• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.199-200
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• 2019

The purpose of the research is assessing the possibility of strength recovery for mortar added with accidently high amount of fly ash. For compressive strength at 28 day, the sample painted with sodium hydroxide showed higher compressive strength than the sample painted with calcium hydroxide. Regarding the curing conditions, the curing temperature 65℃ provided better conditions than the curing temperature 20℃ in aspect of solution penetration depth and reactivity of fly ash. In the case of drying after saturation, the case painted with sodium hydroxid 65℃ showed the clearest engrossing mark.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.5-10
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• 1992

The aim of this study is to decide the optimum replacement method when mineral Admistures as SILCA FUME and FLY ASH are used, as a part of practical use of ultra High-Strength Concrete. For this purpose, Four types of replacement methods are examined and the relationship between replacement methods and concrete properties is studied. As a result, workability and gain of strength are dependent on the replacement method of mineral Admixtures. The methods of using volumn ratio of cement in FIY ASH, weight ratio of cement in SILCA FUME are shown better workability and strength of concrete than any other replacement method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.87-91
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• 2009

This study investigates possibility for practical use through small sized test with OPC and substituted fly ash 10% and return coarse cement (RCC), classed 1100${\sim}$1200 cm2/g, which is made by Cyclone Separator at cement producing process 20% (CF) for OPC. The experimental factors are 48% of W/B and OPC and 2 kinds of concrete proportions. The target slump and air content are $150{\pm}25$ mm and $4.5{\pm}1.5$ %. For the results, the flowalility and air content of CF are less than OPC because it needs more superplasticiser and air-entraining agent. The temperature history of CF is lower than OPC about $6{\sim}10^{\circ}C$. For the strength properties, CF is less than OPC, but their gap is declined at 28 days. The strength of the specimens are ordered by standard curing, field cured specimens, and core specimens.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.139-140
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• 2019

In this study, we conducted a comparative analysis of the effects of resuscitation after the re-application of mortar with much FA replacement on the degree of resuscitation. Results When NaOH was applied to the top of the mortar where 90% of FA was replaced, and maintained for 24 hours, the degree of resuscitation at $40^{\circ}C$ was completely improved. However, when medium curing was carried out, it showed a higher degree of compression than water or lapping curing at 10 MPa in 28 days. The degree of resuscitation on the 28th day was revived from around 10% of the normal level to about 20~30%, and it was analyzed that it was difficult to achieve the OPC reduction by any method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.141-142
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• 2019

In this study, we conducted a comparative analysis of the effects of retention time and resuscitation method on the degree of resuscitation after reapplying mortar with much FA replacement. Results After applying NaOH to the top surface of 60 % FA-substituted mortar, the degree of resuscitation at $40^{\circ}C$ was high enough to increase the overall curing time, but there was no significant difference. However, with regard to the curing method, middle curing showed the greatest manifestation, followed by wrapping and underwater curing, but there was no significant difference. The resuscitation level on the 28th of the lumber was found to be revived to about 70~80 % at around 30 % without resuscitation.

• Korean Journal of Environmental Agriculture
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• v.17 no.2
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• pp.164-169
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• 1998

In order to evaluate the utility of the bituminous coal fly ash, gypsum, oyster shell as soil amendments, acid sandy loam soil with low boron content were amended in the upper 15cm with amendments, and then chinese cabbage was cultivated in fall. Amendments treated were, in metric tons per hectare, i ) none(Check) ; ii) 80 fly ash(FA) ; iii) 4shell(SH) ; iv) 56 fly ash+24gypsum (FG) ; v) 40 fiy ash + 24 gypsum +0.8 shell(FGS). On the whole, amendments imoroved soil chemical properties and contents of N, P, K, Ca, and B in leaves. Among treatmens, FA prominently neutralized soil pH and increased available $P_2O_5$ ,B but decreased Fe contents in soils. FGS also affected the increment of exchangeable Ca, Mg, and available B. Yield response in fresh weight of chinese cabbage was in order of 85% for FGS>77% for FG>66% FA>5% for SH plants. Reducing sugar and vitamin-C contents of leaves depending on treatments showed the same tendencies as that in yields, whereas crude fiber opposite to theme. In particular, FA, FG, and FGS plants showed normal growth without boron deficiency symotoms which appeared in Check and SH plants.Taken together, FGS was an effective combination enable to maximize the utility of fly ash, gypsum, and shell as soil amemdments, especially in cabbage yield and quality.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.550-557
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• 2002

TiO$_2$ particles coated on fly ash composites for use in photocatalyst were synthesized by the precipitation dropping method and heated at $700^{\circ}C$ for 2 h. The pH of reaction solution, the addition rate of NH$_4$HCO$_3$, the stirring speed, the reaction temperature and the concentration of TiC1$_4$ had a pronounced effect on the nature of precipitated TiO$_2$ particles on the surface off fly ash and the crystal structure of precipitated TiO$_2$ particles. At an addition rate of NH$_4$HCO$_3$; 1.0 ml/min, the pH of the reaction solution; 6, the stirring speed; 1,000 rpm and the reaction temperature; 8$0^{\circ}C$, about 10 nm of TiO$_2$ particle size and homogeneous precipitated layer on the surface of a fly ash was achieved. On the contrary, at an addition rate of NH$_4$HCO$_3$; 0.3,0.5 ml/min, the pH of the reaction solution; 2 and 11, the stirring speed; 300~500 rpm and the reaction temperature; lower than 5$0^{\circ}C$:, Inhomogeneous precipitated layer was developed on a fly ash. TiO$_2$ particles with anatase phase was formed as-dried precipitation at the low concentration of Tic14, the high addition rate of NH$_4$HCO$_3$ and the high reaction temperature, the crystalline fraction of anatase increased with raising heat-treatment temperature and rutile phase began to formation at 80$0^{\circ}C$. The crystal size of TiO$_2$ particles increased with raising the heat-treatment temperature, the crystal size was showed about 21 m at $700^{\circ}C$. Anatase type of TiO$_2$ coated on the fly ash heated at $700^{\circ}C$ for 2 h showed 1.25 g/cm$^3$of particle density, 82.8% of strength and 69.5 Lab of whiteness and can be used as a photocatalyst.