• Computers and Concrete
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• 제16권3호
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• pp.449-466
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• 2015

This paper aims to study the local bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete (LWAC). The experimental variables of the local bond stress-slip tests include concrete strength (20, 40 and 60 MPa), deformed steel bar size (#4, #6 and #8) and coarse aggregate (normal weight aggregate, reservoir sludge lightweight aggregate and waterworks sludge lightweight aggregate). The test results show that the ultimate bond strength increased with the increase of concrete compressive strength. Moreover, the larger the rib height to the diameter ratio ($h/d_b$) of the deformed steel bars is, the greater the ultimate bond stress is. In addition, the suggestion value of the CEB-FIP Model Code to the LWAC specimen's ultimate bond stress is more conservative than that of the normal weight concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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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.

• 대한치과교정학회지
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• 제22권2호
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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.

• 대한치과보철학회지
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• 제41권3호
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• pp.379-386
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• 2003

Statement of problem. Resin cements are widely used in adhesive dentistry specially on all ceramic restorations. It is needed to find out adequate bonding strength between different porcelain surface treatments, commercially available porcelains, and different resin cement systems. Purpose. The purpose of this study was to evaluate shear bond strength of resin cements bonded to porcelains in three different modalities; 5 different porcelain surface treatments, 3 different resin cement systems and 3 different commercially available pressable porcelains. Material and Method. This study consisted of 3 parts. Part I examined the effect of five different surface treatments on the pressable porcelain. Fifty discs (5 mm in diameter and 3 mm in height) of Authentic porcelain were randomly divided into 5 groups (n = 10). The specimens were sanded with 320 grit SiC paper followed by 600 grit SiC paper. The specimens were treated as follow: Group 1-Sandblasting (aluminum oxide) only, Group 2 - sandblasting/ silane, Group 3 - sandblasting/ acid etching/ silane, Group 4 - acid etching only, Group 5 - acid etching/ silane. Part II examined the shear bond strength of 3 different resin cement systems (Duolink, Variolink II, Rely X ARC) on acid etching/ silane treated Authentic pressable porcelain. Part 3 examined the shear bond strength of Duolink resin cement on 3 different pressable porcelains (Authentic, Empress I, Finesse). All cemented specimens were stored in distilled water for 2 hours and tested with Ultradent shear bond strength test jig under Universal Instron machine until fracture. An analysis of variance(ANOVA) test was used to evaluate differences in shear bond strength. Result. The shear bond strength test resulted in the following: (1) Acid etched porcelains recorded greater shear bond strength values to the sandblasted porcelains. (2) Silane treated porcelains recorded greater shear bond strength values to non-silane treated porcelains. (3) There was no significant difference between sandblasting/ acid etching/ silane treated and acid etching/ silane treated porcelains. However those values were much higher than other three groups. (4) The shear bond strength with Variolink II was lower than the value of Duolink or Rely X ARC. (5) The shear bond strength of Finesse was lower than the value of Authentic or Empress I.

• 산업기술연구
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• 제23권A호
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• pp.149-156
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• 2003

The development and maintenance of a sound bond are essential requirements of concrete repair and replacement. The bond property of a overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified. A standard or a verified bond strength measurement method is required at field for screening, selecting materials and quality control for overlay or repair materials, but no test method has been adopted as a standard. In this study, a concrete pull off bond strength measurement method for field application is proposed and evaluated. This study compares the splitting tensile test, slant shear test, nipple pipe direct tensile test, flexural adhesion test, briquette tensile test, jumbo nail pull-out test and core pull-off test with their test procedures. From these comparison and investigation, core pull-off test is selected as a main topic of this study because of it's suitability for in situ testing, simplicities in field application and clearness at interface boundary condition. Thus, the proposed core pull off test is evaluated to be the most appropriate method for field application in a simple manner. The fracture surface and fracture mode could be easily determined by visual observation of failure surface of the field specimen. The core pull off test was found to be sensitive to surface condition and latex contents at latex modified concrete.

• Steel and Composite Structures
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• 제45권6호
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• pp.819-830
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• 2022

This paper presented an experimental study of the bond-slip behavior of reactive powder concrete (RPC)-filled square steel tube. A total of 18 short composite specimens were designed forstatic push-out test, and information on their failure patterns, load-slip behavior and bond strength was presented. The effects of width-to-thickness ratio, height-to-width ratio and the compressive strength of RPC on the bond behavior were discussed. The experimental results show that:(1) the push-out specimens remain intact and no visible local buckling appears on the steel tube, and the interfacial scratches are even more pronounced at the internal steel tube of loading end; (2) the bond load-slip curves with different width-to-thickness ratios can be divided into two types, and the main difference is whether the curves have a drop in load with increasing slip; (3) the bond strength decreases with the increase of the width-to-thickness ratio and height-width ratio, while the influence of RPC strength is not consistent; (4) the slippage has no definite correlation with bond strength and the influence of designed parameters on slippage is not evident. On the basis of the above analysis, the expressions of interface friction stress and mechanical interaction stress are determined by neglecting chemical adhesive force, and the calculation model of bond strength for RPC filled in square steel tube specimens is proposed. The theoretical results agree well with the experimental data.

• Computers and Concrete
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• 제16권6호
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• pp.909-918
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• 2015

This paper presents an experimental study for determining the bond performance of lightweight concretes produced using pumice aggregate coated with colemanite-cement paste. For this purpose, eight hinged beam specimens were produced with four different concrete mixtures. 14 mm deformed bars with $10{\Phi}$ development lengths were selected constant for all test specimens. All the specimens were tested in bending and load-slip values were measured experimentally to determine the effect of colemanite-cement coated pumice aggregate on bond performances of lightweight concretes. Test results showed that, colemanite-cement coated pumice aggregate increases compressive strength and bond performance of the lightweight concretes, considerably.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.373-376
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• 2006

The purpose of this study was manufactured and evaluated the bond performance of recycled polyethylene terephthalate(PET) bottle fiber reinforced concrete. Four deformed recycled PET bottle fibers were manufactured and pullout test was conducted in accordance with the JCI-SF 8. Test parameters included four different type of fiber geometry and two types of mortar specimens. According to bond test results, it was found that embossing type recycled PET bottle fiber was significant improving the pullout load and interface toughness.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.361-364
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• 2006

In this study, six specimens were prepared for two type FRP sheets(carbon and polyacetal) to evaluate the behavior of FRP-concrete interfacial bond. A direct tensile test was conducted and the test results show that fiber type influences both bond strength and the shape of strain distribution. The failure mode for carbon type specimens seems to bond failure between concrete and FRP, but for polyacetal type indicates interface failure between FRP and expoxy. The local bond stress-slip relations were obtained from test results, and it was shown good shape for the polyacetal type. But for the carbon type it was scattered.

• 한국구조물진단유지관리공학회 논문집
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• 제20권1호
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• pp.41-47
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• 2016

본 연구에서는 콘크리트에 표면매입된 FRP판의 부착거동에서, 전단키와 연단거리의 효과를 관찰하기 위한 부착시험을 실시하였다. 실험에서의 주요변수는 전단키의 위치, 형태 그리고 연단길이이다. 규격 $3.6mm{\times}16mm$의 FRP를 $400mm{\times}200(300)mm{\times}400mm$ 규격의 콘크리트 블록에 매입하고 에폭시로 고정시켜서 실험변수에 따라 총 10개의 부착실험체를 제작하였다. FRP의 연단에 인장력을 가한 뒤 파괴시까지 실험을 실시하고 하중을 기록하였으며, 미끄러짐과 FRP의 인장변형량을 기록하였다. 실험으로부터, 전단키의 위치는 가력부에서 멀리 떨어질수록 전단강도가 상승하는 것으로 나타났으며, 전단키의 직경이 커질수록 내력이 저하되는 것으로 나타났다. 특히 전단키가 일정 이상의 규격이 되면 전단키가 없는 경우에 비하여 내력이 저하되어 오히려 부착강도에 부정적인 영향을 미칠 수 있는 것으로 나타났다. NSM FRP에서 응력장용방향의 연단거리가 길어짐에 따라 동일 부착길이임에도 불구하고 내력이 일부 증가하는 것으로 나타났다. 표면매입 보강된 FRP의 부착실험에서, FRP와 콘크리트사이의 부착-미끄러짐은 전체거동을 지배하는 것으로 나타나므로 이에 따른 과도한 미끄러짐은 설계에 반드시 고려될 필요가 있다.