• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.11a
• /
• pp.509-512
• /
• 2003

Dehydration and micro crack thermal expansion occur in cement hydrates of concrete structure heated by fire for a long time. The characteristic of concrete exposed to high temperature can be analyzed from distribution of porosity and pore size. Porosity showed a tendency to increase irrespective of specimen types. This is due to both the outbreak of collapse of gel comprising the cement and a micro crack by heating. Porosity did not affect the variety of specimen and increased with the same tendency throughout every specimen. In addition, the deteriorate of compressive strength resulted from increase in porosity

• Journal of the Korea Concrete Institute
• /
• v.12 no.1
• /
• pp.33-44
• /
• 2000

Since the mechanism of chloride diffusion and its ratio in concrete depend on structural conditions and concrete as a micro-structure, if these are analyzed quantitatively, the long-term ageing of structures can be predicted. Although, a quantitative analysis of concrete micro-structure, in which the results are affected by various parameters, is very difficult, this can be done indirectly by the durability test of concrete. In this study, the compressive strength, void ratio and air permeability of concrete. In this study, the compressive strength, void ratio and air permeability of concrete are chosen as the parameters in concrete durability test, and these effects on test results are analysed according to changes of mixing properties. The relationships between parameters and chloride diffusion velocity is used for prediction models of chloride diffusion. The developed prediction models for the chloride diffusion according to mixing and physical properties, can be used to estimate the service life and corrosion initiation of reinforcing bars in marine structures.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.519-523
• /
• 2009

In this study, the base mixing ratio was determinated to estimate the optimal mixing ratio of material with a change of mixing ratio of micro cement, sand, foaming agent, plasticizer by testing the unconfined compressive strength test. The unconfined compressive strength test was performed to grasp a engineering characteristics of with a change of micro cement, bubble. The results of test, the unconfined compressive strength increased with a micro cement's increase and bubble's decrease. In the future, it will be secured that is reliable datas from laboratory of various condition and in-situ tests to develop optimal lightweight foamed concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.23-24
• /
• 2019

In this study, analysis of steel fiber orientation and distribution inside fiber reinforced concrete was performed using micro-CT scanning technology. Samples were extracted from the column according to its height and distance from the mold. Samples were scanned in order to attain the image of steel fibers then region of interest were obtained by binarization process. By calculating the principle moment of inertia of each fiber, direction vector, scale, center postion, volume, and surface area were gained in order to analyze the orientation and distribution. Most of the fibers inside the column tended to be perpendicular to the main axis of the column. Moreover, most of the fibers appeared at the bottom of the column and at the position where it is farthest from the mold.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.05a
• /
• pp.44-45
• /
• 2015

Although the carbonation problem of high-volume slag concrete has been solved by the mixed use of emulsified refine cooling oil as the pilot study, there was an instance of securing air quantity and frost resistance followed by the use of Expancel due to the problem of having vulnerability in frost resistance in result as the air quantity has not been secured. But due to the problem of Expancel not being economical, air quantity and frost resistance of high-volume slag concrete mixed with ERCO are attempted to be secured using micro bubble that can remain in the water for a long time as a relatively economical and very microscopic bubble.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.11a
• /
• pp.75-76
• /
• 2018

MiDF, Micro Defect Free concrete, is the concrete made for high strength development by minimizing the defects such as micro pore and ITZ. Since MiDF exhibits strength through hydro-thermal synthesis reaction, it is essential to select the optimum C/S mole ratio. In this study, the basic characteristics of MiDF were evaluated by controlling the C/S mole ratio by SF and QP.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.11a
• /
• pp.192-193
• /
• 2020

In reinforced concrete adhesion studies, the demolition of the specimen is inevitably involved, and the studies conducted are limited to the macro load-displacement analysis. In order to establish an elaborate model for concrete bonding reinforced rebars, it is necessary to observe the rebar bonding behavior in the in-situ state. In this study, specially manufactured reinforcing bars, micro-UTM and 𝝁-computer tomography (𝝁CT) are used to observe reinforcing bars in the in-situ state. As a result of the monotonic pullout test of the processed reinforcing bar, maximum bond stress were shown to be 16.7MPa, which is slightly higher than the existing 10 to 12 MPa, and then the empty space inside the specimen in which the pullout test was conducted using 𝝁CT was confirmed. Through additional research, the fracture phenomenon of concrete excluding voids will be studied.

• Magazine of the Korea Concrete Institute
• /
• v.12 no.3
• /
• pp.39-44
• /
• 2000

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.185-188
• /
• 2006

During the carbonation process in concrete, the rate of carbonation depends on porosity and moisture content of the concrete. For underground reinforced concrete structures, the interior concrete surface may be exposed to carbonation and the exterior concrete surface exposed to moisture due to wet soil or underground water. In this study, the permeability coefficients in mortar partially carbonated is derived as a function of carbonation depth and porosity of mortar by applying the so-called micro pore structure formation model (MPSFM) which was developed for the modeling of early-aged concrete. The permeability coefficient obtained from the micro-level modeling of carbonated mortar is verified with the results of accelerated carbonation test and water penetration test in cement mortar.

• Journal of the Korea Concrete Institute
• /
• v.12 no.4
• /
• pp.41-48
• /
• 2000

This study is to investigate for the frost resistance of high-strength concrete using finely ground granulated blast-furnace slag with experimental parameters, such as water/binder ratio, replacement proportion of granulated blast-furnace slag, air content and methods of curing. The high-strength concrete using granulated blast-furnace slag is effective to resist frost and decrease scaling. The more increasable replacement proportion of granulated blast-furnace slag is, the better the effect is. The high-strength concrete using granulated blast-furnace slag needs hydrating adequately to prevent deterioration by drying in the early curing period. The micro structure of high-strength concrete, increased to the pore number with diameter of 0.03~0.1mm, is changed by using granulated blast-furnace slag, but is presented differently according to water/binder ration and replacement proportion of granulated blast-furnace slag.