• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.217-222
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• 2002

The purposes of this study are to investigate the material characteristics and strength properties of concrete mixed with waste incinerated bottom ash(BA), and to evaluate the leaching of environmentally harmful heavy metals from the bottom ash itself and from hardened concrete mixed with bottom ash. For this purpose, two reference mixes with W/C ratios of 0.45 and 0.55 were used, and the replacement proportion of BA was varied with the ratios of 0%, 30%, 50%, 70%, and 100% by volume of fine aggregate in the reference mixes. The variation of compressive and splitting tensile strength, workability and unit weight of concrete were considered. Test results showed that the strengths, workability and unit weight decreased with increase in proportion of BA replaced. Leaching test results showed that there would be no environmentally harmful problem from using BA as the substitutes of fine aggregates in concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.501-506
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• 2001

An experimental study was carried out to investigate recycling of an oyster shell, which is disposed in open-dumped way at coastal oyster factory area. For this purpose, the chemical component and reaction of oyster shell with cement paste was examined. And, the characteristics of hardened concrete was quantitatively investigated in terms of fineness modulus and blending rate of the crushed oyster shell. Test results show that interaction between oyster shell and cement paste was not occurred and the crushed oyster shell can be used as the fine aggregate of concrete. And it is found that blending of an oyster shell caused not to reduce the 28 day compressive strength of concrete. Elastic modulus of the concrete blended with crushed oyster shells decreases with increases the blending rate which the modulus reduced about 10% when oyster shells is blended up to the 20% of the sand substitution.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.929-934
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• 2001

As the notion of environment protection changes throughout the world, construction engineers, as part of the effort to resolve environmental problems, have been actively doing research on environmental friendly porous concrete using large and non-uniform aggregate. Concrete having a great deal of continuous porosity enable water and air to pass freely through firmly hardened material, allowing necessary nutrients to reach roots of vegetation, thereby sustaining them. It is possible to prevent the exhaustion of natural resources by recycling waste concrete and industrial by-products, to reduce damage caused by the destruction of nature through effective management of natural resources, to preserve the natural environment and vegetation in urban areas by activating the soil, protecting the underground ecology system, and growing garden plants through the application of environmentally friendly concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.73-78
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• 2001

Portland cement concrete is made with coarse aggregate, fine aggregate, portland cement, water and, in some cases, selected chemical admixtures such as air-entraining agents, water reducer, superplasticizer, and so on, and mineral admixtures such as fly ash, silica fume, slags, etc. Typically, in the concrete, the coarse aggregate and fine aggregate will occupy approximately 80 percent of the total volume of the final mix. Therefore, the coarse and fine aggregates affect to the properties of the portland cement concrete. As the natural sands are drained, it is necessary and economical to utilize crushed sands(manufactured fine aggregate). It is reported that crushed sands differ from natural sands in gradation, particle shape and texture, and the micro fines in the crushed sands affect to the quality of the portland cement concrete. Therefore, the purpose of this paper is to investigate the characteristics of fresh and hardened concrete with high content of micro fines. This study provides firm data for the use of crushed sands with higher micro fines.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.364-367
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• 2004

The purpose of this study is to investigate quality of recycled fine aggregate manufactured by drying manufacturing system which is the manufacture method of high quality recycled fine aggregate, and to analyze on the fresh, hardened and durability properties of recycled concrete using it. Therefore it is to present the fundamental data for structural application of recycled concrete. The results of this study are as follows; Quality of recycled fine aggregate by drying manufacturing system is improved, and compressive and tensile strength of recycled concrete using high quality recycled fine aggregate are similar to those of normal concrete. But, durability such as carbonation, salt damage and dry shrinkage show decreased somewhat.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.439-444
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• 2000

The purpose of this study is to investigate the possibility of Garnet powder as admixture of high strength concrete. The experiment condition is unit water content 160kg/㎥, W/B=30, 35%, S/A=40, 42, 44% and the cement was replaced with Garnet powder to 0, 10% of cement weight on making specimens. The mechanical properties of the fresh and hardened concrete were given as follows. As the time elapsed, the slump loss of 10% replaced concrete was considerably lower than that of 0% replaced concrete. In compressive strength, the 10% replacement case was nearly the same or somewhat high.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.483-486
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• 2005

This study investigates the effect of air contents on concrete properties, compressive strength, chloride migration coefficient and freeze-thaw resistance. Chloride migration and freeze-thawing test conducted in accordance with NT-BUILD 492 and pr-EN 12390-9, respectively. As a result, compressive strength reduced with air contents increase, but chloride migration coefficient more influenced by the water-binder ratios than air contents. Air contents of hardened concrete measured half times that of fresh concrete after mixing. Also, concrete scaling decreased with air contents increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.557-560
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, this study is willing to propose fundamental data for accurate diagnosis of deteriorated concrete structure by fire damage with experiment according to the curing conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.465-468
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, this study is willing to propose fundamental data for quick and accurate diagnosis of deteriorated concrete structure by fire damage with experiment according to the design compressive strength.