• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.365-368
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• 2005

Waste concrete powder(WCP) has been estimated with a great value-added material as by-product of waste concrete manufactured to fine and coarse aggregate for concrete, because it is able to utilized for cement clinker and concrete admixture. Experimental tests were performed as such plastic viscosity of paste, flow and compressive strength of mortar by surface area of WCP. As a result, flow and 28days compressive strength of mortar was decreased according to increased replacement ratio of WCP as compared to control mortar. Also, plastic viscosity of paste used WCP1 and WCP2 was decreased with increasing replacement ratio, but WCP3 was increased with increasing replacement ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.305-308
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• 2008

The purpose of this study is to propose the confinement effectiveness of precast segmental concrete that binding by lateral confining steel in the method of precast segmental concrete pridge piers construction. Generally, the confinement effect of concrete that binding by lateral confining steel is defined by the confinement effectiveness coefficient and the confinement effectiveness coefficient is defined as the ratio of area of effectively confined concrete core to area of confined concrete core. The area of effectively confined concrete core is defined by Arching action occurred on a space of lateral confinement steel and The area of confined concrete core is defined by the ratio of area of longitudinal reinforcement to area of core of section. But in case of precast segmental concrete, concrete cover that exist on top and bottom of concrete segment should be considered.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.175-185
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• 2013

Currently in precast concrete construction, precast concrete and cast-in-place concrete with different concrete strengths are used. However, current design codes do not provide shear design methods for PC-CIP hybrid members using dual concrete strengths. In the present study, the shear strengths of beams using dual concrete compressive strengths (24 MPa, 60 MPa) were tested. The test variables were the area ratio of the two concretes, longitudinal bar ratio, and shear span-to-depth ratio. The shear strengths of test specimens were evaluated by current design methods, using an effective concrete strength (considering the area ratio of the two concrete strengths). The test result showed that when 60 MPa concrete was used in the compressive zone and the longitudinal bar ratio was low, the shear strengths of the test specimens were less than the predictions. On the basis of the results, design recommendations were provided for the shear design of the PC-CIP hybrid beams.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.129-137
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• 1994

This study was performed for the purpose of obtaining the fundamental data to establish the criterion of concrete deterioration and presuming steel corrosion of concrete structures under the environment of seawater. Steel embedded concrete specimens were exposed in seawater for 1year. The soluble chloride content in concrete, corrosion potential and steel corrosion were considered. The results show that soluble chloride content in concrete was decreased with lower water-cement ratio and with mineral admixtures. Half-cell potential is reduced with steel corrosion. Corrosion area ratio is correlative with half-cell potential.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.148-151
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• 1994

Up to now, sea sand without complete removal of salt is being used in the construction works because there is little satisfactory counterplan for the substitute aggregate. In the case that such sea sand is used in the reinforced concrete, the residual salt gives rise to deterioration phenmenon and iron corrosion, reducing durability of the ferro-concrete structures. The paper, an experimental study on the effect of corrosion protection by tighting concrete used SF and FA, is to investigate general steel bar's corrosion and to develop concrete using sea sand economically after it is analyzed and examinated ratio of the corrosion area affected by the autoclave cycle. As a test results, as for corrosion area ratio, it is very effective to use admixrutes such as SF and FA which decrease corrosion area remarkably with increasing the amounts of admixtures. Accordingly the use of admixtures is advantageous for tightening concrete and has an effect of salt damage prevention and rust protection in concrete used sea sand.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.83-88
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• 1997

In this paper, we described the basic elements (relative flowing area ratio and funeling velocity ratio in mortar, flowability and self-compactibility in concrete, and etc.) required for the maximum mix design of the super flowing concrete (SFC) using manufactured sand. Also, manufactured sand and fly ash were used for investigating characteristics of SFC through various experiments (replacement ratio of manufactured sand, optimum mix condition) before producing the concrete in batch plant. As the result of this project, the SFC using manufactured sand up to 50% showed high flowability and self-compactibility in fresh concrete. Furthermore, its compressive strength is higher than normal concrete without manufactured sand. From now on, this study may suggest how to apply manufactured sand in the SFC.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.529-532
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• 2001

In this paper, rust-protection performance of concrete using ground granulated blast-furnace slag are discussed. 4 kinds of W/B in combination with 3 kinds of replacement ratio of ground granulated blast-furnace slag and 2 kinds of chloride ion contents of are selected as experimental parameters. According to the experimental results, as the replacement ratio of ground granulated blast-furnace slag is increased, the corrosion area of steel bar tends to be decreased. However, as the autoclave cycle and chloride ion contents are increased, the corrosion area of steel bar is increased. In conclusion, when the replacement ratio of ground granulated blast-furnace slag is 50%, the strength and rust-protection performance appear to be most excellent.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.86-89
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• 2003

It is recognized that reinforcement corrosion is the main distress behind the present concern regarding concrete durability. In this study, to confirm corrosion of reinforced concrete affected by thickness of cover, kinds of surface coating, measured electric potential, ratio of corrosion area, weight reduction, corrosion velocity of steel bar under environment of complex deterioration. The results showed that an increase in age also increases corrosion of steel bar. Ratio of corrosion area is largely related to ratio of weight reduction. as well, corrosion of steel bar by thickness of cover is superior to l0mm thick than 20mm thick. It showed that an increase in thickness of cover prevent steel bar from deteriorating. The results of this study showed that corrosion velocity was affected by thickness of cover, kinds of surface coating. data on the development of corrosion velocity made with none, organic B, organic A, inorganic B, and inorganic A is shown.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.403-408
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• 2003

The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.57-62
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• 1990

This paper is to study the effect of rectilinear confinement in high-strength concrete subjected to a monotonically increasing compressive axial loads. To investigate behavior of columns rectilinearly confined with lateral ties and longitudinal rebars, twelve specimens including two plain concrete specimens were tested. The main variables in this study are volumetric ratio of lateral ties, cistribution of lateral ties, yield strength of logitudinal steel, ratio of area of longitudinal steel to the area of cross section. The test results were not only compared with an empirical model for the stress-strain curve of rectilinearly confined high-strength concrete but also the existing model. The empirical model used calculating column capacity shows better agreement with the test results tham the existing model.