• 한국도로학회논문집
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• 제20권3호
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• pp.19-26
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• 2018

PURPOSES : The main purpose of this study is suggest of field bond strength evaluation method for more objective evaluation method through Evaluation of Bond Strength Properties with changing aspect ratio and temperature. METHODS : The evaluation is laboratory bond strength test. Using the core machine, the pull-off test method ; the bond strength test of interface layer the universal testing machine. RESULTS : As a result of the laboratory bond strength evaluation, it was verified that the bond strength by aspect ratio decreases linearly with increasing aspect ratio and the bond strength properties by temperature change existed at high and low temperature condition relative to odinary temperature condition. CONCLUSIONS : According to the results of laboratory bond strength evaluation, the field bond strength evaluation results suggest applying the proposed correction factor (0.8, 1.0, 1.4, 1.9) according to aspect ratio(0.5, 0.1, 1.5, 2.0), For more objective evaluation of the bond strength, it is analyzed that the evaluation value is within $6{\sim}32^{\circ}C$ and the result can be obtained within 5% of the coefficient of variation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.653-660
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• 1998

Bond strength of reinforcing bar to high-performance concrete using belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that the specimens with belire cement concrete show higher bond strength than those with portland cement concrete. Bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfies the modification factor for top reinforcement. The results also show that the bond strength is function of the square root of concrete compressive strength and cover thickness. The recently developed high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

• Advances in concrete construction
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• 제10권2호
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• pp.113-125
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• 2020

This paper presents experimental results on bond-slip behavior of steel reinforced high-strength concrete (SRHC) after exposure to elevated temperatures. Three parameters were considered in this test: (a) high temperatures (i.e., 20℃, 200℃, 400℃, 600℃, 800℃); (b) concrete strength (i.e., C60, C70, C80); (c) anchorage length (i.e., 250 mm, 400 mm). A total of 17 SRHC specimens subjected to high temperatures were designed for push out test. The load-slip curves at the loading end and free end were obtained, the influence of various variation parameters on the ultimate bond strength and residual bond strength was analyzed, in addition, the influence of elevated temperatures on the invalidation mechanism was researched in details. Test results show that the shapes of load-slip curves at loading ends and free ends are similar. The ultimate bond strength and residual bond strength of SRHC decrease first and then recover partly with the temperature increasing. The bond strength is proportional to the concrete strength, and the bond strength is proportional to the anchoring length when the temperature is low, while the opposite situation occurs when the temperature is high. What's more, the bond damage of specimens with lower temperature develops earlier and faster than the specimens with higher temperature. From these experimental findings, the bond-slip constitutive formula of SRHC subjected to elevated temperatures is proposed, which fills well with test data.

• Computers and Concrete
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• 제29권3호
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• pp.145-159
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• 2022

In this study, the extreme learning machine and deep learning models were devised to estimate the bond strength of corroded reinforcement in concrete. The six inputs and one output were used in this study. The compressive strength, concrete cover, bond length, steel type, diameter of steel bar, and corrosion level were selected as the input variables. The results of bond strength were used as the output variable. Moreover, the Analysis of variance (Anova) was used to find the effect of input variables on the bond strength of corroded reinforcement in concrete. The prediction results were compared to the experimental results and each other. The extreme learning machine and the deep learning models estimated the bond strength by 99.81% and 99.99% accuracy, respectively. This study found that the deep learning model can be estimated the bond strength of corroded reinforcement with higher accuracy than the extreme learning machine model. The Anova results found that the corrosion level was found to be the input variable that most affects the bond strength of corroded reinforcement in concrete.

• 콘크리트학회지
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• 제8권5호
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• pp.156-162
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• 1996

고강도콘크리트에 매립된 철근의 부착특성을 실험적으로 규명하기 위하여 80개의 보단부형 시험체에 대한 부착실험을 수행하였다. 실험의 변수로는 콘크리트의 압축강도를 주변수로 선정하고 그 외 부착특성에 영향을 미치는 여러 요인 중 부착길이, 피복두께, 철근 직경 등을 변수로 선정하여 각 변수의 영향을 콘크리트의 압축강도와 비교하도록 하였다. 본 연구의 주요 결과를 살펴보면 고강도콘크리트에서의 부착강도는 부착길이의 증가에 직접적으로 비례하지는 않는 것으로 나타났다. 이러한 결과는 콘크리트의 강도가 증대함에 따라 더욱 큰 영향을 미치게 되는데 고강도콘크리트에서는 부착길이를 증가시키더라도 철근과의 부착강도는 상당히 제한된 증가를 나타나는데 불과하였다. 한편 부착강도와 피복두께와의 관계는 콘크리트의 강도에 관계없이 선형으로 비례하는 것으로 나타났으며, 특히 콘크리트의 강도가 증가함에 따라 그 비례상수는 오히려 더 증가함을 알 수 있었다.

• 한국도로학회논문집
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• 제15권4호
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• pp.1-9
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• 2013

PURPOSES : Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance since the overlay layer and the existing pavement perform as a monolithic layer. It is important to have suitable bond strength criteria to secure the performance of bonded concrete overlay. This study aimed to investigate the factors influencing bond strength characteristics between existing concrete pavement and overlay material. METHODS: Bond strength between overlay and existing pavement are measured and analyzed for various conditions such as the type of overlay materials, compressive and flexure strength of overlay and existing pavement, and deterioration status of existing pavement. RESULTS: The strength of overlay material does not significantly influence the bond strength. The overlay of ultra-rapid hardening cement generally gives low bond strength. However, ultra rapid hardening polymer modified concrete gives robust bond strength. The deterioration of existing concrete significantly decrease the bond strength. CONCLUSIONS: Bond strength of bonded concrete overlay highly depends on condition of existing concrete pavement rather than overlay material.

• Structural Engineering and Mechanics
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• 제17권2호
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• pp.141-152
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• 2004

The bonding behaviors of Lightweight Aggregate Concrete (LWAC) and normal weight concrete were investigated experimentally. Pull-out tests were carried out to measure the bond strengths of three groups of specimens with compressive strength levels of 60, 40, and 20 MPa, respectively. Test results showed that the difference in the bond failure pattern between LWAC and normal weight concrete was significant as the concrete compressive strength became lower than 40 MPa. The corresponding bond strengths of LWAC were lower than that for normal weight concrete. As the compressive strength of concrete became relatively high (> 40 MPa), a bond failure pattern in normal weight concrete occurred that was similar to that in LWAC. The bond strength of LWAC is higher than that for normal weight concrete because it possesses higher mortar strength. Stirrup use leads to an increase of approximately 20% in nominal bond strength for both types of concrete at any strength level.

• 콘크리트학회지
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• 제10권6호
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• pp.169-178
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• 1998

고성능 belite 시멘트 콘크리트에 대한 부착특성에 대하여 코\ulcorner리트의 강도, 슬럼프, 배근위치, 피복두께 등의영향요인을 보단부시험체와 이음길이 보시험체를 통해 연구하였다. 동일한 압축강도의 1종 보통 포틀랜드 시멘트 콘크리트에 비해 부착강도는 약 10%증가하였고 압축강도 600kg/$\textrm{cm}^2$의고강도 belite 콘크리트에서 부착강도가 대체로 {{{{ SQRT { f'c} }} }}에 비례하였다. 유동성에 있어서 높은 슬럼프에 비해 ACI 318-95 규준에서 제시하는 상부근 계수 1.3이하의범위에 있었으며 이것은 고유동 belite 콘크리트가 블리이딩이나 골재분리가 적은 것으로 보여졌다. 또한 고강도 belite시멘트 콘크리트를 사용한 이음길이 보시험체에서 부착강도는 기존 예측식의 값보다다소 높게 나타났으며, 실리커흄, 플라이애쉬를 사용한 고강도 콘크리트 부착강도의 기존연구결과인 낮은 값과 차이를 보였다. 이상의 결과로 고유동, 고강도 belite 시멘트 콘크리트는 철근과의 부착성능이 다른 재료에 비해 양호한 것으로 나타났다.

• Restorative Dentistry and Endodontics
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• 제45권3호
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• pp.36.1-36.10
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• 2020

Objectives: This study aims to assess the effect of universal adhesives pretreatment on the bond strength of resin-modified glass ionomer cement to dentin. Materials and Methods: Fifty caries-free human third molars were employed. The teeth were randomly assigned into five groups (n = 10) based on dentin surface pretreatments: Single Bond Universal (3M Oral Care), Gluma Bond Universal (Heraeus Kulzer), Prime&Bond Elect (Dentsply), Cavity Conditioner (GC) and control (no surface treatment). After Fuji II LC (GC) was bonded to the dentin surfaces, the specimens were stored for 7 days at 37℃. The specimens were segmented into microspecimens, and the microspecimens were subjugated to microtensile bond strength testing (1.0 mm/min). The modes of failure analyzed using a stereomicroscope and scanning electron microscopy. Data were statistically analyzed with one-way analysis of variance and Duncan tests (p = 0.05). Results: The surface pretreatments with the universal adhesives and conditioner increased the bond strength of Fuji II LC to dentin (p < 0.05). Single Bond Universal and Gluma Bond Universal provided higher bond strength to Fuji II LC than Cavity Conditioner (p < 0.05). The bond strengths obtained from Prime&Bond Elect and Cavity Conditioner were not statistically different (p > 0.05). Conclusions: The universal adhesives and polyacrylic acid conditioner could increase the bond strength of resin-modified glass ionomer cement (RMGIC) to dentin. The use of universal adhesives before the application of RMGIC may be more beneficial in improving bond strength.

• 콘크리트학회논문집
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• 제19권5호
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• pp.631-637
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• 2007

연구의 촛점은 강섬유 보강 고강도콘크리트와 고장력 철근 사이의 부착 특성을 평가하였다. 강섬유 혼입률에 따른 2가지 종류의 고강도콘크리트에서 고장력 철근의 부착 성능을 평가하기 위하여 직접 부착 실험을 실시하였다. 또한 콘크리트의 압축강도의 영향을 최소로 고려하여 강섬유 혼입률에 따른 부착강도의 영향을 결정하기 위하여 상대 부착강도를 정의하였다. 부착 성능 실험 결과 강섬유의 혼입률이 증가할수록 증가하였으며 강도가 높은 콘크리트 배합에서 더 우수한 결과를 나타내었다. 콘크리트의 강도에 대한 영향을 최소로하여 강섬유 혼입률에 따른 영향을 분석하기 위한 상대부착강도 평가 결과 섬유의 사용량이 증가할수록 상대부착강도가 증가하여 섬유의 혼입률은 고강도콘크리트의 강도에 관계없이 부착강도가 증가하였다.