김민욱
(Coastal Development and Ocean Energy Research Center, Korea Institute of Ocean Science and Technology)
,
정연웅
(Department of Civil and Environmental Engineering, Seoul National University)
,
강성훈
(Department of Civil and Environmental Engineering, Seoul National University)
,
문주혁
(Department of Civil and Environmental Engineering, Seoul National University)
,
이진학
(Coastal Development and Ocean Energy Research Center, Korea Institute of Ocean Science and Technology)
본 연구에서는 해양 항만 콘크리트 구조물의 보수작업을 위한 수중코팅제의 부착 특성을 조사하기 위하여 실험적 연구를 수행하였다. 고려된 실험변수는 코팅제의 종류, 코팅대상 모재의 표면 거칠기, 도포 작업환경(육상 혹은 수중)으로 부착 강도는 Pull-off 방식으로 측정하였다. 코팅제의 부착 강도는 각 수중코팅제의 도포 작업 완료 24시간 후에 ASTM C1583 규정에 따라 측정하였다. 또한, 콘크리트 모재와 코팅제 간의 부착파괴 거동(코팅제, 계면, 콘크리트 모재)을 육안으로 관찰하였으며 측정된 부착 강도 수치에 근거하여 각 실험요인의 비교분석을 수행하였다. 실험결과, 수중에서 도포한 코팅제의 부착 강도가 육상의 경우에 비해 감소하는 경향을 보였으며 수중환경에서는 부착 강도에 미치는 모재 표면 거칠기의 영향이 육상의 경우에 비하여 미비하였다. 마지막으로 수중코팅제의 선정, 사용 시에 유의할 점에 대하여 설명하였다.
본 연구에서는 해양 항만 콘크리트 구조물의 보수작업을 위한 수중코팅제의 부착 특성을 조사하기 위하여 실험적 연구를 수행하였다. 고려된 실험변수는 코팅제의 종류, 코팅대상 모재의 표면 거칠기, 도포 작업환경(육상 혹은 수중)으로 부착 강도는 Pull-off 방식으로 측정하였다. 코팅제의 부착 강도는 각 수중코팅제의 도포 작업 완료 24시간 후에 ASTM C1583 규정에 따라 측정하였다. 또한, 콘크리트 모재와 코팅제 간의 부착파괴 거동(코팅제, 계면, 콘크리트 모재)을 육안으로 관찰하였으며 측정된 부착 강도 수치에 근거하여 각 실험요인의 비교분석을 수행하였다. 실험결과, 수중에서 도포한 코팅제의 부착 강도가 육상의 경우에 비해 감소하는 경향을 보였으며 수중환경에서는 부착 강도에 미치는 모재 표면 거칠기의 영향이 육상의 경우에 비하여 미비하였다. 마지막으로 수중코팅제의 선정, 사용 시에 유의할 점에 대하여 설명하였다.
In this study, we investigated the tensile bond characteristics of underwater coating materials, in order to obtain useful information in support of repair work for marine and coastal concrete structures. Test variables included type of underwater coating, surface conditions of the concrete substrat...
In this study, we investigated the tensile bond characteristics of underwater coating materials, in order to obtain useful information in support of repair work for marine and coastal concrete structures. Test variables included type of underwater coating, surface conditions of the concrete substrate, and environmental conditions. Pull-off tensile bond strength was measured at 24 h after applying underwater coatings to concrete substrates, in compliance with the procedures specified in ASTM C1583. Failure modes (coating, interface, and parent concrete) for each coating were identified through visual inspection, and comparisons were made based on measured bond strength. The tensile bond strength decreased underwater compared to that under dry conditions, while no significant effect of surface roughness on the measured bond strength was observed in underwater tests. Key aspects that need to be considered regarding selection and use of underwater coating materials for marine and coastal concrete structures were discussed.
In this study, we investigated the tensile bond characteristics of underwater coating materials, in order to obtain useful information in support of repair work for marine and coastal concrete structures. Test variables included type of underwater coating, surface conditions of the concrete substrate, and environmental conditions. Pull-off tensile bond strength was measured at 24 h after applying underwater coatings to concrete substrates, in compliance with the procedures specified in ASTM C1583. Failure modes (coating, interface, and parent concrete) for each coating were identified through visual inspection, and comparisons were made based on measured bond strength. The tensile bond strength decreased underwater compared to that under dry conditions, while no significant effect of surface roughness on the measured bond strength was observed in underwater tests. Key aspects that need to be considered regarding selection and use of underwater coating materials for marine and coastal concrete structures were discussed.
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가설 설정
4. Concrete casting and surface preparation: (a) concrete mixing and casting for parent concrete; (b) water-jetting to create a rough surface.
제안 방법
In the research reported here, an experimental program was set up to investigate the effect of variables such as coating type, substrate surface roughness, and environmental conditions, on the performance of underwater coatings, and some suggestions have been made to improve repair work outcomes for marine and coastal concrete structures. Six commercially available coating materials were selected, and comprehensive experimental campaigns were conducted to understand the effects of the test variables on tensile bond strength.
Coating C had the lowest bond strength, but this might be due to different laboratory conditions or human error introduced during the test and/or measurement procedures. In this study, the bond strength measurement was conducted shortly after applying each coating, to prevent concrete failure that might be caused by the low tensile strength of the concrete. These issues and results indicate that further experimental studies are required, to investigate both longer term bond performance, and any effect of underwater coating materials on concrete durability.
In the research reported here, an experimental program was set up to investigate the effect of variables such as coating type, substrate surface roughness, and environmental conditions, on the performance of underwater coatings, and some suggestions have been made to improve repair work outcomes for marine and coastal concrete structures. Six commercially available coating materials were selected, and comprehensive experimental campaigns were conducted to understand the effects of the test variables on tensile bond strength. Each coating was directly applied to prepared concrete specimens in both dry and wet conditions.
Six different, commercially available, epoxy resin coatings, identified in this paper as A, B, C, D, E, and F, were selected for examination, based on underwater applicability and pretest results. Material property information received from manufacturers (bond strength, density, and pot life) has been summarized in Table 1.
, 2012). The authors proposed the reapplication of coating prior to its deterioration, to extend its performance. It should be noted that most previous studies focused on conventional coatings for onshore structures, rather than underwater coatings for offshore structures.
대상 데이터
(a), the size of parent concrete specimens was 600 × 500 × 100 mm3, and 10 specimens were prepared.
이론/모형
5. Tensile bond strength measurement according to ASTM C1583 (Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method)).
성능/효과
(2) Tensile bond strength generally decreased underwater, compared to that achieved in dry conditions.
Parent concrete compressive and splitting tensile strengths were measured, using ASTM C39 and ASTM C496, respectively. The water to cement ratio (w/c) adopted in this study was 0.37, and compressive and tensile strength values after 28 days were 41.3 MPa, and 3.0 MPa, respectively. The concrete surface to be coated was water-jetted after one day of concrete casting, as shown in Fig.
후속연구
In this study, tensile bond strengths were measured just 24 h after application, and further experimentation might help to clarify long term bond performance in the case of underwater coatings applied to actual submerged concrete structures. Based on our experimental results and comparison with information received from manufacturers, some suggestions have been made to improve the success of underwater coatings on marine and coastal concrete structures.
In addition to temperature, appropriate coating material, coating equipment, and repeated pretesting are also important for the successful completion of underwater repair work on marine and coastal concrete structures. It should be noted that most previous studies were carried out under controlled conditions in the laboratory, thus, further experimental study in the field might be necessary.
In other words, appropriate repair procedures and suitable coating equipment must be prepared prior to repair work starting, to reduce both material loss underwater, and total repair cost. Lastly, this research work is part of a research project that is still underway, and research into development of novel underwater coating equipment, developed to improve coating performance, and also into the effects of some equipment on bond performance, will be investigated further and reported in the future.
In this study, however, adhesive failures underwater were only observed and this might be related to the time of measurement. Therefore, further experimental study is necessary to investigate the long-term performance.
In this study, the bond strength measurement was conducted shortly after applying each coating, to prevent concrete failure that might be caused by the low tensile strength of the concrete. These issues and results indicate that further experimental studies are required, to investigate both longer term bond performance, and any effect of underwater coating materials on concrete durability.
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