• Restorative Dentistry and Endodontics
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• v.25 no.2
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• pp.243-253
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• 2000

The purpose of this in vitro study was to evaluate dentin bonding by two different dentin bonding systems(DBS) using acetone based primer or adhesive [All Bond 2(AB2), One Step(OS)] when they were applied by wet or dry bonding technique. Morphology of resin-dentin interface and hybrid layer thickness(HLT) were investigated using Confocal Laser Scanning Microscope(CLSM) and compared to shear bond strength(SBS). 72 extracted sound human molars were randomly divided into 4 groups of 18 teeth each - Group 1.(AW); AB2 by wet bonding. Group 2(AD); AB2 by dry bonding. Group 3.(OW); OS by wet bonding, Group 4.(OD); OS by dry bonding. In 6 teeth of each group, notch-shaped class V cavities(depth 2mm) were prepared on buccal and lingual surface at the cementoenamel juction(12 cavities per group). To obtain color contrast in CLSM observation, bonding resins of each DBS were mixed with rhodamine B and primer of AB2 was mixed with sodium fluorescein. Prepared teeth of each group were treated with AB2, OS, respectively according to the manufacturer's instructions except for dentin surface moisture treatment after acid etching. In group 1 and 3, after acid etching, excess water was removed with wet tissue(Kimwipes), leaving consistently shiny, visibly hydrated dentin surface. In group 2 and 4, dentin surface was dried for 10 seconds at 1 inch distance. The treated teeth were then packed with composite resin(${\AE}$litefil) and light-cured. 12 microscopic samples($60{\sim}80{\mu}m$ thickness) of each group were obtained after longitudinal section and grinding(Exakt cutting and grinding system). Morphological investigation of resin-dentin interface and HLT measurement using CLSM were done. For measurement of SBS, remaining 12 teeth of each group were flattened occlusally to remove all enamel and grinded to 500 grit SiC(Pedemet Specimen Preparation Equipment). After applying DBS on the exposed dentin surface, composite resin was applied in the shape of cylinder, which has 5mm diameter, 1.5mm thickness, and light cured. SBS was measured using Instron with a crosshead speed of 0.5mm/min. It was concluded as follows, 1. HLT of AW(mean: $2.59{\mu}m$) was thicker than any other group, and followed by AD, OW, OD in descending order(mean; 2.37, 2.28, $1.92{\mu}m$). Only OD had statistically significant differences(p<0.05) to AW and AD. 2. There were intimate contact of resin and dentin at the interface in wet bonding groups, but gaps or irregular interfaces were observed in dry bonding groups. 3. The length, diameter, density of resin tags were various even in the same group without significant differences between groups and lots of adhesive lateral branches were observed. 4. There were no statistically significant difference of SBS between AB2 and OS, but SBS of wet bonding groups were significantly higher(p<0.05) than dry bonding groups. 5. There were no consistent relationships between HLT and SBS.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.4
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• pp.93-101
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• 2010

The purpose of this study is to provide basic data for utilization in environment-friendly and economically outstanding CSG construction method by physical and mechanical properties of CSG materials including characteristics of uniaxial compressive strength, microscopic structure and freezing and thawing resistance in accordance with the cement content and curing time of the cement, and size of specimen. In this study, specimens with cement content of 4, 6, 8 and 10% of the total weight were, and, in order to examine the characteristics of the sizes of specimen, specimens with ${\Phi}50{\times}100mm$, ${\Phi}100{\times}200mm$ and ${\Phi}150{\times}300mm$ were manufactured to assess the features including compressive strength, microscopic structure, freezing and thawing, and degree of wet-dry. As results, it was found that with greater size specimen or contents of cement in the specimen, compressive strength, freezing and thawing resistance, and wet-dry resistance increase. Moreover, reactive products for each size of specimen were examined and it was possible to verify that some typical needle structured ettringite was generated due to blending of cement through microscopic structure analysis such as SEM and EDS analysis.

• Computers and Concrete
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• v.31 no.6
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• pp.501-511
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• 2023

The strengthening efficiency of biopolymer treated soil depends on biopolymer type, concentration ratio, soil type, initial water content, curing time and mixing method. In this study, the physical and mechanical properties of xanthan gum (XG) treated kaolinite were investigated through compaction test, Atterberg limit test, triaxial test and unconfined compression test. The results indicated that the optimum water content (OWC) increased from 30.3% of untreated clay to 33.5% of 5% XG treated clay, while the maximum dry density has a slight increase from 13.96 kg/m³ to 14 kg/m³ of 0.2% XG treated clay and decrease to 2.7 kg/m³ of 5% XG treated clay. Meanwhile, the plastic limit of XG treated clay increased with the increase of XG concentration, while 0.5% XG treated clay can be observed the maximum liquid limit with 79.5%. Moreover, there are the ideal water content about 1.3-1.5 times of the optimum water content achieving the maximum dry density and curing time to obtain the maximum compressive strength for different XG contents, which the UCS is 1.52 and 2.07 times of the maximum UCS of untreated soil for 0.5% and 1% XG treated clay, respectively. In addition, hot-dry mixing can achieve highest UCS than other mixing methods (e.g., dry mixing, wet mixing and hot-wet mixing).

• Journal of the Korean Wood Science and Technology
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• v.4 no.1
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• pp.28-32
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• 1976

This study was carried out to know the adaptability of barley flour, potato flour and white ash as extender and filler of urea-formaldehyde resin for plywood as a substitute material of wheat flour. The extenders and filler used at this study were extended by several groups of percentages. Shear strength, moisture contents, and specific gravities were compared among tested groups. The results obtained are summarized as follows. 1) Wet and dry shear strength of plywoods extended by 10% barley flour, 30% potato flour, and wheat flours were shown better results than non extended plywoods. 2) There was no significant difference between plywoods extended until 50% barley flours and non extended plywoods. 3) Shear strength of plywoods extended by 50% potato and 100% barley flours were shown worse result than non extended. 4) Dry and wet shear strength of plywoods extended by white ash were shown worst result. 5) The plywoods extended by potato flours were shown not only better shear strength, but also considered more profitable cost for extending.

• Geomechanics and Engineering
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• v.31 no.4
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• pp.409-422
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• 2022

The use of calcium sulfoaluminate (CSA) cement as a rapid-hardening cement admixture or eco-friendly alternate for ordinary Portland cement (OPC) has been attempted over the years, but the cost of CSA cement and availability of suitable aluminium resource prevent its wide practical application. To propose an effective ground improvement design in sandy soil, this study aims at blending a certain percentage of CSA with OPC to find an optimum blend that would have fast-setting behavior with a lower carbon footprint than OPC without compromising the mechanical properties of the cemented sand. Compared to the 100% CSA case, initial speed of strength development of blended cement is relatively low as it is mixed with OPC. It is found that 80% OPC and 20% CSA blend has low initial strength but eventually produces equivalent ultimate strength (28 days curing) to that of CSA treated sand. The specific OPC-CSA blend (80:20) exhibits significantly higher strength gain than using pure OPC, thus allowing effective geotechnical designs for sustainable and controlled ground improvement. Further parametric studies were conducted for the blended cement under various curing conditions, cement contents, and curing times. Wet-cured cement treated sand had 33% lower strength than that of dry-cured samples, while the stiffness of wet-cured samples was 25% lower than that of dry-cured samples.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.313-320
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• 2017

Flue gas desulfurization gypsum(FDG) is produced when removing sulfur oxides from combustion gas generated by coal power plant. However, the recycling of FDG is still limited to the certain purposes. In order to expand the possible application of FDG, this study aims to utilize FDG as an activator for ground granulated blast furnace slag. FDG produced by dry- and wet-process were used for the experiments. Slag paste specimens were produced by mixing with deionized water and simulated pore solution, and the role of FDG as an activator for blast furnace slag was evaluated using hydration study by XRD analysis and compressive strength development. According to the results, dry-type FDG was found to work as an activator for blast furnace slag without the presence of soluble alkalis. However, wet-type FDG needs assistance by soluble alkalis in order to work as an activator for blast furnace slag. It was also found that the substitution of dry- and wet-type FDG into blast furnace slag can increase the 28 day compressive strength of slag paste. It is expected that efficient and economical recycling of FDG will be possible if quantitative analysis of strength enhancement according to substitution rate of both dry- and wet-type FDG.

• Journal of the Korea Furniture Society
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• v.11 no.1
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• pp.53-59
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• 2000

This study was to measure formaldehyde emission and bonding strength of plywoods manufactured with urea-melamine formaldehyde adhesives, which were made from three different mixing ratios of urea and melamine, and with four different formaldehyde/urea-melamine molar ratios of 1.0,1.1,1.2 and 1.4. The results were as follows 1. Amount of formaldehyde emission was the lowest at the first method of molar ratio(F/(M+U)) 1.0. Amounts of formaldehyde emission of experimental manufactured adhesives were lower than that of commercial adhesive. 2. Bonding strength of dry specimen was the highest at the first method of molar ratio(F/(M+U)) 1.4. Dry bonding strength of molar ratio(F/(M+U)) 1.4 was similar to commercial adhesive. 3. Bonding strength of wet specimen was the highest at the second method of molar ratio(F/(M+U)) 1.4. Bonding strength of wet specimen used by the third method of molar ratio(F/(M+U)) 1.4 was almost equal to commercial adhesive.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1360-1363
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• 1994

Epoxy resin insulator have good electrical properties (high electric strength, high resistivity, low dielectric loss) in addition to high mechanical strength, small dimensions and design versatility. Polymer insulator, however, are subjected to aging processes, caused by the surrounding atmosphere, which may lead to degradation of their properties. This paper describes the results of a important study on the artificial pollution test, Weather-Ometer properties and rotating wheel dip test of high voltage different aging insulators which are the most important factors for outdoor uses. Also, the objects of this paper are to (a)result of insulator under dry(wet) flashover voltage, (b)artificial pollution test of salt spay, (c)Accelerated aging test of Weather-Ometer, (d) wet and dry flashover voltage under rotating wheel dip test.

• Composites Research
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• v.22 no.5
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• pp.30-36
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• 2009

The failure strengths and modes in carbon fiber reinforced polymeric composites, with two serial bolt-fastened composite joints, were investigated to evaluate the typical joint configurations of composite components. The parametric studies were performed experimentally at room temperature dry and elevated temperature wet, $82.2^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, two basic load-displacements curves are observed. Each failure mode has the characteristic curve. It is showed that the bearing failure mode occurs in elevated temperature wet condition. It is analysed that the strength of bearing failure mode is not highly depending on the effective modulus of specimen. The failure strength at elevated temperature wet is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.24.1-24.9
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• 2020

Objectives: It is known that bioactive materials interact with the dentin to undergo biomineralization. The exact role of moisture in this interaction is unknown. Here, we investigate the effects of dentin moisture conditions on the dislocation resistance of two bioactive root canal sealers (MTA Fillapex [Angelus Solucoes Odontologicas] and GuttaFlow BioSeal [Colténe/Whaledent AG]) at 3 weeks and 3 months after obturation. Materials and Methods: Mandibular premolars (n = 120) were prepared and randomly divided into 3 groups based on the dentin condition: group 1, dry dentin; group 2, moist dentin; group 3, wet dentin. Each group was divided into 2 subgroups for root canal filling: MTA Fillapex and GuttaFlow BioSeal. Dislocation resistance was evaluated by measuring the push-out bond strength at 3 weeks and 3 months. Failure modes were examined under a stereomicroscope. Data were statistically analyzed by Kruskal-Wallis test with a significance level of 5%. Results: Moist dentin resulted in higher bond strength values for both materials at both time points. This was significantly higher than wet and dry dentin for both the sealers at the 3 months (p < 0.05), while at 3 weeks it was significant only for GuttaFlow Bioseal. The different moisture conditions demonstrated similar trends in their effects on the dislocation resistance of the 2 root canal sealers. Conclusions: The dentin moisture conditions had a significant impact on its interaction with the bioactive materials tested. Maintaining moist dentin, but not dry or wet dentin, may be advantageous before the filling root canals with bioactive sealers.