• Resources Recycling
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• v.5 no.1
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• pp.9-13
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• 1996

Once-used $CO_2$-silicate bonded sand from domestic foundry is mostly discarded in a reclaimed land because of its bad collapsibility and reproduction properties. So this causes serious environmental problem. We can get 82% recovery of silica from used sand by scrubbing reclamation process in this research. When we repeat the reclamation-recycling of the foundry sand, artificial silica sand is broken down below 2-cycles, but natural silica sand does not destroyed when used repeatedly more than 10-cycles and have a good property of recycling with little change of its size.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.451-454
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• 2005

Recently, Trouble of sand supply is occurred according to exhaustion of natural sand resources. therefore, various measures are proposed for solution of trouble of sand supply and crushed sand among measures is used as one of most universal measures. but because crushed sand have poor particle shape and plenty of makes micro particle, the quality of concrete using crushed sand deteriorated. Therefore, this study evaluated engineering property of concrete with replacement ratio of crushed sand and applied evaluation result to fundamental data for quality control of concrete using crushed sand. The result of this study have shown that quality of concrete using crushed sand independently is poor against general concrete. but, the concrete mixing crushed sand with general sand can be similar in workability of concrete used general sand and increase compressive strength of concrete as against concrete using general sand.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.65-72
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• 2001

Portland cement concrete is made with coarse aggregate, fine aggregate, portland cement, water and, in some cases, selected chemical admixture such as air-entraining agents, water reducer, superplasticizer, and so on, and mineral admixture such as fly ash, silica fume, slags, etc. Typically, in the concrete, the coarse aggregate and fine aggregate will occupy approximately 80 percent of the total volume of the finished mixture. Therefore, the coarse and fine aggregates affect to the properties of the portland cement concrete. As the deposits of natural sands have slowly been depleted, it has become necessary and economical to produce crushed sand(manufactured fine aggregate). It is reported that crushed sand differs from natural sands in gradation, particle shape and texture, and that the content of micro fines in the crushed sand affect to the quality of the portland cement concrete. Therefore, the purpose of this paper is to investigate the characteristics of fresh and hardened concrete with higher micro fines. This study provides a firm data to apply crushed sand with higher micro fines.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.383-388
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• 2000

In these days, there are out of natural sands in the construction field. It is required that development of substitute material for natural material. The blast-furnace slag could be a good alternative material in this situation. It can help resource recycling and the protection of environment. This study presents that the strength properties of mortar using air-cooled blast-furnace slag sand and water-cooled blast-furnace slag sand. The mixing design of this study have a few factors, three type of unit water, four types of W/C, five types of substitution rate. When air-cooled furnace slag sand used in mortar, as substitution rate is higher, 3, 7-days compression strength and flexural strength are going up. But, in case of water-cooled furnace slag sand mortar, strengths are going down.

• Journal of The Geomorphological Association of Korea
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• v.26 no.3
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• pp.31-42
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• 2019

The geomorphological changes of an unvegetated part of the Okjukdong coastal dune were analyzed between 2008 and 2018. Its natural landscape has been destroyed after artificial forestation, but there is no quantitative evidence on these changes. In this study, we measured the unvegetated area using a total station and a network RTK-GPS in 2008, 2014, and 2018. Using Krging method for the three point data sets, we constructed digital elevation models (DEMs) and analyzed topographic changes between the three years. The results showed that the sand of the study area decreased in volume from 2008 to 2014, because sand supply from the nearby beach was blocked by coastal forests. The sand volume temporarily increased from 2014 to 2018, because of the dune nourishment conducted in 2017. It seems that the upper part of the sand dune has shrunk, but the sand at the bottom has increased over the last decade.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.75-81
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• 2012

In case of crushing rock to produce materials for lean concrete subbase layer in concrete pavement, natural sand is used for the gradation adjustment of aggregates, and the percentage of natural sand used is 30%~40% of the weight ratio of aggregate mix. The supply of natural sand that is used in lean concrete as a fine aggregate is getting harder due to the current of exhaustion of source, and the cost for the purchase of natural sand is included in the cost of roadway construction. This study, therefore, was conducted in order to resolve the exhaustion of materials and economize in construction expenditure by the application of screenings, which is by-product of crushing rock in quarry, as an alternative to natural sand. As a result of a comparative analysis on the application of screenings and natural sand with typical types of rock that is produced in domestic, which was conducted in the first year, It is found out that the use of screenings as a fine aggregate showed better unconfined compression strength. Verification of actual application of screenings was conducted in the second year, after test construction and follow-up investigation. The compressive strength, compaction density, settlement of screenings applied case was higher than that of natural sand. Thus, it is expected that application of screenings to construction in field will contribute to the cost saving, material recycling and the protection of environment.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.185-204
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• 2024

This study was conducted for evaluation the geological, physical, and chemical properties of domestic sand by analyzing about 4,800 quality data of natural sand from river and land area surveyed until 2023 through the aggregate resource survey conducted by the Ministry of Land, Infrastructure and Transport. The average depth of the Quaternary unconsolidated sedimentary layer in Korea, which includes a sand layer, is about 10m (maximum depth 66m). The thickness of the sand layer within the sedimentary layer is most dominant in the range of 0.5m to 4.0m. This accounts for about 70% of the entire sand layer. In the sand layer, the ratio of sand, gravel, and clay is 60:20:10. Regardless of the provenance or geology, the sand is mainly composed of quartz, plagioclase, and K-feldspar, and the minor minerals are muscovite, biotite, chlorite, magnetite, epidote. The sand includes in 45~75% of quartz, 5~20% of plagioclase and K-feldspar, each other. And other minor minerals are included in 10%. The average grain size of sand is 0.5mm to 1.0mm, which accounts for 44% of sand samples. The water absorption rate and soundness are estimated to be suitable for aggregate quality standard in almost all sand, and the absolute dry density is suitable for 66%.

• Journal of Environmental Science International
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• v.12 no.2
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• pp.151-155
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• 2003

The resources conservation system is comprehended, making Taean-haean National Park a research material by applying the fact of landowning, designating an LOP and Korea and Japan's Natural Park Act. Following conclusions were obtained in this study; Most of land areas of the National Park are privately owned; Only a few have been designated as Natural Reservation, a core reserved area on LOP, and a sandy beach, a sand dune, a sand spit, a tidal flat, a wetland, etc are distributed in the natural environment area so they were exposed to development; As seen in most of coastal type of National Parks, 13 commercial beaches are established. The annual rush to the beaches appears in July and August; Sand dune areas that have to be managed in terms of conservation, are turned into beaches. Moreover, the collective facilities areas are randomly developed. So they fail to function originally; The current Natural Park Act has no systematic devices for conservation of the natural resources on the seashore or offshore.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2004.05a
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• pp.51-55
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• 2004

Generally, aggregate may limit the strength of concrete, and aggregate with undesirable properties including strength, shape and grading etc. cannot produce good concrete. Also, the properties of aggregate greatly affect the durability and structural performance of concrete. Recently, it has increased the using of crushed aggregate for concrete due to the exhaustion of good natural aggregate. In case of Korea, the using ratio of crushed stone occupies about 97％ of whole coarse aggregate, and ratio of crushed sand occupies about 18.3％ of whole fine aggregate. This is an experimental study to compare and analyze the properties of crushed sand for concrete in capital region and concrete according to the replacement ratio of crushed sand to do suitable mix design and improve the concrete quality. According to results, it was found that nearly all the properties of crushed sand satisfied with the value recommended by KS.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.53-62
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• 2004

The Purpose of this study is to recycle the waste concrete, which is generated in huge quantities, from construction works. in order to achieve this goal, it is important to determine the compressive strength, workability, slump, and ultrasonic velocity of recycled aggregate concrete. Thus, several experiment parameters are considered, such as water-cement ratios, sand percentage, and fine aggregate composition ratios, in order to apply the recycled aggregate concrete to pre-cast artificial fishing reefs. From the results, it has been shown that the proper mix designs for reef concrete are W/C=45%, S/a=50%, SR50:SN50 in recycled sand and natural sand mix combination case, W/C=45%, S/a=50%, SC50:SN50 in crushed sand and natural sand mix combination case, W/C=45%, S/a=50%, SR50:SC50 in recycled sand and crushd sand mix combination case. Also, this study shows that the shape and surface roughness of fine aggregate particles have an effect on the strength, slump, ultrasonic velocity of tested concrete, and the compressive strength ratios of 7days' and 90days' curing ages of recycled aggregate concrete are about 70% and 110% of 28days' curing age.