• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.577-580
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• 2006

As this study is to estimate resistance of cement mortars using crushed sand under chemical attacks. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of silica fume and fly ash(up to 15% and 50% by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days, 60days, 90days and 180days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of silica fume and fly ash was performed.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.519-522
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• 2005

As this study is to test effects of chemical attack on deterioration of cement mortars using in crushed sand. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of slica fume and fly ash(up to $15\%$ and $50\%$ by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of slica fume and fly ash was performed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.271-275
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• 1998

Recently, in the trend of using aggregate, it is common that coarse aggregate is replaced with crushed stone and fine aggregate is replaced with sea sand as a replacing aggregate. In this study, to judge the adaptability of using antiwashout underwater concrete, we used mixed sand (river sand : sea sand= 5 : 5) and changed W/C. After carrying out the research on the strength development of the compressive strength of specimen, tensile strength, fluxural strength which is produced and cured in the air and salt water, we founded that when W/C was low and the amount of AWA and SP were increased, the state of strength development was excellent.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.57-61
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• 2006

Waste foundry sand of industrial waste which is happening by vast quantity according to fast development of industry has much the occurrence amount and processing method is depended on reclamation, and is using by fine aggregate for construction by recycling method among others. In this research Waste foundry sand powder into cement replace fare use possibility availability judge wish to Slump and air content decreased the replacement ratio increases by concrete special quality that do not harden according to experiment result, and unit capacity mass and bleeding increased the replacement ratio increases. Hardening concrete intensity special quality displayed strength improvement to replacement ratio 20%, and tendency that watertightness increases most in replacement ratio loft in watertight property appear. Considering the strength and watertight properties, the adequate usage of waste foundry sand powder is the 10% of replacement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.821-824
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• 2006

As this study is to estimate long term resistance of cement mortars using crushed sand under chemical attacks. Besides tests have been carried out with cement mortars by river sand and crushed sand by fine sand, cement mortars mix various proportions of silica fume and fly ash(up to 15% and 50% by weight for cement) were prepared and immersed in pure water, sodium sulfate solution, magnesium sulfate solution, seawater for 28days, 90days, 180days, 365days. Test on the change in the weight and compressive strength of cement mortars according to the duration of immersion time and the content of silica fume and fly ash was performed.

• Journal of The Geomorphological Association of Korea
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• v.17 no.1
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• pp.15-27
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• 2010

This study investigated the sedimentary environment changes in the Baramarae beach of Anmyeondo through spatio-temporal surface sediment analysis. In the winter season 2009, surface sediments were classified into 7 sedimentary facies such as gravel, sand, gravelly sand, gravelly muddy sand, muddy sand, silty sand, and sandy silt. Time-series analysis of average grain size from 2002 to 2009 revealed that the average grain size of sediments became finer and sorting was much worse. On the contrary, during the same period, the grain size became coarsening-trend and sorting was much better in beach area. These different grain size patterns resulted from the different change characteristics of beach and tidal flats. The southwestern beach area was connected to the open sea and thus fine sediments were removed by the environments with relatively high-energy. The sedimentation of fine sediments in the bay resulted from the tidal current action and the reduction of energy by the topographic effects. Fine sediments in the outer part of southwestern tidal flats could be explained such that the Seomot isle blocked ocean waves and as a result, low-energy environments accelerated sedimentations of fine sediments.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.21-29
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• 2012

Ground failure by liquefaction can occur not only during shaking but also as the result of the post-liquefaction process after an earthquake. During the process of ground deformation and failure, excess pore water pressure in soil is redistributed, which can then lead to changes in the effective stress of soils. Therefore, in order to provide a further understanding of the phenomenon, we have to estimate the properties of effective stress during the recompression process in post-liquefaction as well, not only the total amount of pore water drained. The primary objectives of this study are to determine and compare the recompression properties in the post-liquefaction process in terms of the relationship between volumetric strains and mean effective stresses under the various conditions of relative density and shear stress history. In all experimental cases, the volumetric strains increase greatly in the low effective stress level, almost to the zero zone, and granite soil, which has fine grains, undergoes gradual changes in the relationship between volumetric strains and mean effective stresses compared with fine sand. And, we can also find that recompression properties in the post-liquefaction process by cyclic loading depend highly on the dissipation energy and maximum shear strain, and this fact can be obtained in all cases regardless of the existence of fine content, relative density, and loading history. Especially, granite soil having fine grains can be defined uniformly in the relationship between dissipation energy and maximum volumetric strain, while fine sand cannot be so uniformly defined.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.83-92
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• 2006

Recently, interest grew recently on the quality of aggregates following the diminution of primary resources from river and the growing construction demand which exhausted high-quality sand sources around large cities and incited the use of low grade aggregates like shore sand and sea sand that can be supplied in natural state. Especially, the environmental preservation concern and the augmentation of public grievance about the exploitation of sea sand as substitute to river sand are gradually impeding the supply. This situation aggravated by the recent interdiction to extract sea sand which resulted in sand crisis that even led once to the suspension of construction works. The lack of sea sand and river sand increased the exploitation of crushed sand which occupies now nearly 20% of the whole quantity of fine aggregates. And, the use of crushed sand may be expected to grow continuously in the future. This paper described that the properties of crushed sand and the concrete using the crushed sand, the technologies to improve quality of crushed sand and the concrete in order to provide information for the production of high-quality concrete using crushed sand.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.3
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• pp.115-121
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• 2017

The degradation of the concrete due to deterioration factors, such as corrosion of steel bars, cracks and structural strength of reinforced concrete structures, is a social problem. Especially, concrete structures constructed in seawater, underground water, waste water treatment facilities and sewerage are subject to chemical attack by acid and sulphate. Therefore, this study was conducted to compare sulfated glass and fine aggregate of slag using waste glass fine powder and meta kaolin. The results showed that the slag fine aggregate showed better sulfate resistance than the river sand, and the fine powder of waste glass showed the best performance at 3 % displacement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.481-484
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• 2008

Recently, the recycling and reusing of construction and demolition waste concrete is urgently required because waste concrete is greatly increased according to the rapid increasing of urban redevelopment project, but the problem solution for demand and supply unbalance of fine aggregate is urgently required because of the restriction of collecting sea fine aggregate. So the utilization of high quality recycled fine aggregate using construction and demolition waste concrete as new fine aggregate for construction industry is urgently. Accordingly, In this study, As recycled fine aggregate manufacturing technology with exceeding in economical efficiency, reduction efficiency of environmental load and quality improvement effect of recycled fine aggregate, it is to develop dry manufacturing system composed specific gravity separator of high-speed rotation impact type and centrifugal Force Powder Collector, etc. And it is to examine mechanism of recycled sand dry manufacturing system.