• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.122-127
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• 1990

The transfer of forces across the interface by bond between concrete and steel is of fundamental importance to many aspects of reinforced concrete behavior. Bond stress - slip relationships were studied using a symmetrical tension test specimen. This type of test is intented to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are quite different at different locations along the bar. The present study allows more accurate analysis of reinforced concrete structures by employing more realistic bond stress-slip relations.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.239-243
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• 2003

A reducing bearing angle theory for bond of ribbed reinforcing bars to concrete is proposed to simulate experimental observation. Analytical expressions to determine bond strength for splitting and pullout failure are derived, where the bearing angle is a key variable. As bearing angle is reduced, splitting strength decreases and shearing strength increases. The proposed reducing bearing angle theory is effective to simulate damage of the deformed bar-concrete interface and understand bond mechanism of ribbed reinforcing steel in concrete structures.

• Computers and Concrete
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• v.26 no.3
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• pp.257-273
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• 2020

Concrete bond strength with steel re-bars depends on multiple factors including concrete-steel interface and mechanical properties of concrete. However, the hydration development of cementitious paste, and in turn the mechanical properties of concrete, are negatively affected by cold weather. This study aimed at exploring the concrete-steel bonding behavior in concrete cast and cured under freezing temperatures. Three concrete mixtures were cast and cured at -10 and -20℃. The mixtures were protected using conventional insulation blankets and a hybrid system consisting of insulation blankets and phase change materials. The mixtures comprised General Use cement, fly ash (20%), nano-silica (6%) and calcium nitrate-nitrite as a cold weather admixture system. The mixtures were tested in terms of internal temperature, compressive, tensile strengths, and modulus of elasticity. In addition, the bond strength between concrete and steel re-bars were evaluated by a pull-out test, while the quality of the interface between concrete and steel was assessed by thermal and microscopy studies. In addition, the internal heat evolution and force-slip relationship were modeled based on energy conservation and stress-strain relationships, respectively using three-dimensional (3D) finite-element software. The results showed the reliability of the proposed models to accurately predict concrete heat evolution as well as bond strength relative to experimental data. The hybrid protection system and nano-modified concrete mixtures produced good quality concrete-steel interface with adequate bond strength, without need for heating operations before casting and during curing under freezing temperatures down to -20℃.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.83-90
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• 2007

Buildings become high and large. CFT(Concrete Filled steel Tube) columns have been developed to manage effectively that loads which columns support and cross sections of columns are increased. Because CFT column is the composite structure made of two different materials, many researches have been performed to look into mechanical behaviors. This study is an analytic study about bond stress on interface between concrete core and steel tube in circular and rectangular CFT columns. ABAQUS/Standard Version 5.8 is used to analyze bond stress by bond form and position of shear-connector, and improved analystic method about mechanical characters on interface is suggested.

• Restorative Dentistry and Endodontics
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• v.47 no.3
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• pp.28.1-28.12
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• 2022

Objectives: Metalloproteinase-inhibiting agents, such as chitosan, can prevent collagen degradation in demineralized dental substrates, thereby improving the adhesive interface. This study evaluated the bond strength (BS) and chemical and morphological characterization of the adhesive interface after applying chitosan solution to demineralized dentin. Materials and Methods: The 80 third molars were selected. Forty teeth underwent caries induction using the pH cycling method. The teeth were divided according to the treatment: distilled water (control) and 2.5% chitosan solution. The surfaces were restored using adhesive and composite resins. Half of the specimens in each group were aged, and the other half underwent immediate analyses. The teeth were sectioned and underwent the microtensile bond strength test (µTBS), and chemical and morphological analyses using energy-dispersive spectroscopy and scanning electron microscopy, respectively. Data analysis was performed using 3-way analysis of variance. Results: For µTBS, sound dentin was superior to demineralized dentin (p < 0.001), chitosan-treated specimens had higher bond strength than the untreated ones (p < 0.001), and those that underwent immediate analysis had higher values than the aged specimens (p = 0.019). No significant differences were observed in the chemical or morphological compositions. Conclusions: Chitosan treatment improved bond strength both immediately and after aging, even in demineralized dentin.

• The korean journal of orthodontics
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• v.22 no.2 s.37
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• pp.449-474
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• 1992

The purpose of this study was to evaluate the in vitro shear bond strengths to enamel and the failure sites of three ceramic brackets and one metal bracket in combination with light cured orthodontic adhesive. The brackets were divided into four groups. Each ceramic bracket group had different bonding mechanisms with adhesive. Group A; metal bracket with foil-mesh base (control group) Group B; ceramic bracket with micromechanical retention Group C; ceramic bracket with chemical bonding Group D; ceramic bracket with mechanical retention and chemical bonding. Forty extracted human lower first premolars were prepared for bonding and 10 brackets for each group were bonded to prepared enamel surfaces with $Transbond^{\circledR}$ light cured ortho dontic adhesive. Twenty four hours after bonding, the Instron universal testing machine was used to test the shear bond strength of brackets to enamel. After debonding, brackets and enamel surfaces were examined under stereoscopic microscope to determine the failure sites, Statistical analysis of the data was carried out with ANOVA test and $Scheff\acute{e}$ test using SPSS PC+. The results were as follows. 1 . There were statistically significant differences in mean shear bond strengths of three ceramic bracket groups (p < 0.05). Shear bond strengths of group C and D were significantly higher than that of group B and shear bond strength of group C was significantly higher than that of group D. 2. Group C and D both had significantly higher shear bond strengths than metal bracket (group A), but there were no significant differences in shear bond strengths between group A and B (p < 0.05). 3. The failure sites of four bracket groups were also different. Group C and D failed primarily at enamel-adhesive interface, but group A and B failed primarily at bracket base-adhesive interface. 4. Among all ceramic bracket groups, group B was very similar to metal bracket in the aspect of shear bond strength and failure site.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.280-288
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• 1996

The purpose of this study was to assess comparatively the shear bond strength on dentin of four dentin bonding agents used in conjunction with light-curing composite resins. Clearfil New Bond, Scotchbond Multipurpose Dentin Adhesive, All-Bond 2 and X-R Bond were applicated on labial dentin surfaces just below dentin - enamel juction of bovine incisor teeth. After shear bond strength testing with the universal testing machine, the bonding interface of the specimens were observed under light stereomicroscope. Following results were obtained. 1. The shear bond strength was high in the order of B,C,D,A and group B Scotchbond Multipurpose Dentine Adhesive revealed greater bond strength than Clearfil New Bond and X-R Bond. (p<.001) 2. When using ANOVA and Duncan's multiple range test, there were statistical differences among the four groups, except between group Band C,group D and A. 3. There was no relationship between mode of failure and shear bond strength.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.103-117
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• 1997

The purpose of this experiment was to determind whether the gold electrodeposit on Pd-Ag and Ni-Cr alloys influences on the shear bond strength between veneering resin and silicoated metal surface. All the metal specimens were sandblasted with $250{\mu}m$ aluminum oxide and followed by silicoating and resin veneering. According to the metal surfaces to be veneered, experimental groups were divided into five. Group Prec : Gold alloy without gold coating Group Semi : Pd-Ag alloy without gold coating Group Base : Ni-Cr alloy without gold coating Group Semi-G : Pd-Ag alloy with gold coating Group Base-G : Ni-Cr alloy with gold coating All specimens were thermocycled 1,000 times at temperature of $5^{\circ}C$ to $55^{\circ}C$. The effects of gold electrodeposit on the shear bond strength between resin and metal interface were measured and fractured surface of the resin veneered metal was examined under the scaning electron microscope. The following results were obtained 1. The shear bond strength between resin and metal was $64.51{\pm}11.11Kg/cm^2$ in Prec group, $62.77{\pm}11.23Kg/cm^2$ in Base group and $58.97{\pm}9.20Kg/cm^2$ in Semi Group. There was no significant difference among the groups. 2. The bond strength in groups Semi-G and Base-G decreased about 17%, compared to the nongold-electrodeposit groups(Semi, Base). 3. In groups of non electrodeposit(Prec, Semi, Base), fracture occurred at the interface between alloy and resin, while fracture interface was observed between gold coating and resin in group Semi-G, and between metal substrate and gold coating in group Base-G respectively.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.349-357
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• 2011

Purpose: In this study, for the reasons of observing the changes when using bonding agent with Ni-Cr alloy and Co-Cr alloy and using VM13 and Vintage MP ceramic which have the disparity in coefficient of thermal expansion, it is carried out to evaluate the characteristics of the bonding agent through the analysis of the interface between metal and ceramic and the analysis of bond strength by variable. Methods: The surface treatment was performed on the two kinds of alloy(Ni-Cr alloy and Co-Cr alloy) specimens, which were sandblasted and were treated with bonder application. The metal-ceramic interfaces were analyzed with EPMA in order to ionic diffusion, and the shear test was performed. Results: As a result of observation of metal-ceramic interfacial properties, it was observed that Cr atoms were spread from the alloy body to the ceramic floor in the specimen of Group B. It was also seen that Cr, W atoms were spread from the alloy body to the ceramic floor in the specimen of Group S. In consequence of observing Shear bond strength, it was calculated that the specimen of BSV was 27.75(${\pm}11.21$)MPa, BSM was 27.02(${\pm}5.23$)MPa, BCV was 30.20(${\pm}5.99$)MPa, BCM was 27.94(${\pm}10.76$)MPa, SSV was 20.83(${\pm}2.58$)MPa, SSM was 23.98(${\pm}3.94$)MPa, SCV was 32.32(${\pm}4.68$)MPa, and SCM was 34.54(${\pm}10.63$)MPa. Conclusion: In the metal-ceramic interface of Bellabond plus sample group, diffusion of Cr atoms was incurred and diffusion of C Cr atoms and W atoms in the sample group of $Starloy{(R)}\;C$ was observed. Using bonding agent showed the higher bond strength than using the sand blasting treatment. In the Bellabond plus alloys, the specimen group with the use of binding materials showed higher shear bond strength, but didn't show statistically significant differences (p>0.05). In the $Starloy{(R)}\;C$ alloys, the specimen group with the use of binding materials showed higher shear bond strength and statistically significant differences(p<0.05). In terms of VM13 ceramic, it was in the Bellabond plus alloys that the high shear bond strength was showed, but there's no statistically significant differences(p>0.05). In terms of Vintage MP ceramic, it was in the $Starloy{(R)}\;C$ alloys that the high shear bond strength was showed and statistically significant differences(p<0.05). Metal-ceramic to fracture of the shear strength measurements and an analysis of all aspects of military usage fracture of the composite, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.647-652
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• 2000

The bond strength of latex-modified concrete to normal portland cement concrete measured with direct pull-out test. Using $250\times1100\times1400$mm concrete slab as the base concrete, an overlay of the latex-modified concrete is applied and cured similar to bridge deck and then tested in direct pull-out. The test results not only give values of the bond strength of the overlay tested but also clearly indicate whether the failure is in the bond interface or the materials tested.