• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.575-583
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• 2001

The purpose of this study is to present the method of utilizing the recycled aggregate that are obtained from waste concrete as the concrete aggregate. We manufactured the recycled aggregate concrete with compressive strength of over 300kgf/㎠ to increase its weaker strength than the normal concrete, and compared the physical features of the recycled aggregate concrete with that of the normal concrete. As a result of the study, the mechanical performances such as compressive and tensile strength were generally reduced as the mixing rate of the recycled aggregate increased; however, it was possible to manufacture the concrete with the compressive strength of 300∼600kgf/㎠ using the adequate mixing material such as unit quantity of cement, compounding water and silicafume. However, a continuous study on long-term durability performance is required to manufacture and utilize the recycled aggregate concrete for the structure.

• 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.

• Computers and Concrete
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• v.23 no.3
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• pp.161-170
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• 2019

This paper aims at presenting a numerical method for estimating the elastic modulus of recycled concrete with crushed aggregates. In the method, polygonal aggregates following a given sieve curve are generated, and placed into a square simulation element with the aid of the periodic boundary condition and the overlap criterion of two polygonal aggregates. The mesostructure of recycled concrete is reconstructed by embedding an old interfacial transition zone (ITZ) layer inside each recycled aggregate and by coating all the aggregates with a new ITZ layer. The square simulation element is discretized into a regular grid and a representative point is selected from each sub-element. The iterative method is combined with the fast Fourier transform to evaluate the elastic modulus of recycled concrete. After the validity of the numerical method is verified with experimental results, a sensitivity analysis is conducted to evaluate the effects of key factors on the elastic modulus of recycled concrete. Numerical results show that the elastic modulus of recycled concrete increases with the increase of the total aggregate content and the elastic moduli of old and new ITZ but decreases with increasing the replacement ratio of recycled aggregate and the thicknesses of old and new ITZ. It is also shown that, for a replacement ratio of recycled aggregate smaller than 0.3, the elastic modulus of recycled concrete is reduced by no more than 10%.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.239-246
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• 2012

Pervious concrete is a tailored-property concrete with high water permeability which allow the passage of water to flow through easily through the existing interconnected large pore structure. This paper reports the results of an experimental investigation into the development of pervious concrete with reduced cement content and recycled concrete aggregate for sustainable permeable pavement construction. High fineness ground granulated blast furnace slag was used to replace up to 70 % cement by weight. The properties of the pervious concrete were evaluated by determining the compressive strength at 7 and 28 days, void content and water permeability under falling head. The compressive strength of pervious concrete increased with a reduction in the maximum aggregate size from 20 to 13 mm. The relationship between 28-day compressive strength and porosity for pervious concrete was adversely affected by the use of recycled concrete aggregate instead of natural aggregate. However, the binder materials type, age, aggregate size and test specimen shape had marginal effect on the strength-porosity relationship. The results also showed that the water permeability of pervious concrete is primarily influenced by the porosity and not affected by the use of recycled concrete aggregate in place of natural aggregate. The empirical inter-relationships developed among porosity, compressive strength and water permeability could be used in the mix design of pervious concrete with either natural or recycled concrete aggregates to meet the specification requirements of compressive strength and water permeability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.367-375
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• 2022

In this study, the characteristics of recycled aggregate concrete according to the mixing ratio of recycled fine aggregate were analyzed by design strength to explore its use in the production of ready-mixed concrete. The results show that, depending on the ratio of recycled aggregate, the compressive strength is similar to that of normal concrete and does not deteriorate. Therefore, it is possible to achieve a strength similar to the target design strength. Furthermore, if the ratio of recycled fine aggregate for concrete is up to 25 % of the total aggregate amount (50 % of the to-tal fine aggregate), slump does not cause problems. Our findings show that the higher the de-sign standard strength, the greater the amount of powder, and management of slump reduction, unit quantity, and performance system is necessary. The obtained results show that recycled ag-gregate can be used for the production of ready-mixed concrete after adjusting its mixing ratio and concrete mix proportions.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.316-319
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• 2004

Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. The purposed of this paper is to propose the model for the stress-strain relation of recycled-PET polymer concrete at monotonic uniaxial compression and is to investigate for the stress-strain behavior characteristics of recycled-PET polymer concrete with different variables(strength, resin contents, curing conditions, addition of silane and ages). The maximum stress and strain of recycled-PET polymer concrete was found to increase with an increase in resin content, however, it decreased beyond a particular level of resin content. A ascending and descending branch of stress-strain curve represented more sharply at high temperature curing more than normal temperature curing. In addition, results show that the proposed model accurately predicts the stress-strain relation of recycled-PET polymer concrete.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.359-365
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• 2017

This study examined concrete characteristics depending on the replacement ratio of recycled fine aggregates, which suits the KS F 2573 concrete recycled aggregate standard. As physical properties, slump, air content, changes in the elapse of time and compressive strength were studied in order to provide basic data for activation of recycled fine aggregate recycling. As a result of experimenting recycled fine aggregate concrete, the increase in the replacement ratio of recycled aggregates led to the increase in slump and air content. Also, when the replacement ratio of recycled fine aggregates was 30%, it was judged that there was no problem with constructability. When the replacement ratio was 30%, recycled fine aggregate concrete had a similar tendency to natural aggregate concrete at a compressive strength of 24MPa. When the replacement ratio was 30%, at a target strength of 24MPa, recycled fine aggregate concrete had the same physical characteristics as natural aggregate concrete. This means that a replacement ratio of 30% is appropriate for replacement of recycled fine aggregates. In future, there will be a need to improve the quality of recycled fine aggregates for activating the use of recycled fine aggregates and further research will have to evaluate physical properties of recycled fine aggregate concrete using improved recycled fine aggregates.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.197-208
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• 2003

This paper is to determine the possibility of re-using waste concrete from Incheon city area. The strength test was conducted with five aggregate compounds which was replaced a natural aggregate with recycled aggregate. After checking the physical characteristics of recycled aggregate compounds, the mix design of recycled concrete was conducted. For the relatively comparison between natural and recycled compounds, while the unit aggregate weight was changed, other conditions were fixed. The freezing and thawing test which included fly-ash and super-plastezer were performed to check the durability and workability when recycling waste concrete. In the physical characteristics of recycled aggregate, it was found that the specific gravity of recycled coarse aggregate and recycled fine aggregate satisfied the first grade of recycle specification(KS), and all compounds of recycled aggregate also satisfied the second grade of absorption specification, Especially up to the 50% substitution of recycled aggregate is equal to or a bit lower than that of convention aggregate. In comparison with conventional concrete, the recycled concrete is lower than maximum by 7% in compressive strength decreasing rate after freezing-thawing test. From now, although most of recycled concrete was used to the building lot, subgrade, asphalt admixture, through the result. It was proved that possibility of re-using recycled aggregate as the substructure of bridge, retaining wall, tunnel lining and concrete structure which is not attacked the drying shrinkage severely.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.93-96
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• 2000

In this paper, physical properties of planting concrete using Recycled aggregates made with demolished concrete and construction wastes are investigated. According to the test results. It shows that recycled aggregates made with demolished concrete and construction wastes have low physical properties compared with crushed stone. But, recycled aggregates made with construction wastes shows better performance in absorption ratio, unit weight and thermal conductivity than crushed stone. According it is thought that they are available for being applied to planting concrete considering the sides of efficient recycling of construction wastes and saving the manufacturing cost.