• Journal of Korean Society of Industrial and Systems Engineering
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• v.4 no.5
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• pp.1-10
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• 1981

The purpose of this study is to cut down cost of production and improve the productivity of industry through quality improvement of castings and reduction of defectives by applying the experimental design to the foundry sand mixing operation done at molding department in the foundry. Among the related foundry sand mixing factors which have an effect on casting the experiment of which factors have a dominant effect on quality improvement was performed between two different levels by means of "$2^n$ type orthogonal array." The results cail be summarized as follows ; (1) The optimum conditions per each foundry sand mixing between two different levels proved to be such as $A_2$(used sand) : 24 unit (172.8kg), $B_2$(unused sand ) : 2 unit (15.0kg), $C_2$(binder) : 2.5 unit (4.4kg). $D_2$(addition agent) : 1 unit(1.4kg) and $F_1$(moisture) : 7.4%(14.6kg). (2) As a result of the application of experimental design, the fraction defective during the foundry sand mixing operation turned out to be reduced front 6.6% to 2.04%. (3) For the purpose of cost-down, It was found that the optimum level decision of foundry sand mixing for various castings is required to be made by means of experimental design.al design.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.15-20
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• 2004

To the development on reusing method of the heat-source waste at Daegu Bisan dyeing-complex, this study is aimed to application of it's crushing material (hereafter waste sand) as concrete fine aggregate. The results are as follows; 1. Flow and unit weight of mortar using waste sand as concrete fine aggregate are decreased. 2. At the results of compressive strength test and bending strength test, mortar using waste sand superior to plain mortar within 80％ substitute ratio of waste sand. Because increasing rate of compressive strength is similar through increasing age, waste sand performs as filler's function of no-effect with cement only. 3. At the results of concrete application test, unit weight of concrete using waste sand is similar to plain concrete and compressive strength of concrete is superior to plain likewise the results of mortar test

• 한국해양학회지
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• v.29 no.3
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• pp.278-286
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• 1994

Tidal sand ridges, which develop in Kyeonggi Bay generally parallel to the direction of tidal current on the sea bottom are also well shown in seismic profiles, surface and core samples were obtained from sand ridge field near the Palmi Do for the study of origin and sedimentary environments of these sand ridges. Sand ridge field near Palmi Do can be divided into 3 seismic units(unit A, B, C), and each unit has one sand ridge(ridge A, B, C), Ridge A that shows clinoform prograding southeastwards is generally parallel with tidal current trending northeast to southwest(40$^{\circ}$). It means that sand ridge is migrating to southward. Unit B includes a sand ridge and a channel fill structure in seismic profiles. Compared with ridge A, ridge B has similar direction, magnitude and internal reflectors. So ridge B developed in the similar sedimentary environments to ridge A about 10 m lower than present sea level. As the rise of sea level, channel fill structure formed as the deposit of fine sediments with the shape of conformable bedding or horizontal bedding.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1481-1488
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• 2013

The purpose of this experimental research is to suggest a base data to utilize the fine sand of Nakdong-River actively as an alternative aggregate for concrete. For this purpose, after the typical fine sand samples were collected at the mid stream and down stream of main stream of Nakdong-River, the physical properties of them and the mix characteristics of concrete using those were estimated. As a result, it was observed from the test result that mix characteristics between concrete using fine sand and concrete using well-graded reference sand made little differences since unit water content and unit cement content of concrete using fine sand increased only a little than those of concrete using reference sand for specified compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.157-160
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• 2006

Recently, trouble of sand supply is occurred according to exhaustion of natural sand resources. To solve this problem, sea sand and crushed sand are used. But, necessity of water reducing agent because quality of concrete that use sea sand and crushed sand is deteriorated. Therefore in this study was examined on the engineering properties of concrete with kind of fine aggregate and addition ratio of water reducing agents. As a result, compressive strength appeared similar standard regardless of kind of fine aggregate. Compressive strength, durability was similar in decrease of the unit water content by increase of addition ratio of the water reducing agent. Also, drying shrinkage resistivity was improved because the unit water content decreased.

• The Korean Journal of Quaternary Research
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• v.13 no.1
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• pp.79-89
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• 1999

Three deep borings to obtain vertical continuous samples including weathered basement soils (KP-1, KP-2 and KP-3) were carried out in the reclaimed Kimpo tidal flat with purposes to establish late Quaternary stratigraphy. On the basis of detailed observations and descriptions on color, sedimentary structure and textural composition of cored sediments, four lithostratigraphic units are classified. From the stratigraphic top to bottom, they are Holocene tidal sand and muddy deposit (Unit I), early Holocene freshwater marsh muddy deposit (Unit II), late Pleistocene tidal sand and muddy deposit (Unit III) and late Pleistocene basal fluvial gravel deposit (Unit IV). In particular, Unit III is divided into two parts: the upper part-weathered and cryoturbated part during the Last Glacial Maximum (Unit III-a) and the lower part-unweathered tidal sand and muddy deposit (Unit III-b).

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.21-29
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• 1999

In this study, an experiment was performed to analyze the influence of water-cement ratio on the fundamental characteristics of antiwashout underwater concrete using blended sand (sea sand:river sand = 1:1). The water-cement ratio (45%, 50%, 55%, 60%), andtiwashout underwater agent contents (0.82%, 1.00%, 1.14% of water contents per unit volume of concrete), and superplasticizer contents (1.5%, 2.0%, 2.5% of cement contents per unit volume of concrete) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance, unit weight of hardening concrete and compressive strength were increased as the water-cement ratio decreased and as the antiwashout underwater agent contents increased. On the other hand, the flowability(slump flow) was increased to the 55% of the increase of water-cement ratio, however, it was decreased at the ratio of 60%. From this study, the antiwashout underwater concrete can potentially be used as a materials underwater work of ocean if the water-cement ratio and chemical admixture contents for the suitable balance between cost and performance are properly selected.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.113-117
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• 2000

The objective of this study is to find the long-age strength property and the compressive strength of age which is used as the specified concrete strength. The W/W ratio (45%, 50%, 55%, 60%) fine aggregate of useful river sand or blended sand(river sane : sea sand=1:1) were chosen as the experimental parameters. the experimental results show that pH(it means the material segregation resistance) & suspension were increased larger, so W/C become larger, and slump flow was increased as W/C increased (except W/C=60%), air-contents were decreased as W/C became increase and all of this results are satisfied with the under of 40%. The compressive strength ( a case use only river sand as fine aggregate) is showed less than the case of blended asnd. Because the unit weight of the blended sand is more heavy than the unit weigh of the river sand. The results of the case which haven been used only river sand, and the case have been used blended sand), both case have considered W/C. So it's possible to use the compressive strength of age 28 day like the case of plain concrete.

• KIEAE Journal
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• v.13 no.6
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• pp.137-143
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• 2013

The purpose of this study is to suggest optimum micro-filler experiment method to select the optimal particle size of earth for using in earth construction works and test this suggestion through compressive strength measurement. According to the results of selecting the method to choose the optimum micro-filler mixing of earth and sand, three-stage filling(plate tamping) showed relatively high results and so was estimated to be the proper filling method. According to the results of optimum micro-filler experiment of earth and sand by the maximal sizes of sand, between 80% and 90% showed the highest result values. The larger the maximum size of sand was, the lower the addition ratio of sand was in optimum micro-filler mixing. According to the results of compressive strength experiment by the particle sizes of earth and sand, 90% in the addition ratio of sand showed the highest results, and so tended to be similar to the results of unit volume weight experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.427-432
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• 2001

In this study, crushed sand is blended with river sand and sea sand, to investigate the quality change of antiwashout underwater concrete with variation of blend ratio of crushed sand(0%, 20%, 40%, 60%, 80%, 100%). To see experiment conclusion, the more blend ratio of crushed sand increases, the more unit weight increases. Because the for that specific gravity of crushed sand is higher comparatively than that of river sand and sea sand. Higher compressive strength is measured following the order of river sand, crushed sand, sea sand regardless of age and casting-curing condition. Except for case of using river sand, blend ratio of 40% is appeared on most compressive strength. So the optimum blend ratio of crushed sand is 40% from the view point of compressive strength.