• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.147-152
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• 2010

In this study, the artificial coarse aggregate was manufactured by using coal ash and low grade clay. The characteristics of a coal ash-clay system were investigated using XRD, XRF, TG-DTA, SEM and Dilatometer with various coal ash contents. The chemical compositions are the fly ash, bottom ash and clay, $Al_2O_3$ are 28.5 wt%, 32.4 wt% and 18.1 wt%, and $SiO_2$ are 33.0 wt%, 53.7 wt% and 68.4 wt% in weight ratio, respectively. The shrinkage of specimens started at around $850^{\circ}C$ and changed little up to $1100^{\circ}C$, but increased markedly at above $1100^{\circ}C$. The shrinkage rate is strongly related to the decarbonization amount of coal ash. At the sintering temperature $1150^{\circ}C$, it was found that quartz, mullite, anorthite and albite phase exist in all specimens. It was found that bottom-clay system specimen sintered at $1150^{\circ}C$ had a good compressive strength of 87.5 kg/$cm^2$, and the compressive strength of bottom-clay specimen was higher than that of fly-clay system specimen. The reusability of coal ash as a raw material in the process of shotcrete resources such as artifical coarse aggregate is highly expected.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.99-109
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• 2009

Fine-size exposed aggregate portland cement concrete pavements (FEACP) have surface texture of exposed aggregate by removing upper 2$\sim$3mm mortar of surface of which curing is delayed by using delay-setting agent. FEACPs have advantages of maintaining low-noise and adequate skid-resistance level during the performance period than general portland cement concrete pavements. It is necessary to ensure the durability environmental loading to prevent unexpected distress during the service life of FEACP. In the process of curing, volume change accompanied change in by moisture and temperature could be an important cause of crack in concrete to construct for successful FEACP, The use of chloride containing deicer may accelerate defects of concrete pavement, such as crack and scaling. This study aim to evaluate environmental loading resistance of FEACP, based on the estimation of shrinkage-crack-control-capability by moisture evaporation and scaling by deicer in freeze-thaw reaction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6D
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• pp.719-726
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• 2009

In this study, a series of push-off tests for lean concrete, aggregate, asphalt subbases mainly used in Korea were performed to investigate the friction characteristics between the slab and subbase layers. Use of separation membrane and wet condition of subbase were other parameters in the tests. Horizontal displacements of the slabs and friction coefficients were measured at 1st loading, stable condition (2nd and 3rd loadings), and wet condition (4th loading) by applying 40mm/hour horizontal loadings. Larger maximum friction coefficients were measured in order of the lean concrete, asphalt, aggregate, and subbases using the separation membrane at 1st loading, and in order of the asphalt, aggregate, lean concrete, and subbases using the separation membrane at stable and wet conditions. The friction coefficients of the aggregate and asphalt subbases which did not used the separation membrane decreased by the wet condition while the subbases using the separation membrane were not affected. Additional push-off tests for effects of slab thickness and temperature sensitivity of asphalt will be performed. And, effects of the friction characteristics between the slab and subbase layers on behavior and performance of concrete pavements will be investigated by structural analyses using the test results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2A
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• pp.129-136
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• 2011

Recently studies on functional concrete with a photocatalytic material such as $TiO_2$ have actively been carried out in order to remove air pollutants. The absorbtion of $TiO_2$ from those studies is applied by it being directly mixed into concrete or by suspension coated on the surface. When it comes to the effectiveness, the former process is less than that of the latter compared with the $TiO_2$ use. As a result, the direct coating of $TiO_2$ on materials' surface is more used for effectiveness. The Surface spread of it needs to have a more than $400^{\circ}C$ heat treat done to stimulate the activation and adhesion of photocatalysis. Heat treat consequently leads hydration products in concrete to be dehydrated and shrunk and is the cause of cracking. The study produces $TiO_2$ used Sol-gel method which enables it to be coated with a low temperature treat, applies it to pearlite using Lightweight Aggregate Concrete fixed with a low temperature treat and evaluates the spread performance of it. In addition to this, the size of pearlite is divided into two types: One is 2.5 mm to 5.0 mm and the other is more than 5.0 mm for the benefit of finding out the removal characteristics of $CH_3CHO$ whether they are affected by pearlite size, mixing method and ratio with $TiO_2$ and elapsed time. The result of this experiment shows that although $TiO_2$ produced by Sol-gel method is treated with 120 temperature, it maintains a high spread rate on the XRF(X ray Florescence) quantitative analysis which ranks $TiO_2$ 38 percent, $SiO_2$ 29 percent and CaO 18 percent. In the size of perlite from 2.5 mm to 5.0 mm, the removal characteristic of $CH_3CHO$ from a low temperature heated Lightweight concrete appears 20 percent higher when $TiO_2$ with Sol-gel method is spreaded on the 7 percent of surface. In other words, the removal rate is 94 percent compared with the 72 percent where $TiO_2$ is mixed in 10 percent surface. In more than 5.0 mm sized perlite, the removal rate of $CH_3CHO$, when $TiO_2$ is mixed with 10 percent, is 69 percent, which is similar with that of the previous case. It suggests that the size of pearlite has little effects on the removal rate of $CH_3CHO$. In terms of Elapsed time, the removal characteristic seems apparent at the early stage, where the average removal rate for the first 10 hours takes up 84 percent compared with that of 20 hours.

• Atmosphere
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• v.34 no.2
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• pp.139-151
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• 2024

The Yeongdong region has suffered from severe snowstorms and the relevant damage such as traffic accidents on slippery roads, and the collapse of greenhouses and temporary buildings. While a lot of research on snowfall has been conducted, the detailed study of snow crystals' phase and habit through intensive observations and the relevant microphysical analysis is still lacking. Therefore, a snowflake camera, PARSIVEL, and intensive radiosonde soundings were utilized to investigate phase and habit changes in solid precipitation. Two remarkable episodes of phase and habit changes were selected such as 19 March 2022 and 15 February 2023. Both events occurred in the synoptic condition of the High in the north and the Low passing by the south, which was accompanied by rapid temperature cooling below 2.5 km. During the events of a short period between 3 to 6 hours, the temperature at 850 hPa decreased by about 4 to 6℃. This cooling led to a change in the main habit of snow particles from riming to aggregate, identified with both MASC and PARSIVEL. Meanwhile, the LDAPS model analyses do not successively represent the rapid cooling and short-term variations of solid precipitation, probably by virtue of overestimating low-level equivalent potential temperature during these periods. The underlying causes of these the low-level temperature variations within 6 hours, still remain unclear. It might be associated with mesoscale orographic phenomenon due to the mountains and East Sea effects, which certainly needs an intensive and comprehensive observation campaign.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2663-2670
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• 2013

The purpose of stability testing is to provide evidence about how the quality of a drug varies with time under the influence of a variety of environmental factors. In this study, erythropoietin (EPO) was analyzed under different pH (pH 3 and pH 9) and temperature ($25^{\circ}C$ and $40^{\circ}C$) conditions according to current Good Manufacturing Practice (cGMP) and International Conference on Harmonisation (ICH) guidelines. The molecular weight difference between intact EPO and deglycosylated EPO was determined by SDS-PAGE, and aggregated forms of EPO under thermal stress and high-pH conditions were investigated by size exclusion chromatography. High pH and high temperature induced increases in dimer and high molecular weight aggregate forms of EPO. UPLC-ESI-TOF-MS was applied to analyze the changed modification sites on EPO. Further, normal-phase high-performance liquid chromatography was performed to identify proposed glycan structures and high pH anion exchange chromatography was carried out to investigate any change in carbohydrate composition. The results demonstrated that there were no changes in modification sites or the glycan structure under severe conditions; however, the number of dimers and aggregates increased at $40^{\circ}C$ and pH 9, respectively.

• Journal of the Korean Applied Science and Technology
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• v.26 no.1
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• pp.80-86
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• 2009

This research was performed to evaluate heavy metal leaching characteristics of the sludge from paper mill process with sintering temperature. Heavy metal leaching of the sludge was characterized with Korean Leaching Test and Toxicity Characteristic Leaching Procedure. The test sludge was composed of 70.72% of moisture, 9.5% of volatile solids and 9.76% of fixed solids. As a result of XRF analysis, Fe was the highest inorganic element in approximately 83%, which implies the recycling possibility of the sludge in reuse of Fenton chemicals and artificial lightweight aggregate. Leaching of heavy metals from sintered sludge was lower than the dry ones. However, there was no significant difference in leaching characteristics between the sludges sintered at $350^{\circ}C$ and $650^{\circ}C$. Zn and Fe were leached more greatly in TCLP and KLT methods respectively.

• Computers and Concrete
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• v.13 no.1
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• pp.83-96
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• 2014

Accumulated annual reservoir sedimentation in Taiwan was 14.6 million m3 in 2010, seriously endangering reservoir safety and the water supply. In addition, the sintering temperature of reservoir-sediment aggregates (RSAs) is very high, and very energy consuming consequently. Therefore, to explore the effects of admixtures on sintering behavior and performance of the aggregates, two different admixtures are blended, waste-glass and municipal sewage sludge, into reservoir sediment to make artificial aggregates. Experimental results show that the lightweight characteristics of waste-glass/reservoir-sediment aggregates (WGRSAs) are more significant than those of sewage sludge/reservoir-sediment aggregates (SSRSAs). Moreover, as sintering temperature increases, the specific gravity of WGRSAs drops more apparently. The optimum sintering temperature of pure reservoir-sediment aggregates (PRSAs), SSRSAs, and WGRSAs was $1150^{\circ}C$, $1100^{\circ}C$, and $1050^{\circ}C$, respectively. The PRSAs are normal weight with better strength; the WGRSAs are lightweight and energy-saving; and the SSRSAs are lightweight with normal strength.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.104-105
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• 1999

This study was performend to examine Poisson's ration of polymer-modified asphalt concrete due to temperature variatino . Asphalt binder used in this study was an AC85-100, penetration grade of 85-100, and polymer for modifying asphalt were domestic LDPE(Low-density polyethylene) and SBS(Styrene-butadiene-styrene). Aggregate was a crushed gneiss which was most widely used in the middle part of Korea. Using these materias, asphalt mixture slab(340mm$\times$240mm$\times$80mm) with optimum asphalt content from mix design was made and cut into square pillar (80mm$\times$80mm$\times$160mm). Poisson's ration was measured in various temperture (-15$^{\circ}C$, -1$0^{\circ}C$, -5$^{\circ}C$,$0^{\circ}C$,5$^{\circ}C$,1$0^{\circ}C$ and 2$0^{\circ}C$) under the load of one axis repeated compression mode. Poisson's ration of normal asphalt polymer modified asphalt mixtures in normal temperatures. This indicated that AP mixture was more susceptible to temperature effects. From regression aalysis of experimental results, the difference of Poisson's ration between normal and low temperature showed that polymer modified asphalt mixture were lower than AP mixture except for SBS modified asplat mixture.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.36-43
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• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.