• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.415-420
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• 1999

Dam concrete should have sufficient durability in wet and dry repetition and abrasion due to water lever variance and also in freezing and thawing resistance as well as water penetration capacity. This study presents various experimental performance to enhance the durability of face slab concrete in concrete face rockfill dam by varying the fly ash substitution of 0%, 10%, 15% and 20% in cement quantity. The effect on durability corresponding to the increasing amount of fly-ash was evaluated and the optimum quantity of fly-ash subtitution was finally recommended. The results show that 15% fly-ash substituion was found out to be an optimum quantity and demonstrated an excellent performances in durability.

• Asian Journal of Turfgrass Science
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• v.12 no.4
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• pp.203-210
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• 1998

Environmental concerns arising from synthetic herbicides in plant management systems have led to an interest in plant-derived compounds as natural herbicides. Inhibitory effects of compounds extracted with 50% methanol from corn (Zea mays L.) and pine (Pinus densiflora L.) were evaluated on large crabgrass (Digitaria sanguinalis (L.) Scop.), annual bluegrass Poa annua L.), radish (Raphanus sativus L.), and perennial ryegrass (Lolium perenne L.) The aqueous extracts inhibited seed germination and had postemergence activity on the four species. The stability of biological activity of corn grain, stover, and root extracts was not affected by heating to $135^{\circ}C$ or freezing/thawing treatments when applied at levels above 0.25kg m(sup)-2 based on dry weights of powders before extraction. Heating reduced the activity of pine litter and bark extracts at all levels except the highest application level but had little effect on pine needle extracts.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.150-151
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• 2016

In previous study, researchers studied development of early anti-freezing cement at low temperature (-5℃) using hydration characteristics of reduction slag. In this study, the durability of concrete using reduction slag was conducted. The experiment result, reduction slag makes high temperature and improves compressive strength due to quick setting. And then result of durability show that it is no problem. However, it is considered that further study is needed about high shrinkages which was indicated in dry shrinkage.

• Membrane Journal
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• v.14 no.1
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• pp.1-17
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• 2004

Dehumidification systems have been developed for the various applications, especially for the production of dry compressed air. Compressed air producing system attach $\varepsilon$ d with dehumidification unit have advantages such as high reliability, low error ratio, comfortable working conditions, etc. Conventional dehumidification systems have several economical drawbacks like high electric cost, high cost of adsorbent and it is not environmentally friendly system because freezing agent like a Freon has been used. Membrane dryer is emerging system which have economical advantages and environmental merits.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.1
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• pp.28-43
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• 1988

The purpose of this research is to produce bin weather data for Seoul from Standard Weather Data. The intended use of these data is for input to recently developed models for simplified energy calculations and for generating variable-base degree-day information. The data produced under this study include $3^{\circ}C$ bin data covering the full range of dry-bulb temperatures with mean coincident wet-bulb and daytime coincident solar radiation, wet-bulb bins down to freezing temperature, wind speed bins with prevailing directions, and heating and cooling degree hours to nine different temperature bases. All of these data are tabulated in six separate time periods and total daily categories for monthly and annual periods.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.25-41
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• 2017

In recent years, the amount of sludge ash (SA) has considerably increased due to rapid urbanization and population growth. In addition, its storage in landfills induces environmental pollution and health problems. Therefore, its disposal in an environmentally friendly way has become more important. The main goal of this study is to investigate the reusability of sludge ash as an additive with polypropylene fiber (PF) to stabilize marginal sand based on the compressive strength performances from UCS tests. For this purpose, a series of UCS tests was conducted. Throughout the experimental study, the used inclusion rates were 10, 15, 20 and 30% for sludge ash and 0, 0.5 and 1% for polypropylene fiber by total dry weight of the sand+sludge ash mixture and the prepared samples were cured for 7 and 14 days prior to the testing. Freezing and thawing resistance of the mixture including 10% sludge ash and 0, 0.5 and 1% polypropylene fiber was also examined. On the basis of UCS testing results, it is said that sludge ash inclusion remarkably enhances UCS performance of sand. Moreover, the addition of polypropylene fiber to the admixtures including sand and sludge ash significantly improves their stress-strain characteristics and post-peak strength loss as well as UCS. As a result of this paper, it is suggested that sludge ash be successfully reused with polypropylene fiber for stabilizing sand in soil stabilization applications. It is also believed that the findings of this study will contribute to some environmental concerns such as the disposal problem of sludge ash, recycling, sustainability, environmental pollution, etc. as well as the cost of an engineering project.

• The Korean Journal of Quaternary Research
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• v.18 no.2 s.23
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• pp.33-42
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• 2004

In South Korea a Pedo-sedimentary Sequence(PS) indicating the Last Glacial Maximun(LGM) is typified y a brown to dark brown, relatively stiff paleosol layers formed by repetitive freezing and thawing processes which in turn left characteristi glossic textures in soil-solum, polygolnal structures with a flagipans, vertical soil wedges or freezing cracks, and horizontal foliations, As a pre-LGM sedimentary sequences (older than 25Ka), the Old Fluvial Sequence(OFS) overlain by the Slope Sedimentary Sequence(SS) are distributed commonly at the base level higher than 14-15m above present river-bed along the major river basin. After the LGM (ca. 18Ka), the Young Fluvial Sequence(YFS) appears at an altitude ascending order of sedimentary profiles. In this fluvial organic muds of Jangheungri site(Jinju), Sorori site(Cheonwon), and Youngsan estruarine rivermouth(Mokpo) were exemplified in order to interpret their formation ages and environments. As result of $^{14}C$ datings, the formation ages of te organic muds are Boelling to Alleroed (MIS-1). These organic muds were fomed in fluvial backswamp or local pond/bog in response to shifting fluvial system. On the basis of palynological production dominant with Abies/Picea-Betula and Ranunculaceae, Compositae, Cyperaceae, and Graminae, it was interpreted that more boreal to subboreal condition was prevailed rather than temperate like today during the formation of organic muds and soil moisture condition was a repetition of wet and dry condition.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.5-13
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• 2014

In this research, in order to study insulation effect of commercial XPS and recycled PE aggregates for prevention of frost heave in the roadbed of railroad track from the freezing temperature, model tests were carried out in the large freezing room. For this, thermal conductivities were measured for various dry densities, water contents, temperatures and mixing ratios of PE aggregates. From the tests, it can be seen that thermal conductivities of roadbed decrease with the increase of the ratio of mixed PE aggregates. However it was sensitive to the changes of temperature and water content due to the amount of water in the voids. From the model test of railroad track, it can be seen that the time to reach $0^{\circ}C$ was longer for XPS than that for the PE aggregates. Also the test shows best insulation effect can be achieved when XPS board was installed above the PE aggregate layer rather than the opposite order.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.147-154
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• 1988

Korea has the ground which freezes in winter and melts in warmer seasons by turns. Therefore, in designing civil-structures or buildings on such ground, the depth of seasonal frost penetratio must be considered. In this paper, approximate contours of the maximum depth of frost penetration in Korea is presented. It was found that the maximum depth of frost penetration did not have the linear relationship to square root of the freezing index. In order to establish more reliable method to estimate the maximum depth of frost penetration, a new empirical equation is introduced. In the presented equation, the dry unit weight and water content of soil are considered in addition to the freezing index. And the equation is compared with other previous equations used so far.

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