• Journal of the Korea Institute of Building Construction
• /
• v.17 no.1
• /
• pp.39-46
• /
• 2017

In this research, considering the practical conditions at field, thermal cracking reducing method was suggested based on the comparative analysis between predicted value and actual value obtained from the actual structure member with optimum mix design. The optimum mix design was deduced from the various mix designs with various proportions of cementitious binder for upper and lower placement lifts of mat-foundation mass concrete. Therefore, before field applications, the mix designs were obtained from the theoretical analysis obtained by MIDAS GEN for upper lift was OPC to FA of 85 to 15, and for lower lift was OPC to FA to BS of 50 : 20 : 30. Based on this mix design, the actual concrete for field was determined and all concrete properties were reached within the predicted range. Especially, the temperature properties of mass concrete at core was approximately $39^{\circ}C$ of temperature difference for low-heat mix design, while approximately $54^{\circ}C$ was shown for normal mix design currently used. Additionally, in the case of cracking index, the low heat mix design showed about 1.4 of relatively high value while the normal mix design showed 1.0. Therefore, it can be stated that applying low heat mix design and different heating technique between upper and lower placement lifts for mass concrete are efficient to control the thermal cracking.

• Journal of computational fluids engineering
• /
• v.10 no.1
• /
• pp.94-98
• /
• 2005

Accurate prediction of the fire-induced air velocity, temperature and smoke flow in underground utility tunnel becomes more important for the optimization of design and placement of heat and smoke detectors. In order to improve the safety of underground utility tunnel systems, the behaviors of fire-induced smoke flow and temperature distributions are investigated. Especially, two different cross-sectional shapes of tunnel, such as rectangular and circular types are modeled. Also, fire source is modeled as a volumetric heat source. Three-dimensional thermal-flow characteristics in an underground tunnel are solved by means of FVM using SIMPLE algorithm. The effects of shape geometry on the fire-induced flow characteristics are graphically depicted. It is desirable that heat and smoke detectors are installed on the cables and the top of the wall.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.385-386
• /
• 2009

The temperature crack of concrete structure is caused by the phenomenon which the concrete volume is restricted in the inside or outside part due th the temperature variations induced by the hydration heat of cement. And mass concrete structures are weak in temperature crack. This study performed the hydration heat analysis of Seongdeok dam to analyze the hydration heat according to different interval of placement.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.269-270
• /
• 2012

This study discussed the applicability of double layered bubble sheet(BS) to the concrete for retaining wall to verify the insulation effect as well as prevention of condensation. The BS was applied to the surface of retaining wall, which is contacted with ground. Temperature profile was monitored since placement of concrete. As expected, the application of BS helps the concrete keeping favorable heat insulating, preventing condensation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.117-118
• /
• 2022

In this study, adiabatic temperature rise of concrete depending on binder compositions and CGS contents is studied to provide informations for CGS low-heating aggregate and mixture designs for upper and lower placement lifts. Test nresults indicate that it is desirable to apply the combination of binders between top and bottom lift. For top lift, SESC or ESC is recommended, and for bottom lift, FAC+CGS 50 % is good for material composition.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.5
• /
• pp.116-127
• /
• 2014

The studies were carried out to process one cycle for a day to the large section tunnel lining concrete. Climatic characteristics of the tunnel inside are changed, when the temperature of the concrete placement is low, the mold remove time is increased that the heat of hydration speed be delayed because affects the strength development, to compensate for this, after installing the curing sheet on both sides of the steel form and installation of tunnel entrance, when it comes to providing the additional heat source of $28{\pm}2^{\circ}C$ therein, it was to be achieved early strength development control standards (4.5MPa) presented as a crack control scheme or more, thus, It was able to remove after age of 14hr from mold. On the other hand, under the conditions of $10{\pm}1^{\circ}C$ that a natural curing temperature in the tunnel, it was analyzed must ensure the curing time of 36hr or more after concrete placement. Throughout this study, the concrete strength development and the temperature in the early-age concrete, it can find that reverify the curing temperature is greatly affected, even concrete fly ash is mixed 10%, if it is possible to raise the surface temperature for a predetermined time, is not a problem in the early strength development.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.30 no.2
• /
• pp.68-82
• /
• 2018

Radiant floor heating systems with capillary tubes are energy saving systems in which hot water is circulated into capillary tube with a small diameter. In this study, the heating performance of capillary tube system is investigated in an experimental study and a simulation model. The results of the study showed that, the capillary tube radiant floor heating system maintains a more stable floor surface temperature in comparison a PB pipe system. In terms of energy consumption, the capillary tube radiant floor heating system proved to be more efficient than the PB pipe heating system at $40^{\circ}C$ of low temperature hot water supply. The difference between water temperature and room temperature can be held low for heating which saves energy. Low temperature radiant floor heating system with capillary tubes have significant advantages such as health improvement, low energy cost, optimum use of heat source(boiler) and higher operational efficiency.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.351-354
• /
• 2005

Quality of concrete required to achieve the desired levels of strength and durability depend on the effectiveness of the curing method. During cold weather, the concrete at the time of placement should be taken to prevent damage to concrete due to freezing. Since the cement-water reaction is exothermic by nature, the temperature within mass concrete can be quite high. The temperature control for massive sections should be taken more careful than for shallow sections. However, in the constructing hydraulic structures, the curing temperature control for concrete had been very difficult to be taken in a proper way because the conditions constructing them are poor and contractors are small enterprises. For several. reasons including above, Rural Research Institute has developed a device and program for recording curing temperature history in cold weather concrete and mass. As there are two major advantages of the device, namely cheapness and availability, this program and device has been recommended to the use of curing temperature control in cold weather concrete and mass.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.781-784
• /
• 2008

In this paper, insulating effect and strength development of concrete under low temperature are reported varying curing sheets. According to test results, in temperature -5$^{\circ}$C concrete subject to exposure and air cap condition, result in a frost damage at early age by a fall of below zero temperature. Mean while, the combination of PE film and non-woven fabric maintained around 3 $^{\circ}$C within first 24 hours since placement. For double bubble sheets, concrete temperature maintained above 7$^{\circ}$C due to its excellent heat insulating capability. As a result of core strength test, strength of specimens cured with viny + non-woven fabric and double bubble sheets had higher strength than strength of other specimens due to good heat insulation effect at early age.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.1183-1189
• /
• 2009

The sedimentation rate of particles in a suspension is a function of particle size, initial slurry water content and salinity. Many researches conducted on the behavior of dredged soils have centered on such factors. However, there have been few attempts to assess another important influence factor of seasonal water temperature on designing the placement of dredged materials. In this paper, the effect of seasonal water temperature on sedimentation characteristics of dredged clay was investigated with consideration of three different water temperatures, that are $5^{\circ}C$, $15^{\circ}C$, $35^{\circ}C$, which represent critical water temperatures in winter, spring or fall, and summer, respectively. A series of experimental results reveal that the sedimentation rates for the water temperature of $15^{\circ}C$ and $35^{\circ}C$ are very similar each other, but that of $5^{\circ}C$ that represents a winter season leads to a considerably delayed sedimentation compared to the others. This may be attributable to the retardation of ion-leaching from clay particles at low water temperature.