• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.2
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• pp.59-66
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• 2006

This study is performed to evaluate freezing and thawing properties of polypropylene fiber reinforced eco-concrete using soil, natural coarse aggregate, soil compound and polypropylene fiber. The mass loss ratio is decreased with increasing the content of natural coarse aggregate and soil compound, but it is increased with increasing the content of polypropylene fiber. The ultrasonic pulse velocity, dynamic modulus of elasticity and durability factor are increased with increasing the content of natural coarse aggregate and soil compound, but it is decreased with increasing the content of polypropylene fiber. The mass loss ratio, ultrasonic pulse velocity, dynamic modulus of elasticity and durability factor are $1.49{\sim}3.32%,\;1,870{\sim}2,465\;m/s,\;77X10^2{\sim}225X10^2\;MPa\;and\;84.6{\sim}92.8$ after freezing and thawing 300 cycles, respectively. These eco-concrete can be used for environment-friendly side walk and farm road.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.65-69
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• 2008

The tailings piled in abandoned mines are well-known potential sources of soil contamination. Hydrated limes were applied as cementing materials to solidify heavy metal contaminated tailings for the purpose of reducing their toxicity and migration rates. The optimum mixing ratio of tailings, hydrated lime, and water was determined through a preliminary test. The mixtures of mine tailings and hydrated lime solidified through pozzolanic reaction were tested for their durability against repeated freezing and thawing processes. After repeated freezing and thawing, the uniaxial compressive strengths of all the solidified mixture specimens decreased in comparison with those before test but still higher than $3.5kgf/cm^2$, the standard recommended for land reclamation solids by EPA(Environmental Protection Agency), which suggested that hydrated lime be a potential material to treat the abandoned mine tailings for the environmental purpose.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.331-336
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• 1999

Permeable polymer concrete in this study is one of the environment conscious concrete that can be applied at road, side walks and river embankment, etc. The purpose of this study is to evaluate the effects of mix proportions such as resing content, filler-binder ratio and aggregate ratio on the freezing and thawing resistance of permeable polymer concrete. The permeable polymer concrete are prepared with the resin ratio of 5%, 6% and 7%, filler-binder ratio of 0, 0.5 and 1.0, and 2.5~5mm sized aggregate ratio to standard sand of 10:10, 10:20, 20:10 and 20:20. It is tested for freezing and thawing test according to ASTM C 666092, and then, weight change, length change, relative dynamic modulus, durability factor, and compressive and flexural strengths after test are measured. From the test results, the resistance to freezing and thawing of permeable polymer concrete increased with increase the resing content, filler-binder ratio and fine aggregate ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.48-53
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• 2003

The steel slag, a by-product which is produced on the process of manufacturing steel by refining pig iron is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the volume expanded. Due to this reason it prevents steel slag from being used as aggregate of concrete. But steel slag used in this study is controled by a air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generating of free-CaO in steel slag. In this study, it was investigated that steel slag manufactured by air-jet method affects on concrete in the freezing and thawing. As results of this study, concrete mixed with steel slag was worse in the freezing and thawing than concrete mixed with sand in spite of using air entraining agent. To obtain durability of concrete in the freezing and thawing, it is desirable to mix 50% of steel slag in concrete per unit weight of volume.

• 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.

• Korean Journal of Animal Reproduction
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• v.21 no.2
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• pp.103-109
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• 1997

The studies on the carried out to investigate to determine the optimum thawing temperature and equilibration time and 1 step straw method of frozen bovine embryos. The follicular oocytes were cultured in TCM-199 medium containing 10 IU/ml PMSG(Sigma, USA), 10 IU/ml hCG(Sigma, USA), 1 $\mu\textrm{g}$/ml $\beta$-estradiol(Sigma, USA) and 10% FCS for 24~48 hrs in incubator with 5% CO2 in air at 38.5$^{\circ}C$ and then matured oocytes were again cultured for 12~18 hrs with motile capacitated sperm by preincubation of heparin. The bovine embryos following dehydration by cryoprotective agents and various concentration of sucrose were directly plunged into liquid nitrogen and thawed in 3$0^{\circ}C$ water. Survival and in vitro developmental rate was defined as developmental rate on in vitro culture or FDA-test. The results are summarized as followes : 1. The equilibration time on in vitro developmental rates of bovine embryos was attained after short period of time(2.5~5 min.) in the freezing medium higher than long period of time (10~20 min.). 2. The temperature thawed at 3$0^{\circ}C$ after rapid freezing of bovine embryos resulted in a significantly higher in vitro developmental rate than did at 2$0^{\circ}C$ and 35$^{\circ}C$. 3. The thawing time on in vitro developmental rates of bovine embryos was attained after short period of time(1~5 min.) in the freezing mediuim higher than long period of time(10min.). 4. The in vitro developmental rates of bovine embryos after rapid frozen-thawing by 1 step straw method in the freezing medium added 1.5M, 2.0M glycerol, DMSO, propanediol and 0.25M, 0.50M, 0.75M, 1.00M sucrose were 12.5~19.4%, 10.0~15.6%, 9.1~13.8% and 6.7~12.9%, respectively.

• Korean Journal of Animal Reproduction
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• v.16 no.2
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• pp.125-131
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• 1992

This study was carried out to investigate the effects of concentration and equilibration time of cryoprotective agents on the survival rate of slowly and ultrarapidly frozen porcine embryos. The porcine embryos following dehydration by cryoprotective agents and a various concentration of sucrose were directly plunged into liquid nitrogen and thawed in 38$^{\circ}C$ water bath. Survival rate was defined as development rat to the morula and blastocyst stage after in vitro culture or by FDA test. The results are summarized as follows : 1. The survival rates of porcine embryos after ultrarapid frozen-thawing in the freezing medium of 0.25M sucrose added 2.0, 2.5, 3.0, 3.5, or 4.0M glycerol was 65.3, 61.8, 64.3, 59.4 or 39.4%, respectively. Addition of 0.25M sucrose into the freezing medium containing 2.0M glycerol showed higher survival rate than those of 2.5~4.0M glycerol. 2. The survival rates of porcine embryos after ultraradpid frozen-thawing in the freezing medium of 0.25M sucroese added 2.0, 2.5, 3.0, 3.5 or 4.0M DMSO was 65.6, 67.6, 68.6, 60.6 or 23.6%, respectively. However, addition of 0.25M sucrose into the freezing medium containing 3.0M DMSO showed higher survival rate than those of 2.0, 2.5, 3.5 or 4.0M DMSO. 3. The survival rates of porcine embryos after ultrapid frozen-thawing in the freezing medium of 0.25M sucrose added 2.0, 2.5, 3.0, 3.5 or 4.0M propanediol was 63.2, 60.3, 62.1, 52.3 or 24.3%, respectively. Addition of 0.25M sucroese into the freezing medium containing 2.0M propanediol showed higher survival rate than those of 2.5~4.0M glycerol. 4. The survival rates of porcine embryos after ultrarapid frozen-thawing the freezing medium of 2.0M glycerol added 0.10, 0.25, 0.50 or 0.75M sucrose was 61.8, 70.8, 67.6 or 52.2%, respectively. Addition of 2.0M glycerol into the freezing medium containing 0.25M sucreose showed higher survival rate than that those of 0.10, 0.50 or 0.75M sucrose. 5. The higher suvival rate of porcine embryos were attained at short period of equilibration time 92.5~5min.) in the freezing medium added 0.25M sucreose and 3.0M compared to those of 10 or 20min. equilibration time in the same condition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.151-152
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• 2015

Concrete parking slab is often deteriorated severely after winter season because of concrete's freezing and thawing phenomenon. In this study, some methods to improve resistance against freezing-thawing is experimentally tested.: 1) concrete strength, 2) air content in concrete, 3) saw-cut effect and finish material. After experiment, in case of no finishes, 24MPa concrete with 4% air content is tested best result in terms of relative elastics modulus among testes ones. In case of concrete with finishes, all specimens are improved regardless of finishes compared to concrete with no finishes. Improvement degree compared to no finish is as follows : Polyurea > Resin-mortar > hardener and the number of improvement degree is 5, 4, 2% respectively. Further work is required considering construction site condition such as gaining water on surface and remicon in order to reflect site condition.

• Korean Journal of Animal Reproduction
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• v.13 no.3
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• pp.141-148
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• 1989

The effects of seeding method and optimum time for freezing embryos according to the developmental stages on embryo survival rates after rapid freezing were determined using the FDA-test. The summarized results are as follows : 1. In the rapid freezing of embryos, the sucrose added medium together with Co-seeding or non-seeding showed the FDA scores of 4.67 and 4.20, respectively, but, raffinose addition obtained FDA scores of 4.27 and 3.97. 2. The developmental stage of embryos at freezing was most critical on the survival of embryos after thawing. Higher FDA scores were obtained in the order of blastocyst stage(4.94), morula stage(3.82) and ealy stage(2.65) in sucrose added medium. The same trend was observed in the raffinose added medium with an order or 4.91, 4.47 and 2.32. 3. Microscopic study of embryo before freezing and post-thawing indicated that the embryo showed shrinkage within 5 minutes after the embryo was transfer to the freezing medium. When thawed embryo was tranfered to the dilution medium, swelling of the embryo was observed and there after it reshrank indicating the removal of cryoprotectant from the embryo. The size of the embryo recovered to the original state when it was moved into a PBS-solution.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.682-687
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• 1999

The destruction of tissues by volume increase at food freezing is accepted as one of the factor responsible for quality damage. For this reason, the internal pressure developed in meats were investigated with a pressure transducer during freezing, frozen storage and thawing. Increasement of 6.33% for volume and $942.17\;kg/cm^2$ for density at $-20^{\circ}C$ for beef were shown. In quick and slow freezing of beef, internal pressure reached to highest point after reached to the lowest point at initial of the zone of ice crystal formation. The internal pressure was approximately $8{\sim}10\;psig$ and pressure difference was about 1 psig, which was bigger in immersion freezing than that of still-air freezing. During frozen storage of pork, internal pressure of $1.84{\sim}2.32\;psig$ occurred repeatedly as a function of sample weight at material temperature difference of ${\pm}1^{\circ}C$. The internal pressure during thawing of pork was decreased slowly after rapid increase to the maximum for less than 5min at the beginning of thawing. Internal pressure value at thawing was higher than that at freezing in most cases. Internal pressure of beef with thermal equalized freezing was about $1{\sim}4\;psig$, which was lower than that of non-thermal equalized freezing. Also, freezing time was shortened to $10{\sim}20%$.