• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.97-103
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• 2009

This study was performed to evaluate the strength and durability properties of recycled polymer concrete using unsaturated polyester resin and recycled aggregates. Unsaturated polyester resin, natural and recycled aggregates and fly ash were used. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate sizes (5-10 and 5-25 mm) and unit binder contents (10% and 12%). Tests for the compressive and flexural strength, freezing and thawing and durability for 20% sulfuric solution were performed. The compressive and flexural strength of recycled polymer concrete were in the range of 85~97 MPa and 17.9~20.8 MPa, respectively. The strengths of recycled polymer concrete using recycled aggregate have similar or slightly decreased compared to polymer concrete using natural aggregate. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of recycled polymer concrete were in the range of 0.13~1.42% and 94~99, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.70-76
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• 1996

The purpose of this study is to investigate workability and strength of concrete containing rice husk ash. For this purpose, concrete with and without rice husk ash were tested and analyzed on the workability and the characteristics fo their strength such as compressive, tensile and flexural strength according to unit weight of binder. Also, performances of rice husk ash as an admixture of concrete were compared with those of silica hume being widely used for high-strength concrete. As a result, workability and strength of rice husk ash as an admixture of concrete were analogous to those of silica hume.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.177-185
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• 1997

The purpose of this study is to investigate the mechanical properties of super-workable concrete using O.P.C., blast-furnace slag, and fly ash respectively. For this purpose, after determining the optimum mix proportion of super-workable concrete according to unit weight of binder and percentage of fine aggregate respectively, mechanical properties of super-workable concrete such as compressive, tensile and flexural strength as well as elastic modules were tested and analyzed. Also, the mechanical performances of super-workable concrete were compared with those of high-strength concrete with equal mix proportion of concrete. As a result, super-workable concrete have an excellent mobility, placeability, and segregation-resistance, but the strength of super-workable concrete was shown to be somewhat lower than that of high-strength concrete with equal mix proportion of concrete.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.30-34
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• 2000

The concretes cast in the sea water would be likely to be rich mix and mass concrete. Therefore it is important to check out the hydration heat of concrete and to reduce it to prevent the concrete from processing the temperature crack. Recently the antiwashout agent is used on underwater concrete for preventing from the segregation of concrete in the water. The experimental studies were done for the combined cement replaced by fly ash 30%unit weight of binder to study on the characteristics of hydration heat of antiwashout underwater concrete, and its characteristic was discussed by comparing on cast in sea water with anther one in air. The present paper showed that the hydration heat concrete replaced by 30%of fly ash was more significantly reduced than the normal concrete. The hydration heat of antiwashout underwater concrete was highter than that of normal concrete, but it was reduced lower than the normal concrete by adding fly ash.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.93-95
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• 2013

Recently, with the increase in the construction of ultra-high buildings and long-span structures, there is great demand for high-strength concrete which can reduce the structural weight and thickness of member sections. While developing high-strength concrete to meet performance requirements, certain issues at the design stage must also be considered. The issues include diseconomy from a great amount of per-unit cement, spalling failure by fire at ultra-high building, autogenous shrinkage caused by increased hydration activity of binder from use of a superplasticizer. Therefore, the purpose of this study is examined the strain characteristics of Fiber-reinforced-high-strength concrete(FRHSC), which differ from those of general concrete owing to autogenous shrinkage. Based on the experimental data, we proposed an autogenous shrinkage prediction model.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.68-71
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• 2013

Reactive Powder Concrete (RPC) is an ultra high strength and high ductility cement-based composite material and has shown some promise as a new generation concrete in construction field. It is characterized by a silica fume-cement mixture with very low water-binder (w/b) ratio and very dense microstructure, which is formed using various powders such as cement, silica fume and very fine quartz sand (0.15~0.4mm) instead of ordinary coarse aggregate. However, the unit weight of cement in RPC is as high as 900~1,000 kg/㎥ due to the use of very fine sand instead of coarse aggregate, and a large volume of relatively expensive silica fume as a high reactivity pozzolan is also used, which is not produced in Korea and thus must be imported. Since the density of RPC has a heavy weight at 2.5~3.0 g/㎤. In this study, the modified RPC was made by the combination of ternary pozzolanic materials such as blast furnace slag and fly ash, silica fume in order to economically and practically feasible for Korea's situation. The fire resistance and structural behavior of the modified RPC exposed to high temperature were investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.116-121
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• 2019

In order to evaluating applicability of RAP (recycled aggregate powder) in mortar, in this study, physical and mechanical tests was carried out. Material characteristics of recycled aggregate and RAP were evaluated and the mechanical properties of mortar replaced with RAP were analyzed. Test result of sieve analysis showed that as the milling time increased the fineness modulus was decreased and the distribution of 0.6 mm particle size was found to increase. The fluidity of mortar mixture substituted with RAP tended to increase than Plain mixture. It was result that the increasing fluidity was affected by unreacted surplus water in the mortar as the binder was replaced with RAP. From the compressive strength result of the mortar subjected to RAP, it was found that the RAP was able to replace up to about 10% of unit binder weight although the compressive strength of mortar was decreased as the RAP replacement increased. From the above study, it can be concluded that the physical properties of RAP satisfied the quality standard of aggregate for replacement with fine aggregate. Moreover, in case of the RAP was replaced up to 10% of unit cement weight, it was able to be possible to improve fluidity and compressive strength of mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.191-198
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• 1999

The purpose of this study is investigating characteristics of the concrete containing Fly-ash according to different 4 mix design, that is, the first mix design is partial replace Fly-ash of cement, second is partial replace Fly-ash of cement and fine aggregate, third is partial replace Fly-ash of fine aggregate, fourth partial replacement of fine and coarse aggregate. For this purpose, selected test variables were water-binder ratio with two levels of 45%, 50%, and Fly-ash contents with four levels 0%, 10%, 20%, 30%, As the result of this study are as follow. 1) The result of mix design of a partial replacement of cement, the slump-flow value was appeared a promotive effect of viscosity. But in case of the over with Fly-ash 10% and the other mix design was not changed slump value. 2) The unit weight of the mixing rate with Fly-ash 0% was $1.875{\sim}1.884t/m^3$, the other mix design 10% over with Fly-ash was $1.846{\sim}1.615t/m^3$, the difference was appeared less about 15% than that. 3) In design, partial replace Fly-ash of fine aggregate, this compressive strength was appeared that the concrete age after 7 days was higher than in partial replacement of cement, therefore, the default of a concrete with Fly-ash, that is the earlier compressive strength was to lessen, was improved. 4) The thermal conductivity of the all mix design was $0.447{\sim}1.144kcal/mh^{\circ}C$, this value was as good as a lightweight aggregate concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.428-434
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• 2022

This study intends to develop an eco-friendly concrete panel mixed with biochars. Experiments about mechanical and thermal properties were conducted on porous biochar concrete, which has insulation and carbon-capture performance. The concrete has a mixing ratio of 0, 5, 10, and 15 % for biochar and a water-binder ratio of 0.35. The unit weight, porosity, and permeability were measured to evaluate the mechanical characteristics. From the results, as the biochar mixing rate increased, the porosity and the permeability increased, but the unit weight decreased. Even though a decreased trend was observed in the compressive strength results, they satisfied the design standard. Since the thermal conductivity was decreased during the increase of contents, biochar could be considered an excellent material for insulation performance. In addition, regression analyses were conducted regarding the relationship of unit weight with porosity, compressive strength with thermal conductivity, and porous with thermal conductivity. From the regression, significant variables for expanding the scope of the application of biochar were presented.

• KIEAE Journal
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• v.11 no.4
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• pp.95-101
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• 2011

Earth has been used as a building material not only our country but also many foreign countries in the world. In foreign countries, we can often find the high-storied earthen houses which have been maintained for over several hundred years, which means the fact that earth differs in durability according to the methods of utilizing earth. So, the purpose of this study is to progress the fundamental research for utilizing earth as a wall material. Also, the another purpose of this study is to utilize the optimum micro-filler effect which adjusts the grain size of earth and the lime composite which promotes chemical combining power, and so examine whether earth material ensures its high compressive strength. This study applied both of rammed earth method and pour earth method among earth architecture methods. This study investigated compressive strength, slump, and air content according to unit binder weight. On the basis of such experimental results, this study derived the following conclusions. 1) Optimum micro-filler mixtures reduce a lot of fine particles contained in earth. If optimum micro-filler mixtures are used as aggregates, they develop lower W/B and relatively higher strength than general earth. 2) In this study, which uses optimum micro-filler earth mixtures and lime composite, rammed earth method develops 29MPa and pour earth method develops 28MPa in 28 days compressive strength. Such strengths can be utilized in building walls.