• Korean Journal of Environmental Agriculture
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• v.19 no.2
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• pp.122-127
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• 2000

A stream purification system was applied to the upper reaches of the Masan Reservoir to improve the water quality. This system consisted of two channels which were constructed on both sides of the stream, one side packed with crushed gravels and the other with plastic filter media. The system operated under low pollutant concentrations and high hydraulic loadings during a dry season to avoid clogging of the filter media. Removal rate and efficiency of chemical oxygen demand (COD) in the channel packed with crushed gravel were $14.8g/m^3/d$ and 11.5%, and for the channel with plastic filter media, $50.1g/m^3/d$ and 13.5%, respectively. Removal efficiencies of total phosphorus (T-P) were 6.6% (gravel) and 10.0% (plastic media). These results indicated plastic filter media having relatively high specific surface areas were more efficient than crushed gravels in removing pollutants. However, due to low influent water quality during dry season, the removal efficiencies were low. The proportion of nitrate nitrogen to total nitrogen (T-N) of the inflow was high but, as the system operated under aerobic condition, nitrate nitrogen could not denitrified. Accordingly, total nitrogen was not attenuated with this system. To improve the reservoir water quality effectively, this system should be able to treat the storm runoff containing higher pollutant loadings. When the filter materials are clogged by the storm runoff instead of backwashing, it would be more efficient to replace them, Therefore, the use of natural materials which are light, easily obtaining and replaceable, and have high specific surface areas is recommended.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.285-292
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• 2001

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented for mixture of high strength concrete using crushed sands. Mixing design of concretes are various water-cement ratios(w/c) such as 25%, 40%, 55% and different replacement ratio of crushed sands to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strength of concretes with w/c lower than 40% and 25% is higher than $400kgf/cm^2$ and $600kgf/cm^2$ respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.2
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• pp.107-116
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• 2002

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented fur analysis on mechanical properties of high strength concrete using fly ash and crushed sand. The material functions in mixing design of concretes are various water-cement ratios(w/c) such as 0.25, 0.40, 0.55 and different replacement ratio of crushed sand to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strengths of concretes with W/C lower than 0.40 and 0.25 are higher than 400 kgf/$\textrm{cm}^2$ and 600 kgf/$\textrm{cm}^2$ respectively. It is also concluded that the results of rapid chloride permeability tests of concrete are evaluated to negligible. The conclusions of this study is that it is possible to use fly ash and crushed sand fur high strength concrete.

• The Journal of the Petrological Society of Korea
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• v.24 no.3
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• pp.253-272
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• 2015

The necessity of aggregate resources in Korea has been increased with a rapid economic growth since the 1990s. Construction activities have been increased drastically for last two decades. Such economic activities are much concentrated at big cities in Korea, and recently new neighbouring cities, such as multifunctional administrative city, enterprise city and innocity, are under construction at the surroundings of the cities. This new urbanization asked for an appropriate supply of raw construction materials such as cement, sands and gravels. The aim of this study is to understand and discuss the analysis and prospect of supply and demand of domestic sand and gravel. On the early years, 1990s, about 25% of the total consumption of these sands and gravels comes from riverine deposits; 20% to 25% from marine sands, 40% to 45% from forest rocks and the rest 5% to 15% from old fluvial deposits and crushed rocks. But nowaday the river aggregate, including both sands and gravels of a present river channel and those of the old fluviatile system are decreasing, while the crushed and forest aggregates and marine sand are now the main source of infrastructure resources. Thus it is increasingly necessary to investigate the forest and crushed aggregate resources potential in Korea where a current analysis indicate that the supply of riverine aggregates gradually decreases.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.322-325
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• 2003

Recently, as quality river aggregates like sands and gravels become scarce, use of crushed stones and sands, seashore sands, and seashore gravels is increasing abruptly. And, aggregates recycled from slags and waste concretes are used. However, since the converter slag easily expands and breaks due to free lime, differently from the blast-furnace slag, it is not suitable for use as concrete aggregates. Since the atomized steel slag aggregate has slippery surface and spherical shape, the mortar flowing characteristics improved as the atomized steel slag content increases, without regard to the aggregates coarseness and water/cement ratio. The flow characteristics loss rate of the mortar manufactured from steel slag aggregates was similar to that of the mortar manufactured from washed sand only. The compact strength of the mortar manufactured from coarse PS Ball were larger than that manufactured from washing sand only.

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.235-245
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• 1998

Adquate friction resistance is needed to prevent pavement slipperiness and to allow vehicles to stop in a reasonable distance. Performance of the aggregates is reduced over time by wear and polishing as a consequence of vehicular traffic. In this research, the objective was to develop a laboratory method to test Indiana gravel aggregates to predict field performance, and determine causes for the range of values amang gravel aggregates. The assessment of gravel sources was primarily on the basis of individual rock types and those proportions comprising the gravel. Polish and friction values were determined in the laboratory with the British Wheel and Pendulum. The gravels of this study were composed primarily of carbonate aggregates that showed considerable variability in polishing thresholds. Igneous and metamorphic constituents polished to a lesser degree and are expected to improve overall aggregate performance. Estimates of the IFV (Initial Friction Value) and PV (Polished Value) for crushed gravel samples can be made based on the percentage of rock types present in the sample. A weighted average is used to make this calculation.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.39-43
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• 2015

In this study, the infiltration quantity of fine-grained soil into coarse-grained soil or aggregate for methods to accelerate consolidation drainage is checked by laboratory tests under various conditions and those characteristics on infiltration are examined closely. Irrespectively of pressures to fine-grained soil corresponding to stresses in a soil mass or moisture contents of fine-grained soil, fine-grained soil does not infiltrate into standard sand and marine sand, so it is verified that drain-resistance into sand mass of drainage / pile does not occur entirely and its shear strength would increase highly by water compaction. It is known that the infiltration depth of fine-grained soil into aggregate increases according that those size is larger in case of aggregates and it increases according that the pressure or the moisture contents is higher in case of same size aggregate. It is thought that drain-resistance into aggregate mass of drainage / pile would occurs by infiltrated fine-grained soil in advance though the infiltration depth of fine-grained soi of lower moisture content than liquid limit into 13 mm aggregate is low quietly. So gravel drain method or gravel compaction pile method, etc. using aggregate of gravels or crushed stones, etc. larger than sand particle size should be not applied in very soft fine-grained soil mass of higher natural moisture contents than liquid limit, and it is thought that its applying is not nearly efficient also in soft fine-grained soil mass of lower natural moisture contents than liquid limit.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.81-91
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• 2005

'Coarse grained material' refers to crushed stones or gravels, and the behaviour of soil containing coarse grained material is not easily defined using the conventional soil mechanics theory due to the influences of large particles, therefore large scale test is essential to investigate their effects. Previous studies have identified the major factors affecting the properties of coarse grained materials by using large scale shear testing apparatus, such as maximum particle size, water content, density and uniformity coefficients. In this paper, the effect of variation of maximum particle size and water content on shear strength was analyzed from the results of large scale shear test. In addition, the fiction coefficient at critical state per vertical load was estimated using the equation proposed by Wood (1998). The sample for the test was obtained from the local quarry sites. Tests results show that the shear strength for 50.8 m maximum particle size is relatively larger than that of 76.3 m and air-dry sample has larger shear strength than saturated sample. In the meantime, the friction coefficient at critical state shows $1.0\sim1.6$ according to the test conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.339-347
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• 2008

The penetration of the probe produces the excess pore pressure due to the disturbance. The objective of this study is to evaluate the disturbance zone by using the dissipation of the excess pore water pressure, which was generated due to the penetration of the penetrometer with different size. The CPT, DMT and FVP (Field Velocity Probe) are adopted for in-situ tests. The tests are carried out in the construction site of north container pier of Busan new port, Korea where is accelerating the consolidation settlement using plastic board drains (PBD) and surcharges by crushed gravels. The coefficient of consolidation $(C_h)$ and soil properties are deduced by the laboratory test. The in-site tests are performed after the predrilling the surcharge zone at the point of 90% degree of consolidation. To minimize the penetration effect, the horizontal distance between penetration tests is 3m, the change of the pore pressure is monitored at the fixed depth of 24m. The coefficient of consolidation $(C_h)$ and the $t_{50}s$ are calculated based on the laboratory test and the in-situ data, respectively. The equvalent radi based on the $t_{50}$ shows that the FVP and the DMT produce the smallest and the greatest equivalent radi, respectively.