• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.698-704
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• 1989

Basic investigation for the flexural strength and water stability of hardened cement pastes using ordinary portland cement with water-soluble polyer (hydroxypropyl methyl cellulose ; HPMC) was carried out with 0.2 of water cement ratio. For molding of the specimen, the paste was mixed by twin roll mill. According to increase in the content of HPMC, the setting time of cement paste was delayed and the flexural strength was increased. The maximum flexural strength of hardened cement paste with 5.0wt% of HPMC was about 330 kg/$\textrm{cm}^2$. The expansion of the hardened cement paste immersed in water was increased with the content of water soluble polymer(HPMC). Consequently, the strength and the water stability of the hardened cement pastes were remarkably reduced by the expansion of them.

• Journal of Welding and Joining
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• v.22 no.1
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• pp.43-49
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• 2004

Contact tip is located so near to welding arc that it is heated to high temperature during long time welding. In such a situation, tip changes in its microstructure and in turn its mechanical properties. This study was intended to investigate those changes by using simulated heat treatment. As a result of this study, it was confirmed that tip of Cu-P alloy hardened with severe cold deformation lose its initial hardness to a large extent within 60 min due to the occurrence of rapid recrystallization while that of Cu-Cr composition hardened by proper aging treatment can preserve its intial hardness for about 1,000 min or longer. Based on these results, suggested was a guideline that can classify contact tips into two different grades: deformation-hardened type and precipitation-hardened type. Following a guideline, a tip with Cu-Cr composition can be classified into the deformation-hardened type if it is in the over-aged condition. Such a guideline is well described.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.791-796
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• 1998

Air voids existed in hardened concrete have an important influence on concrete deterioration such as carbonation, freezing and thawing, and corrosion of embedded steel in concrete. Therefore it is very significant to investigate the pore structure of system(size, number and continuity of air voids) to solve the reason caused concrete deterioration. The purpose of this study is to develop the standard method of measuring air voids which affect properties in hardened concrete using image analyzing system. This paper presents the settlement of rapid and exact experimental method which extracts fine bubbles, calculates the number of air voids, and determines air-void distribution using image analyzing system with computer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.429-436
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• 2013

This study considers how the fatigue behavior and probabilistic properties of SAE1055 steel are related to its hardness level. SAE1055 steel was heat-treated using induction hardening. Five types of specimens were prepared (A: base material, B: through hardened material with HV390, C: through hardened material with HV510, D: through hardened material with HV700, and E: surface hardened material with HV700). Fatigue tests were performed under a stress ratio of R = -1 using a 4-point rotary bending fatigue tester. The fatigue behaviors were greatly influenced by the hardness, but the fatigue limit did not increase over a hardness of HV510. In addition, the effect of the hardness level on the failure mechanism was evaluated using a scanning electron microscope. The probabilistic properties of the fatigue life were investigated using a probabilistic S-N approach, and the effect of the hardness level on these properties was evaluated using a residue analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.69-72
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• 1999

In this study, we blended 2 grades of ultra fine cement using the results of previous stud. And the cement slurry was produced by water each water/cement ratio. The slurries were observed hydration phenomena during 28 days with SEM, XRD and DSC. The specimen made by slurry were evaluated with the hardened properties such as compressive strength, flexural strength length change and water absorption. And were tested the adhesive strength of specimen made by injecting the slurry between mortar bars.

• Journal of the Korean Chemical Society
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• v.9 no.4
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• pp.190-200
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• 1965

It is a fundamental study for the hardened bodies of $CaO-SiO_2-H_2O$ system to clear up various physical properties and structures of the products, using the Seosan quartz and $Ca(OH)_2$(C. P. grade) as raw materials. Various samples were obtained by varying $CaO/SiO_2$ mole ratio (0.3∼2.1) and hydrothermal conditions ($100∼220^{\circ}C$ and 2∼14hr.) within the given limit. It was found that tobermorite phase as hydrate is contained in the hardened bodies and that the development of crystal has a great influence on the strengths and other physical properties of hardened bodies.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.116-117
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• 2018

The aim of this study is to investigate the properties of hardened mortar with chlorine by-pass system(CBS) in cement production in blast furnace slag(BS) mixed cement. Compressive strength had a tendency to be increased when the CBS Dust was replaced by 10% at the BS replacement rate of 0%. The 65% combination of BS showed a tendency to decrease as the CBS Dust exchange rate increases. Flexural strength was reduced as CBS Dust exchange rate increases in BS replacement ratio of 0%. The use of 5% of CBS dust can contribute to enhance the quality of non reinforced concrete.

• Korean Journal of Metals and Materials
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• v.47 no.5
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• pp.267-273
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• 2009

Three types of structural intermetallic compounds, $Ni_3Al$, NiAl and TiAl, having each single phase structure without pores were produced by arc-melting process. Their sliding wear properties were investigated against a hardened tool steel. It was shown that the wear of the intermetallic compounds was hardly occurred against the hardened tool steel. TiAl compound showed the best wear resistance among them. In this case, wear was preferentially occurred on the surface of the hardened tool steel of the mating material which has higher hardness. It could be found that the wear mode on intermetallics without pores by arc-melting process was different from that on its porous layer coated on steel by combustion synthesis.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.57-60
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• 2006

This study proposes the physical properties of the hardened lightweight cement using the polyethylene tube and to make the fundamental data regarding a new lightweight concrete development. The aerated concrete is displaying various effects such as lightweight, insulation characteristic and it is coming to be widely applied the slab layer of apartment as an insulating material but currently the aerated concrete has many problems. Therefore, demonstrating similar property of former aerated concrete and improving the defects, developing new hardened cement is needed. In this study, we predict adopting possibility of hollow core polyethylene tube, as a material to make cement hardening containing a lot of void. So we changed the mixing ratio, a diameter and length of the polyethylene tube and improved the compressive strength and unit capacity weight of the lightweight cement hardening body. From the test results, we judge that the aerated concrete is a developmental possibility.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.35-38
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• 1993

Although bonding material content of the high strength flowing concrete is very important in engineering properties, in rich mix concrete increasing the bonding material content may not follow more good properties. This study is to investigate the influence of the bonding material content affecting on the engineering properties of high strength flowing concrete, and this paper is to analyze the properties of hardened concrete. The results reveal that the strength of concrete having loss bonding material content is higher than that of concrete having more bonding material content, and that in proportion to increasing of concrete strength brittleness factors decrease, and that the static modulus of elasticity in this study is less than that in specification.