• 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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.137-138
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• 2020

The purpose of this study is to evaluate the absorption ratio reduction of recycled coarse aggregate for concrete coated by polymer dispersions. The surface of recycled coarse aggregate is treated by polymer dispersion such as SBR and SAE with solid contents of 2%, 5% and 10%. From the test results, The minimum absorption ratio of the coated recycled coarse aggregate is 1.60 times smaller than that of uncoated recycle coarse aggregate. It is apparent that the absorption ratio of recycled coarse aggregate is much more improved by surface coating with polymer dispersions.

• Journal of the Korea Institute of Building Construction
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• v.4 no.3
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• pp.133-141
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• 2004

The object of this study is to investigate experimentally the shear behavior of reinforced concrete beams using recycled coarse aggregate. At first, the specimens are manufactured for the compressive strength of 210kgf/$\textrm{cm}^2$ with recycled coarse aggregate ratio of 0%, 20%, 40%, 60%, 80%, 100%, respectively. From the results, Reinforced concrete beams using recycled coarse aggregate were made with recycled coarse aggregate ratio of 0%, 20%, 40%, 60%, 80%, with stirrups and recycled coarse aggregate ratio of 0%, 20%, 40% without stirrups. The results of crack pattern and failure mode, load-displacement curve(center point and load point) and load-steel curve(compressive, tensile, stirrup) were analysed. It is concluded from the test that the shear behavior of recycled concrete beams is determined to have similar behavior of normal concrete beams. Therefore, from this study the application of recycled concrete to concrete structures may be possible. But, for using the recycled concrete widely, it is expected that the more studies on quality control, substitution ratio and mix design related with recycled concrete are necessary.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.2
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• pp.55-61
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• 2005

This study was performed to evaluate fluidity of super flow concrete using recycled coarse aggregate. The unit weight was $2,246{\sim}2,344\;kg/m^3$, the unit weights of these concrete were decreased with increasing the content of fly ash and recycled coarse aggregate. The slump flow was $58{\sim}63\;cm$, the Box type passing was $3.4{\sim}6.8\;cm$, respectively. The L type compacting was excellent in the fly ash content $10\%\;and\;20\%$, but, it was showed in good in the fly ash content $30\%$. The super flow concretes using recycled coarse aggregate were improved by substitution in the range of less than the fly ash content $20\%$ and recycled coarse aggregate content $75\%$. This recycled coarse aggregate can be used for super flow concrete.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.1
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• pp.25-32
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• 2005

This study was performed to evaluate strengths and non-destruction properties of super flow concrete using recycled coarse aggregate. At the curing age of 28 days, the compressive strength was 22.7-37.5 MPa, the splitting tensile strength was $2.65\~3.73$ MPa, the flexural strength was $5.78\~6.86$ MPa, the ultrasonic pulse velocity was $3,103\~3,480$ mis, the dynamic modulus of elasticity was $3.401{\times}104\~4.521{\times}104$MPa, respectively. The strengths, ultrasonic pulse velocity and dynamic modulus of elasticity of super flow concrete were decreased with increasing the content of recycled coarse aggregate. The super flow concretes using recycled coarse aggregate were improved by substitution in the range of less than the fly ash content 30010 and recycled coarse aggregate content $75\%$.

• Advances in concrete construction
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• v.4 no.1
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• pp.27-35
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• 2016

The quantity of construction and demolition waste has been greatly increasing recently. It causes many problems to the environment. For this reason, demolition waste management becomes inevitable in order to overcome the environmental issues. The present study aims to evaluate the effects of using recycled coarse aggregate, which is generated from construction and demolition waste, on the properties of recycled aggregate concrete. An experimental investigation on the strength characteristics of concrete made with recycled coarse aggregate is presented and discussed in this paper. In this study, Portland Pozzolana Cement (fly ash based) is used instead of ordinary Portland cement. The results of this investigation show the possibility of the use of recycled coarse aggregates in the production of fresh concrete. Use of demolition waste as coarse aggregate will lead to a cleaner environment with a significant reduction of the consumption of natural resources. A comparative study on the strength characteristics of recycled aggregate concrete made with Ordinary Portland Cement and Portland Pozzolana Cement is presented and discussed in this paper.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.94-97
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• 2003

Recently, owing to the deterioration of reconstruction and the construction, much of the construction waste is discharged in our construction field, and the amount of construction waste are rapidly increased. These waste are raised to financial and environmental problems, so the method of reusing waste concretes has been studied and carried out many direction. Especially being want of resources, if waste concrete could be recycled as aggregate for concrete, it will contribute to solve the exhaustion of natural aggregate, in terms of saving resources and protecting environment. This study is that the floating properties of concrete with recycled coarse aggregate were investigated for the substitution of recycled coarse aggregate. The result of this study, in case of water reducing, the property of harden concrete for the substitution ratio of recycled coarse aggregate was increased. The Quality of recycled coarse aggregate concrete was improved by water reducing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.73-74
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• 2012

The elastic modulus of recycled aggregate concrete (RAC) can be evaluated by using composite models with experiment. In this study, Hashin's composite model was adapted to evaluate elastic modulus considering physical properties of recycled coarse aggregate (RCA) that mortar is attached. Elastic modulus testes for cement paste, mortar and recycled coarse aggregate concrete were carried out considering W/C and recycled coarse aggregate content rate. As a result, the elastic modulus of RAC was evaluated comparing with both experiment results and the existing estimation formula. Those can be used for further studies as a preliminary data.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.87-91
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• 2009

Recycling demolished concrete as an alternative source of coarse aggregates for the production of new concrete can help solve the growing waste disposal crisis and the problem of depleted natural aggregates. The purpose of this study is to investigate chloride migration of recycled aggregate concrete containing pozzolanic materials by chloride migration coefficient. The specimens were made with recycled coarse aggregate as various replacement ratio(10, 30, 50%) and metakaolin, blast furnace slag, fly ash is replaced for recycled concrete with mixing ratio 20%. The major results are as follows. 1) Compressive strength of recycled aggregate concrete containing pozzolanic materials increase as curing age and chloride migration decrease. 2) When the replacement ratio of recycled coarse aggregate is 30%, the chloride migration coefficient of recycled concrete containing blast furnace slag, metakaolin shows the similar or lower value than plain concrete at all ages.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.178-187
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• 2024

In this study, it was determined that it was necessary to consider the replacement rate when applying recycled coarse aggregate to concrete, so data on existing research trends and results were collected and the mechanical properties of concrete according to the replacement rate of recycled coarse aggregate were analyzed. In collecting data on recycled coarse aggregate, data without processes such as compressive strength and removal of residual mortar attached to recycled coarse aggregate were collected among the concrete measurement items. In the case of concrete with 50 % and 100 % replacement of recycled coarse aggregate, it was confirmed that the mechanical properties were lower or higher than ordinary concrete by -36.0 ~ 9.9 % and -40.0 ~ 10.4 %, respectively, on average. Accordingly, it is judged that additional water should be mixed in consideration of the absorption rate when mixing, and the replacement rate of recycled coarse aggregate, which has mechanical properties of 80 % or more compared to ordinary concrete, should be less than 50 %.