• Title/Summary/Keyword: Recycled-aggregate

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Concrete Recycling considering Risk Evaluation of Impurities in Recycled Aggregate (순환골재 불순물의 위험성을 고려한 콘크리트 리사이클링)

  • Park, Won-Jun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2012.05a
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    • pp.95-97
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    • 2012
  • Recycled aggregate (RA) produced from demolished concrete waste can bring about several problems on concrete performance, when it is used as aggregate for new concrete. Because RA generally has lower quality than natural aggregate due to the residual cement paste attached on RA and various impurities. It is also very difficult to ensure that the quality of RA remains consistent, because generally RA is produced variously. Thus, in concrete recycling, it is extremely important to estimate the risk of the impurities which could affect performances of recycled aggregate concrete (RAC) focusing on the material flow of concrete waste and its recycling. This study suggests an evaluation result to expect the possibility of impurity mixing in RA production procedure. and suggests a risk evaluation model to expect the changes of RAC performances based on conventional data in Japan.

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An effect of Reclaimed Asphalt Concrete on the Strength Development of Concrete using Recycled-Aggregate (폐아스콘을 함유한 재생콘크리트의 강도발현 특성평가)

  • Lee Wook Jae;Seo Ki Won;Kim Hag Youn;Kim Nam Ho
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.205-208
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    • 2004
  • The purpose of this study is to recycle waste concrete and reuse reclaimed asphalt concrete as a concrete coarse aggregate. In this experiment, recycled coarse aggregate was substitute for natural crushed aggregate at the rate of 0, 30, $50\%$, and reclaimed asphalt concrete was substitute for recycled coarse aggregate at the rate of 0, 10, 20, $30\%$. According to the experimental results, as the reclaimed asphalt concrete content has influence on the properties of recycled aggregate concrete such as compressive and tensile strength, the criteria for the substitute ratio should be required to be set.

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A Comparative Study on the Quality of Recycled Aggregate for Concrete by Crushing Method (파쇄 방법에 따른 콘크리트용 순환골재의 품질 비교 연구)

  • Choi, Won-Young;Lee, Sae-Hyun;Kim, Seoung-Hwan
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.2
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    • pp.121-129
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    • 2017
  • In this study, the quality of recycled aggregate for concrete was investigated as the number of recycled aggregate crushing cycles, grinder and crusher, peeling and crushing. First, the quality of density, absorption ratio and solid content was improved as the separation distance decreased and the number of crushing increased, depending on the number of crushing of recycled aggregate and the distance between mantle and cone cave. The quality of density, absorption ratio and solid content was improved as the wire mesh used in striking plate and the number of hammers increased, depending on the type of striking plate and the number of hammers.

Strength and behaviour of recycled aggregate geopolymer concrete beams

  • Deepa, Raj S;Jithin, Bhoopesh
    • Advances in concrete construction
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    • v.5 no.2
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    • pp.145-154
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    • 2017
  • In the present day scenario, concrete construction is rapidly becoming uneconomical and non sustainable practice, due to the scarcity of raw materials and environmental pollution caused by the manufacturing of cement. In this study an attempt has been made to propose recycled aggregates from demolition wastes as coarse aggregate in geopolymer concrete (GPC). Experimental investigations have been conducted to find optimum percentage of recycled aggregates (RA) in GPC by replacing 20%, 30%, 40%, 50% and 60% of coarse aggregates by RA to produce recycled aggregate geopolymer concrete (RGPC). From the study it has been found that the optimum replacement percentage of recycled aggregates was 40% based on mechanical properties and workability. In order to study and compare the flexural behaviour of RGPC and GPC four beams of size $175mm{\times}150mm{\times}1200mm$ were prepared and tested under two point loading. Test results were evaluated with respect to first crack load, ultimate load, load-deflection characteristics, ductility and energy absorption characteristics. Form the experimental study it can be concluded that the addition of recycled aggregate in GPC causes slight reduction in its strength and ductility. Since the percentage reduction in strength and behaviour of RGPC is meager compared to GPC it can be recommended as a sustainable and environment friendly construction material.

Toughness and microscopic pore structure analysis of pasture fiber recycled concrete

  • Hailong Wang;Lei Wang;Hong Yang
    • Advances in concrete construction
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    • v.16 no.3
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    • pp.141-153
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    • 2023
  • In order to develop and take full advantage of pasture fiber and waste concrete, this article studied how different amounts of pasture fiber influenced the toughness and pore structure of concrete with different replacement rates of recycled fine aggregate. Pasture fiber recycled concrete constitutive equations were established under idealized stiffness and toughness damage rate, based on fracture energy and damage mechanics theories. The relationship between pore structure and toughness was studied utilizing nuclear magnetic resonance and fractal theory. The toughness of text groups (0% (JZ), 10% (ZS10), 20% (ZS20)) first increased and then decreased with increasing amounts of pasture fiber, based on the damage rate of toughness. The toughness of concrete samples with recycled fine aggregate and pasture fiber is negatively correlated to the fractal dimension of small and medium-sized pores with a pore size of 0-500 nm. At a replacement rate of 10% of the recycled fine aggregate, the fractal dimension of the air voids (r: 500-9000 nm, i.e., Lg(r) ∈ [2.7, 3.9]) shows a gradual decrease with the increase of grass fiber dosage, indicating that with such a replacement rate of the recycled fine aggregate, the increase of pasture fiber can reduce the complexity of the pore structure of the air voids (500-9000 nm).

A Study on the Bond Stress of Rebar in Reinforced Concrete Pavement using Recycled Aggregate (재생골재 활용 철근콘크리트포장 내 철근의 부착특성에 대한 연구)

  • Kim, Nak-Seok;Kim, Kwang-Tae;Jeon, Chan-Ki;Jeon, Joong-Kyu
    • Journal of the Korean Society of Hazard Mitigation
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    • v.5 no.1 s.16
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    • pp.77-84
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    • 2005
  • Amount of demolished concretes is highly produced as dismantlement of structures to increased owing to usage alteration and deteriorated of concrete structures, but most of them have been used as material for simple reclamation. Therefore, if demolished concrete could be recycled as aggregate for concrete. it will contribute to solve the exhaustion of nature aggregate, in terms of saving resources and protecting environment, especially being want of resources in Korea. In this study it was investigated into experimental results that were carried out demolished concrete recycled aggregate gained from dismantled real structures and source concrete recycled aggregate produced according to respectively 5 steps of replacement ratio for recycling as pavement concrete aggregate.

Durability properties of mortars with fly ash containing recycled aggregates

  • Kurbetci, Sirin;Nas, Memduh;Sahin, Mustafa
    • Advances in concrete construction
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    • v.13 no.1
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    • pp.101-111
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    • 2022
  • The rapid development of the construction industry in the world causes a rapid increase in the consumption of aggregate resources, which leads to the depletion of existing aggregate reserves. The use of recycled aggregate in the production of concrete and mortar may be a good solution to reduce the use of natural raw materials and to reduce demolition waste in the environment. In this study investigating the use of recycled aggregate in mortar production, mortar mixtures were produced by substituting 0%, 25%, 50% and 100% fine recycled aggregate (FRA) instead of natural aggregate. The effect of 20% and 40% fly ash (FA) substitutes on cement mortar performance was also investigated. Compressive and flexural strength, drying shrinkage, abrasion resistance, water absorption and capillary water absorption were investigated on the produced mortars. The increase in the use of FRA reduced the compressive and flexural strengths of mortars. While the capillarity coefficients, water absorption, rapid chloride permeability and drying shrinkage of the mortars increased with the increase in the use of FRA, the effect of the use of fly ash on the rate of increase remained lower. The increased use of FRA has improved abrasion resistance as well.

Properties of Eco-friendly Artificial Stone according to the mixing ratio of Geopolymer-based recycled Aggregate (지오폴리머 기반 순환골재 혼입율에 따른 친환경성 인조석재의 특성)

  • Kyung, Seok-Hyun;Choi, Byung-Cheol;Kang, Yeon-Woo;Lee, Sang-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.06a
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    • pp.126-127
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    • 2020
  • Recently, as interest in environmental issues increases, minimizing carbon dioxide generated during cement manufacturing is a problem to be solved. In order to solve such a problem, it is required to use an industrial by-product of recycled aggregate, blast furnace slag, and circulating fluidized bed boiler fly ash to replace it on the basis of geopolymer(=cementless). This study examines the characteristics of eco-friendly artificial stone according to the mixing ratio of geopolymer-based recycled aggregate. As a result of the experiment, when the addition rate of the alkali stimulant was 15% and the mixing ratio of the circulating aggregate was 70%, the flexural strength and compressive strength were the highest. Density and water absorption decreased as density of circulating aggregates increased and water absorption increased. However, when the mixing ratio of the circulating aggregate exceeded 70%, the flexural strength and compressive strength decreased. Therefore, in order to obtain strengths meeting the KS standards, the mixing ratio of recycled aggregate was set to 70%, and artificial stone was manufactured using industrial by-products.

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Improvement on the Properties of Recycled Aggregate Concrete Using Pozzolanic Materials (포졸란 재료를 사용한 순환골재 콘크리트의 품질 개선)

  • Moon, Dae-Joong;Kim, Wan-Jong;Kim, Hak-Soo
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.1
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    • pp.117-124
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    • 2010
  • The aggregate, which does not satisfy the standard of KS F 2573, was selected for this investigation. The 28day compressive strength of recycled aggregate concrete without pozzolan material was 21.7MPa, which was less than the strength of concrete made with crushed stone. However, the compressive strength at 28 days was improved by mixing early rapid hardening cement to the cement at the weight ratio of 2.5%. Furthermore, the compressive strength at 91 days and 180 days increased significantly by adding fly ash, slag powder, and diatom powder. The tensile strength of recycled aggregate concrete with pozzolan material also increased about 40% compared to the general concrete. Futhermore, the shrinkage and creep of recycled aggregate concrete with fly ash and slag powder was a little decreased that of recycled aggregate concrete with fly ash and diatom powder. Relationship between compressive strength and creep coefficient was shown to the linear relation like as ${\sigma}_c=-30CF+404$.

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Flexural Performance of Reinforced Concrete Beams with Recycled Aggregates Suffering from Sustained Load (지속하중을 경험한 철근콘크리트 보의 골재 종류에 따른 휨거동 특성)

  • Ji, Sang-Kyu;Yun, Hyun-Do;Kim, Sun-Woo;Lee, Eon-Young
    • 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.