• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.23-30
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• 2011

In this study, deterioration degrees of concrete were investigated at laboratory under seawater attack and cycling freeze-thaw, which are major durability performance deterioration factors of concrete. Deteriorations of mixed concrete using Portland & blended cement were examined by instrumental analysis of changes in relative dynamic modulus of elasticity and compressive strength. After 520 cycles of freeze-thaw, relative dynamic modulus of elasticity and compressive strength of concrete mixed with normal Portland and LHC over 75% showed relatively low resistance of approximately 44% of those values of SRC. Concrete replaced with 50% fine powder of blast furnace slag showed the most excellent freeze-thaw resistance among the tested blended cement concrete.

• Korean Journal of Animal Reproduction
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• v.16 no.3
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• pp.193-198
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• 1992

본 실험은 ICR계통 생쥐의 8세포배 및 상실배를 Vitrification(VS3) 동결보존액을 이용하여 초급속동결-융해를 실시하여 배반포배까지의 체외발생한 배반포배를 이식하였을 때 수태율에 미치는 영향을 조사하여 다음과 같은 결과를 얻었다. 1. 8세포배의 평형시간(3분 및 6분)에 따른 초급속 동결-융해후 배반포배까지의 체외발생율은 57.6% 및 59.5%여TEk. 2. 상실배의 평형시간(3분 및 6분)에 따른 초급속 동결-융해후 배반포배까지의 체외발생율은 64.4% 및 68.2%였다. 3. 8세포배와 상실배를 초급속 동결-융해를 실시하여 배반포배까지 체외발생한 배를 위임신되어진 수란쥐에 19개 및 20개를 이식하여 7필(36.8%)과 10필(50.0%)의 산자를 얻었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.21-22
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• 2009

This paper presents the results of an experimental study on flexural behavior and cracking process of concrete beams subjected to cycles of freezing and thawing after patch-repaired with strain-hardening cement composites (SHCCs). The SHCCs were reinforced with hybrid 0.75% PVA and 0.75% PE fibers. Experimental testing of concrete beams patch-repaired with SHCCs revealed that the SHCC patch-repair system without freeze thaw (FT) exposure showed average 3.31 times increased load carrying capacity and for beams exposed to 300 FT cycles, load carrying capacity increased up to 2.42 times. Cracking damage of SHCC patch-repaired beams mitigated compared to plain concrete beams but this trend decreased under FT exposure.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.529-536
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• 2020

This paper presents experimental investigations about compressive strength and durability of reinforced concrete compressive members repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 24 RC specimens of 100x100x400mm size were tested by compressive strength test and freezing and thawing test by KS F 2456. The specimens were reinforced using 4D10 steels and repaired on 4 sides expect on top cycle. Test results showed that the specimens repaired using fiber carbon sheet revealed about 5% higher values of the compressive strength compared than the cases of DFRCC motar. On the other hand, the resurts did not showed meaningful differences in the aspect of durability. For further research, considerations of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.91-96
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• 1993

본 연구의 목적은 콘크리트의 열화손상을 주는 요인 중 특히 수분의 공급이 충분한 동결융해작용에 대한 영향인자에 대한 실험적 연구이다. 콘크리트의 열화에 영향을 주는 여러 영향인자 중에서 주로 공기량 및 물-시멘트비를 다루었다.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.111-122
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• 2014

For accurate laboratory evaluations of soil deposits, it is essential that the samples are undisturbed. An artificial ground-freezing system is the one of the most effective methods for obtaining undisturbed samples from sand deposits. The objective of this study is to estimate the shear strengths and the characteristics of elastic waves of frozen-thawed and unfrozen specimens through the undrained triaxial compression test. For the experiments, Jumunjin standard sands are used to prepare frozen and unfrozen specimens with similar relative densities (60% and 80%). The water pluviation method is used to simulate the fully saturated condition under the groundwater table. When thawing the frozen specimens, the temperature is measured every minute. After the specimens are completely thawed, undrained triaxial compression tests are conducted using the same procedures as for the unfrozen specimens. During the triaxial tests (saturation, consolidation, and shear phase), compressional and shear waves are measured. The results show that the freeze-thaw process has minor effects on the peak deviatoric stress and shear strength values, and that the process does not affect the internal friction angle. The compressional wave velocity increases with increasing B-value to 1800 m/s in the saturation phase, but tends to remain constant in the process of consolidation and shearing. The shear wave velocity decreases with increasing B-value in the process of saturation, but changes velocity in accordance with the change in effective stress in the processes of consolidation and shearing. The compressional wave velocity has similar values regardless of the freeze-thaw process, but values of shear wave velocity are slighly lower in frozen-thawed specimens than in unfrozen specimens. This study is a preliminary experiment for estimating the shear strength and characteristics of elastic wave velocity in undisturbed frozen specimens that have been obtained using the artificial ground-freezing method.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.587-593
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• 2019

This study were subjected to accelerated weathering test under freeze-thaw and pressure conditions to observe initiation and propagation of cracks using CLSM. Applied stress was set at 50 MPa, 55 MPa, 70 MPa for 3 samples each by using compressor and freeze-thaw experiment was conducted while samples maintained that condition. In freeze-thaw experiments, a temperature range was set to -20~40℃ which was 1 cycle for 6 hours. The freeze-thaw cycle was composed of time which reached to set temperature for 1 hour and holding time for 2 hours. On the basis of this cycle, surface of samples was observed by CLSM after each 20 freeze-thaw cycle. From this research, according to increase freeze-thaw cycle, there were 7, 10, 19 each cracks and High pressured sample's accumulate length was longer than low pressured sample's. High pressured sample's crack velocities were also faster than low pressured sample's which were calculated by accumulate length and freeze-thaw cycle.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.13-23
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• 2001

Rock slope near the road or railroad is affected by the outside temperature and iterative freezing-thawing process during winter and early spring. The purpose of this study is to analyze the stability of rock slope which is iniluenced by deterioration due to the freezing-thawing. Method of analysis is homogenization method which find the strength property of discontinuous rock mass and as a strength failure criterion, Drucker-Prager failure criterion is used, The deterioration property of real rock is obtained by a freezing-thawing labordtory test of tuff and this quantitative property is used as a basic data of stability analysis of rock mass. To evaluate the deterioration depth due to the freezing-thawing in the field rock slope, one dimensional heat conductivity equation is used and as a a result we can find the depth of which is affected by a temperature. After determined the freezing-thawing depth of model slope, the pattern of rock mass strength value of model rock slope which excess the limit of self-load is analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.67-74
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• 2015

In this study, effects of micropores on the freezing-thawing resistance of high volume slag concrete are reviewed. Concrete was made with slag which contains the ground granulated blast furnace slag(GGBS) and the pig iron preliminary treatment slag(PS) by replacing 0, 40, 70 %, then compressive strength, freezing-thawing resistance, micropores were reviewed. Also, specified design strength, target air contents were set. Deterioration was induced by using 14-day-age specimen which has low compressive strength for evaluating deterioration by freeze-thawing action. As results of the experiment, despite of specified design strength which has been set similarly and ensured target air contents, the pore size distribution of the concrete showed different results. Micropores in GGBS70 specimen have small amount of water which is likely to freeze because there is small amount of pore volume of 10~100 nm size at 0 cycle which has not been influenced by freezing-thawing. For these reasons, it was confirmed that the freezing-thawing resistance performance of GGBS70 is significantly superior than other specimens because relatively small expansion pressure is generated compared to the other specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.182-189
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• 2010

The strengthening performance of FRPs(Fiber Reinforced Polymers) is directly affected by the environmental conditions such as freezing-thawing and moisture because FRPs are usually bonded on the concrete surface. It is, therefore, strongly required to evaluate a durability of bond between FRPs and concrete as well as FRP materials itself. The freezing-thawing resistance of FRPs is evaluated in this study with the variables of freezing-thawing conditions, types of FRP and freezing-thawing cycles. From the test results, it is found that tensile strength and pull-off strength of CFRP are not affected by the freezing-thawing. On the other hands, those of GFRP show a little degradation because of continuous water immersion during thawing process. But, cautions are needed on the bond durability between FRPs and concrete in case of continuous water supplying from adjacent to the concrete.