• Title/Summary/Keyword: Recycled aggregates

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A Study on Rational Evaluation of Recycled Aggregates Extracted from Demolished Concrete (폐콘크리트로부터 재생된 골재의 합리적 평가에 관한 연구)

  • 송하원;변근주;하주형
    • Journal of the Korea Concrete Institute
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    • v.12 no.5
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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.

Experimental Study on Mechanical Properties and Deformation Behavior of Concrete with Recycled Aggregates and Steel Fiber (순환골재 및 강섬유를 혼입한 콘크리트의 역학적 특성 및 변형 거동에 관한 실험적 연구)

  • Lee, Hyun-Ho;Lee, Tae-Wang
    • Journal of the Korea Concrete Institute
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    • v.28 no.3
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    • pp.357-363
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    • 2016
  • To solve the exhaustion problem of natural aggregate which were create the high value in construction and environmental industry, recycled aggregates have considerable benefits than other materials. However, even though many researches have been conducted with recycled aggregates, building structures with recycled aggregated are rarely constructed because it has lower quality than natural aggregates have. In this study, mechanical and strain properties of recycled aggregates concrete containing steel fibers have been reviewed in order to complement performance of recycled aggregates concrete. As results, recycled aggregates concrete showed lower compressive strength and elastic modulus than plain concrete. But, recycled aggregates concrete containing steel fibers showed equivalent performance with plain concrete. In review of drying shrinkage and creep coefficient, recycled aggregates concrete containing steel fibers showed similar behavior with plain concrete in the range of 0.5 Vol.% fiber content rate by internal restraint effect, moisture transport restraint effect and strength enhancement effect of steel fiber. Therefore, it is considered that mixing steel fibers with concrete is the effective method as a active application plan for recycled aggregates.

Thermal Resistivity Measurement of Recycled Aggregates and Comparison with Conventional Prediction Model (송배전관로 되메움용 순환골재의 열저항 측정 및 기존 열저항 예측 모델과의 비교)

  • Wi, Jihae;Hong, Sungyun;Choi, Hangseok
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.11a
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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.

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A Study on the Development of Forced Carbonation Reforming Technology for Recycled Aggregates (순환골재의 강제 탄산화 개질 기술 개발을 위한 기초적 연구)

  • Lim, Myung-Kwan;Park, Won-Jun;Lee, Huck;Kim, Do-Yun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2016.05a
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    • pp.207-208
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    • 2016
  • The most important things for the production of recycled aggregates are saving energy, suppressing the generation of by-product fine particles and sustaining the performance of concrete. As solutions, this study proposes this technology of improving the performance of recycled aggregates through forced carbonation.1) It is to stimulate and carbonate the bond paste part that causes the deterioration of recycled aggregates. Particularly, the purpose of this technology is to fill and chemically stabilize pores inside the bond paste, further improving the quality of recycled aggregates with a decreased absorption rate and an enhanced aggregate strength. Ultimately, it is possible to obtain a carbonation model, depending on the paste ratio and particle-size distribution of recycled aggregates. Moreover, by calculating the optimum carbonation period through the verification of this carbonation model, it is possible to examine how much the strength is improved by the reformation of recycled aggregated.

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Reinforced fibrous recycled aggregate concrete element subjected to uniaxial tensile loading

  • Hameed, R.;Hasnain, K.;Riaz, M. Rizwan;Khan, Qasim S.;Siddiqi, Zahid A.
    • Advances in concrete construction
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    • v.9 no.2
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    • pp.195-205
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    • 2020
  • In this study, effect of recycled aggregates and polypropylene fibers on the response of conventionally reinforced concrete element subjected to tensile loading in terms of tension stiffening and strain development was experimentally investigated. For this purpose, concrete prisms of 100 × 100 mm cross section and 500 mm length having one central deformed steel re-bar were cast using fibrous and non-fibrous Recycled Aggregate Concrete (RAC) with varying percentages of recycled aggregates (0%, 25%, 50%, 75% and 100%) and tested under uniaxial tensile load. For all fibrous RAC mixes, polypropylene fibers were used at constant dosage of 3.15 kg/㎥. Effect of recycled aggregates and fibers on the compressive strength of concrete was also explored in this study. Through studying tensile load versus global axial deformation of composite and strain development in concrete and steel, it was found that replacement of natural aggregates with recycled aggregates in concrete negatively affected the cracking load, tension stiffening and strain development, and this negative effect was observed to be increased with increasing contents of recycled aggregates in concrete. The results of this study showed that it was possible to minimize the negative effect of recycled aggregates in concrete by the addition of polypropylene fibers. Reinforced concrete element constructed using concrete containing 50% recycled aggregates and polypropylene fibers exhibited cracking behavior, tension stiffening and strain development response almost similar to that of concrete element constructed using natural aggregate concrete without fiber.

A Study on the Properties of Recycled Aggregate Concrete applied to Mock-up (Mock-up에 적용한 재생골재콘크리트의 특성 연구)

  • Shim Jong-Woo;Lee Sea-Hyun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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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$\%$.

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pH Characteristics of the Recycled Aggregate Being carbonated by Dry Ice (드라이아이스로 탄산화 처리한 순환골재의 pH 특성)

  • Hong, Sung-Rog;Bok, Young-Jae;Sung, Jong-Hyun;Lee, Il-Sun;Kim, Jin-Man
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2013.05a
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    • pp.337-338
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    • 2013
  • Recent research is needed for the reduction of the pH of the recycled aggregates, recycled aggregates for alkali social problems have emerged. This was confirmed through preliminary experiments using a self-made reactor with dry ice, the possibility of reducing the pH of the recycled aggregates. The pH reduction of coarse recycled aggregates plant was made to apply the field to the middle of construction waste treatment process to reduce the pH of the plant room, and measured the pH change with time. The measurement results showed that dry ice after the reaction, the pH of the aggregate 5% reduction than untreated recycled aggregates.

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Field Test of Recycled Aggregates and Crushed Stone as Horizontal Drains (수평배수재용 순환골재와 쇄석의 현장시험)

  • Kim, Si-Jung;Lee, Dal-Won
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.1
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    • pp.39-45
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    • 2012
  • In this study, field test on utilization of recycled aggregates and crushed stone as horizontal drains to use an alternative material of sand in soft ground is practiced. The settlement with time showed similarly ranged from 28.4-30.3 cm in the all horizontal materials. The excess pore water pressure of the recycled aggregates and crushed stone showed smaller than sand. The small the excess pore water pressure becomes faster the consolidation period and it can reduces the amount of residual settlement. Therefore, it was verified as having enough to an alternative materials that the field applicability is excellent. The distribution of earth pressure with time showed similarly in the all horizontal materials. The recycled aggregates and crushed stone was very applicable to practice because there is no mat resistance in the horizontal drains layer. The penetration rate in the SCP and PVD improvement sections did not show large differences as the grain size and the horizontal drainage height increases.