• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.481-484
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• 2003

This study is intended to investigate application of mica waste(MS) to fine aggregate for mortar by comparing it with cement mortar in which crushed sand(CS) and river sand(NS) are used. According to the results, as the physical properties of aggregate, specific gravity is large in order of MS, NS and CS, absorption ratio in order of MS, CS and NS, and unit weight and solid volume percentage in order of NS, CS and MS. In the case of MS mortar, mechanical properties, drying shrinkage and heat conduction ratio are reduced, but the radiative amount of infrared light is excellent compared with NS mortar. Fluidity and unit weight of MS mortar is larger than those of CS mortar, and strength does not make differences. Length change by drying shrinkage is larger, but heat conduction ratio and radiative amount of infrared light are smaller than CS mortar. Thus, it proves that MS can be used in place of NS and CS, but its quality is deteriorated slightly.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.533-536
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• 2003

The objective of in this study makes investigation into the characteristics of antiwashout underwater concrete as to mix proportion, casting and curing water through experimental researches. in this study, sea sand is blended with river sand, crushed sand is blended with river sand and sea sand as to investigate the quality change and characteristics of antiwashout underwater concrete with variation of blend ratio of sea sand and crushed sand(0, 20, 40, 60, 80, 100%). Higher compressive strength is measured following the order of river sand, sea sand, crushed sand regardless of age and casting condition. Except for case of using river sand, blended ratio of 40% is appeared on most compressive strength.

• 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.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.161-175
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• 2024

Aggregate typically refers to sand and gravel formed by the transportation of rocks in rivers or artificially crushed, constituting a core resource in the construction industry. Gyeongsangbuk-do, the largest administrative area in South Korea, produces various sources of gravel, including forest, land (excluding other sources), river, and crushed stone. As of 2022, it has extracted approximately 6.96 million cubic meters of aggregate, with permitted production totaling around 4.07 million cubic meters and reported production of about 2.88 million cubic meters. The aggregate demand in Gyeongsangbuk-do is estimated to be 12.39 million cubic meters according to the estimation method in Ready-Mix Concrete. From the supply perspective, about 120 extraction sites are operational, with most municipalities maintaining an appropriate balance between aggregate demand and supply. However, in some areas, there is inbound and outbound transportation of aggregate to neighboring regions. Regions with significant inbound and outbound aggregate transportation in Gyeongsangbuk-do are areas connected to Daegu Metropolitan City and Pohang City along the Gyeongbu rail line, showing a high correlation with population distribution. Gyeongsangbuk-do faces challenges such as population decline, aging rural areas, and insufficient balanced regional development. Analysis using GIS reveals these trends in gravel demand and supply. Currently in this study, Gyeongsangbuk-do meets its demand for aggregate through the supply of various aggregate sources, maintaining stable aggregate procurement. River and terrestrial aggregates may be sustained as short-term supply strategies due to the difficulty of longterm development. Considering the reliance on raw material supply for selective crushing, it suggests the need for raw material management to maintain stability. Gyeongsangbuk-do highlights quarries in the forest as an important resource for sustainable aggregate supply, advocating for the development of large-scale aggregate quarries as a long-term alternative. These research findings are expected to provide valuable insights for formulating strategies for sustainable management and stable utilization of aggregate resources.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.755-769
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• 2020

In 2019, about 134 million ㎥ of aggregate was produced in an estimated 880 quarries and pits in 17 metropolitan governments. Leading producing metropolitan cities were Gyeonggi-do, Gyeongsangnam-do, Chungcheongbuk-do, Gangwon-do, Gyeongsangbuk- do, Chungcheongnam-do, in order decreasing volume, which together accounted for about 71% of total product. Of the total domestic aggregates produced in 2019, about 31 % was sand and about 69% was gravel. It estimated that of the 134 million ㎥ of aggregates in Korea in 2019, about 50.3% was produced by screening crushed aggregate by 41.4% by forest aggregate, 3.3% by land aggregate, 1.7% by sea aggregate and 1.7% by washing each other, and 0.7% by river aggregate. This indicates that screening crushed aggregate and forest aggregate are the main producers of domestic aggregates. The most crushed and forest aggregate was extracted at the Gyeonggi-do and Gyeongsangnam-do, respectively. Land aggregate was mainly extracted at Gyeongsangbuk-do and Gangwon-do. Therefore, in the future supply and demand of aggregate resources, it is judged that there should be a primary policy direction for screening crushed and forest aggregate.

• Economic and Environmental Geology
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• v.54 no.4
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• pp.427-439
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• 2021

On the base of the aggregate extraction statistics, this study tried to analyse the demand and supply of aggregate resources of each local government and provide directions for the stable and sustainable supply and demand of aggregate resources in the future. In 2019, aggregates were produced in 148 cities, about 65% of the 229 cities of Korea, but in 7 metropolitan cities with 74 local governments, only 19 cities developed the aggregate. It means that aggregate extraction is taking place in almost all regions in Korea. Sand and gravel were produced in 110 districts and 132 districts, respectively. By aggregate source, river aggregates were extracted in 4 local governments, land aggregates in 42 local governments, forest aggregates in 75 local governments, crushed aggregates in 105 local governments, and washing aggregates in 15 local governments. In other words, 81 district in Korea have not extracted land-based aggregate at all. 71 local governments produced only one type of aggregate, and 55 local governments developed two types of aggregate, and 22 local governments developed more that three types of aggregate. In 2019, the leading producing local government were, in descending order of volume, Ulju-gun, followed by Hwaseong-si, Cheongju-si, Pocheon-si, Paju-si, Yongin-si, Gimhae-si, Gwangju-si in Gyeonggi-do. 41 local governments have developed aggregates of more than 1 million m³, and the combined production of the 41 cities accounted for about 70% of national total. This shows that the aggregate extraction trend of local governments is becoming larger and more concentrated.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.495-503
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• 2021

Aggregate is a major natural resource used in SOC construction, such as housing, roads, ports, etc., and is a fundamental material for national construction. Although aggregates account for only about 4% of the construction cost, aggregates occupy about 80% of the construction volume and are essential factors that determine the quantity and quality of buildings. For river, underwater, riverbed, sea, and land aggregates, it is difficult to rapidly increase the production of aggregates when there is difficulty in supply and demand due to environmental problems and limited resources during production, whereas forest aggregates are relatively easy to increase production. Forest aggregates are considered promising as alternative aggregate resources in the future when reducing other aggregates due to their abundance of natural resources, and are an effective aggregate source that can flexibly respond to aggregate demand in accordance with well-organized plans and policies. This study proposed the plan for activating the development of forest aggregates in the case of long and short transport distances, which is a factor that has a great influence on the development, and measures for the current difficulties in forest aggregate development

• Magazine of the Korean Society of Agricultural Engineers
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• v.13 no.3
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• pp.2342-2348
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• 1971

In concrete, the mater over aggregate is ever demanding each year in paralled with rapid development of Construction works from a couple of years ago. Want of most of them which is river gravel among aggregate has made us uneasy to get good gravel in quality. So far, we have counted on gravel, however, the time to turn the use of normal concrete into that of crushed concrete is closing at hand, I think. According to the results of study by Kaplan, Zeitman, Murdock, Hanada, Yamamodo, the shape of aggregate particle have a great effect on workability of concrete, as we know, is well known to the world. Crushed stone, particularly, is inconvenient to handle on account of jagged, angled particle form and rugged surface structure, give rise to inpediments in works, its unit water stands at about $15-20kg/m^3$, and w/c shows the increasing rate of approximately 5-10%, but it is unsuitable to use in terms of regidity. In order to research all of these, I have experimentalized and reviewed the physical character of aggregate and the regidity of concrete, in addition, its relative ratio of the elastic disposition as to gravel and crushed stone.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.45-52
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• 1999

It is difficult to keep the balance of supply and demand for natural aggregates in recent years, because natural resources have become to be almost exhausted. Crushed stone is already used for coarse aggregate instead of river gravel at present. Now, crushed sand or sea sand should be used for fine aggregate, because natural sand also has been exhausted with a few exceptions around Nakdong River. The sea sand has a lot of problems which are the corrosion of reinforcement bars, the investment of facility for cleansing salt and the cost increase due to the insufficiency of industrial water. Therefore, it is necessary to produce and to utilize the crushed sand very actively, but some material properties which are related to water absorption, strength and chemical durability, prevent from determining the generalized criteria because its rocks make much differences in its physical and chemical characteristics. In this paper, fundamental physical properties of crushed sand, which comes from Daegu Subway construction fields, have been investigated for the usability on basic material of concrete. The optimum replacement ratio and the strength estimation method of crushed sand replacing natural sand also have been presented here through the compressive strength test of ready-mixed concrete cylinders.

• Computers and Concrete
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• v.21 no.6
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• pp.697-703
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• 2018

Compressive strength is one of the most important engineering properties of concrete, and testing of the compressive strength of concrete specimens is often costly and time consuming. In order to provide the time for concrete form removal, re-shoring to slab, project scheduling and quality control, it is necessary to predict the concrete strength based upon the early strength data. However, concrete compressive strength is affected by many factors, such as quality of raw materials, water cement ratio, ratio of fine aggregate to coarse aggregate, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete. The concrete compressive strength is a quite nonlinear function that changes depend on the materials used in the concrete and the time. This paper presents an adaptive neuro-fuzzy inference system (ANFIS) for the prediction of concrete compressive strength. The training of fuzzy system was performed by a hybrid method of gradient descent method and least squares algorithm, and the subtractive clustering algorithm (SCA) was utilized for optimizing the number of fuzzy rules. Experimental data on concrete compressive strength in the literature were used to validate and evaluate the performance of the proposed ANFIS model. Further, predictions from three models (the back propagation neural network model, the statistics model, and the ANFIS model) were compared with the experimental data. The results show that the proposed ANFIS model is a feasible, efficient, and accurate tool for predicting the concrete compressive strength.