• 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.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.169-175
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• 2011

Strength is one of the very important factors to evaluate the physical properties of concrete. Aggregate forms the most parts in concrete. Cement as a binder in concrete is also closely related to strength. This experiment was tested to understand the effect of the characteristics of aggregate and cement on the relationship between concrete compressive strength and Shear Wave velocity. It was experimented by the different types of cement and maximum coarse aggregate sizes. Type I cement and rapid setting cement was used. Aggregates from three different regions were used. Aggregate of 19mm and 13mm maximum coarse aggregate sizes was used for grading. The relationship between compressive strength and Shear Wave velocity was tested under the condition of same mixture. LA wear test was used to quantify the characteristics of aggregate. As a result, the relationship between concrete compressive strength and Shear Wave velocity was affected by the types of cement, but regular relationship was appeared regardless of types of aggregate, grading and abrasion ratio.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.498-505
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• 2020

Aggregate occupies about 70-85% of the concrete volume and is an important factor in reducing the drying shrinkage of concrete. However, when constructing high-rise buildings, it acts as a problem due to the high load of natural aggregates. If the load becomes large during the construction of a high-rise building, creep may occur and the ground may be eroded. Material costs increase and there are financial problems. In order to reduce the load on concrete, we are working to reduce the weight of aggregates. However, artificial lightweight aggregates affect the interface between the aggregate and the paste due to its higher absorption rate and lower adhesion strength than natural aggregates, affecting the overall strength of concrete. Therefore, in this study, in order to grasp the interface between natural aggregate and lightweight aggregate by type, we adopted a method of measuring electrical resistance using an EIS measuring device, which is a non-destructive test, and lightweight bone. The change in the state of the interface was tested on the outside of the material through a blast furnace slag coating. As a result of the experiment, it was confirmed that the electric resistance was about 90% lower than that in the air-dried state through the electrolyte immersion, and the electric resistance differs depending on the type of aggregate and the presence or absence of coating. As a result of the experiment, the difference in compressive strength depending on the type of aggregate and the presence or absence of coating was shown, and the difference in impedance value and phase angle for each type of lightweight aggregate was shown.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.113-119
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• 2006

It is now established that more than two types of blended aggregate have beneficial effects on quality and supply of concrete in the long run. However, studies on blended aggregate have not widely been progressive and the evaluation method of its most favorable mixture proportion is still needed. Therefore this study investigated the most favorable mixture proportion through the physical experiment of fresh and hardened state's cement mortar, in response to three types of composite ratio, natural fine aggregate(Ns), crushed fine aggregate(Cs) and recycled fine aggregate(Rs). Test showed that increase of blending ratio of Ns and Cs improved fluidity of mot1ar. For the properties of compressive and flexural strength, mortar blending Ns and Cs properly, exhibited similar value to one using only Cs, while mortar mixing Rs showed lower strength value as less as 6% of control one. Mortar using only Rs exhibited the largest drying shrinkage value. In addition, even thought it is not a clear quantitative analysis, technical-imaging-skill presenting the most favorable mixture proportion 3-dimensionally is proposed in this research, in order to notify the proportion easily.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.05a
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• pp.19-24
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• 1997

콘크리트 구조물이 고온에 가열되면 그 성질이 변화하여 구조물은 다양한 영향을 받는다. 콘크리트 구조물의 고온에서의 성상은 시멘트의 종류, 골재의 성질, 배합비, 함수율, 재령 등에 의해 다르다. 콘크리트의 열성질에 관한 외국에서의 연구는 다수 보고되었으나 국내에서 연구한 결과는 없으며 특히 시멘트의 종류, 골재의 성질 등에 따라 고온에서의 성상이 다르기 때문에 본 연구에서는 국내에서 생산되는 시멘트, 골재를 대상으로 하였다. 또한 콘크리트 배합을 일반 구조물 및 아파트 현장에서 사용하는 배합비로 시험체를 제작ㆍ실험하였다. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.4
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• pp.485-492
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• 2019

In this study, the effect of moisture conditions of recycled coarse aggregates on the compressive strength of concrete was evaluated with the water/binder ratios and the curing conditions. The saturated recycled aggregates seemed to have the negative effect on the strength development of concrete. This is the because of the decrease in bond strength between aggregate and cement paste due to the increase of surface water according to the high absorption of recycled aggregates. The effect of types and moisture conditions of aggregates according to the change of water/binder ratio was similar. However, the curing conditions had a significant effect on the compressive strength of the concrete with the different types of aggregates. In the case of curing in air, the recycled aggregates with high absorption reduced the moisture required for hydration and increased the rate of vaporizing, and these result in interfering strength development. The moisture conditions of the recycled aggregates have a considerable effect on the compressive strength of the concrete, and it is necessary to control the moisture conditions of aggregates in the production of concrete with recycled coarse aggregate. And the control of the curing condition is very important for the concrete with recycled aggregate.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.53-66
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• 2002

Asphalt binder characteristics in asphalt mixture are changed due to aging. However. depending upon aggregate and binder used, asphalt mixture dose not show the same level of stiffness and brittleness under the same ageing level. The factors affecting Physical Properties change of the asphalt binder within aged asphalt concrete are not well known and there is limited study which is dealing with this topic This study dealt with evaluation of physical properties of asphalt binder recovered from the mixtures after short-term and long-term aging. Two asphalts. two aggregates. two gradations and four polymers were used to make 32 mixture combinations. The mixtures were prepared and aged artificially in a forced draft oven. The measured physical properties included absolute viscosity, kinematic viscosity and penetration. Statistical analyses were carried out to find out the factor(s) having a significant effect on change of physical property of asphalt binder due to asphalt mixture aging. The results of study shown that aggregate, gradation and polymer had a significant effect on change of physical properties of asphalt binder.

• Magazine of the Korea Concrete Institute
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• v.22 no.3
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• pp.41-46
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• 2010

• 레미콘
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• no.1 s.62
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• pp.13-26
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• 2000

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.135-143
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• 2007

This paper presents results of an experimental study designed to investigate the effect of sustained load on the flexural performance of reinforced recycled aggregate concrete beams. In this experimental program, three beams with recycled aggregate replacement percentages(natural 100%, recycled coarse aggregate 100%, recycled fine aggregate 50%) were tested up to failure after sustained loading($0.5M_n$) for one year. The experimental results showed that reinforced concrete beams using recycled aggregate(water absorption : 1.86~3.64%) concrete showed the same flexural performance as that of natural aggregate concrete beam. Current the ACI code underestimated experimental obtained ultimate flexural strength of beams irrespective of usage of recycled aggregates.