• Journal of Advanced Marine Engineering and Technology
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• 제19권3호
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• pp.62-69
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• 1995

In order to investigate the effect of TiN coating on corrosion fatigue behavior of metal, the rotary bending corrosion fatigue tests were carried out in 3% NaCl solution by using the round bar specimens of high-speed steel, SKH-9, coated with TiN by PVD method. From the experimental results, fatigue strength of TiN coating steel in air was obvious improvement as compared with that of the substrate because of the restriction of dislocation movement in near surface of the substrate by hard thin film. In 3% NaCl solution, corrosion fatigue life of TiN coating specimen in high stress level was improvement same as in air. But in low stress level, corrosion fatigue life of TiN coating one was equivalent to that without coating, due to much crack initiated from corrosion pits formed at the substrate by failure of coating layer.

• 비파괴검사학회지
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• 제31권1호
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• pp.24-31
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• 2011

콘크리트 벽체 구조물에 매입된 철근의 정량적인 부식률을 측정하기 위하여 자연전위 측정법과 적외선 열화상법을 이용하였다. 벽체 실험체는 부식률(0, 1, 3, 5, 7%)과 피복 두께(30 mm, 40 mm), 그리고 철근 배근 간격에 변수를 주어 콘크리트 표면에서 저항 및 전류를 측정하고 온도를 측정하였으며, 콘크리트 표면 상태에서 얻은 결과를 분석하여 다음과 같은 결론을 얻었다. 전류밀도 분포는 부식률이 증가할수록 그값이 증가하였으며 피복 두께가 클수록 분포도가 넓게 나타났다. 적외선 촬영으로 얻어진 열화상 정보는 서로 다른 부식률과 피복 두께에서는 현저한 차이를 보였으며 주변 온도 및 철근 배근 간격에 대해서는 그 영향이 미비하게 나타났다. 제시된 부식 모델을 통해서 콘크리트 표면의 전류나 온도를 측정하여 내부에 매입되어 있는 철근의 부식률을 정량적으로 측정할 수 있는 것으로 나타났다.

• 콘크리트학회논문집
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• 제17권4호
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• pp.663-670
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• 2005

The present study concerns the influence of binder type on the chloride-induced corrosion being accompanied by the chloride threshold level (CTL), chloride transport and as their results the corrosion-free lift. Two levels of cement content, $30\%$ PFA and $65\%$ GGBS concrete were employed. It was found that the most dominant factor to the CTL is the entrapped air void content at the steel-concrete interface, irrespective of the chloride binding capacity, binder type and acid neutralisation capacity of cement matrix. The CTL for lower interfacial air void contents was significantly increased up to $1.52\%$ by weight of cement, whereas a same mix produced $0.35\%$ for a higher level of voids. Because of a remarkable reduction in the diffusion fur GGBS concrete, its time to corrosion ranges from 255 to 1,250 days, while the corrosion-free life for control varies from 20 to 199 days sand for $30\%$ PFA concrete from 200 to 331 days.

• Computers and Concrete
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• 제25권5호
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• pp.447-460
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• 2020

This paper deals with the characteristics of reinforcement corrosion in concrete beams under the influence of sustained loads. The evolution and distribution laws of the reinforcement corrosion were measured periodically over time. The results show that sustained load exhibits a pronounced exacerbating effect on the reinforcement corrosion, and enlarges the nonuniformity level of corrosion as the load level increases. Accompanied with the continuous formation of the rust, the corrosion rate was also observed to be highly nonlinear and time-dependent. Moreover, to visually and quantitatively analyze the distribution of reinforcement corrosion, the 3D scanning technology combined with the probability statistics analysis was adopted, and the observed nonuniformity can be well described by the Gumbel distribution. Finally, an approach based on the three-phase spherical model was proposed to estimate the reinforcement corrosion, taking account of the effects of sustained load on the changes of concrete porosity and oxygen diffusivity.

• 콘크리트학회논문집
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• 제11권3호
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• pp.171-179
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• 1999

The present research investigated the interaction among loading level, corrosion rate and flexural deflection of reinforced concrete beams. 10cm$\times$15cm$\times$110cm reinforced concrete beams were prepared and subjected to different levels of flexural loading, including 0%, 45% and 75% of the ultimate load. The beams with either a pre-load or a sustained load were also exposed to a laboratory environment with ponding and wetting/drying cycling at room temperature. Half cell potential and galvanized current measurements were taken to monitor corrosion process of reinforcing steel. After corrosion initiation, external current was applied to some of the beams to accelerate corrosion propagation. The beam deflections were recorded during the entire tests. The results indicate that loading level has significant effect on corrosion rate. The beams under a sustained load had much higher corrosion rate than the pre-loaded and then unloaded beams. Significant corrosion may result in an increase in beam deflection and affect serviceability of the structure. The present research may provide an insight into structural condition evaluation and service life predictions of reinforced concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.281-286
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• 1997

Recent construction activities and maintenance of marine facilities have been accelerating to keep up with rapid economic growth in Korea. Marine concrete structures are exposed to salts an chloride from ocean environments. The corrosion of reinforcement steel caused by chloride-penetration into concrete may severely effect the durability of concrete structures. The objective of this research is to develop a durable concrete by investigating the corrosion resistance of various corrosion protection systems utilizing different water/cement ratio, silica fumes, corrosion inhibitors and etc. A tow-year verification test on various corrosion protection systems has been doing in the laboratory and at the seaside. Corrosion investigations on reinforcement steel are now under progress for more than 180 concrete specimen. Corrosion-related measurements include macrocell corrosion current, instant-off voltage between corroding and noncorroding reinforcement, chloride contents, the corroded surface areas on the reinforcement steel, and etc. A low level of corrosion is investigated on reinforcement steels in concrete specimen made with corrosion inhibitors or applied aqueous impregnating corrosion inhibitors into their surface, even though high chloride contents of concrete specimen.

• 비파괴검사학회지
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• 제27권2호
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• pp.142-147
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• 2007

콘크리트에 매입된 철근의 정량적인 부식률을 측정하기 위해 적외선 열화상법을 이용하였다. 적외선 촬영 실험에서는 부식률(0, 1, 3, 5, 7, 10%)과 대기온도(16, 21, 25, $28^{\circ}C$), 피복두께(10 mm, 20 mm, 30 mm)에 변수를 주어 콘크리트 표면온도를 측정하였으며, 콘크리트 표면온도의 초기 온도상승률에 대해서 측정결과를 분석하여 다음과 같은 결론을 얻었다. 적외선 촬영으로 얻어진 열화상 정보는 서로 다른 부식률과 피복두께에서는 현저한 차이를 보였으나 대기온도에 대해서는 그 영향이 미비하게 나타났다. 철근의 부식률에 따른 열 발생량이 콘크리트 표면온도에 부식률에 비례하여 열을 발생시킴으로써 철근의 부식률을 정량적으로 평가할 수 있는 분석기법을 연구하였다.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.43-52
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• 2016

The degradation of the load-bearing capacity of reinforced concrete beams due to corrosion has a profoundly negative impact on the structural safety and integrity of a structure. The literature is limited with regard to models of bond characteristics that relate to the reinforcement corrosion percentage. In this study, uniaxial tensile tests were conducted on specimens with irregular corrosion of their reinforced concrete. The development of cracks in the corroded area was found to be dependent on the level of corrosion, and transverse cracks developed due to tensile loading. Based on this crack development, the average stress versus deformation in the rebar and concrete could be determined experimentally and numerically. The results, determined via finite element analysis, were calibrated using the experimental results. In addition, bond elements for reinforced concrete with corrosion are proposed in this paper along with a relationship between the shear stiffness and corrosion level of rebar.

• Corrosion Science and Technology
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• 제22권1호
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• pp.55-63
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• 2023

The aim of this study was to propose a multiple linear regression (MLR) equation to predict ultimate tensile strength (UTS) of 316L stainless steel with unspecified pit corrosion. Tensile specimens with pit corrosion were prepared using a potentiostatic acceleration test method. Pit corrosion was characterized by measuring ten factors using a confocal laser microscope. Data were collected from 22 tensile tests. At 85% confidence level, total pit volume, maximum pit depth, mean ratio of surface area, and mean area were significant factors showing linear relationships with UTS. The MLR equation using these three significant factors at a 85% confidence level showed considerable prediction performance for UTS. Determination coefficient (R²) was 0.903 with training and test data sets. The yield strength ratio of 316L stainless steel was found to be around 0.85. All specimens with a pit corrosion presented a yield ratio of approximately 0.85 with R² of 0.998. Therefore, pit corrosion did not affect the yield ratio.

• 한국구조물진단유지관리공학회 논문집
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• 제21권3호
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• pp.19-26
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• 2017

콘크리트는 다공성 건설재료이며, 매립된 철근의 부식은 내구성 및 안전성에 큰 영향을 미친다. 본 연구는 비파괴 검사인 반전위측정값과 생성된 부식량과의 상관성을 피복두께, 물-시멘트비를 고려하여 도출하는 것이다. 이를 위해, 3가지 수준의 물-시멘트비와 4가지 수준의 피복두께를 가진 시멘트 모르타르 시편이 제조되었으며, 3가지 수준의 촉진부식기간을 고려하여 부식량 및 반전위를 측정하였다. 습윤상태에서는 반전위가 크게 증가하였으며, 부식량과 촉진기간은 선형적인 관계를 가지고 있었다. 부식량이 증가할수록, 피복두께가 감소할수록, 물-시멘트비가 증가할수록 반전위는 증가하였다. 전체의 반전위 측정값을 부식량과 비교할 경우 0.67의 낮은 결정계수를 가지고 있었으나 부식량(촉진기간)을 고려하여 3가지 수준을 고려할 경우 0.90이상의 높은 결정계수를 가지고 있었다. 실내조건과 같이 온도가 일정하고 포화상태일 경우, 측정된 반전위는 부식량과 선형적인 상관성을 가지고 있었으며, 피복두께, 물-시멘트비, 철근직경, HCP의 측정범위를 알 수 있다면, 매립된 철근의 부식량을 예측할 수 있다고 판단된다.