• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.207-208
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• 2016

The most important things for the production of recycled aggregates are saving energy, suppressing the generation of by-product fine particles and sustaining the performance of concrete. As solutions, this study proposes this technology of improving the performance of recycled aggregates through forced carbonation.1) It is to stimulate and carbonate the bond paste part that causes the deterioration of recycled aggregates. Particularly, the purpose of this technology is to fill and chemically stabilize pores inside the bond paste, further improving the quality of recycled aggregates with a decreased absorption rate and an enhanced aggregate strength. Ultimately, it is possible to obtain a carbonation model, depending on the paste ratio and particle-size distribution of recycled aggregates. Moreover, by calculating the optimum carbonation period through the verification of this carbonation model, it is possible to examine how much the strength is improved by the reformation of recycled aggregated.

• Advances in concrete construction
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• v.9 no.2
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• pp.195-205
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• 2020

In this study, effect of recycled aggregates and polypropylene fibers on the response of conventionally reinforced concrete element subjected to tensile loading in terms of tension stiffening and strain development was experimentally investigated. For this purpose, concrete prisms of 100 × 100 mm cross section and 500 mm length having one central deformed steel re-bar were cast using fibrous and non-fibrous Recycled Aggregate Concrete (RAC) with varying percentages of recycled aggregates (0%, 25%, 50%, 75% and 100%) and tested under uniaxial tensile load. For all fibrous RAC mixes, polypropylene fibers were used at constant dosage of 3.15 kg/㎥. Effect of recycled aggregates and fibers on the compressive strength of concrete was also explored in this study. Through studying tensile load versus global axial deformation of composite and strain development in concrete and steel, it was found that replacement of natural aggregates with recycled aggregates in concrete negatively affected the cracking load, tension stiffening and strain development, and this negative effect was observed to be increased with increasing contents of recycled aggregates in concrete. The results of this study showed that it was possible to minimize the negative effect of recycled aggregates in concrete by the addition of polypropylene fibers. Reinforced concrete element constructed using concrete containing 50% recycled aggregates and polypropylene fibers exhibited cracking behavior, tension stiffening and strain development response almost similar to that of concrete element constructed using natural aggregate concrete without fiber.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.41-46
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• 2003

Until now, the quantity to recycle wasted concrete as the great supplementary value was very little. But considering a insufficiency of the present state of aggregates, the recycling of wasted aggregates is indispensable. This study will offer the basic application data of the recycled aggregates to make by the new attempt and offer the basic data of the great supplementary value of recycled aggregate to make good use of precast process. The result of compressive strength, tensile strength, flexural strength and drying shrinkage test of concrete by recycled aggregates were similar to the property of normal aggregate concrete, and the contrary effect of recycled aggregate by high temperature steam curing do not have been found out. Therefore the great supplementary value of recycled aggregate to make good use of precast process is possible way to be helpful to a insufficiency of the present state of aggregates.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.132-133
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• 2014

In this study, high volume of industrial by-products including blast furnace slag, recycled aggregate powder and incineration ash have been utilized on the slurry of the foamed lightweight concrete. As to decrease the price of the lightweight foam concrete, mortar based slurry and concrete based slurry has been fixed. As the variation of the foam conduction ratio and aggregates, the foam ratio and compressive strength has been tested. Results showed that using recycled aggregates in the slurry showed better effect than using natural aggregates due to the alkali properties of the recycled aggregates could activate the potential hydraulic properties of the blast furnace slag. Consider about the low price of the recycled aggregates, it could be identified that using recycled aggregates in high volume blast furnace slag blended lightweight concrete showed better compressive strength than natural aggregates.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.337-338
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• 2013

Recent research is needed for the reduction of the pH of the recycled aggregates, recycled aggregates for alkali social problems have emerged. This was confirmed through preliminary experiments using a self-made reactor with dry ice, the possibility of reducing the pH of the recycled aggregates. The pH reduction of coarse recycled aggregates plant was made to apply the field to the middle of construction waste treatment process to reduce the pH of the plant room, and measured the pH change with time. The measurement results showed that dry ice after the reaction, the pH of the aggregate 5% reduction than untreated recycled aggregates.

• Advances in concrete construction
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• v.3 no.3
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• pp.187-202
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• 2015

The present study addresses about the development of sustainable concrete utilizing recycled coarse aggregates manufactured form waste concrete and colloidal Nano-Silica. Experimental investigations are carried out to determine compressive and tensile strength of concrete mixes designed with recycled coarse aggregates and different percentages of Nano-Silica. Moreover, water absorption, density and volume voids of concrete mixes are also examined to ascertain the influence of Nano-Silica on behavior of recycled aggregate concrete. The outcomes of the research depict that properties of concrete mixes are significantly affected with the introduction of recycled coarse aggregates in place of the natural coarse aggregates. However, the study reveals that the depletion of behavior of recycled aggregate concrete could be restored with the incorporation of little amount (3%) of Nano-Silica.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.133-136
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• 2006

This study tested gravity separation with heavy-medium to produce structural recycled aggregates. A result that could produce recycled aggregates attached mortar hardly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.4
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• pp.485-492
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• 2019

In this study, the effect of moisture conditions of recycled coarse aggregates on the compressive strength of concrete was evaluated with the water/binder ratios and the curing conditions. The saturated recycled aggregates seemed to have the negative effect on the strength development of concrete. This is the because of the decrease in bond strength between aggregate and cement paste due to the increase of surface water according to the high absorption of recycled aggregates. The effect of types and moisture conditions of aggregates according to the change of water/binder ratio was similar. However, the curing conditions had a significant effect on the compressive strength of the concrete with the different types of aggregates. In the case of curing in air, the recycled aggregates with high absorption reduced the moisture required for hydration and increased the rate of vaporizing, and these result in interfering strength development. The moisture conditions of the recycled aggregates have a considerable effect on the compressive strength of the concrete, and it is necessary to control the moisture conditions of aggregates in the production of concrete with recycled coarse aggregate. And the control of the curing condition is very important for the concrete with recycled aggregate.

• International Journal of Highway Engineering
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• v.15 no.2
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• pp.83-94
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• 2013

PURPOSES : In Korea, most designs of pavement had been mainly performed by considering CBR of granular materials before KPRP(Korea Pavement Research Program) and 86 AASHTO design method were introduced. Since then, the trend of the pavement designs gradually have moved to using mechanical characteristics throughout the resilient modulus based on the test results up to recently. In this study, we should like to research the mechanical characteristics of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. METHODS : The kinds of materials were tested; coarse grained subbase materials, refining aggregates base materials and recycled aggregates. RESULTS : The present study aims to figure out the resilient modulus of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. CONCLUSIONS : The test results revealed that the engineering properties of the recycled aggregates were more excellent than the those of others.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.172-179
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• 1996

Recently, the broken concrete lumps resulting from the demolition of concrete structures are creshed for reuse as aggregates(i.e. recycled fine and gravel). And also, in the processing of crusing, the recycled powder of an equivalent of between 20% to 30% by wt.% of the broken concrete lumps is generated. The extensive research of recycled concrete aggregates has been carried out in various parts of the world. But less reseatch on the reuse of recycled concrete powder has been carried out. It is the purpose of this report that the study on the quality evaluation of recycled aggregates for recycled concrete. In specially, this report deals with the properties such as flow, compressive strength, bending strength, drying shrinkage and wight loss rate of mortars replaced standard fine aggregate with recycled powders at the rate of 3, 7, 15, 20 and 30 wt.%. Since the characteristics of recycled mortars with the recycled powders were comparable to those of the normal mortar without the recycled powders as described above, its concretes could be found extensive application in such field as concrete products.