• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.579-588
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• 2007

Statement of problem: A tenderness of the dentin after tapering of teeth for dental prosthesis is a common phenomenon. In practice, the alternative desensitizer may be used for minor pain after tapering of teeth. Purpose: In this study, the desensitizers were used to investigate the affect decreasing of shear bond strength according to the use of various cement, such as resin, Glass Ionomer, and phosphate cement. Material and method: Three different desensitizers were used on this study Compositions of two dentin desensitizers were HEMA(hydroxyethylmethacrylate) and glutaraldehyde. The other one is oxalic acid. Three dentin desensitizers applied on 12 degrees taper teeth. Then, Ni-Cr crowns were bonded with Resin cement, Zinc Phosphate (ZPC) cement and Glass Ionomer (GIC) cement. 120 human premolar teeth were used for specimens. The specimens were divided into four group as the reference and the empirical each with thirty specimens, then further divided into 12 group according to type of desensitizers and cement types. The shear bond strength were measured by Instron multi task instrument. Results: According to the result, the measured shear bond strength in order from the weakest to the strongest in general was ZPC, Resin, and GIC. And it is found that the application of desensitizers on dentin surface does not affect the shear bond strength. Conclusion: Dentin desensitizers that alleviate or prevent a dentin tenderness, usually contains HEMA and glutaraldehyde compounds. Such desensitizers are widely used in clinical studies. By applying the dentin desensitizer on the exposed dentin surface, the dentin capillary are blocked and periodontal membrane and cementum can not be drawn in pulp cavity. Since HEMA and glutaraldehyde may cause harm to the pulp cavity, an alternative desensitizer was developed.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.169-177
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• 2000

The purpose of this study was to compare the retention of complete cast crown over amalgam ores, composite resin cores, and cast gold cores when cemented with three different luting agents. Eighteen core specimens each of amalgam(Bestaloy, Dong Myung, Seoul, Korea), composite resin (Z100, 3M Dental product, st. Paul, Minn) and type IV gold alloy (Ba-4, Heesung Engelhard Corp., Korea) were made in a customized milling stainless steel die. A wax pattern with a loop attached to occlusal surface was made for each core and a type II gold alloy casting was fabricated. The castings which had clinically acceptable marginal fit were used as test samples. The following luting cements were used to cement cast crowns on each core material : (1) zinc phosphate cement (Confi-dental Products Co., USA) (2) glass-ionomer cement (Fuji Plus, GC Industrial Corp., Tokyo, Japan) (3) resin cement (Panavia 21, Kuraray Co., USA). All cements were mixed according to manufacturers' instructions. A static load of 5kg was then applied for 10 minutes on the crowns. All specimens were stored in saline solution for 24 hours at $37^{\circ}C$ and thermocycled for 500 cycles. After storage and cycling, the tensile bond strengths were measured by using a universal testing machine (Instron Corp., Canton, Mass.) at a crosshead speed of 0.5mm/min. The results were as follows 1. The retentive strength of resin cement was the highest of alt three types of cement for resin core (p<0.05). 2. There was no statistical difference among the retentive strengths of three cements for amalgam core (p>0.05). 3. The retentive strength of resin cement was higher than that of zinc phosphate for cast core, but there was no difference between the retentive strength of glass ionomer cement and those of rein and zinc phosphate cement. 4. The retentive strength of the zinc phosphate cement for amalgam core was the highest of all type of cores.

• Advances in concrete construction
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• v.7 no.4
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• pp.277-288
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• 2019

The formulation of self-compacting concretes (SCC) and the study of their properties at the laboratory level were currently well mastered. The aim of this work is to characterize SCC under hot climatic conditions and their effects on the properties of fresh and hardened SCC. Particularly, the effect of the initial wet curing time on the mechanical behavior such as the compressive strength and the durability of the SCCs (acid and sulfate attack) as well as the microstructure of SCCs mixtures. In this study, we used two types of cement, Portland cement and slag cement, three water/binder (W/B) ratio (0.32, 0.38 and 0.44) and five curing modes. The obtained results shows that the compressive strength is strongly influenced by the curing methods, 7-days of curing in the water and then followed by a maturing in a hot climate was the optimal duration for the development of a better compressive strength, regardless of the type of binder and the W/B ratio.

• Computers and Concrete
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• v.21 no.4
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• pp.367-376
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• 2018

This study reports the results of nondestructive monitoring of macro void developments in mortars manufactured with both ordinary Portland cement and sulfate resistant cement. Two types of curing were utilized; tap water curing and another curing environment that contains 5% $Na_2(SO_4)$ solution. Being the primary objective of this study, macro void developments of the mortar specimens were monitored by X-ray Medical Computerized Tomography. Compressive strength tests and water absorption tests were conducted on specimens that were kept in both curing environments for a duration of 560 days. Data analyses yielded consistent results among the three tests used in this experimental study. Macro void ratios of mortars decreased at the beginning of experiments for a certain period; afterwards, macro void ratios increased. The objective of this study was accomplished as anticipated since X-CT image analysis was able to nondestructively monitor macro void development process in cement mortars.

• Journal of the Korea Furniture Society
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• v.11 no.2
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• pp.67-72
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• 2000

Some physical characteristics as thickness swelling, heat conduction, and bending properties of composite hoards made of waste wood chip and charcoal were measured. Wood-charcoal composite boards of three types and cement board were prepared for this study as shown in Table 1, Keeping duration of strawberries in the boxes($25cm{\times}25cm{\times}25cm$) manufactured with the boards was also examined. Thickness swelling and bending properties(MOR and MOE) of board B and C were lower than those of board A. Among the wood-charcoal composite boards except cement board, there were no differences in heat conduction(mm/sec.). Strawberries in the box with board C were kept longer duration in fresh condition than that with cement board. From the results, it is suggested that wood-charcoal composite boards can be used for eco-material.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.171-176
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• 1998

Recently, the Belite cement having the high fluidity, high strength, and low heat properties, was developed, and is being promoted the efforts for application on the real structures. Accordingly, for the purpose of practical use of high strength concrete using the Belite cement, was carried out the performance evaluation experiments about the structural members(column, beam, column-beam joint, steel bond strength etc.). Specimens were made in three types of concrete(Belite:350, 600kg/$\textrm{cm}^2$, OPC:350kg/$\textrm{cm}^2$) by taking into account the key parameters. In this paper, were summarized the comparative experimental results on the material properties and structural performance of Belite concrete.

• Smart Structures and Systems
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• v.8 no.3
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• pp.321-341
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• 2011

Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.103-106
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• 2006

This study investigates spalling properties of 60MPa class, high performance concrete, made with the various influential parameters, such as, blaine of cement, mineral admixture and polypropylene(PP) fiber contents. Totally 21 parameters of ${\phi}100{\times}200mm$ in size was fabricated; three specimens for variance in blaine of cement, 4 specimens for combination of mineral admixture type, along with 0.05, 0.1, 0.15% of fiber adding ratio. After that, one hour unloading fire test was conducted, and then spalling appearance and spalling degree of specimens was examined. Test showed that a specimen made with high blaine of cement(H) improved early strength but exhibited similar value to a specimen made with low blaine(L) at the age of 28 days, thus indicating comparable spalling appearance. In conclusion, spalling easily occur in higher strength and smaller particle shape of cement and mineral admixture.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.1
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• pp.51-59
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which that can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the unconfined compressive strength properties and freezing and thawing resistance of CSG materials with unit cement content. The three types of CSG-80, CSG-100 and CSG-120 with cement content were designed to evaluate the optimum water content, dry density, strength, stress-strain, micro structure and durability factor. As the results, the optimum water content ratio with cement content showed almost similar tendency, and the unconfined compressive strength and dry density increased as cement content increases. The strength ratio of 7 days for 28 days were in the range of 55~61 % and the strain ratio in stress-strain curve were in the range of 0.8~1.6 % nearby maximum strength in 28 days. It is expected that this study will contribute to increasing application of CSG method as well as to increasing the utilizing of CSG materials as a environmentally friendly CSG method.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.73-80
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• 2013

Polymer cement slurry (PCS) made from organic polymer dispersion and cement has good adhesion to steel, waterproofness and acid resistance due to being of polymer films formed in cement slurry. The purpose of this study is to evaluate the mix design conditions at early curing age of PCS-coating material effected on improvement in bond strength of coated rebar. The test pieces are prepared with two types of polymer dispersions such as St/BA and EVA, four polymer-cement ratios, two types of cement, four coating thicknesses and three curing ages, and tested for the bond strength test. From the test results, in general, bond strength of PCS-coated rebar is better than that of uncoated rebar and epoxy-coated rebar. It is also high bond strength at curing ages of 7-day or less, and coating thicknesses of $75{\mu}m$ and $100{\mu}m$. The maximum bond strength of PCS-coated rebar at curing age of 3-hour is almost same as that of curing age of 1-day and 7-day. The maximum bond strength of PCS-coated rebar with ultra high-early strength cement and St/BA at polymer-cement ratio of 80%, and coating thickness of $100{\mu}m$ is about 1.52 and 1.58 times respectively, the strength of uncoated rebar and epoxy-coated rebar. It is apparent that the curing age, coating thickness, type of polymer and cement are very important factors to improve the bond strength of PCS-coated rebar to cement concrete. We can have basic information that PCS-coated rebar with curing age at 3-hour and coating thickness of $100{\mu}m$ can replace epoxy-coated rebar.