• Journal of Ginseng Research
• /
• v.20 no.2
• /
• pp.179-183
• /
• 1996

One exotherm was detected in the intact ginseng seeds containing more than 35% water, but in seeds with 20% there was no exotherm. The shapes of exotherm were remarkably uniform without relation to water content above 35%. The temperature at the initiation of freezing varied from -3.5$^{\circ}C$ to -9.6$^{\circ}C$ with the different water content in the seeds, and the Initial temperature of freezing delayed with the decrease of water content. The resistance damage at low temperature appeared in order of maln body, rhizome, lateral root of 3-year-old yearling rhizome, and fine root of 3-year-old. Ginseng roots didn't receive any damage at -5$^{\circ}C$ for 24 hours. Otherwise they received serious damage below -1$0^{\circ}C$ even for 5 hours'exposure. Hence, alternative low temperature gave more severe damage compared to constant low temperature. This result suggests that the Possibility of receiving injury at low temperature was higher during the thawing season of the early spring than in the winter.

• International Journal of Highway Engineering
• /
• v.20 no.3
• /
• pp.11-18
• /
• 2018

PURPOSES : Durability of concrete is traditionally based on evaluating the effect of a single deterioration mechanism such as freezing & thawing action, chloride attack, carbonation and chemical attack. In reality, however, concrete structures are subjected to varying environmental exposure conditions which often results in multi-deterioration mechanism occurring. This study presents the experimental results on the durability of concrete incorporating air-cooled slag(AS) and/or water-cooled slag(WS) exposed to multi-deterioration environments of chloride attack and freezing & thawing action. METHODS : In order to evaluate durable performance of concretes exposed to single- and multi-deterioration, relative dynamic modulus of elasticity, mass ratio and compressive strength measurements were performed. RESULTS :It was observed that multi-deterioration severely affected durability of concrete compared with single deterioration irrespective of concrete types. Additionally, the replacement of cement by AS and WS showed a beneficial effect on enhancement of concrete durability. CONCLUSIONS : It is concluded that resistance to single- and/or multi-deterioration of concrete is highly dependent on the types of binder used in the concrete. Showing the a good resistance to multi-deterioration with concrete incorporating AS, it is also concluded that the AS possibly is an option for concrete materials, especially under severe environments.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.2
• /
• pp.60-66
• /
• 2019

Many researches have been performed on hybrid fiber reinforced concrete for years, which is to improve some of the weak material properties of concrete. Researches on characteristics of hybrid fiber reinforced concrete using amorphous steel fiber and organic fiber, however, yet remain to be done. Therefore, the purpose of this research is to estimate the compressive strength, long term drying shrinkage, and resistance to freezing and thawing of hybrid fiber reinforced concrete(HFRC) using amorphous steel fiber and polyamide fiber as one of organic fibers. For this purpose, HFRCs containing amorphous steel fiber and polyamide fiber were made according to their total volume fraction of 1.0% for target compressive strength of 40 and 60 MPa, respectively, and then the compressive strength, length change, and resistance to freezing and thawing of these were evaluated. As a result, the long term length change ratio of HFRC used in this study decreased by more than 30%, 25% than plain concrete at 365 and 730 days, respectively, and the durability factor of HFRC was very excellent as more than 90%.

• International Journal of Concrete Structures and Materials
• /
• v.11 no.2
• /
• pp.315-325
• /
• 2017

The purpose of the paper is to determine the influence of two widely used steel fibers and polypropylene fibers on the sulphate crystallization resistance, freeze-thaw resistance and surface wettability of ultra-high performance concrete (UHPC). Tests were carried out on cubes and cylinders of plain UHPC and fiber reinforced UHPC with varying contents ranging from 0.25 to 1% steel fibers and/or polypropylene fibers. Extensive data from the salt resistance test, frost resistance test, dynamic modulus of elasticity test before and after freezing-thawing, as well as the contact angle test were recorded and analyzed. Fiber hybridization relatively increased the resistance to salt crystallization and freeze-thaw resistance of UHPC in comparison with a single type of fiber in UHPC at the same fiber volume fraction. The experimental results indicate that hybrid fibers can significantly improve the adhesion properties and reduce the wettability of the UHPC surface.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.2
• /
• pp.75-86
• /
• 2012

This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.34 no.s02
• /
• pp.96-114
• /
• 1989

There are several meterorolgical stresses in the winter cereal crops. Among these stresses, cold injury is one of the most important stresses for wheat and barley production in Korea. The reduction in grain yield of the wheat and barley due to cold injury has occurred almost every year in Korea. The objective of the study was to get the basic information in relation to the cold injury and to detect the method minimizing the damage of cold injury. When the air temperature was the ranges of -13$^{\circ}C$ to -15$^{\circ}C$, the soil temperature at the crown part of the plant was very stable, whereas in the ranges of -2$^{\circ}C$ to -3$^{\circ}C$ the soil surface temperature was more unstable and cold than air and subterranean temperatures. The different parts of the plant in wheat and barley possess the different levels of cold hardiness. In comparison to the cold hardiness of plant parts, the leaf and crown are the less sensitive to cold injury than root and vascular transitional zone. The type and extent of stress is determined by the redistribution pattern of water during freezing. These types from freezing processes were three types: a) Equilibrium freezing pattern b) Non -equilibrium freezing pattern, c) Non-equilibrium freezing pattern typical of tender tissues. Cold hardiness in wheat plants were more harder than barley plants at vegitative stage, but inverted at the reproductive stage. Injuries by low temperature during the seasons of barley cultivation in Korea were occured mainly in four stage; in the first and third stage, frost injury occurs, the second stage, freezing injury, and the fourth stage, chilling injury.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2001.11a
• /
• pp.22-27
• /
• 2001

The purpose of this study is development of dry floor tile method that practically used for improving wet method's defect, with resin mat design. PE resin used mat which satisfied with bonding test, waterproof test, resistance to chemical attack test, resistance to impact test and freezing and thawing test is confirmed the basic property.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1995.10a
• /
• pp.155-158
• /
• 1995

High durabitiy concrete increasingly sutudied in various countries. This report presents the data on durability related properties such as the chloride ion permeability, the resistance to freezing-thawing, the corrosion of steel and the resistance attack. To promote the actual application of high durability concrete, several series of high durability concrete have been made and applied to actual structures.

• 한국도로학회:학술대회논문집
• /
• 2009.11a
• /
• pp.139-143
• /
• 2009

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.4
• /
• pp.270-278
• /
• 2005

Recycled aggregate concrete has lower strength and durability compared to concrete with natural aggregate. Therefore, metakaolin is used to improve the properties of recycled aggregate concrete. Main components of metakaolin are $SiO_2$ and $Al_2O_3$. and specific surface area is 9 times larger than that of ordinary portland cement. Quality of demolished-recycled aggregate(DRA) satisfies the type 1 of KS F 2573, but quality of source-recycled aggregate(SRA) does not satisfy with the type 2 of KS F 2573. When metakaolin was replaced with 20% of cement, compressive strength of concrete with SRA and DRA develops about 40~64% of control concrete. Water absorption ratio was reduced about 2% by replacing 20% metakaolin and it represents low compared to the natural aggregate concrete without metakaolin. In addition, the resistance to freezing and thawing, of concrete with DRA is indicated to remarkably enhanced due to the contribution of metakaolin. However, when metakaolin is replaced with 20% of cement, relative dynamic modulus of elasticity of concrete with SRA was below 60% at 210 freezing and thawing cycles.