• International Journal of Highway Engineering
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• v.17 no.2
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• pp.47-53
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• 2015

PURPOSES: The scaling of a concrete surface caused by the combined effects of frost and de-icing salts is one of the main reasons for the need to repair transportation infrastructures in cold-climate regions. This study describes the results of attempts to determine the scaling resistance of concrete incorporating mineral admixtures such as fly ash, GGBFS, and silica fume, and subjected to the actions of frost and salt. METHODS : Conventionally, to evaluate the fundamental properties of concrete, flexural and compressive strength measurements are regularly performed. Based on the ASTM C 672 standard, concrete is subjected to 2%, 4%, and 8% $CaCl_2$ salt solutions along with repeated sets of 50 freeze/thaw cycles, and the scaling resistance was evaluated based on the mass of the scale and a visual examination. RESULTS : It was observed that silica fume is very effective in enhancing the scaling resistance of concrete. Meanwhile, concrete incorporating GGBFS exhibited poor resistance to scaling, especially in the first ten freeze/thaw cycles. However, fly ash concrete generally exhibited the maximum amount of damage as a result of the frost-salt attack, regardless of the concentrations of the solutions. CONCLUSIONS: It can be concluded that the scaling resistance of concrete is highly dependent on the type of the mineral admixture used in the concrete. Therefore, to provide a durable concrete pavement for use in cold-climate regions, the selection of a suitable binder is essential.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.542-546
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• 2001

Converter slag has some compositional similarities to portland cement. But it has no hydration properties due to it's quite high concentrations of FeO(20-35%), MnO(4-6.5%). So it is needed to reduce the concentrations of iron and manganese of converter slag to use as cement additives by enhancing it's hydration properties. In this study, converter slag was modified it's composition by mixing of silica, alumina and quenched BF slag and reduced in induction furnace and quenched in running water. The hydraulic properties and structures of modified and quenched converter slag are significantly changed depend on the amount and kinds of additives. The addition of alumina up to 10% and BFQ slag up to 20% by weight on converter slag was effective to enhance the hydraulic properties of modified and quenched slag. The addition of reduced and quenched converter slag up to 20% by weight in replacement of portland cement in mixing of concrete mortar were shown higher compressive strength than 100% cement concrete mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.267-270
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• 2003

This study is intended to investigate the engineering properties of concrete, in which cement and fine aggregate are replaced with cement kiln dust(CKD), such as the properties of fresh concrete and hardened concrete and hydration heat history, for effective using method of CKD, a by-product produced in the process of making cement. According to the results, as the replacing ratio of CKD increases, slump and air content of concrete decreases remarkably due to an increase of viscosity and filling of the pores. As the properties of setting, initial and final setting time are shortened with an increase of the replacing ratio of CKD, and as the replacement of CKD for fine aggregate increases, setting time is shortened more greatly. Compressive strength increases due to filling of the pores and reduction of air content in comparison with plain concrete. When the replacement ratio of CKD for cement is 10% and 15%, peak temperature of hydration heat lowers slightly, but it goes up in the case of replacement of CKD for fine aggregate. Also, when cement and fine aggregate is replaced with CKD by 2.5% and 7.5% respectively(1C3S) in the case of replacement of CKD for cement and fine aggregate, it is highest.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.113-117
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• 2003

In this study is investigated the various properties of concrete with the kinds of stabilizing agent of recycling water and solid content in order to suggest a practical use of recycling water. According to the results, fluidity and air content varies slightly with the kinds of stabilizing agent and solid content, but does not make a big difference. Setting time does not differ remarkably from plain concrete at 20℃, but is shortened with an increase of solid content. Bleeding is reduced more largely in the case of S than in the case of R, and is not influenced by solid content. Compressive strength is equal or decreases in comparison with plain concrete at solid content of I and 50%, and shows the highest value at solid content of 3%. Length change by drying shrinkage is larger than plain concrete at solid content of 5%, and decreases at solid content of I and 3%. Therefore, it proves that the influence of the kinds of stabilizing agent is minute, and solid content is most effective at 3%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.401-406
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• 2013

This paper presents experimental evaluation of IRE (isolation roller bearing) seismic isolation device. From the combination of base isolation on the IRE system displacement response spectrum and acceleration response spectrum, the compressive strength and the coefficient of friction experiments. Also the IRE system is evaluated by environment test according to KS standards. Both the resonance and seismic experiments using a combination of the IRE and Natural Rubber Bearing (NRB) are performed in order to analyze the seismic isolation of the IRE system dynamic characteristics. For the given load and exciting frequency, the resonant frequency becomes lower, but the resonant magnification remains to be same. However, it is shown that when we consider the IRE only, the vibration on the table with the horizontal movement and the independent horizontal displacement due to the rolling motion of the plate and roller are significantly reduced. This result verifies that the proposed optimal design method of the IRE system is very effective.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.604-611
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• 2005

The relationship between floor impact sound and vibration has been studied by field measurements, and the vibration modal characteristics have been analyzed. Vibration levels impacted by a standard heavy-weight impact source have been predicted according to the main design parameters using finite element method. Experimental results show that the dominant frequencies of the heavy impact sounds range below 100 Hz and that they are coincident with natural frequencies of the concrete slab. In addition, simple 2-dimensional finite element models are proposed to substitute 2 types of 3-dimensional models of complicated floor structural slabs those by The analytical result shows that the natural frequencies from first to fifth mode well correspond to those by experiments with an error of less than $12\%$, and acceleration peak value iscoincident with an error of less than $2\%$. Using the finite element model. vibration levels areestimated according to the design Parameters, slab thickness, compressive strength, and as a result, the thickness is revealed as effective to increase natural frequencies by $20\~30\%$ and to reduce the vibration level by 3$\~$4 dB per 30 mm of extra thickness.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.139-145
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• 2003

Ternary blended concrete, which contains both fly ash and granulated blast furnace slag, has an initial cost effective and is environment friendly. Furthermore, it has a lot of technical advantages such as the improvement of long term compressive strength, high workability, and the reduction of hydration heat. However, as the use and study on the performance of ternary blended concrete is limited, it is worthwhile studying the actual performance of this technology. This study examined the durability performance of ternary blended concrete, compared to binary blended concrete and ordinary portland concrete. It led to the conclusion that ternary blended concrete is very suitable for submerged members under marine environment. However, it should be noticed that ternary blended concrete becomes weak on carbonation, when it is situated on combined deterioration environment of carbonation and chloride. Therefore, the curing duration of ternary blended concrete should be prolonged in order to enhance the resistance of carbonation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.85-88
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• 2006

This study investigated influence of fine aggregate types on fundamental properties of cement mortar. Test showed that concrete using lime stone crushed fine aggregate(L) exhibited the most favorable fluidity due to grain shape and particle distribution, and next was blending aggregate miting L and G, blending aggregate mixing L and N, granite crushed fine aggregate(G), natural fine aggregate(N) in an order. Concrete using N had the highest air content and L was the smallest value because of the effective filling performance by continuos particle distribution. Compressive, tensile and flexural strength of all concrete using L had the highest value due to the smallest value of air content. It is also found that concrete using L resulted in decrease of drying shrinkage length change ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.113-117
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• 2003

In this study is investigated the various properties of concrete with the kinds of stabilizing agent of recycling water and solid content in order to suggest a practical use of recycling water According to the results. fluidity and air content varies slightly with the kinds of stabilizing agent and solid content, but does not make a big difference. Setting time does not differ remarkably from plain concrete at 2$0^{\circ}C$, but is shortened with an increase of solid content. Bleeding is reduced more largely in the case of S than in the case of R, and is not influenced by solid content. Compressive strength is equal or decreases in comparison with plain concrete at solid content of 1 and 5%, and shows the highest value at solid content of 3%. Length change by drying shrinkage is larger than plain concrete at solid content of 5%, and decreases at solid content of 1 and 3%. Therefore, it proves that the influence of the kinds of stabilizing agent is minute, and solid content is most effective at 3%.

• Journal of Powder Materials
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• v.11 no.2
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• pp.97-104
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• 2004

In this paper processing and mechanical properties of Al-20 wt％ Si alloy was studied. A bulk form of Al-20Si alloy was prepared by gas atomizing powders having the powder size of 106-145 ${\mu}m$ and powder extrusion. The powder extrudate was subsequently equal channel angular pressed up to 8 passes in order to refine grain and Si particle. The microstructure of the gas atomized powders, powder extrudates and equal channel angular pressed samples were investigated using a scanning electron microscope and X-ray diffraction. The mechanical properties of the bulk sample were measured by compressive tests and a micro Victors hardness test. Equal channel angular pressing was found to be effective in matrix grain and Si particle refinement, which enhanced the strength and hardness of the Al-2OSi alloy without deteriorating ductility in the range of experimental strain of 30％.