• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.549-555
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• 2007

Although blast furnace slag has been widely used in concrete as a cementitious admixture or aggregate for many years, the slowly cooled steel slag is not used in concrete but mainly in road. Its use in concrete operates problem such as the lack of volume stability due to high free CaO content, which can be potentially hazardous in concrete. However, the rapidly cooled steel slag by atomization has a low free CaO content, a high density, and a spherical shape, so it is expected to use in concrete so much. This paper is to understand the probability that the rapid cooled steel slag can replace the silica sand used as aggregate in the epoxy mortar. We did the experimental study on the properties of the epoxy mortar having various replacement proportion of rapidly cooled steel slag. This study shown that increasing content of the rapidly cooled steel slag in epoxy mortar lead to increase largely the passing time of nozzle by O-lot, compressive strength and flexural strength. However except the flow is almost same level. So we understand that the rapidly cooled steel slag has positive effect on increasing of properties in epoxy mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.125-133
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• 2011

The requirement for durability of concrete bridge deck is increasing as the deterioration for the concrete bridge deck exposed to severe environment has been increased. For this reason, the concern about high-durable concrete is being high. Recently, a metakaolin is highly spotlighted as new admixture because its strength and durability are equivalent to silica fume. On the other hands, there are few researches for the metakaolin concrete bridge deck in domestic. So many various long-term data on the mechanical property and durability is needed to apply metakaolin concrete at the concrete bridge deck construction field. This study is aim to evaluate the long-term mechanical properties and durability of metakaolin concrete bridge deck with curing age. Mechanical properties are estimated by the compressive and flexural strength, and the drying shrinkage, the chloride resistance, the scaling, and freezing and thawing characteristics are compared with curing age. According to the results, when the metakaolin concrete is used, the development of compressive and flexural strength proceed in both the early and old ages. It is also improved the resistance of chloride penetration, freezing and thawing in concrete. It was showed that replacement of metakaolin was efficient for the reduction of the drying shrinkage.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.339-345
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• 2013

This study is to derive from the required performances and the optimum mix proportion of the roof concrete placed in the in-ground LNG storage tank with a capacity of 200000 $m^3$, and propose the actual data for site concrete work. The concrete placing work without sliding and segregation in the fresh concrete condition is very important because the slope of domed roof is varied in the large range by its curvature. Also the control of hydration heat and the strength development at test ages are classified with massive section about 1.4 m thick and considered to the pre-stressing work and removal of air support after concrete placing work. Considering above condition, slump range is selected $100{\pm}25$ mm under the slope $20^{\circ}$ and $150{\pm}25$ mm over the slope $20^{\circ}$ s until 60 minutes of elapsed time. Also, the roof concrete is satisfied with compressive strength range including design strength at 91 days (30 MPa), pre-stressing work at 7 days (10 MPa), air support removal work at 21 days (14 MPa). Replacement ratio of limestone powder is determined by confined water ratio test and main design factors include water-cement ratio (W/C), sand-aggregate ratio and dosage of admixture. As test results, the optimum mix proportion of the roof concrete used low heat cement is as followings. 1) Replacement ratio of limestone powder 25% by confined water ratio test 2) Water-cement ratio 57.8% 3) Sand-aggregate ratio 42.0%. Also, test results for the adiabatic temperature rising test is satisfied with its criteria and shown the lower value compared to preceding storage tank (TK-13, 14). These required performances and the optimum mix proportion is to apply the actual construction work.

• Korean Journal of Food Science and Technology
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• v.5 no.1
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• pp.16-24
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• 1973

Breads were made from composite flours based on domestic resources and their quality was assessed to obtain the following results. 1) When barley bread was made according to the formula for standard wheat bread, its specific loaf volume (SLV) was quite low (1.3 at 100% addition of water) in comparison with 3.3 for wheat bread. Addition of 10% defatted soy flour increased its SLV to 1.7 (at 100% water). Among various flour-improving additives, the use of 1.5% GMS + 0.5% CSL gave best results (SLV: 2.0 at 100% water). Admixture of wheat flour with the composite flour based on barley was most effective. Replacement of barley flour with 25% wheat flour gave SLV of 2.8 (at 90% water) and that with 50% wheat flour gave SLV of 3.2 (at 90% water), comparable to standard wheat bread with respect to loaf volume, color and texture. 2) Sweet potato bread had the characteristics of turning black-brown on baking. Use of 20% defatted soy flour and GMS + CSL gave higher SLV (1.9 at 100% water). Addition of wheat flour at 25% or 50% level to the composite flour based on sweet potato flour gave SLV of 2.3 and 2.6, respectively, at 90% water and its color and texture were improved 3) Potato flour was different from sweet potato flour in baking, the effect of GMS + CSL being quite low. Bread from corn flour was different from barley flour bread and defatted rice bran was not suitable for bread-making. 4) Bread was made from following composite flours based on naked barley and sweet potato flours along with the use of proper additives: (a) naked barley flour + defatted soy flour + wheat flour (45 : 10 : 45) (b) naked barley flour + defatted soy flour + wheat flour (67 : 10 : 23) (c) naked barley flour + defatted soy flour (90 : 10) (d) sweet potato flour + defatted soy flour + wheat flour (40 : 20 : 40) (e) sweet potato flour + defatted soy flour (60 : 20 : 20) Sensory evaluation of above breads in comparison with standard wheat bread (So) gave the following decreasing order of scores, So>(a)>(b)>(c)>(e)>(d) and Duncan's multiple range test showed that bread (a) was not different from standard wheat bread significantly at 5% level, in overall evaluation including color, texture, taste and flavor.