• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.1-5
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• 1993

In the country, due to short comings of natural aggregates of good quality, it is common to use crushed stones. However, the investigation has not been done on the chemical reaction of crushed stones. This study tested and analyzed the aggregate chemical reaction by petrographic examination(ASTM C 295) for the test aggregates which had been tested by chemical method(ASTM C 289) in the first year. As a result, most of test aggregates didn't show any reaction but many have common deleterious mineral. Therefore, there exists the possibility of chemical reaction in petrogrphic point of view

• Journal of the Mineralogical Society of Korea
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• v.14 no.2
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• pp.85-98
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• 2001

This study deals with the petrographic examination of aggregates(ASTM C 295) which is one of the methods to diagnose the quality of aggregates for concrete artifacts. A number of examinations including size and sieve analysis, test on the coating material, description of the weathering and contamination condition, petrographic description, and qualitative and quantitative analyses on the rocks and minerals potential to alkali-aggregates reactivity are carried out to examine the quality of aggregates. Petrographic description method examined on the fluvial aggregates from Maewhacheon A, B area, Uljin-gun, Kyungnam province shows that weathering grade ranges from F(fresh) to WS(slightly weathered) and coating material and contamination are not in a harmful condition. The weight percentage of the alkali-aggregates reactive minerals or structurally unstable rocks of the aggregates from study area covers 26% and 19% of all aggregates, respectively. So it is necessary to further identify their quality through the chemical(ASTM C 289) and mortar-bar method (ASTM C 227).

• Proceedings of the Korea Concrete Institute Conference
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• 1989.10a
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• pp.1-4
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• 1989

Recently, as the natural aggregates are exhausted, using the crashed stones bring the possibility of the alkali-aggregate reactivity. In this study, the samples are collected from the stony moutains chosen by using a geoligical survey map and analyzed in terms of the amount and the shape of the reaction minerals by a polarization microscope and X-ray diffraction which beling to the petrographic examination of aggregates for concrete. From this study, most samples of the sedimentary rocks and the granitte of the ignious rocks show the possibility of the alkali-aggregate reactivity.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.97-102
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• 1993

In the country, due to short comings of natural aggregates of good quality, it is common to use crushed stones. However, the investigation has not been done on the chemical reaction of crushed stones. This study tested and analyzed the aggregate chemical reaction by Petrographic Examination(ASTM C 295),Chemical Metho(ASTM C 289) and Mortar-Bar Method (ASTM C 227). As a result, most of test aggregates didn't show any reaction but many have common deleterious mineral. Therefore, there exists the possibility of chemical reaction in petrographic point of view.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.589-599
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• 2007

For the preliminary judgement on the chemical stability of concrete aggregates mixed with cement paste, ASTM C 295 method can be applied prior to the long-term chemical test methods. By using this standard test method, the petrographic study on the appropriateness of natural KEDO aggregates for concrete was carried out. With the natural gravel and sand aggregates, the polarized microscope, stereoscopic microscope, and X-ray diffractometer were used for examination. The result shows the 23% of gravel aggregates and 5.1% of sand aggregates are chemically unstable. To select the favorable KEDO concrete aggregates, it is required to exclude the highly metamorphosed rocks, acidic volcanic rocks, highly foliated rocks, and expansive rocks identified from mortar-bar test. Further chemical test and mortar-bar test method integrated with this study is recommended for the suitability assessment of natural KEDO concrete aggregates.

• The Journal of Engineering Geology
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• v.2 no.1
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• pp.36-46
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• 1992

Granite core samples and bulk samples were first subjected to petrographic examination to determine weathering degrees. Secondly, their physical or mechanical properties including specific gravity, porosity, sonic wave velocity and uniaxial compressive strength were measured. The results were correlated to investigate the influences between properties including physical and mechanical properties, weathering degrees, and rock textures. Porosity and P wave velocity were found the most useful indices in determining the weathering degrees of granites.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.363-368
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• 2000

This paper is an introduction of pessimum program for the identification of alkali-silica reaction of alkali-aggregate reaction which is known as one of a major factor of concrete deterioration. A series of gel-pat testing program was undertaken to observe the reactivity of potentially alkali-silica reactive concrete aggregates which were found to be reactive by previous petrographic examination (ASTM C 295). And then a pessimum program was performed in accordance with mortar-bar test method (ASTM C 227) with different percentage of those reactive components included in the fine aggregate source to determine the pessimum quantity. Chert and quartzite were found to be major components of reactive mineral/rock, and the pessimum condition for chert was about 3%, even though the test was performed with up to 25% of the component. In the case of quartzite, however, the mortar-bar expansion appeared to be directly proportional to the amount of quartzite sample with increasing tested quantity up to 35%. Both of the expansion results were well 3 and 6 month specified maximum limitation of 0.05% and of 0.1% respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.13-18
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• 2003

The concrete structure can be easily damaged due to alkali-aggregate reaction. The alkali-aggregate reaction is a reaction between the alkalies(K or Na) in cement and an unstable mineral of the aggregates. There are several test methods to identify alkali reactivity of aggregates. In general, crushed stones are tested by petrographic examination, chemical method and 모르타르 바 method. This study tested alkali-aggregate reactivity of crushed stones that has different rock types such as granitic, volcanic, metamorphic and sedimentary rocks. Samples are collected from 12 local aggregate production companies. Alkali-reactivity of various rock types was evaluated by using ASTM C 227 and C 1260, and compared the test results of two test methods.

• Journal of the Korean Ceramic Society
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• v.18 no.1
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• pp.13-22
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• 1981

This study is to investigate the effective mineralizer in the manufacture of forsterite porcelain as a high frequency insulator. A mixture of $Mg(OH)_2$. and $SiO_2$.($\alpha$-Quartz) corresponding to the molar ratio of 2.0 MgO: 1.0 $SiO_2$ was prepared from the materials of high purity. It was heated to 140$0^{\circ}C$ at the rate of 20$0^{\circ}C$/hr, which was kept constantly for 1 hour, and one has made chamotte after cooling. Six kinds of glasses were prepared by an 0.1 atomic equivalent of K ions substitution-Ba, Bi, Zn, Cd, Zr-to the basic K-glass (0.333 $K_2O$.1.14 $SiO_2$) and were melted approximately at 150$0^{\circ}C$. The forsterite bodies were provided by adding each glass (10, 15, 20, 25, 30%) to the forsterite chamotte, which was fired at 1320, 1360, 1400, 144$0^{\circ}C$. (1 hr). One has examined the physical and dielectric properties for the specimens. The results of the experiments are as follows; 1. As for water absorption: Bodies were better vitrified with an addition and temperature change of Ba, Bi, Zn-glasses. The specimen containing Cd-glass showed deviation of slow decreasing, where as K-glass was completely not vitrified. 2. Bodies containing Ba, Zn, Bi-glasses appeared comparatively high Modulus of Rupture at 136$0^{\circ}C$, while containing Zr-glass had the highest Modulus of Rupture as the addition changes remarkably at 140$0^{\circ}C$. 3. It was estimated that 20-25% glass present in a forsterite bodies were in good conditions as for physical properties. 4. Specimens of Ba, Bi, Zr-glasses were superior as for dielectric properties, where among Ba-glass was most excellent. 5. Dielectric constant commonly increases in a slight gradient as firing temperature rises. 6. The petrographic examination showed that the bodies containing Ba, Bi-glasses had fine crystals, and were observed distinctly large mosaic crystals in the Zn-glass.