• 콘크리트학회논문집
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• 제12권5호
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• pp.3-12
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• 2000

Recently, the amount of disposed construction materials like demolished concrete is growing fast and the shortage of natural concrete aggregates is becoming serious. Therefore, recycling of aggregates extracted from the demolished concrete is getting important and use of the recycled aggregates for concrete has been seriously considered. However, the use of the recycled aggregates even for low performance concretes is very limited because there are few rational standard evaluation criteria for recycled aggregates which should be different from that for natural aggregates. In this study, rational evaluation criteria for the recycled aggregates are proposed for their use as concrete aggregates. The study also shows that the performance for both the recycled aggregates and the recycled concrete manufactured with the recycled aggregates can be evaluated effectively according to water absorption ratio of recycled aggregates.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.723-726
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• 2005

As the importance of recycled materials is being emphasized more in the Korean construction market, the production quality has been improved to a significantly high level. Compared to the high quality, however, there are used very limitedly. Among recycled construction materials, recycled aggregates produced through the retreatment of waste concrete are drawing attention because of lack of natural aggregate and heightened consciousness of resource saving and environmental protection and, as a consequence, they are close to natural aggregates in terms of production technology and quality. Despite the high quality and productivity, however,. the utilization of recycled aggregates is very low. Thus, in order to maximize the utility of recycled aggregates, the present study examined the usability of recycled aggregates using both recycled coarse aggregates and recycled fine aggregates together and derived optimal quantity and mixture ratio in the combined use of the two types of recycled aggregate.

• KCI Concrete Journal
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• 제11권3호
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• pp.89-97
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• 1999

The purpose of this research is to investigate the utilization of recycled fine aggregates as a material to apply to a building finished walls or as a decorating material in combination with a polymer. The strengths of two resin mortars using recycled fine aggregates and natural fine aggregates was made. In order to improve the workability and the strength of the resin mortar with recycled fine aggregates, partial replacement of recycled fine aggregates with natural ones was made with the application of various type of fillers. The results, it show that the compressive strength and flexural strength of resin mortar using the recycled fine aggregates were about 70% to 100% of those of resin mortar using natural fine aggregates. It was enough to assure the utilization of the recycled fine aggregates as a material for the production of resin mortar. From the result of partial replacement of recycled fine aggregates with natural ones, the compressive strength was Increased from 5% to 15% and the flexural strength was much as 5% to 20% as a result of 70% substitution It was also found that the use of garnet powder shows a similar tendency in the compressive strength and slag powder does in the flexural strength and tensile strength.

• Geomechanics and Engineering
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• 제34권2호
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• pp.173-186
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• 2023

In order to prevent environmental pollution, initiatives to increase the sustainability of resources are supported by society. However, the performance of recycled materials does not generally match that of natural materials. This study looks into the use of geogrid to improve various types of recycled aggregates. For this purpose, five different recycled aggregates were created by recycling wastes from the construction industry. Besides, direct shear tests (DS tests) were carried out on these recycled aggregates to determine their shear strengths. Following that, a triaxial geogrid was placed in the recycled aggregates to provide reinforcement, and the DS tests were conducted on the reinforced recycled aggregates. The results of the tests were also compared to those of tests performed on natural aggregates (NA). In conclusion, it was found that the recycled aggregates have lower shear strengths than the NA. Nonetheless, when reinforced with geogrid, the shear strength of the recycled concrete aggregates (RCA) and construction and demolition wastes (CDW) exceeded that of the NA. Furthermore, the geogrid reinforcement increased the shear strength of the recycled crushed bricks (CB), though not to the level of the NA.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.93-96
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• 2005

In this study, Mock-up was manufactured using recycled aggregate concrete and then analyzed with respect to physical properties. Finally, the applicability of recycled aggregates as constructional aggregates was reviewed by practically putting recycled aggregates concrete into construction. Right after mixing, the slump of recycled-aggregates concrete showed decreased slump as time goes by because the surface mortar of recycled aggregates absorbed the mix water with time passing. The air contents of recycled-aggregates concrete overall increase a little due to the effect of surface mortar of the aggregates. For strengths, the strengths of recycled aggregate concrete tended to decrease from the proportion of 30$\%$ to 100$\%$.

• 콘크리트학회논문집
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• 제28권3호
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• pp.357-363
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• 2016

순환골재는 천연골재의 고갈문제를 해결하고 고부가가치를 창출할 수 있는 등 건설, 환경산업 부분에서 상당한 효용성을 갖고 있다. 그러나 순환골재의 활용을 위한 사회적 기반이 정립되고 다양한 연구가 진행되었음에도 불구하고, 천연골재에 비해 품질이 떨어지는 문제 때문에 이를 사용한 콘크리트 구조물은 매우 적은 실정이다. 본 연구에서는 순환골재에 의한 콘크리트 성능저하를 보완하기 위한 방안으로서 강섬유를 혼입한 콘크리트의 역학적 특성 및 변형 특성을 검토하였다. 그 결과, 순환골재를 혼입한 콘크리트는 천연골재만을 사용한 콘크리트(plain)에 비해 낮은 압축강도 및 탄성계수를 나타내었으나, 강섬유의 혼입에 의해 plain과 동등 수준의 성능을 확보할 수 있었다. 또한, 건조수축 및 크리프계수에 있어서도 강섬유의 내부구속효과, 수분 이동 구속효과 및 강도의 증진 등에 기인하여 혼입률 0.5 Vol.%의 범위에서 plain과 유사한 거동을 나타낼 수 있었다. 따라서 순환골재 콘크리트를 적극적으로 활용하기 위한 방안으로서 강섬유의 혼입은 매우 효과적일 것으로 판단된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.199.1-199.1
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• 2010

Use of recycled aggregates that are constituents of concrete or asphalt-based structures has become popular because the recycling is an eco-friendly way to overcome the depletion of natural aggregates. In order to adopt the recycled aggregates for backfilling a power transmission pipeline trench, their thermal resistivity should be low enough to prevent thermal runaway in the transmission system. In this study, a series of laboratory tests with QTM-500 and KD2 Pro was performed to measure the thermal resistivity of recycled aggregates prepared from various sources. Relationships between the thermal resistivity of recycled aggregates and the water content have been obtained with consideration of compaction effort. Similar to natural soils, the thermal resistivity of the recycled aggregates decreases with increasing the water content. In addition, this study compared the experimental data with conventional prediction models for the thermal resistivity in the literature, which suggests the availability of the recycled aggregates as backfill material substituting for natural aggregates when backfilling the power transmission pipeline trench.

• Advances in concrete construction
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• 제9권1호
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• pp.9-22
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• 2020

The present work looks at the possibilities of recycling more than once demolished concrete as coarse aggregates, to produce new concrete. Different concrete mixes were made with substitutions of 50%, 75% and 100% of recycled concrete aggregates respectively as coarse aggregates. The physico-mechanical characterization tests carried out on the recycled concrete aggregates revealed that they are suitable for use in obtaining a structural concrete. The resulting concrete materials had rheological parameters, compressive strengths and tensile strengths very slightly lower than those of the original concrete even when 100% of two cycles recycled concrete aggregates were used. The durability of the recycled aggregates concrete was assessed through water permeability, water absorption and chemical attacks. The obtained concretes were thought fit for use as structural materials. A linear regression was developed between the strength of the material and the number of cycles of concrete recycling to anticipate the strength of the recycled aggregates concrete. From the results, it appear clear that recycling demolished concrete represents a valuable resource for aggregates supply to the concrete industry and a the same time plays a key role in meeting the challenge for a sustainable development.

• 자원리싸이클링
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• 제24권5호
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• pp.63-71
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• 2015

본 연구는 재생 굵은골재와 산업부산물인 급냉 제강슬래그 잔골재를 이용한 친환경 재생 콘크리트의 재료적 특성을 파악하고 적정 혼합비를 도출하는데 그 목적이 있다. 이를 위해서 재생 굵은골재의 치환율은 30%에서 50%까지 증가시켰으며, 급냉 제강슬래그 잔골재는 10%에서 50%까지 증가시켜서 물성실험을 수행하였다. 그 결과, 재생골재의 치환율이 증가함에 따라 강도가 감소하였으나 급냉 제강슬래그 잔골재의 혼입율을 증가함에 따라 강도가 증가됨을 알 수 있었다. 더불어 급냉 제강슬래그 잔골재의 적정 치환율은 압축강도 및 탄성계수 등을 고려했을때 20~30%로 판단되며, 재생 굵은골재의 치환율 증가에도 도움이 될 것으로 사료된다.

• Structural Engineering and Mechanics
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• 제88권2호
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• pp.141-157
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• 2023

In the present paper, the effect of recycled aggregates on the rheological and mechanical properties of self-consolidating concrete is investigated experimentally and numerically. Hence, the specimen with two types of recycled aggregates, i.e., known and unknown resistance origins, are utilized for the studied specimens. The experiments in this study are designed using the Box-Behnken method, which is one of the response surface methods. Input variables in mixtures include silica fume in the range of 5-15% as a percentage substitute for cement weight and recycled coarse and fine aggregates in the range of 0-50% for both series of recycled materials as a substitute for natural materials. The studied responses are slump flow, V funnel, compressive strength, tensile strength, and durability. The results indicate that the increase in the amount of recycled aggregates reduces the rheological and mechanical properties of the mixtures, while silica fume effectively improves the mechanical properties. In addition, the results demonstrate that the fine recycled aggregates affect the total response of the concrete significantly. The results of tensile and compressive strengths indicate that the mixtures including 50% recycled materials with known resistance origin demonstrate better responses up to 8 and 10% compared to the materials with unknown resistance origins, respectively. Recycled materials with a specific resistance origin also show better results than recycled materials with an unknown resistance origin. Durability test results represent those concretes containing recycled coarse aggregates have lower strength compared to recycled fine aggregates. Also, a series of mathematical relationships for all the responses are presented using variance analysis to predict mixtures' rheological and mechanical properties.