• The Korean Journal of Petroleum Geology
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• v.2 no.2 s.3
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• pp.91-99
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• 1994

In the Heunghae area, genetic relationships among sedimentary facies, lithology, stratigraphy and diagenetic mineral facies of the Yeonil Group, are discussed. Conglomerate and sandstone of lower to middle parts of the Yeonil Group contain considerable amounts of volcaniclastic sediments, which were derived from the Tertiary volcanics exposed in the western margins of the sedimentary basin. A new stratigraphic division of the Yeonil Group into the Chunbuk and Pohang Formations is proposed on the basis of sedimentary facies, lithologic characteristics including volcaniclastic feature, and the presence of a key bed of siliceous mudstone overlying the Chunbuk Formation. Diagenetic mineral facies largely depend on the lithology and composition of sediments. Heulandite, smectite, calcite, and opal-CT are commonly found as diagenetic minerals in the Yeonil Group. Among these authigenic minerals, heulandite occurs as the coarse- grained main cement in conglomerates and sandstones of the Chunbuk Formation. Formation of the zeolite cement is favored by partial volcaniclastic lithology of the Chunbuk Formation. Smectite composition and diagenetic mineral facies such as heulandite and opal-CT may reflect that the Yeoil Group has undergone a shallow rial temperature ranging $40{\~}60^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.133-138
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• 1982

Two kinds of clinker liquid melts, one containing 2.0% of $K_2O$ and the other without $K_2O$, were prepared with the similar composition as those developed during the firing of portland cement clinker. One portion of melt was quenched and found to consist of glass together with traces of proto-$C_3A$, and the other portion was allowed to cool spontaneously to crystallize $C_3A$ and calciumferrite well. The product obtained by crystallization of the melt without $K_2O$showed cubic $C_3A$, while orthorhombic $C_3A$ was formed from the crystallized product containing $K_2O$. Studies on the hydration behavior of the samples made from the melts with 30% of gypsum were carried out for 24 hours by observation at regular intervals ettringite, monosulphate hydrates and gypsum which were formed or consumed during hydration. The samples without $K_2O$ in the melts were hydrated wth addition of proper amount of $K_2SO_4$ in the water for hydration. Hydration behavior of glassified $C_3A$ showed that it has low reactivity relative to crystallized $C_3A$, and also hydration reactivity of orthorhombic $C_3A$ was much lower than that of cubic $C_3A$ in 60 minutes. Potassium sulphate in the solution reduced the hydration reactivity of $C_3A$ . Evolution peaks of hydration heat examined by twin-type conduction micro-calorimeter showed that glassified $C_3A$ without $K_2O$ had secondary peak after 9 hours and $C_3A$ containing $K_2O$ after 12 hours. When crystallized $C_3A$ was hydrated, initial peaks of hydration heat were considerably high and there was no secondary peak for cubic $C_3A$ but the secondary peak of orthorhombic $C_3A$ appeared after 4 hours.

• Journal of Environmental Health Sciences
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• v.34 no.1
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• pp.108-115
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• 2008

This study was performed to investigate the current status, in Korea, of the production of asbestos containing products (ACPs) such as asbestos cement products, asbestos friction materials, asbestos joint sheets, asbestos textile products, and other asbestos-containing products from May 2 to July 30, 2007. The information on ACPs was obtained through written questionnaires from 16 of the 27 companies that produce ACPs in Korea. The production amounts of asbestos containing gaskets were 70 tons in 2004, 90 tons in 2005, and 55 tons in 2006 in 4 companies and that of asbestos friction materials were 435.5 tons in 2004, 540.4 tons in 2005, and 454.3s ton in 2006 in 10 companies. The type and number of ACPs were:- 19 asbestos cement products, produced by 2 companies; 47 asbestos friction materials produced by 18 companies; 12 asbestos joint sheets productes by 4 companies; 18 asbestos textile products from 3 companies, and 6 other asbestos products from 5 companies. The database of ACPs was constructed to include the products name, identification number, name of company, production year, composition, asbestos content (%), usage, specification, and a picture. The database will be used to efficiently identify ACPs and to avoid asbestos exposure in workers and the general population.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.644-647
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• 2004

Modulus of rupture (MOR) and flexural toughness in hybrid fiber reinforced cement pastes mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber) and replaced with silica fume according to the fixed ratio were researched. Reinforcing efficiency in specimens were estimated by two factors, such as strengthening factor $(F_s)$ and toughening factor $(F_t)$, which were calculated from the analysis of variance (ANOVA) of the response values, such as MOR and absorbtion energy $(W_0)$. According to the experimental design by the fractional orthogonal array, nine hybrid fibrous reinforced paste series and one non-reinforced control paste were manufactured. Specimens of each series were tested by the INSTRON Inc. 8502(model) equipment in three-points bending and then measured the load-deflection response relationships. Considerable strengthening of cement pastes resulted in' the case of other factors without carbon fiber and toughening of cement pastes about all factors showed high. Based on the significance of factors related to response values from ANOVA, following assessments were available; $F_s$ or MOR: silica fume $\gg$ steel fiber $\gg$ carbon fiber; $F_t\;or\;W_0$: steel fiber > carbon fiber > silica fume. Optimized composition condition was estimated by steel fiber of $1.5\%$, carbon fiber of $0.5\%$ and silica fume $7.5\%$ in side of strengthening and steel fiber of $1.5\%$, carbon fiber of $0.75\%$ and silica fume $7.5\%$ in side of toughening.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.313-319
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• 2017

In general, various factors such as grain size, chemical composition, amorphous amount, amorphous Si and Al content of fly ash affect the reaction with cement. In this study, we investigate the effect of fly ash particle characteristics on compressive strength. The standard sand was pulverized to a particle size similar to that of fly ash and the compressive strength was measured by blending with the cement as in fly. Using the measured compressive strength results, strength enhancement by cement hydration reaction and strength enhancement by particle filling effect were confirmed. Strength increment by pozzolanic reaction of fly ash was calculated by using the compressive strength results of mortar substituted with standard powder. As a result of comparison between compressive strengths and the particle characteristics of fly ash, the blaine showed a weak correlation with the compressive strength and the PI(Pozzolanic Index) showed good correlation with the 10% penetration diameter(D10) and the 50% Respectively. Therefore, it is expected that PI will be a good means to evaluate the fly ash characteristics together with the chemical characteristics of fly ash.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.301-307
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• 2011

Purpose: If the tooth structure is damaged, then it is impossible to regenerate the tooth. The materials used to restore the tooth structure are not related to the composition of the tooth. The materials used to restore the structure can't replace the natural tooth because they just fill the defective structure. Calcium phosphate cement remineralizes the dentin and almost replaces the natural tooth, but there are some disadvantages. We conducted basic tests with Biomimetic CPC (Bio-CPC) to make sure of the possibility of the biomaterial to remineralize the defective tooth structure. Methods: In this study, the bioactivity and biocompatibility of Bio-CPC were evaluated for its potential value as the bio-material for regeneration of damaged tooth structure by conducting a cell toxicity assay (WST-1 assay), a cytokinesis-block micronucleus assay, a chromosomal aberration test, total RNA extraction and RT-PCR on MDPC-23 mouse odontoblast-like cells. Results: The in vitro cytotoxicity test showed that the Bio-CPC was fairly cytocompatible for the MDPC-23 mouse odontoblast-like cells. Conclusion: Bio-CPC has a possibility to be a new biomaterial and further study of Bio-CPC is needed.

• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.77-85
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• 1987

Hardened cement paste is mainly affected by corrosion of sulphate and chlorine ions in sea water. In this investigation, many specimens were made with the cement clinker minerals such as C3S, C3A, C4AF and their mixture according to cement composition added various blending materials. After the specimens were immersed in 4% MgSO4 and MgCl2 solutions, the product of reaction, the microstructure of specimen and Ca+2 ion leached in the solution were studied. The formation of Ca(OH)2 in the specimen of C3S is reduced relatively by adding pozzolanic admixtures. The chlorine ion is easily diffuse into the C3S specimen and produced CaCl2 compound, and it makes the specimen porous by leaching out itself into the solution. The specimen of C3A, C4AF are broken down by expanding reaction of ettringite and gypsum compound produced in the MgSO4 solution. At a later period, the ettringite is transformed into gypsum and 5MgO.2Al2O3·15H2O. The C3A in the MgCl2 solution combines chlorine ion to form Friedel's salt and prevents the diffusion reaction of chlorine ion into the specimen. Granulated slag shows inferior effect on the resistance of the specimen in MgSO4 solution by forming ettringite and gypsum, but good result in MgCl2 solution. Pozzolanic materials, on the whole, offer noticable effect on the resistance of the specimen in both solutions.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.460-468
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• 2021

Owing to the production of conventional concrete/cement, the climate crises is increasing and is mainly caused greenhouse gas (GHG) emission into the environment by industrial process. To reduce the emission of GHG, and excessive consumption of energy, research on geopolymer binder is increasing as it is environmentally friendly compared to the conventional binders such as Portland cement. The research on improving the strength and durability of geopolymer cement becomes one of the trending researches. Generally, the strength and durability of geopolymer binders are improved by altering alkaline solution & its concentration, the precursor materials and curing temperature & time, which significantly influence the chemical composition and microstructure of geopolymer to which the strength and durability of geopolymers relies. This paper included the detailed discussion on the factors affecting the mechanical properties and durability of geopolymer binder and the influence of reaction mechanism on the strength and durability of geopolymer is also discussed in this paper.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.48-54
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• 2023

In this research, The basic physical properties and EMP shielding performance by thickness were evaluated for optimum composition of EMP shield concrete that can be applied on-site by mixing carbon-based materials with high conductivity into concrete that uses electric furnace oxidized slag (EOS). As a result of the evaluation, it was confirmed that the slump decreased as the amount of mixed carbon fib er (CF) increased, and increased when milled carb on (MCF) was mixed. As for the compressive strength, it was confirmed that EOS enhanced the strength compared to NA, and it was confirmed that the strength decreased when CF and MCF were mixed. As the thickness of the EMP shielding measurement increases, the shielding rate increases, and it was confirmed that the type of conductive material and the thickness of the test specimen have a greater influence on the shielding rate than the Amount of conductive material added. As a result of a comparative evaluation, EOS CF 0.2 is considered suitable for EMP shield concrete formulation.

• The Journal of Advanced Prosthodontics
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• v.16 no.2
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• pp.105-114
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• 2024

PURPOSE. This study aimed to evaluate the effect of pretreatment of three different universal adhesives (Single Bond Universal [SBU], All-Bond Universal [ABU], and Prime&Bond universal [PBU]) on the bonding durability of an adhesive (Panavia F 2.0, PF) and a conventional (Duo-Link, DL) resin cements to air-abraded zirconia. MATERIALS AND METHODS. Rectangular-shaped zirconia specimens were prepared. The chemical composition and surface energy parameters of the materials were studied by Fourier transform infrared spectroscopy and contact angle measurement, respectively. To evaluate resin bonding to the zirconia, all the bonding specimens were immersed in water for 24 h and the specimens to be aged were additionally thermocycled 10000 times before the shear bond strength (SBS) test. RESULTS. The materials showed different surface energy parameters, including the degree of hydrophilicity/hydrophobicity. While the DL/CON (no pretreatment) showed the lowest SBS and a significant decrease in the value after thermocycling (P < .001), the PF/CON obtained a higher SBS value than the DL/CON (P < .001) and no decrease even after thermocycling (P = .839). When the universal adhesives were used with DL, their SBS values were higher than the CON (P < .05), but the trend was adhesive-specific. In conjunction with PF, the PF/SBU produced the highest SBS followed by the PF/ABU (P = .002), showing no significant decrease after thermocycling (P > .05). The initial SBS of the PF/PBU was similar to the PF/CON (P = .999), but the value decreased after thermocycling (P < .001). CONCLUSION. The universal adhesive pretreatment did not necessarily show a synergistic effect on the bonding performance of an adhesive resin cement, whereas the pretreatment was beneficial to bond strength and durability of a conventional resin cement.