• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.11a
• /
• pp.24-25
• /
• 2015

To secure fundamental materials for the performance change in concrete structure damaged by fire, this study analyzed SEM and XRD of hardened cement depending on high temperature conditions. As a result, at more than 200℃, SEM and XRD were not observed because of dehydration of Ettringite; at more than 500℃, calcium hydroxide was rapidly decomposed; at more than 700℃, calcium oxide was found; at 1000℃, the highest peak point appeared.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.15-16
• /
• 2017

The properties of concrete damaged by fire change according to the temperature. Diffusion coefficient of chloride ion also can change which affect the life expectation under salt circumstance. Diffusion coefficient was measured by NT BUILD 492 using the concrete specimen damaged by high temperature. FEM analysis was performed to predict the life expectancy which can help to diagnose the concrete diagnose and to design maintenance strategy.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.195-196
• /
• 2019

The temperature and relative humidity in concrete change with the passage of time depending on factors such as compressive strength. They are also different depending upon internal depth of concrete. In this study, we have measured the change of the temperature and relative humidity in the concrete for two years to act as the parameters to evaluate the concrete durability and effective maintenance.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.05a
• /
• pp.197-198
• /
• 2021

The temperature and humidity inside concrete affects the depth of carbonation. In this study, the temperature and humidity inside concrete were predicted by the numerical method under the boundary conditions of ambient temperature, humidity, solar radiation, and wind. Using the results of the thermal humidity analysis, diffusion of carbon dioxide and the reaction of cement hydration products were calculated for carbonation depth.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.85-86
• /
• 2022

In this study, a simulation using Company A's COMSOL heat flow program was used to analyze the thermal diffusion simulation according to the depth of the high-temperature exposed cement paste. As a result of the analysis, it showed a similar relationship with the measured temperature as of 180 minutes.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.142-143
• /
• 2007

A 1MW class HTS(High-Temperature Superconducting) synchronous motor has been developed. This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of Neon thermosiphon mechanism and the stator coil is cooled by water through hollow copper conductor. This paper describes performance test results of our motor, which was conducted at steady state in generator mode and motor mode.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.4
• /
• pp.115-121
• /
• 2008

The present study performed low-pressure steam curing with mortar specimens in order to examine the temperature profile and strength development of steam curing in high-strength specimens of 100MPa. In addition, as a basic research to utilize PC products, we examined the effects of curing temperature and time in steam curing cycle on strength development resulting from the hydration of cement within the range of high strength by changing four factors affecting the quality of PC displacement time, peak curing temperature, peak temperature duration, and ascending and descending gradient of temperature - in various patterns, and analyzed the optimal strength development characteristic based on the relation between temperature profile and strength development. With regard to the high-temperature curing characteristic of PC, we performed an experiment on the strength characteristic according to the temperature profile of high-strength mortar, and from the results of the experiment according to curing characteristic, displacement time, peak curing temperature, peak temperature duration, and ascending and descending gradient of temperature, we drew conclusions as follows.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.3
• /
• pp.219-227
• /
• 2016

In this study, we have proposed a method of monitoring of bridges under construction in view of the long-term behavior of the prestress concrete bridge of which the Free Cantilever Method is applied. As a method to confirm the ability of the long-term behavior of the concrete box girder, temperature sensors and strain gauges were installed, and the measured data was used to calculate creep coefficient. Moreover, we have measured the stress of the concrete box girder during construction which was applied with creep coefficient and compared with the changes in temperature to analyze the vertical displacement along the segment. In conclusion, monitoring of the FCM bridge during construction in consideration of the long-term behavior can be analyzed efficiently by suing temperature and displacement data without the use of laser displacement meter or laser delfectometer.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.2
• /
• pp.151-156
• /
• 2002

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods for resolve these problems is to reduce freezing temperature of concrete by the use of chemical admixture called Accelerators for freezing resistance. In this study, we investigate the effect on strength development of cement mortar using accelerators for freezing resistance with the variance curing condition. As the result of this study, the mortar using accelerators for freezing resistance show that continuously strength development in curing condition of -5$^{\circ}C$. And compressive strength under the variance temperature condition was higher than constant temperature condition in same maturity.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.11a
• /
• pp.11-12
• /
• 2012

This study investigates the temperature rise of reinforcement bars located in the middle of the form (for reinforcement concrete) during hot weather condition. The temperature was measured for three consecutive days before placing concrete. Test results showed that the temperature started to increase at 7:00 AM before sun rised, and peaked at around 2:00 PM. It was found that the thinner the diameter of a reinforcement bar, the higher is the speed of temperature rise and drop of the bar. The peak level of temperature for D13, D19, D25 and D32 was 54.4℃, 55.2℃, 56.4℃ and 60.2℃, respectively.