• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.97-100
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• 2006

The efforts have improved the absorbtion that in order to high the quality of recycled aggregates, and the shape. For the shape of recycled aggregates, the shape of usually aggregates can affect the strength of concrete in an indirect way. So that, in the study, effects is investigated the shape of recycled aggregates that affects the compressive strength and slump. In the result, the a improved shape have a beneficial effect on compressive strength and slump for of a high quality recycled aggregate, and these appear a larger effects in unit water ; $175kg/m^3$ or specified strength ; 24MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.124-127
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• 2003

Sewage sludge and clay used as raw materials in the study. Green aggregates contain different contents by dried weight of the sewage sludge, up to 80 percent is manufactured and burning conditions of soak temperature, soak time and rate of temperature increase. influence of burning condition and mixing ratio on specific gravity of burned aggregate are discussed. The appropriate burning condition to all aggregates is evaluated. Aggregates result form the thermal treatment get specific gravity under 0.8, water absorption fewer than 7.5 percent, and aggregate crushing value from 28 to 53. As the result, aggregates can be available as the lightweight aggregate for non-structural concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.47-48
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• 2010

In this study, simple beam tests proposed by Ichinose were performed to estimate the bond performance of reinforced concrete beams using electric arc furnace slag aggregates. As results of the test, the specimens with the electric arc furnace oxidizing slag aggregates showed higher bond capacity as compared to the one with natural aggregates.

• Computers and Concrete
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• v.19 no.5
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• pp.451-455
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• 2017

Technological advancements in the field of building materials are achieved day by day. In this study, a new lightweight concrete aggregate is produced by mixing certain rates of colemanite (0%, 7.5%, 12.5%, 17.5%), cement and coating the surface of pumice aggregate with this mixture. Thin aggregate sections are analyzed with specific gravity, unit weight, water absorption, impact, and crushing experiments. In this way, the production of cement and cement+colemanite coated lightweight concrete aggregates is investigated and an opinion on the likely behavior of these concrete types is provided.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.137-140
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• 2005

The objective of this experimental study is to grasp an influence of moisture state of aggregate on the characteristics of the recycled aggregate concrete. The moisture states of the aggregates were controlled at prewetted, oven-dried and saturated surface-dried states prior to use. To maintain the designed mix proportioning unchanged, the amounts of water and aggregates used in mixing were adjusted according to the actual moisture contents of the aggregates. Test results showed that the saturated surface-dried state aggregate concretes exhibited the highest compressive strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.167-174
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• 2020

Many researches have been conducted to utilize recycled aggregates in Korea, but since most sources of recycled aggregates are not clear, there is a lot of uncertainty in applying the existing research results on recycle of aggregates generated from nuclear power plants. In this study, therefore, in order to investigate the possibility of recycling coarse aggregates generated through dismantling of nuclear power plants in Korea, recycled coarse aggregates were produced from concrete simulating nuclear power plants in Korea. Using the recycled coarse aggregates, concrete was mixed in consideration of the mixing ratio of the recycled coarse aggregates, and the mechanical properties were experimentally investigated. From the test results, as the mixing ratio of recycled coarse aggregates increased. concrete compressive strength, tensile strength, and elastic modulus generally decreased up to 36, 37, and 27% from the mechanical properties of normal concrete, respectively. Therefore, it can be concluded that limitation on the mixing ratio of recycled coarse aggregates is necessary when coarse aggregates are recycled through dismantling of nuclear power plants.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.105-113
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• 2016

OBJECTIVES : This study is to develop the optimum mixing proportions for cement concrete pavement with using recycled aggregates. METHODS : The mixture varied recycled coarse aggregates content from 50 % to 100 % to replace the natural coarse aggregates by weight. Tests for fundamental properties as a cement concrete pavement were conducted before and after hardening of the concrete. RESULTS : It was found that the variation in the amount of the recycled aggregate affected the compressive and flexural strength development, as well as the chloride ion penetration resistance. As the amount of the recycled aggregate content increased the compressive and flexural strength and the resistance to chloride ion penetration decreased. However, the resistance to freeze-thaw reaction was affected significantly. In addition, the gradation of the aggregate became worse and hence so did the coarseness factor as the recycled aggregate amount increased. CONCLUSIONS : The fundamental properties of the concrete with recycled aggregate does not seem to be appropriate when the recycled aggregate quality is not guaranteed up to a some level and its replacement ratio is over 50%. The optimized gradation of the aggregates should also be sought when the recycled aggregate is used for the cement concrete pavement materials.

• Computers and Concrete
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• v.7 no.5
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• pp.469-482
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• 2010

This paper investigates the concrete permeability through a numerical and statistical approach. Concrete is considered as a random heterogeneous composite of three phases: aggregates, interfacial transition zones (ITZ) and matrix. The paper begins with some classical bound and estimate theories applied to concrete permeability and the influence of ITZ on these bound and estimate values is discussed. Numerical samples for permeability analysis are established through random aggregate structure (RAS) scheme, each numerical sample containing randomly distributed aggregates coated with ITZ and dispersed in a homogeneous matrix. The volumetric fraction of aggregates is fixed and the size distribution of aggregates observes Fuller's curve. Then finite element method is used to solve the steady permeation problem on 2D numerical samples and the overall permeability is deduced from flux-pressure relation. The impact of ITZ on overall permeability is analyzed in terms of ITZ width and contrast ratio between ITZ and matrix permeabilities. Hereafter, 3680 samples are generated for 23 sample sizes and 4 contrast ratios, and statistical analysis is performed on the permeability dispersion in terms of sample size and ITZ characteristics. By sample theory, the size of representative volume element (RVE) for permeability is then quantified considering sample realization number and expected error. Concluding remarks are provided for the impact of ITZ on concrete permeability and its statistical characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.233-238
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• 2002

In this paper, the characteristics of fresh and hardened recycled concrete were experimentally compared to investigate the applicability of the recycled fine aggregates with the substitution ratio. Test results show that the workability of the recycled concrete decreases with the increment of substitution ratio of the recycled fine aggregates except for type-D case which has a lower absorption ratio. Also air content was increased with increasing substitution ratio. It was found that the compressive strength and elastic modulus of recycled concrete were decreased with increasing substitution ratio of the recycled fine aggregates. And, the superplasticizer was more effective on the workability recovery of the recycled concrete.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.2
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• pp.132-139
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• 2001

This study deals with coal-mine waste (CMW) for use in concrete as a replacement of normal aggregates. The CMW was collected from Sabuk region. Ganwon-do. Fine and coarse aggregates from CMW were prepared by using a crusher and separating debris with #4 sieve. CMW aggregates showed good physical and mechanical properties with having specific gravity over 2.65, absorption less than 1%, and abrasion ratio below 20%. However, particle shape of CMW was poor because of non-isotropic nature of matrix which cause particles to be long or flat. Since irregular particles caused a poor workability, to make workability better, a 1/4 of coarse aggregate was replaced with normal aggregate together with a superplasticizer. Compressive strength and other mechanical properties of CMW concrete were very good. Color of the concrete was darker than normal concrete due to black color of CMW. In conclusion, characteristics of CMW concrete was acceptable for use as a structural concrete material.