• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.433-436
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• 2008

Deterioration in the concrete structure are due to carbonation, chloride ion attack and frost attack. Therefore, concrete structure is needed to surface protection for increase durability using silicate impregnants. Thus, this study is concerned with self-cleaning and durability of silicate hydrophilic impregnants of concrete structure using lithium and potassium silicates. From the experimental test results, lithium and potassium silicates have a good properties as a carbonation resistance. Lithium and potassium silicates make good use of hydrophilic impregnants of concrete structures.

• Journal of Korean Society of Forest Science
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• v.48 no.1
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• pp.25-28
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• 1980

This study examined the cold hardiness of eight cultivars of common persimmon and six cultivars of sweet persimmon growing at the southern part of Korea, to know the most susceptible tissue part, timing of damage, and the difference in freezing resistance between the cultivars during the winter of '77-'78. The cold hardiness of winter bud, cambium and xylem parenchyma of the current year twig was measured on three collection dates; 10 / 26 / 77, 1 / 26 / 78 and 3 / 26 / 78. The results were obtained as follows, 1. The least cold hardy tissue part was winter bud during mid winter and early spring. 2. On the basis of the cold hardiness of the winter bud sweet persimmon cultivars appeared to be less cold hardy than common persimmon cultivars. In the cold hardiness of cambium and xylem parenchyma, there was no consistance differece between the two group of cultivars. 3. The late frost during early spring appeared to cause the most critical damage to the winter bud of persimmon.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.276-281
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• 2023

Water pipes manufactured using existing Portland cement suffer from the problem of rapid deterioration and reduced durability due to the hydration product of cement being vulnerable to acids. Therefore, in this study, water pipes were manufactured using slag and fly ash, which are industrial by-products from various industries, and their characteristics were analyzed. As a result of the experiment, slump in unhardened concrete tended to increase due to the ball bearing action of fly ash, and the amount of air was reduced due to unburned coal, indicating that measures for frost resistance were needed. In addition, the initial strength of the compressive strength was increased through steam curing, and the results were equal to or better than OPC when mixing more than 50 % of slag. The acid resistance results showed that the mass reduction rate was less than 5 %, showing excellent durability performance, and the bending failure load of the water pipe also exceeded the KS standards, so it is judged to be commercializable.

• Journal of Korean Society of Forest Science
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• v.51 no.1
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• pp.22-35
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• 1981

This study was designed to know difference in degree of dehardening and rehardening respectively by artificial high and low temperature treatments among different clonal seedlings and seedlings from different seed sources of Cryptomeria japonica which have been grown under the cold areas in Japan and Korea. High temperature treatment was done with 15 to $20^{\circ}C$ under 100% relative humidity for one to nine days and low temperature treatment was carried with $-7^{\circ}C$ for one to three days. Occasionaly, high temperature treatment was combined and followed by low temperature treatment. The ability of stem section to delay dehardening by high temperature treatment and/or to hasten rehardening by low temperature treatment was used as an indicator of adaptability under extreme temperature fluctuation in nature. Clones and seedlings from different seed sources which showed greater freezing resistance than others after artificial high and/or low temperature treatments were selected over two to three time periods: early winter, mid winter and early spring in 1977 to 1980. These were Seoul #7, and #9, Namboo #3, and #4, Sung-Kang #11, Chung-Sam #8 and Huek-Suk #9. These selected seedlings might have survival advantage to withstand early and late frost damage, especially the critical frost damage of the basal stem, since it was known to be induced by lowering freezing resistance of the basal part when exposed to the high temperature near the ground during the day. Large variation in freezing resistance and degree of dehardening and rehardening was found among clonal or seed sources and among individuals within a seed source, but was not related to the difference in climatic conditions where the parent trees was selected. These indicated the possibility of future breeding work for more cold resistant family of Cryptomeria japonica.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.589-592
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• 2008

This study was conducted to assess the durability of Chloride-inhibiting Low-Heat Cement while being subjected to freezing-thawing during winter seasons. Although durability varies slightly depending on the conditions of the jobsite, frost damage to concrete resulting from repeated freezing and thawing over the course of seasonal changes is the leading cause behind lowered concrete durability. in addition, concrete that has been subjected to freezing and thawing during the winter season develops a significant amount of expansive force at the core and begins to exhibit signs of damage, such as cracking, peeling, and detachment from the aggregate. Therefore, this study fabricated test specimens using a Chloride-inhibiting Low-Heat Cement(CLC) and the widely used blast furnace slag cement(BFS) and Ordinary Portland Cement(OPC) with water-to-cement ratios of 35%, 40% and 45%, respectively, to assess the durability index of the CLC as per resistance to freezing-thawing. The specimens were then tested using the KS F 2456 method (Testing method for resistance of concrete to rapid freezing and thawing) to measure the dynamic modulus of elasticity. The dynamic modulus of elasticity measurements were then used to derive the durability indices. By comparing the durability indices, it was confirmed that CLC, BFS, and OPC all had superior durability.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.5
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• pp.215-221
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• 2019

Ceramic tiles, which are widely used as interior and exterior materials for construction, have recently been required to have pollution prevention function. In order to remove contaminants, many researches of ceramic tiles with hydrophilic surface property through $TiO_2$ coating and hydrophobic surface property by improving the flow of water droplets have been proceeded. Expecially, it is very important to develop a surface glaze having hydrophobicity through a sintering process above $1000^{\circ}C$ without an additional coating process and the degradation of mechanical properties. In this study, surface glaze with copper powder was applied to manufacture of ceramic tile. Contact angle of ceramic tile according to thickness of surface glaze layer was investigated after the conventional sintering process. The contact angle of the ceramic tile surface without the copper powder was shown to be $25.3^{\circ}$, which is close to hydrophilic surface. However, the contact angle was increased up to $109.8^{\circ}$ when the thickness of surface glaze with the copper powder was $150{\mu}m$. The excellent hydrophobic property of the surface glaze with copper powder was resulted from the cellular structure of copper particles on the glaze surface. In addition, the mechanical properties of the developed hydrophobic ceramic tiles such as bending strength, chemical resistance, abrasion resistance, and frost resistance were well maintained and meet the criteria of 'KS L 1001 Ceramic tile'.

• Journal of Korean Society of Forest Science
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• v.53 no.1
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• pp.37-43
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• 1981

This study was aimed at expanding the tea plant culture in Korea to further north, and the leaf-form and the cold resistance of the tea plants selected form 7 districts(around Korea) were investigated. 1. The length of tea leaf is 5.1cm to 8.4cm, the width of the leaf is 2.3cm to 3.6cm, but the area of tea leaf in Mt. Mudung is $26.88cm^2$ and that is the widest of all. 2. The tooth number of the tea leaf in 43 to 73 but the number of Mt. Borim is remarkably number of all. The tooth number is increased or decreased in proportion to the leaf width and to the leaf length. 3. The lateral vein number is generally 13 to 19. The vein number of Mt. Borim is especially number of all. That is also increased or decreased in proportion to the leaf width and to the leaf length. 4. In general, the number of leaf formation index is 2 to 3, and ablong. 5. In general, those which come upper lands are remarkably small in length and width of the tea leaf and those which come from level lands are large. 6. All kinds of tea plant which is growing in Korea, area, are the same as those imported from China : Thea sinensis Linne var. Bohea. 7. I supposed that the external form of tea plant has a little changed by geography or climate for many a long day, since the tea plant had been transplanted in Mt. Samsin. 8. In the treatment of low temperature and duration of vernalization of their plants, those selected from Mt. Mudung and Mt. Hwaun were the coldest resistance, those from Mt. Samsin and Mt. Borim were medium and those from Mt. Joge and Nursery were cold sensitive. 9. The critical temperature of the tea plant from Mt. Mudung, Mt, Hwaum, Mt, Samsin and Mt. Borim was about $-10^{\circ}C$, and that from Mt. Joga and Nursery was about $-5^{\circ}C$. The critical temperature of frost injury of all tea plants in this experiments was $-15^{\circ}C$. 10. In spite of increasing the vernalization time, the critical temperature was not effected, but the treatments over critical temperature were increased their frost injuries. Based on these results, the coldest resistance, Mt. Mudung tea plant, was considered expanding their culture to further north improvement yields of the tea plants in Korea.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.605-608
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• 2008

This study investigated fundamental properties corresponding to mixtures for the high strength, and their properties of spalling prevention after a fire test. The results were summarized as following. For the flowability of using mixtures for the high strength, the target flow was satisfied with a small quantity of high performance reducing water agent to compare with silica fume. For the compressive strength in the case of using mixtures for the high strength, it was higher to compare with silica fume at 7 days, so it was proved that using mixtures for the high strength was profitable to prevent early frost damage. The compressive strength at the 28 days of silica fume and mixtures for the high strength were similar. There was no reduced tendency at the compressive strength according fiber contents, so it found out that the bonding strength between the fiber and concrete was hardly effective. For the spalling properties, the specimens without fibers were destroyed, however using over 0.05% of NY and PP fibers was effective to prevent spalling on the high strength concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.40-45
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• 2014

Although the accelerators are used at the early stage to control setting-time and strength of concrete when cold-weather concrete is utilized, no security of workability occurs because the early hydration makes them react rapidly. Therefore, the tablet used in previous study is applied in this study. In particular, because a small amount of fly-ash being replaced in cold weather concrete of domestic, fly-ash concrete incorporating the tablet is discussed in workability by elapsed time, early strength to ensure the development of adequate strength, and freezing-thawing resistance. As a result, both 0.5 and 1.0% tablets were found to be superior. Thus, it was verified in cold weather concrete incorporating fly-ash that workability can be secured, as well as the development of early strength to prevent early frost.

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