• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.366-373
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• 2015

Construction waste is recycled and used for the efficient and eco-friendly disposal of construction waste increasing due to reconstruction and redevelopment project and so on. There is recycled aggregate as a typical case. And this recycled aggregate shows strong alkalinity due to calcium hydroxide, and causes many environmental problems. Therefore, this is a study on reduction in the strong alkalinity of recycled aggregate by using sodium phosphate based ammonium in order to reduce the pH of recycled aggregate. Besides, a possibility that a pH reducing agent of recycled aggregate could be applied to a site was evaluated. As a result, it was possible to verify that pH decreased as the percentage of pH reducing agent increased. It is thought that the pH reducing agent can be applied to a site by methods such as immersion and spray using the pH reducing agent in the process of producing recycled aggregates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.213-218
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• 2006

As a manufacturing process of recycled aggregate improves the quality of recycled aggregate shall be sufficient enough to be used for structural concrete. This study characterized compressive strength and elastic modulus of concrete that used recycled coarse and fine aggregate. Before the strength tests, the fundamental characteristics of recycled aggregate were preliminarily analyzed and the recycled aggregate satisfied the class 1 requirements in KS F 2573. As the replacement ratio increased, the compressive strength and elastic modulus of recycled aggregate concrete decreased. When the coarse and fine aggregates were completely replaced with the recycled, the compressive strength and elastic modulus were decreased by 13% and 31%, respectively. Based on the test results, this study suggests equations for predicting the compressive strength and elastic modulus of the recycled aggregate concrete with respect to the replacement ratio. The values from the equations were in good agreement with the test data from this study and others.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.91-96
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• 2002

본 연구는 화력발전소에서 발생하는 fly ash의 재활용 분야중 하나인 fly ash 경량골재 생산과정에서 소성(sintering)온도를 결정하는 미연탄소의 연소 현상을 분석함으로서 공정에 적용 가능한 단일 입자 연소 모델 개발을 목적으로 한다. fly ash 경량골재는 미연탄소를 포함한 fly ash를 점결제를 이용하여 성형하고, 함유된 미연탄소를 연소시켜, 그 연소열을 이용하여 fly ash를 소성 시켜 형성된다.(중략)

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.05a
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• pp.19-24
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• 1997

콘크리트 구조물이 고온에 가열되면 그 성질이 변화하여 구조물은 다양한 영향을 받는다. 콘크리트 구조물의 고온에서의 성상은 시멘트의 종류, 골재의 성질, 배합비, 함수율, 재령 등에 의해 다르다. 콘크리트의 열성질에 관한 외국에서의 연구는 다수 보고되었으나 국내에서 연구한 결과는 없으며 특히 시멘트의 종류, 골재의 성질 등에 따라 고온에서의 성상이 다르기 때문에 본 연구에서는 국내에서 생산되는 시멘트, 골재를 대상으로 하였다. 또한 콘크리트 배합을 일반 구조물 및 아파트 현장에서 사용하는 배합비로 시험체를 제작ㆍ실험하였다. (중략)

• 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.

• 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 Institute of Building Construction
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• v.15 no.6
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• pp.545-551
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• 2015

The aim of this research is suggesting application method of the wasted rock obtained from the limestone quarry of raw material for cement as a coarse aggregate for high strength concrete after crushing and sieving processes. The wasted rock has been normally wasted because of its low quality as a material for cement production. In this research, the concrete using this wasted limestone coarse aggregate was evaluated the constructability based on the performances of workability, air content, and compressive strength. From the experiment, a favorable performance was achieved with a limestone coarse aggregate for high strength concrete comparing to the high strength concrete using granite coarse aggregate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.307-312
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• 2015

This paper addresses mechanical properties and length change performance of the recycled aggregate concretes(RAC) in which natural coarse was replaced by recycled coarse aggregate(RCA) by compressive strength levels(20, 35, 50 MPa). A total of 9 RAC were produced and classified into three series, each of which included three mixes designed with three compressive strength levels of 20 MPa, 35 MPa and 50 MPa and three RCA replacement ratios of 0, 50 and 100%. Physical/Mechanical properties of RAC were tested for slump test, compressive strength, and length change. The test results indicated that the workability of RC could be improved or same by RCA replacement ratios, when compared with that containing no RCA. This is probably because of the RCA shape improving the workability of RAC. Also, the test results showed that the compressive strength was decreased by 9~10% as the RCA replacement ratios increase. However, the length change ratio by the RCA replacement ratios increased regardless of compressive strength levels. At 20 MPa level, the length change ratio was 8~40% which was much higher than that of 4~17% at both 35 and 50 MPa levels. Therefore, it was considered that such admixture addition preventing dry shrinkage is required in order to improve the properties of the RAC at 20 MPa level.

• Cement
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• s.163
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• pp.33-43
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• 2004

• 레미콘
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• no.1 s.46
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• pp.69-87
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• 1996