It is impending problem to recycle shell powder as it requires high expense for burying and temporary outside heap and causes severe environmental pollution being a main factor of ocean waste. To suggest the basic data for development of eco-friendly and high-function Wall Coatings Thin Textured Finishes, a wall coating sample was applied to indoor walls of a mock-up and temperature and humidity were measured to assess the thermal performance of it, and a survey of preference for the color sense and feel of the materials with a movie of specimens. The results of the study are following; 1) High insulation performance is shown from the assessment result of the room polystyrene board adhered on the walls then high humidity controlling performance is shown from that of the room polystyrene board coated by shell powder. This point out that shell powder has superiority for humidity controlling. 2) The result of thermal and humidity assessment shows that shell powder makes up for thermal conduction of the polystyrene board and same result can be expected from the assessment with materials which has similar thermal characteristics with polystyrene.3) Ranking of preferred specimens is; 1st Case 13, 2nd Case 17, 3rd Case 16, and 4th Case 12. Preferred shell powder was the ark shell. Preferred powder for plaster was the powder mixed with that sifted by 0.8mm, 100mesh and 40mesh, and for spray was the fine powder mixed with that sifted by 100mesh and 40mesh.