• Title/Summary/Keyword: 완전 순환형 콘크리트

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Recovering Hydration Performance of Cementitious Powder by Concret Waste according to Burning Temperature (폐콘크리트계 미분말의 소성조건에따른 수화성 회복)

  • 강태훈;정민수;안재철;강병희
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.81-87
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    • 2003
  • The purpose of this study is the development of a recycling process to recover the hydrated ability of cement hydrate which accounts for a large proportion of cementitious powder by concrete waste in order to recycle cementitious powder by concrete waste as recycle cement. Therefore, after having theoretical consideration based on the properties of high-heated concrete, we consider the properties of hydration of cementitious powder in hardened mortar under various temperature conditions. As a result of experiment, it is revealed that an effective development of recycling cement is possible since the cementitious powder by concrete waste recovers a hydraulic property during burning at $600^{\circ}C$ or $700^{\circ}C$. And it is shown that the fluidity of mortar decreases rapidly as the burning temperature of recycle cement increases. however, the improved effect of fluidity is predominant if adding the additive such as fly-ash or blast furnace slag.

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The Improvement of Properties of Recycled aggregates using Concrete Waste by Pre-heating Method. (예비가열법에 의한 폐콘크리트 재생골재의 물성개선)

  • 최현수;김효열;최봉철;강병희
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2003.05a
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    • pp.73.2-79
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    • 2003
  • The purpose of this study is to provide the basic data on the optimum method for interfacial separation for an effective recycle of concrete waste by using the thermal properties of concrete. Therefore, this study is proceeded by dividing the interface of concrete into cement paste and fine aggregates or mortar and coarse aggregate, considering the aspect of recycled cement and aggregate as the recycling use of concrete waste. As results of the experiment, in case of recycle cement, the interfacial separation is easily appeared, but it is shown that the mixed amount of powder included in fine aggregate doesn't greatly decrease. But, in case of recycle coarse aggregate, the effect of interfacial separation by preliminary heating is predominant. Especially, the bonding rate of mortar is the lowest when it is heated 5 times for 120 minutes at $300^{\circ}C$. Hence, it is considered that it will be an excellent effect of quality control when the results of this study is applied to a manufacturing system of recycle coarse aggregate which is about to put into practical use.

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Flexural Behavior of Segmental U-Girder and Composite U-Girder Using Ultra High Performance Concrete (초고강도 섬유보강 콘크리트를 사용한 분절형 U거더 및 합성 U거더의 휨거동)

  • Lee, Seung-Jae;Makhbal, Tsas-Orgilmaa;Kim, Sung-Tae;Han, Sang-Mook
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.3
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    • pp.290-297
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    • 2017
  • The flexural behavior tests of UHPC segmental U-girder and composite U-girder which has 160MPa compressive strength and 15.4m length were carried out. The test variables are volume fraction of steel fibers and slab over the U-girder. Each U-girder has longitudinal re-bars in web and lower flange. PS tendons which has 2 of 15.2mm diameter in upper flange and PS tendons which has 7 of 15.2mm diameter in lower flange were arranged and prestressed at onetime in U-girder connection stage. Enough strong prestressing force which applied to U-girder due to ultra high performance concrete strength can withstand the self weight and dead load in U-girder stage. By comparison with the brittle behavior of U-girder, composite U-girder showed the stable and ductile behavior. After the construction of slab over U-girder, flexural load capacity of composite U-girder can bear the design load in final construction stage with only one time prestressing operation which already carried out in U-girder stage. This simple prestressing method due to the ultra high strength concrete have the advantage in construction step and cost. The shear key which has narrow space has the strong composite connection between ultra high strength concrete U-girder and high strength concrete slab didn't show any slip and opening right before failure load.