• Economic and Environmental Geology
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• v.57 no.2
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• pp.177-184
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• 2024

This study was conducted to find a way to reduce the production of cakes generated in the domestic aggregate production process. Cakes from 8 wet aggregate producers were collected and particle size was analyzed. Samples were collected step by step from an aggregate producer A, particle size analysis was performed, and the material balance was calculated before and after an sand recovery unit by modeling the production process. As a result of the particle size analysis of eight cakes, one sample contained 50% sand, and the rest contained about 5% to 25% sand. The results showing that the cake contained a variety of sand in cakes may indicate that the recovery efficiency of the sand recovery units in the field varied. Sieve analysis of the samples showed that the generation of sand particles increased 2.8 times during the third crushing compared to the second crushing, and more cake particles were generated. As a result of simulating the sand recovery unit model, the lower the cut point of the cyclone and dewatering screen, the higher the sand production and the less cake production appeared. In order to reduce the production of cake in the field, it was determined that an optimal operation of the sand recovery unit was necessary in the aggregate production process.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.3
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• pp.159-168
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• 2015

Aggregate Production Planning determines levels of production, human resources, inventory to maximize company's profits and fulfill customer's demands based on demand forecasts. Since performance of aggregate production planning heavily depends on accuracy of given forecasting demands, choosing an accurate forecasting method should be antecedent for achieving a good aggregate production planning. Generally, typical forecasting error metrics such as MSE (Mean Squared Error), MAD (Mean Absolute Deviation), MAPE (Mean Absolute Percentage Error), and CFE (Cumulated Forecast Error) are utilized to choose a proper forecasting method for an aggregate production planning. However, these metrics are designed only to measure a difference between real and forecast demands and they are not able to consider any results such as increasing cost or decreasing profit caused by forecasting error. Consequently, the traditional metrics fail to give enough explanation to select a good forecasting method in aggregate production planning. To overcome this limitation of typical metrics for forecasting method this study suggests a new metric, WACFE (Weighted Absolute and Cumulative Forecast Error), to evaluate forecasting methods. Basically, the WACFE is designed to consider not only forecasting errors but also costs which the errors might cause in for Aggregate Production Planning. The WACFE is a product sum of cumulative forecasting error and weight factors for backorder and inventory costs. We demonstrate the effectiveness of the proposed metric by conducting intensive experiments with demand data sets from M3-competition. Finally, we showed that the WACFE provides a higher correlation with the total cost than other metrics and, consequently, is a better performance in selection of forecasting methods for aggregate production planning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.435-443
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• 2004

Although RSVP is a strong signaling protocol in providing QoS support, it is not scalable. Thus, the IETF introduced the concept of aggregation into RSVP However, the specification for the aggregation of RSVP does not specify how to compute the size of aggregate reservation for a path, but only describes how the resources are reserved and released with a given size. This paper proposes the method of properly determining the size of aggregate reservation on the path condition, when aggregate reservation is performed through RSVP for guaranteeing QoS of multimedia traffic. Simulation results show that the proposed method improves efficiency of the aggregation of RSVP.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.25-30
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• 2003

Owing to the deterioration of reconstruction and the construction, much of the construction waste is discharged in our construction field. By supplementing aggregate resources that are insufficient by recycling waste concrete, it is considered that the resource-preserving effect according to the saving and reuse of resource as well as eco-friendly effect that is regarded as important in recent industrial society may be expected. In this study conducted an experiment by setting up 15 levels according to the variations in the rate of substitution of recycled coarse aggregate by the water cement ratio(40, 50, 60%). As the result of it, the slump and air contents was increased by ratio of coarse aggregate, and the elapsed characteristics by the ratio of recycled coarse aggregate showed that there is no clear difference in slump and the air contents. Further, in the characteristics of strength development, the lower the water cement ratio, the higher the compressive strength at early ages, compared with crushed stone, while the compression declined according to the increase of substitution rate of recycled gravel as it was tending upward long-term ages.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.871-885
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• 2023

In 2022, the total of 129 million m³ of aggregate was produced in Korea, a slightly decrease from the total production of 2021. Of these, about 44 million m³ of sand and about 84 million m³ of gravel were produced. About 41% of total quantity of aggregates were produced by permission and the rest were produced after declaration. It estimated that of the 129 million m³ of aggregates in Korea in 2022, about 54.9% was produced by screening crushed aggregate, by 32.8% by forest aggregate, 2.2% by land aggregate, 6.2% by marine aggregate and 3.1% by washing aggregate, and 0.3% by river aggregate. This indicates that screening crushed and forest aggregate are the main producers of domestic aggregate in 2022. Leading producing metropolitan governments were Gyeonggi-do, Gyeongsangnam-do, Chungcheongnam-do, Incheon, Jeollanam-do, Chungcheongbuk-do, Gangwon-do, Gyeongsangbuk-do in order decreasing volume. In 2022, aggregates were produced in 147 local governments, and the 10 leading producing local governments were, in descending order of volume, Hwaseong, Pocheon, Paju, Ongjin, Youngin, Gwangju, west EEZ, Incheon Seo-gu, Namyangju, Asan. The combined production of the 10 leading local governments accounted for 31% of the national total. And 44 local governments have produced aggregates of more than 1 million m³ each other. In 148 local governments that produced aggregate, a total of 800 active operations produced aggregate with 350 operations by river, land and forest aggregate, 450 operations by selective crushed and washing aggregate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.265-271
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• 2014

It is strongly needed to investigate the fine sand as an alternative fine aggregate of well-graded river sand because the fine sand which is being enormously distributed in the midstream and downstream of Nakdong-River in Korea has a poor grading but good quality as a fine aggregate for concrete. Thus, the purpose of this experimental research is to evaluate the durability of concrete using the fine sand to utilize it actively as a fine aggregate. For this purpose, the concrete specimens using different fine sand were made for the specified concrete strength of 35MPa, and then their durability such as the resistance to freezing and thawing and carbonation, and drying shrinkage were evaluated. It was observed from the test results that the resistance to freezing and thawing and carbonation of concrete using the fine sand was similar to that of concrete using reference sand, but the drying shrinkage of concrete using the fine sand with small fineness was comparatively lager than that of concrete using reference sand.

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.2
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• pp.27-35
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• 2012

Concrete produced from the construction wastes has been largely used as the recycled aggregate. These wastes, however, is mostly used as filling materials. For any recycled aggregate like waste concrete to be used as normal construction materials, it is necessary to actively find out the proper market places as much as possible with the improved quality. In this study, we have investigated the present status on the occurrence and treatment of both domestic and abroad construction wastes, and also the recycling status and related legislation with some inhibitory factors. Based on these investigations, we suggested some effective ways to increase the recycling of construction wastes.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.118-124
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• 2016

The purpose of this study is to analyze the rheology characteristics of insulating concrete for each type of insulation performance improvement material and utilize the result as preliminary data for optimal flow designing and pumping analysis. As a result, when lightweight aggregate was mixed, the yield stress decreased significantly, and in case of type 2, the combination of micro form cell admixture (MFA) and calcined diatomite powder (DM) showed the most ideal flow characteristics. In case of type 3, the combination of micro form cell admixture (MFA), calcined diatomite powder (DM) and lightweight aggregate (L) showed the best flow characteristics.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.1-8
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• 2022

In this study, the mechanical properties of concrete with recycled coarse aggregate (RG) selected by multi-stage wind pressure (MSWP) treatment were evaluated. After evaluating the basic properties of natural and recycled coarse aggregates, the mechanical performance of the recycled coarse aggregates concrete was experimentally investigated. As a result, it was found that the MSWP technique could improve the fundamental properties such as density and water absorption of RG. In addition, the concrete with RG selected by MSWP showed a better mechanical performance, indicating a higher strength values, surface electric resistivity and a lower absorption. Thus, it seems that the MSWP technique can be effective for the production of high-quality RG.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.605-613
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• 2021

When crushing rocks to produce aggregates, solid stone dust or sludge is generated as a by-product. These by-products are classified as waste and are not utilized, and most of them are disposed of landfills. This by-product differs in mineral composition, chemical composition, and physical properties depending on the rock type and aggregate production process. Therefore, if a technology that can make good use of the inherent physical or chemical properties of by-products is developed, economic and environmental benefits can be achieved instead of disposal. In this study, stone dust and sludge were collected from domestic aggregate producers and physical and chemical properties were investigated by performing XRD mineral analysis, particle size analysis, and chemical analysis. In addition, the research trend was identified through a domestic and international research case studies on the use of stone powder and sludge.