• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.175-178
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• 1999

In most domestic construction fields, excessive cement content has been used because of stubborn official inspection. The purpose of this study is to reduce the cement content of mix proportioning for the decrease of hydration heat, brittleness and drying shrinkage which governs durability of concrete significantly. Parameters includes the compressive strengths, type and dosage rate of chemical and mineral admixtures and types of concrete. It is found that the chemical admixture is efficient to the reduction of cement content for high strength concrete (400kg/$\textrm{cm}^2$) and the effectiveness of mineral admixtures in the low strength concrete is somewhat higher than the high strength concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.89-92
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• 1999

The purpose of this study is to evaluate the capability to use with cement admixture materials because Paper Sludge Ash consists of Si, Ca and Al which are chief content in Pozzolan. For the derivation of Pozzolanic reaction in Paper Sludge Ash, it is measured compressive strength on cement mortar which is replaced mixing of Paper Sludge Ash and inorganic admixture ; ie, gypsum, lime and slaked lime, regularly. In the result of test, the strength decrease remarkably when cement is only replaced with Paper Sludge Ash, but the strength is almost equal when cement is replaced with Paper Sludge Ash is mixed with inorganic admixture material in proportions of 5~15%. Consequently, It is possible to use Paper Sluge Ash with admixture materials of cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.859-864
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• 2001

For earthquake resistance design, a response modification factor is used to reduce the design strength and it reflects ductility, reserve strength, redundancy and damping effect. But this factor has not theoretical basis. In this study, two response modification factors are compared and analyzed for shear wall apartment building.; the one is introduced by ATC-19 Procedures, the other is suggested FEMA-273 and ATC-40 through nonlinear static analysis. For the results, ATC-19 procedure gives a reasonable estimation to R factor. But $R_{u}$ by using FEAM-273 and ATC-40 methods is estimated so small in case of a minor or moderate earthquake region. Due to this fact, response modification factor is smaller than suggested load criterion 3.0. So, it needs to decrease wall volume and reduce the global strength and system stiffness for proper ductile behavior matching to domestic load criterion.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.953-958
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• 2001

The concrete which has placed under cold weather has some defects such as the decrease of initial strength by hydration delay, strength unrecover at unhardened concrete freezing and structural failure and crack by expansion pressure. So, in this study, we tried to develope the concrete which can be made under cold weather without defect by using of do-icing agency In concrete test, the used do-icing agency has the characteristics of de-icing and rapid hydration. By test results, Co{$NH_{2}$$]_{2}$is unsuitable for workability, and NaN$O_{2}$ is the most suitable agency for cold weather. And for curing, the cured concrete at $21^{\circ}C$ for 24 hours has the safe strength.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.105-109
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• 1997

The effects of surface conditions of the C-2 cemented carbide substrate on the adhesion of diamond film were investigated. The substrates were pretreated for different times with Murakami's reagent and then the acid solution of an H2SO4-H2O2. The adhesion strength was estimated by a peeling area around the Rockwell-A indentation. The cutting performance of the diamond-coated tools was evaluated by measuring flank wears in dry turning of Al-17% Si alloy. The morphology of deposited diamond crystallites was dominated by (111) and (220) surfaces with a cubooctahedral shape. The diamond film quality was hardly affected by the surface conditions of the substrate. The variation of tool life with longer substrate etching times resulted from a compromies between the increase of film adhesion at the interface and the decrease of toughness at the substrate surface. The coated tools were mainly deteriorated by chipping and flaking of the diamond film form a lock of adhesion strength, differently from the wear phenomena of PCD tools.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.165-165
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• 1982

In order to improve decaying properties of the plywood, the effectiveness of the Malenit treatment on the shear strength and decaying properties of the plywood has been investigated. The results are as follows. 1. No decrease of the shear strength of the plywood has shown despite of plywood treatment with Malenit right after plywood made or veneer treated with the same preservative prior to plywood manu. factured. 2. The effectiveness of Malenit treatment on decaying property of the plywood has shown much greater than that of the untreated plywood and red pine sapwood. 3. Weight decreases of the test specimens due to the infection of the different fungi have seen in different ways. If fungi infected weight decreases of the specimens are different in it's degree due to the fungi.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.25-28
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• 2005

This study shows the early quality improvement of concrete with calcium sulfa aluminate(CSA). For the properties of slump, plain concrete incorporating BS $35\%$ and UP $15\%$ resulted in high fluidity compared with OPC without any admixture. As displacement ratio of CSA increased. the fluidity decreased. The fluidity also declined with setting time. Increase of incorporation ratio of CSA declined bleeding and accelerated setting time. Importantly, using more CSA helped to improve early compressive strength and decrease drying shrinkage. In term of water curing, drying shrinkage hardly ever occurred.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.235-239
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• 1994

Polymer mortars are mainly used as protective coatings in concrete, reinforced concrete, and more rarely, steel, while polymer concretes represent a new type of structural material capable of withstanding highly corrosive environments. The mechanical properties, chemical stability, and some other useful properties are the reasons research, design, and production organizations. However polymer mortars and polymer concretes have been introduced only recently, and many of their properties are still imperfectly known. And, the main technique in producing polymer concrete is to minimize void volume in the aggregate mass so as to reduce the quantity of the relatively impressive polymer necessary for binding the aggregate. In this study, compressive strength and flexural strength of unsaturated polyester resin concrete are related to quantity of resin and solid volume of aggregate. It was founded that the more solid volume of aggregate increase, the less using quantity of resin decrease with out reducing mechnical properties. When solid volume ratio of aggregate is 70.6%, using quantity of resin is minimized to 10wt.%.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.300-303
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• 2004

In this study, the mixing contents of ceramic powder and of shrinkage-reducing agent (SRA) influencing on the strength properties of MMA-modified polymer paste were examined. Regardless of SRA content, the flexural. the compressive and the adhesive strengths of the MMA-modified polymer paste tended to increase as the mixing content of ceramic powder increased. On the other hand, those strengths of the polymer paste tended to decrease as the mixing content of SRA increased without regard to the paste content. Furthermore. the adhesive strength of MMA-modified polymer paste in a wet condition decreased about $30-40\%$ of that in an air-dry condition without regard to the mixing content of ceramic powder and SRA.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.941-948
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• 1994

An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.