Influence of substrate roughness and bonding agents on the bond strength between old and new concrete

Magbool, Hassan M.,Tayeh, Bassam A. Techno-Press 2021 Advances in concrete construction Vol.12 No.1

This research aims to study factors affecting the strength of adhesion between old concrete and new concrete. Among the factors that have been studied in this research are the type of bonding material and the roughness of the surface adhesion, four types of bonding materials (EPICHOR-1768, C-Latex, SikaBond-T21, EPICHOR-500) have been selected because they are available in local markets. A wire brush is used in order to increase the roughness of sample surfaces. The pull-off and slant shear tests have been adopted to assess the bonding strength between the test the old and new concrete. 30 cylindrical samples (7 cm diameter) have been examined by pull-off test, also slant shear test was conducted on 40 samples (10 cm×10 cm×30 cm). The obtained results showed that there is an active role for the bonding material as well as the surface roughness to increase the strength of adhesion between the old and new concrete. Also, it showed that the best of these bonding materials is EPICHOR-1768 because of its significant impact in increasing the strength of the adhesion between the old and new concrete where the percentage of increase 124% in the pull-off test and 48% in slant shear test, compared to the reference sample for each test. As well, as a result of roughening the surface by brush, the strength of adhesion reaches 4% increase in the pull-off test and 23% in the slant shear test compared with the reference sample for each test, which demonstrates the importance of surface roughness to increase the bonding strength between the old and new concrete.

Using scratch test to evaluate cohesive bond strength of Mo composite coating

Koiprasert, Hathaipat,Thaiwatthana, Sirinee,Sheppard, Panadda The International Promotion Agency of Culture Tech 2015 International Journal of Advanced Culture Technolo Vol.3 No.2

Bonding strength of a thermal sprayed coating is difficult to measure using a conventional pull-off test method. Scratch test is a potential alternative testing method. An adhesive and a cohesive bond strength of the coating can be measured by the pull-off test while the scratch test performed on the cross-section of the thermal sprayed coating can only demonstrate the cohesive bond strength of the coating. Nevertheless, it is still beneficial to perform the scratch testing on the cross-section of the coating for the sake of comparison thus providing an alternative to the pull-off test. The scratch test method can reduce testing time and cost in the long run due to a significant cost reduction in consumables and energy and time saving from the curing step of the glue used in the pull-off test. This research investigates the possibility of using the scratch test to measure the cohesive bond strength of Mo/NiCrBSi composite coating. The results from the pull-off test and the scratch test indicate that the cohesive bond strengths of the Mo composite coating show similar trend and that the cohesive bond strength are increased when increasing NiCrBSi content.

Using scratch test to evaluate cohesive bond strength of Mo composite coating

Hathaipat Koiprasert,Sirinee Thaiwatthana,Panadda Sheppard 국제문화기술진흥원 2015 International Journal of Advanced Culture Technolo Vol.3 No.2

Bonding strength of a thermal sprayed coating is difficult to measure using a conventional pull-off test method. Scratch test is a potential alternative testing method. An adhesive and a cohesive bond strength of the coating can be measured by the pull-off test while the scratch test performed on the cross- section of the thermal sprayed coating can only demonstrate the cohesive bond strength of the coating. Nevertheless, it is still beneficial to perform the scratch testing on the cross-section of the coating for the sake of comparison thus providing an alternative to the pull-off test. The scratch test method can reduce testing time and cost in the long run due to a significant cost reduction in consumables and energy and time saving from the curing step of the glue used in the pull-off test. This research investigates the possibility of using the scratch test to measure the cohesive bond strength of Mo/NiCrBSi composite coating. The results from the pull-off test and the scratch test indicate that the cohesive bond strengths of the Mo composite coating show similar trend and that the cohesive bond strength are increased when increasing NiCrBSi content.

박스 형태의 복합레진 수복시 충전법 및 와동벽에 따른 결합력 차이에 관한 연구

고은주,신동훈 大韓齒科保存學會 2009 Restorative Dentistry & Endodontics Vol.34 No.4

복합 레진은 중합되는 동안 수축으로 인한 응력이 발생하게 되고 이는 결합력 실패를 야기한다. 치질과의 결합력은 접착면의 성질에 영향을 받게 되는데 대부분의 연구들은 편평한 접착면상에서 이루어졌으며 와동내 와벽 위치에 따른 결합력 차이에 관한 연구는 미미한 실정이다. 이에 본 연구에서는 I 급 복합레진 수복시 단일 충전한 경우와 적층 충전한 경우에 있어서 와동의 치수벽과 측벽에서의 결합력 차이를 알아보고자 하였다. 발거된 20개의 건전한 제3 대구치를 대상으로 6 × 4 × 3 mm 크기의 박스 형태로 와동을 형성한 후 레진 충전방법과 와동벽에 따라 4개 군으로 분류하였다. 단일 충전하고 치수벽의 결합력을 측정한 A군, 단일 충전하고 측벽의 결합력을 측정한 B군, 적층 충전하고 치수벽의 결합력을 측정한 C군, 적층 충전하고 측벽의 결합력을 측정한 D군으로 설정하였다. 제조사의 지시에 따라 Clearfil SE bond^(Ⓡ) (Kuraray Corp., Osaka, Japan)로 치면 처리한 후 Filteck Z 250^(Ⓡ)(3M/ESPE., St. Paul, USA)을 사용하여 와동을 충전하였다. 적층 충전군의 경우 1.5 mm씩 두 번에 나누어 충전하고 각각 40초씩 중합하였다. 37℃의 증류수에서 24시간 보관 후 교합면쪽 법랑질을 제거하고 수복물의 근원심 폭의 절반되는 지점에서 협설 방향으로 치아를 잘랐다. 주수하에 고속 diamond saw를 사용하여 각 치아의 접착면에 수직으로 1 × 1 × 7 mm의 막대 형태의 시편을 만들었으며 만능시험기에 부착하고 1 mm/min의 속도로 미세인장 결합강도를 측정하였다. 2-way ANOVA test와 t-test를 이용하여 95% 유의수준으로 통계 분석한 결과는 다음과 같다. 1. 충전 방법의 경우, 적층 충전군이 단일 충전군보다 높은 평균값을 보였으나 통계적 유의성은 없었다. 2. 와동벽에 따른 결합력 차이의 경우, 치수벽 군이 측벽 군보다 결합력이 큰 것으로 나타났으나 유의성은 없었다. 본 연구 결과만을 토대로 볼 때 , 충전 방법과 와동벽의 두 가지 요소가 치질과의 결합력에 미치는 영향이 크지 않았다. Bond strength depends on characteristics of bonding surface and restorative technique. The majority of studies dealing with dentin bond strength were carried out on flat bonding surface, therefore, difference of bond strength between axial wall and pulpal wall is not clear yet. This study evaluated bonding difference between cavity walls in class I composite resin restoration with different filling techniques. Twenty extracted caries-free human third molars were used. Cavities were prepared in 6 × 4 × 3 mm box-type and divided into four groups according to filling technique and bonding surface: Group I; bulk filling - pulpal wall, Group II; bulk filling - axial wall, Group III; incremental filling - pulpal wall, Group IV ; incremental filling - axial wall. Cavities were filled with Filtek Z250^(Ⓡ) (3M/ESPE., USA) and Clearfill SE bond^(Ⓡ) (Kuraray, Japan). After 24 hour-storage in 37℃ water, the resin bonded teeth were sectioned bucco-lingualy at the center of cavity. Specimens were vertically sectioned into 1.0 × 1.0 mm thick serial sticks perpendicular to the bond surface using a low-speed diamond saw (Accutom 50, Struers, Copenhagen, Denmark) under water cooling. The trimmed specimens were then attached to the testing device and in turn, was placed in a universal testing machine (EZ test, Shimadzu Co., Kyoto, Japan) for micro-tensile testing at a cross-head speed of 1mm/min. The results obtained were statistically analyzed using 2-way ANOVA and t-test at a significance 1eve1 of 95%. The results were as follows: 1. There was no significant difference between bulk filling and incremental filling. 2. There was no significant difference between pulpal wall and axial wall, either. Within the limit of this study, it was concluded that microtensile bond strength was not affected by the filling technique and the site of cavity walls.

낙엽송 소경각재의 종접합 성능평가

이인환 ( In-hwan Lee ),박주현 ( Ju-hyun Pack ),송다빈 ( Da-bin Song ),홍순일 ( Soon-il Hong ) 한국목재공학회 2018 목재공학 Vol.46 No.1

In order to use glued built up timber beam as a structural member for post and beam construction, it must be possible to manufacture long-span lumber. In this study, the researchers conducted a performance evaluation for longitudinal bonding of lumber (cross-section 89 × 120 mm) made from larch. The specimens were prepared in six different forms using the longitudinal bonding method. The bonding strength of these specimens was tested through tensile strength tests and bending strength tests. The tensile strength test result of the longitudinally bonded parts was better than that of the double lap specimens. And, the tensile strength value of the scarf specimen was better than that of the hooked scarf specimen. The tensile strength of the GFRP (Glass Fiber Reinforced Plastic) rod insertion bonding specimen was 3.6 MPa, which was the highest. As for the bending strength test result of the longitudinally bonded part, the average MOR (modulus of rupture) of the specimen where a GFRP rod was inserted and bonded measured 29 MPa, while the specimens of other bonded parts showed a MOR no more than 11 MPa. Toughness destruction was observed in specimens where a GFRP rod was insertion-bonded. The rest of the specimens showed brittle destruction. The average MOR strength of the Rod + Lap specimen was 30.5 MPa, which was the highest among all longitudinally bonded specimens. The bending strength of the Rod + Lap specimens showed an effective strength that was 66% of that of the control group which were not longitudinally bonded.

콘크리트에 표면매입 보강된 FRP판의 전단키 및 연단거리 효과

서수연 한국구조물진단유지관리공학회 2016 한국구조물진단유지관리공학회 논문집 Vol.20 No.1

본 연구에서는 콘크리트에 표면매입된 FRP판의 부착거동에서, 전단키와 연단거리의 효과를 관찰하기 위한 부착시험을 실시하였 다. 실험에서의 주요변수는 전단키의 위치, 형태 그리고 연단길이이다. 규격 3.6 ㎜×16 ㎜의 FRP를 400 ㎜×200(300) ㎜×400 ㎜ 규격의 콘크리 트 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 떨어 질수록 전단강도가 상승하는 것으로 나타났으며, 전단키의 직경이 커질수록 내력이 저하되는 것으로 나타났다. 특히 전단키가 일정 이상의 규 격이 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. This paper presents a bond test to find the effect of shear key and edge length from the bonded FRP in near surface-mounted(NSM) retrofit using FRP plate. Main parameters in the test are the location and size of shear key and the edge length. For the test, 10 specimens were made by embedding FRP plate of 3.6 ㎜×16 ㎜ into 400 ㎜×200(300) ㎜×400 ㎜ concrete block and fixing it by using epoxy. Tensile load was applied to the FRP of the specimens until failure and was recorded at each load increase. In addition, the bond slip and elongation of FRP were measured during the test. From the test, it was found that the further the shear key located from the loading, the higher strength we could get. The bond strength inversely depended on the size of shear key. Especially, when the size of shear key was to be lagger than certain size, the bond strength decreased to very low value; even less than that of the case without shear key. The bond strength somewhat increased corresponding to the increase of edge length from the bonded end of FRP to loading in spite of same bond length. The bond-slip between FRP and concrete governed overall deformation in the bond test of NSM FRP so that the effect of excessive slip is necessary to be considered in the design.

Bond and durability investigation of basalt fiber and PEN fiber reinforced composites for concrete applications

최동욱,김영호,Batzaya Baasankuu,CHINZORIGT GOMBOSUREN 아시아콘크리트학회 2020 Journal of Asian Concrete Federation Vol.6 No.1

Bond and durability characteristics of basalt fiber reinforced polymer (BFRP) and polyethylene naphthalate (PEN) fiber/PEN FRP were investigated. Magnitude and distribution of the bond stress between BFRP/PEN FRP and concrete were investigated by double lap shear test. Four different types of durability test were performed: (1) Beam bond test following accelerated conditioning protocols by ACI 440.9R using plain concrete beams strengthened with BFRP or PEN FRP; (2) tensile test of PEN fiber/PEN FRP after immersion in 1N NaOH, 3% NaCl solutions, and water up to 6 months; (3) tensile test of PEN fiber/PEN FRP after immersion in 5% and 10% diluted solutions of HCl; and (4) exposure to natural outdoor environment. Bond test results indicated high bond stress developing over relatively short distance for BFRP that has high elastic modulus (EBF = 68.4 GPa) while relatively low bond stress developing over longer length for PEN FRP that has low elastic modulus (EPEN = 17.4 GPa). In the beam bond test, very good behavior was shown by PEN FRP after 4 month’s exposure to wet and alkaline conditions while moderate behavior was shown by BFRP. Overall, the performance of PEN fiber/FRP was satisfactory in all durability tests conducted in this study.

Bond stress between conventional reinforcement and steel fibre reinforced reactive powder concrete

Bae, B.I.,Choi, H.K.,Choi, C.S. Butterworth Scientific ; Elsevier Science Ltd 2016 Construction and Building Materials Vol.112 No.-

In this study, we investigated bond stress between steel-fibre-reinforced reactive powder concrete (SF-RPC) and conventional reinforcement to determine specific values for design bond stress. Test results were compared with previously suggested analysis methods. Tests were carried out using the direct pull-out test. The main variables are compressive strength of the concrete, concrete cover, and inclusion ratio of steel fibre. The increase rate of ultimate bond stress between SF-RPC and conventional reinforcement was decreased although the ultimate bond stress was increased with increasing compressive strength of the SF-RPC matrix. The effect of the concrete cover on ultimate bond stress and its increase rate was similar to that of the compressive strength of concrete. However, an even more significant change was observed with change in concrete cover. We also observed an effect of steel fibre inclusion. Inclusion of a 1% volume fraction of steel fibre increases the ultimate bond stress by two times the bond stress between the plain RPC matrix and conventional reinforcement. However, a 2% steel fibre volume fraction does not increase the ultimate bond stress significantly. In order to obtain safety for bond design of SF-RPC precast members, previously suggested analysis methods for ultimate bond stress and empirical equations for ultimate bond stress were evaluated. Most empirical ultimate bond stress equations cannot estimate the ultimate bond stress accurately. Analysis methods suggested by Tepfers can predict the ultimate bond stress more accurately than these empirical equations because the RPC matrix behaves as a linear elastic material until experiencing splitting failure.

Bond behaviour at concrete-concrete interface with quantitative roughness tooth

Ayinde, Olawale O.,Wu, Erjun,Zhou, Guangdong Techno-Press 2022 Advances in concrete construction Vol.13 No.3

The roughness of substrate concrete interfaces before new concrete placement has a major effect on the interface bond behaviour. However, there are challenges associated with the consistency of the final roughness interface prepared using conventional roughness preparation methods which influences the interface bond performance. In this study, five quantitative interface roughness textures with different roughness tooth angles, depths, and tooth distribution were created to ensure consistency of interface roughness and to evaluate the bond behaviour at a precast and new concrete interface using the splitting tensile test, slant shear test, and double-shear test. In addition, smooth interface specimens and two separate the pitting interface roughness were also utilized. Obtained results indicate that the quantitative roughness has a very limited effect on the interface tensile bond strength if no extra micro-roughness or bonding agent is added at the interface. The roughness method however causes enhanced shear bond strength at the interface. Increased tooth depth improved both the tensile and shear bond strength of the interfaces, while the tooth distribution mainly influenced the shear bond strength. Major failure modes of the test specimens include interface failure, splitting cracks, and sliding failure, and are influenced by the tooth depth and tooth distribution. Furthermore, the interface properties were obtained and presented while a comparison between the different testing methods, in terms of bond strength, was performed.

초음파 플립칩 접합 모듈의 위상최적화 설계 및 성능 실험

김지수,김종민,이수일,Kim, Ji Soo,Kim, Jong Min,Lee, Soo Il 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.6

Ultrasonic bonding is the novel packaging method for flip-chip with high yield and low-temperature bonding. The bonding module is a core part of the bonding machine, which can transfer the ultrasonic energy into the bonding spot. In this paper, we propose topology optimization technique which can make new design of boding modules due to the constraints on resonance frequency and mode shapes. The designed bonding module using topology optimization was fabricated in order to evaluate the bonding performance and reliable operation during the continuous bonding process. The actual production models based on the proposed design satisfied the target frequency range and ultrasonic power. The bonding test was performed using flip-chip with lead-free Sn-based bumps, the results confirmed that the bonding strength was sufficient with the designed bonding modules. Also the performance degradation of the bonding module was not observed after the 300-hour continuous process with bonding conditions.