• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.167-176
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• 1998

골재의수요는 매년 크게 증가하고 있으나 천연골재는 점차 고갈되어 가고 있다. 따라서 기존석산들에서 발생되는 폐석자원을 쇄석골재로 활용하면 일거양득의 효과가 있다. 본 연구는 국내에서 가장 대규모 석산단지인 포천 및 익산지역 기존석산에서 발생되는 석산폐석에 대한 물리적, 화학적 및 광물학적 시험.분석을 실시하여, 쇄석골재로서 석산폐석의 특성규명과 활용가능성을 평가하였다. 연구결과, 포천과 익산지역에서 발생되는 석산폐석을 쇄석골재로 활용할 수 있을 것으로 판단되었으며, 폐석자원을 쇄석골재로 활용함으로써 골재의 수요에 보충하고, 산림 및 자연경관의 훼손과 환경오염을 야기할 수 있는 석산골재 신규개발의 억제에도 효과가 기대된다.

• 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.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.331-338
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• 2013

Under the paradigm of sustainable green growth at the national level, various researches and applications for energy saving in the construction field has been attempted. As a part of energy saving efforts, lightweight concrete was investigated for thermal insulation concrete with phase change material (PCM) which has high heat storage capacity. As a part of energy saving efforts, thermal insulation concrete was investigated and evaluated with lightweight aggregate impregnated by PCM which has high heat storage capacity. As a result, it is found that concrete with lightweight aggregate impregnated by PCM is effective to prevent its quality deterioration by reducing water absorption rate of lightweight aggregate. In addition, it has shown that concretes using lightweight aggregate and impregnated lightweight aggregate improve heat insulation property 33% and 40~43% compared with using normal aggregate, respectively. It is that the lightweight aggregate concrete with impregnated lightweight aggregate has 12~14% lower thermal conductivity than unimpregnated.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.69-76
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• 2012

A recent shortage in Korean aggregate market leads a social demand to utilize recycled aggregate to more advanced level, such as the use in concrete structures or paving materials for surface and base layers. Government announced a recycled aggregate guideline in 2009 to provide an institutional framework for recycled aggregate in such an up-scaled use. The use of recycled aggregate in such use; however, is very minimal. This paper evaluates the validity of the impurity content criteria of recycled aggregate for lean concrete base through a series of material tests. The analysis results shows that reclaimed asphalt pavement (RAP) in recycled aggregate not only influence a strength lean concrete adversely, but also influence negatively on an absorption and abrasion characteristics of aggregate system significantly that made those two indices lower. Since absorption and abrasion characteristics are very important indices for recycled aggregate quality, RAP in recycled aggregate could significantly mislead the recycled aggregate qualification. This paper provides a suggestion to resolve these problems.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.116-122
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• 2016

This study was intended to evaluate the properties of concrete incorporating stone powders which are created during crushing natural stones to produce crushed aggregates. For concretes with 0~30 wt.% partial replacement fine aggregates with stone powders, experiments of slump, air content, strength and drying shrinkage were carried out. The experiments found that the increase of the amount of stone powders sharply decreased slump and air content. Partially using stone powders instead of fine aggregates was found to increase both compressive and tensile strength slightly. Substituting higher amount of stone powders presented higher drying shrinkage. When HRWRA was added into the concrete with stone powders in order to obtain workability similar to that of plain concrete without stone powders for the same water-cement ratio and unit weight of cement, air content increased with the amount of HRWRA but strength and drying shrinkage were hardly affected by adding HRWRA.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.30-39
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• 2017

This paper concerns flexural strength of reinforced concrete beams containing recycled coarse aggregate (RCA) with compressive strength ranging from 31 to 38 MPa. The experimental parameters were replacement ratio of RCA and rebar ratio. Replacement ratio of RCA was 0, 30, 50 and 100%, and rebar ratio was 0.50, 0.79 and 1.14%. The RCA concrete beams were tested by using four-point bending test, and experimental results were discussed regarding crack and failure patterns, load-deflection relationship. Crack pattern of concrete beams with RCA was similar to that of concrete beams with natural coarse aggregate (NCA) but overall crack spacing of concrete beams with RCA was smaller than that of concrete beams with NCA. The crack width of RCA and NCA concrete beams was similar to each other. In addition, the test results of flexural strength were compared to the design code predictions. The design code predictions for flexural strength underestimated the experimental results. Therefore, the design code predictions for flexural strength of RCA concrete beams would offer conservative design.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.125-135
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• 2016

The objective of this paper is to provide integrated Korea industrial standards(KS) for concrete aggregates, which has been separately provided with ten kinds of KS, in order to improve the way of quality management of concrete aggregate and to prevent distribution of unsuitable aggregates. For the sequences of the paper, typical foreign standards related to concrete aggregates including ASTM for US, EN for EU, JIS for Japan are reviewed and compared to provide necessities and feasibilities of the paper. Based on the analysis above results, existing KS for concrete aggregates, which have been separately provided with ten kinds being lack of correlation between each KS is integrated to KS F 2526 "Aggregates for concrete" in this paper. By doing this, in terms of terminology, the expression of the aggregate, which has been currently classified into specified terminologies of aggregates depending on sources, manufacturing methods of each aggregates, is able to be integrated to single expression of the aggregate for concrete. It is believed that integrated KS presented herein provides more desirable way in terms of its better accessibility, easier revision and closer connection between each aggregate kinds.

• Resources Recycling
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• v.16 no.6
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• pp.20-27
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• 2007

This paper presents a detailed experimental study on the durability properties of mortar matrix made with two kind of recycled fine aggregates(RAA, RAB) and five replacement levels (0, 25, 40, 75 and 100) of the recycled fine aggregates as a partial replacement of natural fine aggregate (NA). The durability properties of mortar matrix was evaluated using compressive strength, chloride ion ingress, sulfate attack and carbonation. The test results indicated that the water absorption and Adhered mortar of the recycled fine aggregate was a major factor controlling durability properties. Hereafter, when using built recycled fine aggregate is expected, appropriate removal Adhered mortar and reasonable replacement ratio of recycled fine aggregates was 25% weight of cement are advised to apply to the concrete materials.

• 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.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.557-563
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• 2008

Recently, the amount of disposed construction materials like demolished concrete is growing fast and the shortage of natural concrete aggregate is becoming serious. Therefore, recycling of aggregate extracted from the demolished concrete is getting important and use of the recycled aggregate for concrete has been seriously considered. However, the use of the recycled aggregate even for low performance concrete is very limited because recycled aggregate which contains large amount of old mortar has very low quality. Therefore, removing the paste sticked to the recycled aggregate is very important in the manufacturing of high quality recycled aggregate. We have studied a series of research according to complex crushing method, which is removed the ingredient of cement paste from recycled fine aggregate using both the low speed wet abrasion crusher as mechanical process and the acid treatment as chemical processes. This paper is to analyze the quality of the recycled fine aggregate produced by those complex method and investigate optimum manufacturing condition for recycled fine aggregate by the design of experiments. The experimental parameters considered are water ratio, coase aggregate ratio, and abrasion time. As a result, data concerning the properties of recycled sand were obtained. It was found that high quality recycled fine aggregate could be to obtain at the condition of the fifteen minute of abrasion-crusher time and the over 1.0 of recycled coarse aggregate ratio.