• 한국농공학회논문집
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• 제46권3호
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• pp.73-81
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• 2004

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surfaces and coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and CFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.81-85
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• 1991

The object of this study is to propose the bending moment-curvature relationships based on the bond properties between concrete and steel for noncraking zone, and evaluate the flexural displacement of reinforced concrete members. The bond-slip relationship and the strain hardening effect of steel were taken into account in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double intergral of the equivalent curvature. Calculated values are in good agreement with the experimental data.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.281-287
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• 2004

The purposes of this study were to evaluate the effect of adhesive property on microtensile bond strength and to determine the failure mode. Flat occlusal dentin surfaces were prepared using low-speed diamond saw. The dentin was etched with 37％ phosphoric acid. The following adhesives were applied to the etched dentin to manufacturer's directions： Scotchbond Multi-Purpose in group SM, Prime＆Bond NT in group NT, Scotchbond Multi-Purpose followed by Tetric-flow in group TR. After adhesive application, a cylinder of resin-based composite was built up on the occlusal surface. Each tooth was sectioned vertically to obtain the $1{\;}{\times}{\;}1\textrm{mm}^2$ "sticks". Microtensile bond strength were determined. Each specimen was observed under stereomicroscope and scanning electron microscope (SEM) to examine the failure mode. Data were analyzed using one way ANOVA. The results of this study were as follows：1. The microtensile bond strength value were：group SM ($18.98{\pm}3.01MPa$). group NT ($16.01{\pm}4.82MPa$) and group TR ($17.56{\pm}3.22MPa$). No significant statistical differences were observed among the groups (P>0.05). 2. Most of specimens showed mixed failure. In group TR, there was a higher number of specimens showing areas of cohesive failure in resin.

• 콘크리트학회논문집
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• 제21권3호
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• pp.275-282
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• 2009

본 연구에서는 CFRP 보강근과 고강도콘크리트의 부착강도에 미치는 보강섬유의 표면처리 방법의 효과를 평가하였다. 표면을 친수성 물질로 코팅된 구조용 PVA 섬유 및 기하학적 변형으로 변형된 절곡형 폴리올레핀계 구조용 합성섬유를 보강섬유로 사용하였다. 섬유의 표면처리 방법에 따른 고강도콘크리트의 강도특성을 평가하기 위하여 압축강도 실험을 실시하였다. 고강도콘크리트와 CFRP 보강근 사이의 부착특성은 직접 부착강도시험을 의하여 평가하였다. 시험 결과는 섬유의 표면처리 방법은 고강도콘크리트와 CFRP 보강근 사이의 부착거동에 영향을 미쳤다. 또한 고강도콘크리트에 섬유의 첨가는 할렬균열의 발생 및 성장을 조절함으로써 고강도콘크리트와 CFRP 보강근 사이의 부착거동, 부착강도 및 상대부착강도의 증가시켰다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권5호
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• pp.68-74
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• 2019

본 연구에서는 부착성능 향상 모르타르 숏크리트의 역학적 특성 및 내구성능에 대한 실험적 연구를 수행하였다. 모르타르 숏크리트는 도로공사 표준시방서에서 제시하고 있는 숏크리트 배합에서 굵은 골재를 100% 잔골재로 치환한 배합을 이용하였다. 바인더로는 OPC와 GGBFS, 무수석고를 이용하였으며, 폴리머는 바인더의 각각 1, 2% 치환하여 사용하였다. 실험을 통해 폴리머를 사용하는 경우 압축강도가 감소하나 부착강도는 Plain 대비 50% 정도 향상되는 것을 확인하였다. 또한 폴리머 혼입 시 건조수축이 감소하고 탄산화 저항성도 향상되었다. 반면 초기 수화 반응에 의한 발열량은 감소하였는데, 이로 인해 초기 압축 강도가 감소한 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.597-600
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• 2003

The development and maintenance of a sound bond are an essential requirements of concrete repair and replacement. The bond property of a bonded 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. This study compares the nipple pipe direct tensile test, flexural adhesion test, and core pull-off test with their test results. Substantial differences in the failure stresses of three test methods were attributed to their different geometries and loading conditions. From these comparison and investigation, core pull-off test was relatively good because the coefficient of variation values were about 2%. It would be suitable for use in-situ because of its simplicity and accuracy.

• 한국의류학회지
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• 제18권5호
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• pp.674-681
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• 1994

In this study, four kinds of vapor-permeable waterproofed fabrics were selected and their properties and the changes of properties were investigated after laundering, petroleum drycleaning or tetrachloroethylene drycleaning (each 1, 5, 10 times). The results were as follows: 1) In the water resistance, only Gore Tex satisfied its minimum property requirements, $1.0kg/cm^2$ It decreased after laddering and drycleaning. Hipora-1000, Hipora-2000, Aitac decreased slightly by petroleum drycleaning and Gore Tex decreased slightly by all three methods. 2) In the moisture vapor transmission, three except Hipora-2000 satisfied its minimum property requirement, $4000g/m^2{\cdot}24hr$.24hr. After laundering and drycleaning, it increased regardless of cleaning methods. 3) In the water repellency, Hipora-lOOG, Hipora-2000 were not almost decreased after laundering and drycleaning. Aitac decreased slightly by petrolem drycleaning and Gore Tex decreased slightly by laundering and petroleum drycleaning. 4) Air permeability of Aitac increased with increasing of cleaning times regardless of cleaning methods. 5) In the bond strength, only Gore Tex dissatisfied its minimum property requirements, 250g/cm. Regardless of cleaning method, bond strength decreased with increasing of cleaning times. 6) Color difference was large in case of Hipora-1000 by laundering, Hipora-2000 by laundering and tetrachloroethylene drycleaning Aitac by tetrachloroethylene drycleaning, Gore Tex by laundering. To diminish property change of vaper-permeable waterproofed fabric, petroleum drycleaning is more effective than laundering and tetrachloroethylene drycleaning.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.190-191
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• 2020

The bonding of steel bar to concrete is closely related to the roughness and corrosion degree of steel bar surface. The accelerated corrosion of concrete specimens with different reinforcement diameters was carried out in this test. Through the pullout test of the corroded concrete specimens, the relationship between the bond stress and the displacement of the corroded concrete specimens under the corresponding corrosion degree was obtained. The bond stress of reinforced concrete with different size and corrosion degree are compared and analyzed to find out the influence of corrosion on the bonding property of reinforced concrete.

• 콘크리트학회지
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• 제3권4호
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• pp.97-106
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• 1991

본 연구의 목적은 휨거동을 하는 철근콘크리트 부재의 변위를 해석적으로 정확하게 구하기 위해 평균 휨균열간격 및 휨모멘트-등가곡률 관계(M-$\Phi_eg$)의 해석법을 제안한 것이다. 제안식은 비균열 구간에서의 철근과 콘크리트 간의 부착특성 및 재료의 소성영역을 고려하여 정확한 곡률분포를 계산함으로써 구할 수 있다. 제안된 해석법의 타당성을 검증하기 위해 34개의 철근콘크리트 보 부재를 제작, 휨재하 실험을 실시하였으며 해석치와 비교검토하였다. 그 결과 실험치와 해석치는 매우 잘 일치하여 본 해석법의 실용성 및 정확성이 입증되었다.

• Computers and Concrete
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• 제33권5호
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• pp.519-533
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• 2024

Many materials including cementitious concrete-type materials undergo material property changes during high-rate loading. There is a wealth of research regarding this phenomenon for concrete in compression and tension. However, there is minimal knowledge about how mortar material used in concrete masonry unit (CMU) construction behaves in high-rate shear loading. A series of experiments was conducted to examine the bond strength of mortar bonded to CMU units under high-rate shear loading. A novel experimental setup using a shock tube and dynamic ram were used to load specially constructed shear triplets in a double lap shear configuration with no pre-compression. The Finite Element Method was leveraged in conjunction with data from the experimental investigation to establish if the shear bond between concrete masonry units and mortar exhibits any rate dependency. An increase in shear bond strength was observed when loaded at a high strain rate. This data indicates that the CMU-mortar bond exhibits a rate dependent strength change and illustrates the need for further study of the CMU-mortar interface characteristics at high strain rates.