• Journal of the Korea Institute of Building Construction
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• v.7 no.2 s.24
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• pp.85-92
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• 2007

In the past, recycled aggregate was used very limitedly in low value-added areas such as the base layer of roads. However, in response to the shortage of natural aggregate, high consciousness of resource saving and changed idea on environment, the quality of recycled aggregate has been improved considerably, and the percentage of recycled construction waste is increasing every year compared to simple landfill or incineration. Recently the Act on the Promotion of Construction Waste Recycling was enacted on December 2003 for the efficient use of recycled aggregate, and the Standards for the Quality of Recycled Aggregate for Concrete (Proposal) were announced in order to use and manage recycled aggregate according to quality. According to the Standards for the Quality of Recycled Aggregate for Concrete (Proposal), it is recommended to substitute recycled coarse aggregate and fine aggregate below 30% each. However, compared to the trend of recycling, the recycling rate of aggregate is still quite low. It is because of low performance of recycled aggregate, users' lack of understanding, etc. These problems basically come from the decrease of strength of recycled concrete resulting from the use of recycled aggregate, and recycled aggregate is still considered not reliable because there have been not many cases of actual application. If the basic problem of strength decrease is solved and data on recycled aggregate is provided through actual field placing, we may maximize the use of recycled aggregate. Thus, in order to maximize the use of recycled aggregate that satisfy the recycled aggregate quality standards, the present study made a mock-up similar to real structures, evaluated its performance and examined the field applicability of recycled aggregate concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.169-172
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• 2004

Recently, because of the shortage of natural aggregate and the environment regulation of government, the application of recycled aggregate by solution method is observed according as the concern for the reuse of waste concrete. But because the quality of recycled aggregate is poor and quantitative quality judgment standard of recycled aggregate is fluffy, construction field application is difficult. Therefore, this study compares and investigates effect that quality of recycled aggregate influencing recycled concrete. As the result of this study, the more quality of aggregate increases, the more recycled concrete quality increased and high quality recycled aggregate generally displayed performance of similar level with nature aggregate. But, durability of recycled concrete using recycled aggregate appeared lower than concrete using natural aggregate without reference to aggregate quality.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.384-387
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• 2004

Though recycled aggregate is useful resources for concrete, its application to structural frame is not frequent, because of low quality of recycled aggregate. Owing to the development of manufacturing technology to recycled aggregate, it is possible to produce high quality recycled aggregate. The purpose of this study is to confirm the applicability of the high quality recycled aggregate, instead of the natural aggregate, to normal concrete. Main factors of this study are substitute proportion of recycled aggregate, types of recycled aggregate, targeting compressive strength of recycled concrete. From the results of the study, we concluded that it is possible to use high quality recycled aggregate, to get the same strength as concrete using normal aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.15-19
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• 2004

The production of waste concrete is increased continuously by urban renewal, reconstruction, remodeling, and so on. So the positive use of recycled aggregate concrete is needed. Research for recycled aggregate concrete that use recycled aggregate from the mid-80s to solve environmental problem of aggregate insufficiency and waste concrete is consisting vigorously. However, specifications and mix design about waste concrete's use are evading use of recycled aggregate concrete yet in spot being not taken a triangular position. Therefore. it analyze existing research data for recycled aggregate concrete collection to develop strength estimate program in this research. Recycled aggregate concrete's strength estimate program if specifications and mix design about recycled aggregate concrete are taken a triangular position to foundation recycled aggregate concrete's practical use to increase judge.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.271-272
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• 2018

As the supply and demand of natural aggregate becomes more difficult in the domestic construction site continuously, many studies related to the recycled aggregate produced in the construction waste are going on. However, because of the safety and performance of the recycled aggregate, it is not used as aggregate for the structure, and it is mainly used as a nonstructural material. In addition, as the "recycled aggregate quality standard" has been revised in 2017, quality standards for various properties of recycled aggregate have been adjusted, and production technology suitable for recycled aggregate quality standards for concrete is needed. In this study, to improve the quality of recycled aggregate, we applied multistage wind pressure treatment method to the existing recycled aggregate production facility and compared the density, absorption rate, particle size before and after recycled aggregate treatment. As a result, quality criteria in various properties were analyzed satisfactorily.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.643-648
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• 2002

A research for recycling the demolished-concrete as concrete aggregate has been concerned in all over the world. There, however, are some problems that qualities of recycled aggregates are not only largely different, but also mechanical properties of recycled aggregate concrete decrease a little in comparison with that of natural aggregate concrete. In this study, the resistance of freezing and thawing of concrete using source-concrete recycled aggregate(SRN) and demolished-concrete recycled aggregate(DRA) was investigated. Futhermore a research for improvement of freeze and thaw durability of recycled aggregate concrete was performed. Relative dynamic modulus of elasticity of SRN and DRA recycled aggregate concrete was dropped 60% before 150 of freezing and thawing cycle, and was much lower than that of control concrete. Relative dynamic modulus of elasticity of recycled aggregate concrete was increased to decrease water-cement ratio, but the freeze and thaw durability of recycled aggregate concrete was not enough improved. Futhermore, when metakaolin and silica fume were repalced, the freeze and thaw durability of recycled aggregate concrete containg metakaolin was more improved than that of silica fume.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.515-522
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• 2011

As Construction and Demolition (C&D) debris increases every year, systems have been adopted to compel the use of recycled aggregate made from C&D debris, and the use of recycled aggregate in the construction field has increased. But environmental problems linked to the alkalinity of recycled aggregate have occurred, and a study on approaches to lower the alkalinity of recycled aggregate is needed. It was certified by this study that a large amount of recycled aggregate could be carbonated in the C&D debris midterm-treatment field. As a result, the density and the water absorption of recycled aggregate after carbonation reaction was improved, and pH of recycled aggregate was lowered from over 11 to 9.4. X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Thermogravimetry/Differential Thermal Analysis (TG/DTA) methods also indicated the carbonation of recycled aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.81-84
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• 2006

This study is intended for how to utilize the recycled fine aggregate which is produced by concrete wastes. It analyzes the quality of the fine aggregate which is reproduced through the acid treatment process, and comprehends the characteristics of mortar using the recycled fine aggregate to review whether it can be put to practical use for concrete. The conclusion of the study are as follows 1. The recycled fine aggregate through the acid treat shows the low rate of absorption and high density. 2. Compared to the mortar made from acid liquid precipitated recycled fine aggregate, using nature water precipitated one reduces the flow. 3. The compressive strength of mortar using recycled fine aggregate tends to be reduced according to the kind of precipitated water. Based on the above results, the recycled fine aggregate through the acid treatment process satisfies the quality standards of the first-grade recycled fine aggregate of KS F 2573 (recycled fine aggregate for concrete) but it is concluded that the recycled fine aggregate through the acid treatment process can not used as fine aggregate used concrete because it has destructive characteristics when the mortar is produced

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.19-24
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• 2015

PURPOSES : The objective of this study is to evaluate the effect of the residual mortar of recycled concrete aggregate on the expansion behavior during alkali silica reaction (ASR). METHODS: In order to evaluate the net effect of residual mortar on ASR expansion behavior, two aggregate samples with the same original virgin aggregate source but different residual mortar volumes were used. ASTM C1260 test was used to evaluate the ASR expansion behavior of these two aggregates and the original virgin aggregate. RESULTS: The greater the amount of residual mortar in recycled concrete aggregates, the less is the induced ASR expansion. Depending on the amount of residual mortar in recycled concrete aggregate, the ASR expansion of recycled concrete aggregate may be less than half of that of the original virgin aggregate. CONCLUSIONS: The residual mortar of recycled concrete aggregate may lead to the under estimation of the ASR expansion behavior of the original virgin aggregate.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.345-358
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• 2003

Recently, the reuse of coarse aggregate derived from demolished concrete was introduced into practice with two environmental aspects: protection of natural sources of aggregate and recycling of construction waste. However, recycled aggregate has been used for the very limited application such as subbase material for pavement and constructional filling material because it was considered as low quality constructional materials. In the present study, in order to examine the possibility that recycled aggregate can be used for concrete mixing, we conducted various experimental tests to identify mineralogical, chemical and mechanical properties of recycled aggregate and to determine the workability and mechanical properties of recycled aggregate concrete (RAC). The cement paste and mortar contained in recycled aggregate significantly affect the basic mechanical properties of aggregate and the workability and mechanical properties of RAC. However, RCA mixed with the proper replacement ratio of recycled aggregate shows the comparable compressive strength and freeze and thaw resistance to those of normal concrete. Therefore, it is considered that recycled aggregate can be widely used for concrete if the cement paste and mortar can be efficiently removed from recycled aggregate and/or if the effective replacement ratios of recycled aggregate are applied for mixing concrete.