• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.1023-1030
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• 2002

From the early 1980s, the New Austrian Tunnelling Method (NATM) has been developed as a one of the standard tunneling method in Korea. Approximately 10 years ago, wet-mix shotcrete with sodium silicate accelerator (waterglass) was introduced and widely used to tunnel lining and underground support. However, this accelerator had some disadvantages due to the decrease of long-term strength compared to plain concrete (without accelerator) and low quality of the hardened shotcrete. In order to compensate for these disadvantages, recently developed alkali-free accelerator has been successfully demonstrated in numerous projects and applications as a new material to make tunnels more durable and safer. An experimental investigation was carried out in order to verify the strength behavior of wet-mix Steel Fiber Reinforced Shotcrete (SFRS) with alkali-free accelerator. Compressive strength, flexural strength and equivalent flexural strength were measured by testing specimens extracted from the shotcrete panels. From the results, wet-mix SFRS with alkali-free accelerator exhibited excellent strength improvement compared to the conventional shotcrete accelerator.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.5
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• pp.1-9
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• 2003

Effectiveness of the microparticle retention systems in improving drainage, retention, formation has been recognized for many years. In this study the effectiveness of crosslinked cationic corn starches and silica-based microgels as components of Compozil system has been evaluated. It was shown that improvements in retention and strength could be achieved by employing crosslinked cationic corn starches especially at high conductivity. Silica-based microgels with better performance in retention and drainage than a commercial colloidal silica sol have been made through a reaction of sulfuric acid and sodium silicate solutions.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.711-714
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• 2005

This paper focused on development of geopolymer for wood wool ceramic board. Geopolymer can substitude ordinary portland cement and its accelerator of wood wool cement board as inorganic polymer. In this study, what we would obtain geopolymer's properties such as initial setting time(KS L 5108), flow(KS L 5102) and compressive strength of 3days aged(KS L 5105), was less than 1 hour, more than $110\%$, more than 40Mpa. Geopolymer have three essential materials called filler, hardener and geopolymer liquor. So, We applied filler by quartz, hardener by blast furnace slag powder, metakaoline and fly ash, geopolymer liquor by NaOH, KOH and sodium silicate solution. As result of this experiment, what we could obtain best fitted geopolymer's properties such as initial setting time, flow and compressive strength of 3days aged, was 45min, $116\%$ and 43.6Mpa. This result can be applicable to commercial wood wool ceramic board.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.87-89
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• 2008

A nano structured silica aerogel thin film was manufactured from inexpensive sodium silicate (water glass) using an ambient pressure drying method. High purity silicic sol was prepared by passing a water glass solution through an ion exchange resin, and the gel films were prepared on a modified glass substrate via dip coating. The dip coating conditions, such as coating time and solvent, were optimized. The optical and physical properties of the obtained silica aerogel thin film were characterized using a UV-visable spectrometer and a scanning electron microscope.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.37-42
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• 2000

To reduce shrinkage and the possibility of fracture during ambient pressure drying, it is of great importance to increase the strength and stiffness of the wet gels. In this paper is presented the strengthening and stiffening of wet silica gels prepared from sodium silicate (water glass) as well as properties of the corresponding xerogels. By washing gels containing different initial silica contents in water solutions at elevated pH, a maximum in shear modulus of ~4 MPa was obtained. The maximum stiffness enabled xerogels with bulk density of 0.28g/$\textrm{cm}^3$ to be made regardless of silica content and washing conditions. However, by aging the wet gels in a solution providing fresh monomers to the gel network, a shear modulus of 20 MPa was obtained after 27h. By this method monolithic xerogels with a density down to ~0.2g/$\textrm{cm}^3$ was prepared. The results are compared to alkoxide based gels.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.714-717
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• 2000

To consider sulfate resistance of cement pastes and motars for 3 types of portland cements which have different $C_3A$ contents an silicate ratio($C_3S/C_2S$), they were immersed in 5% sodium sulfate solution for 400 days. SEM analysis and ($Ca(OH)_2$ contents of cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of ($C_3$ and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement pastes, and compressive strength and length change of cement mortars, were performed to investigate the effects of C3A and ($Ca(OH)_2$ contents. According to the results of this study, low heat portland cement had a good sulfate resistances because of a small quantity of gypsum and ettringite due to less ($Ca(OH)_2$ contents. However, ordinary portland cement had an adverse result. This was also confirmed by SEM analysis.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.180-184
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• 1998

It was examined that the rheological behaviors of fly ash 70wt%-clay 30wt% slip in which nonplastic fly ash was a major component. We have systematically investigated the effects of deflocculant(Tetrasodium pyrophosphate ; Na4P2O7 nH2O Sodium silicate; Na2SiO3) and coagulant(CaSO4) on the rheological behavior of ash-clay slip. Ash-clay slip have been characterized on the basis of the time dependent rheology which was done out by the gel-curve test. Dispersion mechanism of ash-clay slip is the steric stabilization by the Na2SiO3 coating of cenospheres surface. Coagulated slip seems to have the new network structure and shows the gellation behaviors which makes it possible to direct coagulated casting(DCC).

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.43-49
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• 1999

Effectiveness of the microparticle retention systems in improving dramage, retention, formation has been recognized for many years (1, 2, 3, 4, 5). In this study the effectiveness of crosslinked cationic corn starches and silica-based microgels as components of Compozil system has been evaluated. It was shown that improvements in retention and strength could be achieved by employing crosslinked cationic corn starches especially at high conductivity. Silica-based microgels with better performance in retention and dramage than a commercial colloidal silica sol have been made through a reaction of sulfuric acid and sodium silicate solutions.

• Journal of Korea Foundry Society
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• v.4 no.2
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• pp.102-107
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• 1984

The variations of the mold compression strength were studied by varing the contents of the silicon powder and water glass, silion purities, and molecule rates of the water glass, when domestic JA EUN DO sand is mixed with water glass (sodium silicate) and metallic silicon or ferro - silicon powder by the self - hardening N - PROCESS method. The results obtained from this experiment are as follows; 1) The compression strength of the mold used with metalic powder was higher and more stable than to be used ferro - silicon powder. 2) 6% water glass of 2.8 molecule rate and 1.5% of ferro - silicon of 75% purity for the N - PROCESS used with JA EUN DO sand was suitable mixing rate. 3) The compression strength increased with self - hardening time, and the PH values of the mixture of silicon powder and water glass did not change after 2 hours, but the compression strength increased steadily due to the reaction of remained silicon. 4) It is recommended to take 24 hours for self - hardening time at least.

• Journal of the Korea Safety Management & Science
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• v.21 no.4
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• pp.45-49
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• 2019

The basalt fiber is expected to become a trend for industrial fibers as they have better properties of heat-resistant, non-combustion, absorbent, soundproof, moistureproof, lightweight, corrosion resistant, and high strength properties. Also, the fiber is found to be non-toxic and harmless to the human body. Therefore, in this study, we analyzed the chemical and mineral compositions of powdered sludge of basalt produced at seven sites on Jeju Island for the development of fire resistance insulating material for a building. The results showed that the basalt stone sludge is made from only sodium calcium aluminum silicate and ferridioside components unlike the basalt rock.