• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.93-98
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• 2001

Using waste glass in concrete can cause crack and strength loss by the expansion of alkali-silica reaction(ASR). In this study, ASR expansion and properties of strength were analyzed in terms of clear waste glass grading, and by-products(fly ash, blast-furnace slag) and by-products content for reduction ASR expansion due to waste glass. In this accelerated ASTM C 1260 test of waste glass, pessimum grading can be found. Also, when the by-products are used with waste glass, there is an effect on reduction of expansion and strength loss due to ASR between the alkali in the cement paste and the silica in the waste glass.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.35-40
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• 1992

Porous glass in the ZrO2-SiO2 system containing up to 30 mol% zirconia were prepared from the mixed solutions of Zr(O.nC3H7)4 and partially prehydrolyzed TEOS by the sol-gel method. Pore characteristics, physical properties and alkali resistance were investigated. The gels converted into the porous glass by heating at $700^{\circ}C$, it was found that the glass like skeleton was already made up in lower temperature regions. The specific surface area of the porous glass was 227 $m^2$/g, average mean pore size was about 19$\AA$ and porosity was 19.2%, pore characteristics and physical properties depended on heating temperature. Alkali resistance of the porous glass increased as the zirconia content increased, because of the appearance of Zr-enriched layer at glass surface.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.103-107
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• 1993

The Alkali Aggregate Reaction(AAR), reported first by T. E. Stanton in 1940, is a reaction between certain siliceous aggregate and hydroxyl ions present in the pore fluid of a concrete. The damage of concrete structures, deteriorated by AAR, have been reported since using the crushed stones caused by the exhaustion of natural aggregates. This study was performed to investigate the AAR of crushed stones using chemical analysis, polarization microscope, XRD, chemical method(KS F 2545, ASTM C 289), mortar bar method(KS F 2546, ASTM C 227) and Scanning Electron Microscope(SEM) and Energy Dispersive X-ray Analysis (EDXA) of reaction products by AAR in mortar bar.

• Advanced Composite Materials
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• v.18 no.3
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• pp.197-208
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• 2009

Changes occurring in jute and coir fiber composites with 2-8% concentration of a NaOH treatment for 24 h were investigated, respectively, for void content, microscopy images, mechanical properties and water absorption. The jute and coir fibers were vacuum dried before molding composite specimens. Mechanical properties indicated good adhesion between natural fibers and PP. Jute fibers, when alkali-treated with 2% concentration for 24 h, showed best improvement in tensile strength by 40% and modulus by 9%, respectively, while coir fibers, when alkali-treated with 6% concentration for 24 h, showed best improvement in tensile strengths by 62% and modulus by 17%, respectively. With 2% concentration of alkali-treatments, the elongation of jute and coir composites reached 8% and 13.5%, respectively. Moisture absorption for jute and coir composites are 50% and 60% lower than untreated fiber composites, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.115-116
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• 2022

This study incorporates fine waste glass (GS) as a replacement for natural sand (NS) in fly ash (FA) based alkali activated mortar (AAm). AAms were heated at elevated temperature of 200℃, 400℃, 600℃, and 800℃ to explore the residual mass, compressive strength, thermal expansion and change in microstructure of matrix. Results showed greater resistance of AAms with increasing GS content to 50% at each temperature. Owing to the melting of GS at 800℃, the greater matrix bond was observed for AAm incorporating 75% and 100% GS as a result, the residual compressive strength was increased.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.112-116
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• 2018

In this study, the mixing characteristics of water glass and additives (Si, alkali metal), which are one of the main raw materials of silicate based binder used in the production of molds during casting process, were examined. Molecular structures of water glass, additives and mixtures were analyzed FT-IR and viscosity measurements and their correlation were compared. The addition of Si source to the water glass accelerated the Si networking in the material and increased the viscosity. When the alkali metal was added, the viscosity of the water glass decreased by suppressing the Si networking of the water glass. Viscosities of the water glass and lithium silicate (LS) mixtures increased when the content of LS was less than 20 wt% and gradually decreased when the content was more than 20 wt%. By adding KOH to the water glass, the viscosity could be lowered and it could be used effectively to mix with colloidal silica (CS) or potassium methyl siliconate (PMS).

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.170-176
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• 2014

This study examined the effect of chemical attack on the stress-strain relationship of alkali-activated Hwangtoh concrete. Water-to-binder ratio and air content were selected as mixture parameters. The stress-strain relationship of concrete was measured at chemical immersion times of 0, 7, 28, 56, and 91 days from an age of 28 days. Based on the test results, the reduction in compressive strength of alkali-activated hwangtoh concrete owing to chemical attack was formulated. In sddition the present study demonstrated that the stress-strain behavior of concrete under chemical attack is significantly dependent on the air content and chemical immersion time, indicating the rate of decrease of modulus of elasticity was greater than that of compressive strength at the same immersion time. As a result, the stress-strain behavior of concrete under chemical attack was significantly inconsistent with the conventional models specified in the CEB-FIP provision.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.75-84
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• 2016

This paper presents an investigation of the mechanical properties on non-sintered cement pastes immersed in sea waters at three different temperatures. The non-sintered cement pastes were synthesized using blended binder(Class F fly ash; FA and ground granulated blast furnace slag; GGBFS) and alkali activator(sodium hydroxide and sodium silicate). Binders were prepared by mixing the FA and GGBFS in different blend weight ratios of 6:4, 7:3 and 8:2. The alkali activators were used 5wt% of blended binder, respectively. Calcium carbonate was used as an chemical additive. The compressive strength, bulk density and absorption of alkali-activated FA-GGBFS blends pastes were measured at 3 and 28 days after immersed in sea waters at three different temperatures($5^{\circ}C$, $15^{\circ}C$ and $25^{\circ}C$). The XRD and SEM tests of the pastes were conducted at 28 days. Water-soluble chloride(free chloride) and acid-soluble chloride(total chloride) contents in the pastes were also measured after 28 days immersion in sea water. The experimental results showed that increasing the content of FA in alkali-activated FA-GGBFS blends pastes immersed in sea water increases the absorption, water-soluble chloride content and acid-soluble chloride content, and reduces the compressive strength and bulk density. And it was found that there was a variation of strength change for the alkali-activated FA-GGBFS blends pastes immersed in sea waters at three different temperatures that depends on the blending ratio of FA and GGBFS.

• International Journal of Concrete Structures and Materials
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• v.8 no.4
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• pp.315-326
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• 2014

This study evaluates the dosages of Class F fly ash, lithium nitrate and their combinations to suppress the excessive expansion caused by alkali-silica reactivity (ASR). In order to serve the proposed objective, the mortar bar specimens were prepared from (1) four dosages of Class F fly ash, such as 15, 20, 25 and 30 % as a partial replacement of Portland cement, (2) up to six dosages of lithium nitrate, such as lithium-to-alkali molar ratios of 0.59, 0.74, 0.89, 1.04, 1.19 and 1.33, and (3) the combination of lithium salt (lithium-to-alkali molar ratio of 0.74) and two dosages of Class F fly ash (15 and 20 % as a partial replacement of Portland cement). Percent contribution to ASR-induced expansion due to the fly ash or lithium content, test duration and their interaction was also evaluated. The results showed that the ASR-induced expansion decreased with an increase in the admixtures in the mortar bar. However, the specimens made with the both Class F fly ash and lithium salt produced more effective mitigation approach when compared to those prepared with fly ash or lithium salt alone. The ASR-induced expansions of fly ash or lithium bearing mortar bars by the proposed models generated a good correlation with those obtained by the experimental procedures.

• Food Science and Biotechnology
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• v.14 no.5
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• pp.645-650
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• 2005

To reduce ammonia-like odor in chondroitin sulfate, longnose skate (Rasa rhina) cartilage was processed by washing, autoclaving, and alkali pretreatments. Content of total volatile basic nitrogen (TVB-N), index of ammonia-like odor, of raw skate cartilage without pretreatment was 254 mg/100 g, whereas those of skate cartilage pretreated with washing and autoclaving increased to 630 and 636 mg/100 g, respectively. TVB-N of skate cartilage pretreated with sodium hydroxide sharply decreased to 15 mg/l00 g at optimal condition of 0.12 M and 3.6 volume of NaOH, as determined by surface response methodology of central composite design for optimization. Alkali pretreatment resulted in 97.6% deodorizing. Washing and autoclaving pretreatments had almost no effect on the yield of chondroitin sulfate (approximately 30%), whereas decreased to 16.0% after alkali pretreatment, showing chondroitin sulfate of skate cartilage as chondroitin sulfate C.