• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.2
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• pp.59-66
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• 2004

This study was performed to evaluate the freezing and thawing properties of the high strength concrete using recycled coarse aggregate. The recycled coarse aggregate replaced natural crushed aggregate by 0%, 25%, 50%, 75% and 100%. The compressive strength of the concrete using recycled coarse aggregate showed more than 300 kgf/$cm^2$ at the curing age 28 days. The mass loss ratio by freezing and thawing was less than 1% at all mix type. The relative dynamic modulus of elasticity was decreased with increasing the freezing and thawing cycles. Also, the durability factor by the freezing and thawing was decreased with increasing the content of recycled coarse aggregate. But, the recycled concrete except 100% recycled coarse aggregate showed 60 or more durability factor in the freezing and thawing 300 cycles. Accordingly, these recycled coarse aggregate can be used for high strength concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.125-130
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• 2010

It is necessary to re-establish the code and to control the quality of the recycled aggregate itself for ensuring the useability of the recycled aggregate using waste concrete. Generally, adhering mortar cause of the water absorption ratio increment and strength decreased at the surface of the aggregate of the recycled aggregate using waste concrete, thus removing the adhering mortar could increase the useability of the recycled aggregate in the concrete industry. In this study, as a quality control method of the recycled aggregate using waste concrete, the quality characteristic of the recycled aggregate according to the mixing proportion between the recycled and the natural aggregate is obtained Therefore, a system is established to reuse the recycled aggregate in the construction industry.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.7-15
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• 2017

The purpose of this study was to evaluate the properties of recycled aggregate concrete (RAC) using low quality recycled aggregate with or without washing before usage. The recycled aggregate concrete evaluated in this study contained various amounts of low quality recycled aggregate, viz. 30%, 60% and 100%. To evaluate the performance of the recycled aggregate concrete, various test methods were employed to assess its compressive strength, absorption, surface resistance, ultrasound velocity, chloride ion resistance, etc. The properties of the RAC with 30% and 60% washed recycled aggregate were similar those of the natural aggregate. However, the properties of the RAC with 100% washed recycled aggregate were slightly lower than those of the other versions. Also, the RAC with the non-washed recycled aggregate exhibited lower performance results. The results showed that the RAC with washed recycled aggregate had similar properties to normal concrete (concrete using natural aggregate). This implies that the recycled aggregate should be washed to improve the RCA.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.326-329
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• 2003

In practice, recycled aggregate is not used for a structural member due to its high absorbability and abrasion. It is, however, highly expected that the usage of recycled aggregate increases as the processing technique of the recycled aggregate progresses. In this study herein, the compressive strength of the recycled aggregate concrete was investigated. Coarse aggregate was replaced with 100% of the recycled aggregate, and cement and fine aggregate was replaced with various amount. The specimen was steam-cured at $80^{\circ}C$. It was shown that the concrete can obtain desirable strength when fine aggregate was replaced with up to 60% of recycled fine aggregate, and when cement was replaced with up to 15% of fly ash.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.105-108
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• 2005

This study investigated fundamental properties of the recycled aggregate which was produced through recent hi-techniques of recycling. In addition, the mechanical properties of the concrete that used the recycled aggregate were compared to the concrete used the natural aggregate. From the results of the mechanical property tests, as the recycled aggregate replacement ratio increased, the compressive strength and elastic modulus decreased. When the recycled aggregate completely replaced the natural aggregate, the compressive strength and elastic modulus was about 15$\%$ and 35$\%$ lower than the natural aggregate concrete, respectively. Based on the test results, equations for prediction of compressive strength and elastic modulus were suggested in the consideration of the amount of the replaced recycled aggregate. Based on the test results and study, the equation predicting the required development length of the recycled aggregate concrete is proposed.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.105-113
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• 2016

OBJECTIVES : This study is to develop the optimum mixing proportions for cement concrete pavement with using recycled aggregates. METHODS : The mixture varied recycled coarse aggregates content from 50 % to 100 % to replace the natural coarse aggregates by weight. Tests for fundamental properties as a cement concrete pavement were conducted before and after hardening of the concrete. RESULTS : It was found that the variation in the amount of the recycled aggregate affected the compressive and flexural strength development, as well as the chloride ion penetration resistance. As the amount of the recycled aggregate content increased the compressive and flexural strength and the resistance to chloride ion penetration decreased. However, the resistance to freeze-thaw reaction was affected significantly. In addition, the gradation of the aggregate became worse and hence so did the coarseness factor as the recycled aggregate amount increased. CONCLUSIONS : The fundamental properties of the concrete with recycled aggregate does not seem to be appropriate when the recycled aggregate quality is not guaranteed up to a some level and its replacement ratio is over 50%. The optimized gradation of the aggregates should also be sought when the recycled aggregate is used for the cement concrete pavement materials.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.186-191
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• 1996

The recycled aggregate obtained from the recycled concrete may be used in road construction as crushed aggregate. The properties of recycled aggregate are reached to the values in accordance with specification for the subbase layer of the road construction. However, for the base layer of road construction, the mixtures of recycled aggregate and crushed aggregate have to be used in order to satisfy the specification. In the Batch Leaching Test the recycled aggregate has lower content of heavy matal and organic matter than those written in environmental pollution law. So it does not occur the environmental pollution.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.65-68
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• 2009

Recycled aggregate by the recycling construction waste has a lot of advantage such as the developing the alternative resource and protecting of environment. However, recycled aggregate is used as the low quality grade, because the technic to remove old mortar from aggregate is low level. To use the recycled aggregate as high quality grade, it is important to develop the technic to produce the high quality recycled aggregate. To manufacture the high quality recycled aggregate, old mortar attached on the aggregates should remove efficiently. Therefore, in this study, we suggested the optimum condition to remove old mortar effectively using sulfuric acid and low speed wet rotary mill for high quality recycled fine aggregate. The results shows that the recycled aggregate satisfy on the standards of KS F 2573 in density, absorption and solid volume when, adequate condition of sulfuric mole ratio and aggregate ratio are make.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.197-200
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• 2004

The increase of the use of recycled aggregate is necessary for the decrease of building waste, but it is not possible to use concrete because of the various range of quality. Therefore, the quality grade and application method of recycled aggregate should be prescribed before the site application so in that this study we investigated the effect of the quality of recycled aggregate on the compressive strength, resistance freezing and thawing. As results of this study, the compressive strength of recycled aggregate concrete used recycled aggregate, as if it had high quality recycled aggregate is similar or higher to that of crushed stone. Also, this high quality recycled aggregate affect the increase of resistance freezing and thawing.

• Computers and Concrete
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• v.16 no.2
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• pp.275-285
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• 2015

This paper reports the results of an experimental study on the compressive strength and the stress-strain curve (SSC) of recycled fine glass aggregate concrete with different replacement percentages of recycled fine glass aggregate. The results show that the recycled fine glass aggregate contents have significant impact on the workability, compressive strength, the elastic modulus, the peak and the ultimate strains of recycled fine glass aggregate concrete. Analytical expressions for the stress-strain relationship of recycled fine glass aggregate concrete are given, which can satisfactorily describe the effect of the recycled fine glass aggregate on the SSC.