• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.709-712
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• 2008

This study evaluated a mechanical performance of recycled polyethylene terephthalate(PET) fiber reinforced concrete on chemical environment. This study applied to three types of environmental condition including alkaline, salt, $CaCl_2$ in water solution and measured a reduction of mechanical performance of recycled PET fiber reinforced concrete for 30, 60, 90 days under chemical solutions. The mechanical performance of recycled PET fiber reinforced concrete evaluated to carried out a compressive strength test. As the result of test, it was found that the mechanical performance decreased as the exposure time to alkaline environment and indicated a excellence performance under salt, $CaCl_2$ environment conditions.

• Journal of Ocean Engineering and Technology
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• v.24 no.3
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• pp.52-58
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• 2010

This study investigated the engineering properties of waste tire powder-bottom ash added composite soil, which was developed to recycle dredged soil, bottom ash, and waste tire powder. Test specimens were prepared using 5 different percentages of waste tire powder content(0%, 25%, 50%, 75%, and 100% by weight of the dry dredged soil), three different percentages of bottom ash content (0%, 50%, and 100% by weight of the dry dredged soil), and three different particle sizes of waste tire powder (0.1~2 mm, 0.9~5 mm, and 2~10 mm). Several series of unconfined compression tests, direct shear tests, and flow tests were conducted. The experimental results indicated that the waste tire powder content, particle size of waste tire powder, and bottom ash content influenced the strength and stress-strain behavior of the composite soil. The flow value increased with an increase in water content, but decreased with an increase in waste tire powder content.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.77-81
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• 1999

In order to investigate the effect of fineness on the properties of Portland cement, we prepared five kinds of portland cements with different Blaine values(2300, 2500, 3000, 3500, 45oo $\textrm{cm}^2$/g) and measured Ca(OH)2 analysis, hydration heat, the fluidity and the physical properties of them. According to the results, as the Blain value of cement is lower, the rate of hydration is delayed, and the hydration heat and the compressive strength are decreased. But the fluidity of cement paste is improved. Especially, the hydration heat of the cement with 2500$\textrm{cm}^2$/g of Blaine value is decreased about 15% compared with 3500 $\textrm{cm}^2$/g cement.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.96-100
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• 1980

The castable refractory, CaO.$2Al_2O_3$ is a useful alumina cement for iron, steel and cement for iron, steel and cement industries, however it is difficult to produce CaO.$2Al_2O_3$because of its high melting point(180$0^{\circ}C$) and narrow firing range. In this study, the coprecipitation method was used to produce CaO.$2Al_2O_3$ for lower temperature firing . This method involved the titration of mixed solution of calicum and aluminate which extracted from domestic kaolin with $NH4_OH$ solution under blowing $CO_2$ gas into the solution. The coprecipitate and its clacined products were analyzed by X-ray diffraction and DTA. The calcined products fired between 400 and 90$0^{\circ}C$ were amorphous, but at 100$0^{\circ}C$ the coprecipitate was converted into one compound, CaO$2Al_2O_3$. From those experimental results, it was found that we could synthesizze CaO.$2Al_2O_3$ at about 100$0^{\circ}C$ which is lower than conventional firing temperature by around 80$0^{\circ}C$. The refractoriness of this alumina cement was SK 34 and the compressive strength ( 1 day) was about 250kg/$\textrm{cm}^2$.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.676-681
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• 2016

For the purpose of reducing the amount of limestone, which is used as a desulfurization agent to absorbing $SO_X$ gas in thermal power plants, and to recycle limestone sludge generated from a steel mill, limestone sludge was utilized as a desulfurization agent. In this study, cement, made of flue gas desulfurization (FGD) gypsum obtained in a desulfurization process using limestone sludge, was manufactured then, experiments were conducted to identify the physical properties of the paste and mortar using the cement. The results of the crystal phase and microstructure analyses showed that the hydration product of the manufactured cement was similar to that of ordinary Portland cement. No significant decline of workability or compressive strength was observed for any of the specimens. From the results of the experiment, it was determined that FGD gypsum manufactured from limestone sludge did not influence the physical properties of the cement also, quality change did not occur with the use of limestone sludge in the flue gas desulfurization process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.86-90
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• 2000

The mixed body of clay and flyash containing unburnt carbon was examined at various sintering conditions in order to recycle flyash as environment-affinitive construction materials. Experimental results can be summarized as follows : when large aggregate of 2.54 cm dia. was sintered at a heating rate of $20^{\circ}C$/min, heterogeneous phase with bulgings, inner pores, and cracks were observed at the sintering temperature of $1200^{\circ}C$. Accordingly, heating patterns for the complete removal of the heterogeneous phase were proposed as countermeasures. The compressive strength of finally obtained aggregate was 670~870kg/$\textrm{cm}^2$, which is over two and a half times stronger than the minimum requirement of 200kg/$\textrm{cm}^2$.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1511-1516
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• 2009

In recent years, the large-scale shaft have been appling in domestic mine for mass production using a large machine, the safety of mine also have been increasing. And the new trial that shotcrete of tunnel field was apply to mine support was progressed. But, the conditions of domestic mine was different from that of tunnel, so, the batch plant of tunnel could not be installed in mine field because of low economical efficiency and difficulty for selection of site. Ready-mixed Shotcrete that mixed with high quality materials and could be controled shotcrete quality is producted in plants and transported to field, so do not need to batch plant. In this study, The Field test of the Ready-mixed Shotcrete was performed in the large-scale mine and was compared with the quality of Field mix shotcrete. As the result of the Field test, compressive strength and rebound of Ready-mixed Shotcrete were superior to these of Field mix shotcrete.

• Journal of the Korean Society of Safety
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• v.24 no.6
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• pp.103-110
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• 2009

Since the mechanical properties of cement-based materials are time-dependent due to the prolonged cement hydration process, those of fiber reinforced concrete(FRC) may also be time-dependent. Toughness is one of important properties of FRC. Therefore, it should be investigated toughness development of FRCs with curing ages to fully understand the time-dependent characteristics of FRCs. To this end, the effect of curing ages on flexural toughness development of steel fiber reinforced concrete is studied. Three point bending test with notched beam specimen was adapted for this study. Hooked-end steel fiber(DRAMIX 40/30) was used as a fiber ingredient to investigate w/c ratio and fiber volume fraction effect on toughness development during curing. Three different water-cement ratios(0.44, 0.5 and 0.6) and fiber volume fractions(0%, 0.5% and 1%) were used as influence factors. Each mixture specimens were tested at five different ages, 0.5, 1, 3, 7 and 28 days. The study shows that flexure toughness development with age is quite different than other concrete material properties such as compressive strength. The study also shows that the toughness development trend correlates more closely to water/cement ratio than to fiber volume fraction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.13-16
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• 2006

This study investigates filed application in Daebul Free Trade Zone of a flowing method using drying shrinkage-reducing superplasticizer(SRS) and an insulating curing method using double bubble sheets. Test showed that fresh concrete satisfied target slump and air content. A structure adding SRS significantly decreased the total bleeding capacity and accelerated the setting time. As for the crack occurrence, the structure applying the flowing method and double bubble sheets simultaneously exhibited the most favorable crack endurance, while conventional concrete showed more than 1mm size of crack in overall, and a structure applying only the flowing method partially presented micro crack. For the area proportion of crack occurrence, the structure using the double bubble sheets indicated 9.8%, while others applying flowing method was 28%, compared with 100% of conventional one. Standard curing specimens had about $3{\sim}6%$ higher compressive strength than that of specimens cured at adjacent field construction. In addition, using SRS improved about $5{\sim}7MPa$, than that of conventional concrete at 91 days elapse.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.151-154
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• 2006

It is generally referred that life cycle of concrete construction is depend on whether durability of concrete is obtained or not. Nevertheless, it has not been yet applied that new material and technology to improve durability of concrete such as seaside concrete construction. In this study, chemical agent which is capable of improving durability added to 2 types seaside concrete mixs and evaluated engineering properties such as slump, air content, setting time and compressive strength. Besides shrinkage crack with an restraint condition and chloride ion penetration tests were executed to measure resistance of concrete added chemical agent and then compared non-added. It was appeared that engineering properties and resistant for chlorides was possible to improved. But resistant for shrinkage crack was not noticeable improvement than non-added. Therefore it is necessary that more consideration and following study to improve durability aspect to shrinkage crack and chlorides resistant.