• Computers and Concrete
• /
• v.15 no.4
• /
• pp.589-606
• /
• 2015

It is well-documented that the major deterioration of coastal RC structures is chloride-induced corrosion. Therefore, regional investigations are necessary for durability based design and evaluation of the proposed service life prdiction models. In this paper, four reinforced concrete jetties exposed to severe marine environment were monitored to assess the long term chloride penetration at 6 months to 96 months. Also, some accelerated durability tests were performed on standard samples in laboratory. As a result, two time-dependent equations are proposed for basic parameters of chloride diffusion into concrete and then the corrosion initiation time is estimated by a developed probabilistic service life model Also, two famous service life prediction models are compared using chloride profiles obtained from structures after about 40 years in the tidal exposure conditions. The results confirm that the influence of concrete quality on diffusion coefficients is related to the concrete pore structure and the time dependence is due to chemical reactions of sea water ions with hydration products which lead a reduction in pore structure. Also, proper attention to the durability properties of concrete may extend the service life of marine structures greater than fifty years, even in harsh environments.

• Structural Engineering and Mechanics
• /
• v.85 no.2
• /
• pp.197-206
• /
• 2023

The deterioration caused by chloride penetration and carbonation plays a significant role in a concrete structure in a marine environment. The chloride corrosion in some marine concrete structures is invisible but can be dangerous in a sudden collapse. Therefore, as a novelty, this research investigates the ability of a non-destructive damage detection method named the Power Spectral Density (PSD) to diagnose damages caused only by chloride ions in concrete structures. Furthermore, the accuracy of this method in estimating the amount of annual damage caused by chloride in various parts and positions exposed to seawater was investigated. For this purpose, the RC Arosa bridge in Spain, which connects the island to the mainland via seawater, was numerically modeled and analyzed. As the first step, each element's bridge position was calculated, along with the chloride corrosion percentage in the reinforcements. The next step predicted the existence, location, and timing of damage to the entire concrete part of the bridge based on the amount of rebar corrosion each year. The PSD method was used to monitor the annual loss of reinforcement cross-section area, changes in dynamic characteristics such as stiffness and mass, and each year of the bridge structure's life using sensitivity equations and the linear least squares algorithm. This study showed that using different approaches to the PSD method based on rebar chloride corrosion and assuming 10% errors in software analysis can help predict the location and almost exact amount of damage zones over time.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.549-552
• /
• 2008

Corrosion of reinforcing steel is prohibited under normal condition by the alkalinity of the pore water in the concrete. But the probability of steel corrosion becomes higher when the chloride ions are introduced into the concrete. Steel corrosion is decisive factor for the determination of service life of the marine concrete structures because chloride ions are abundant in the sea. In this paper, chloride penetration analysis for the rectangular pier in the marine environment is performed considering the diffusion movement of chlorides. Result reveals that the chloride concentration in the corner bar is higher than that of in the side bar with rectangular pier. Also the time to the specified accumulation of chloride in the corner bar is much shorter than that in the side bar. Because the corrosion initiation time of corner bar is half as much as that of side bar, service life for the rectangular pier in marine environment should be determined with respect to the coner bar.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.694-699
• /
• 2000

Recently, the degradation of reinforced concrete structures due to physical and chemical attack has been a major issue in construction engineering. One of the main causes of degradation of concrete structures can be ascribed to chloride-induced corrosion, i.e., the rapid penetration of chloride ions into concrete. To estimate durability of reinforced concrete structures exposed to marine environment, many different kinds of accelerated tests to evaluate the concrete diffusivity were proposed. In this study, present test methods are reviewed and a proper test method for concrete is selected. The diffusion coefficients of concrete with corrosion inhibitor are measured using the proposed method, and then, measured values are compared to those of concrete without corrosion inhibitor. It is found from experimental results that diffusion coefficient re decreased with curing ages.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05b
• /
• pp.249-252
• /
• 2005

Chloride ingress is a common cause of deterioration of reinforced concrete structures. Modeling the chloride ingress is an important basis for designing reinforced concrete structures and for assessing the reliability of an existing structure. The modelling is also needed for predicting the deterioration of a reinforced structure. This paper presents an approach for the probabilistic modeling of the chloride-induced corrosion of reinforcement steel in concrete structures that takes into account the uncertainties in the physical models. The parameters of the models are modeled as random variables and the distribution of the corrosion time and probability of corrosion are determined by using Monte Carlo simulation. The predictions of the proposed model is very effective to do the decision-making about initiation time and deterioration degree.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.5
• /
• pp.67-75
• /
• 1993

This study was performed for the purpose of estimating steel corrosion and of considering a countermeasure to prevent steel corrosion of concrete structures under the environment of seawater or using seasand. The corrosion of steel was accelerated in artificial seawater with seven kinds of specimen which was embedded steel in mortar. To assume the degree of steel corrosion, soluble chloride content in mortar, $Cl^-$ binding capacity, half cell potential and corrosion area ratio were measured. The results show that corrosion area ratio was correlative with half cell potential and soluble chloride content in mortar.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.413-416
• /
• 2008

Reinforcement corrosion is generally prohibited under normal condition by the alkalinity of the pore water in the concrete. However, concrete structures in marine environment are subjected to chloride attack due to the high salinity of the sea water. Thus the probability of steel corrosion becomes higher when the chloride ions are introduced into the concrete. Steel corrosion is a decisive factor for the determination of service life of the marine concrete structure because chloride ions are abundant in the sea, and piers are the typical construction elements in concrete structures in marine environment. Hence, it is of great importance to evaluate the service life of the piers. In this paper, chloride penetration analysis for the rectangular pier in the marine environment is performed considering the diffusion and convection movement of chlorides. Result reveals that the service life of the reinforcement with drying-wetting cycles is much shorter than that of the reinforcement with saturated condition. This may be due to the fact that moisture movement is much faster that chloride diffusion.

• Advances in concrete construction
• /
• v.9 no.2
• /
• pp.149-159
• /
• 2020

The present work proposes new engineering models for determining corrosion initiation time in concrete reinforcing steels in marine environment. The models are based on Fick's second law that is commonly used for chloride diffusion. The latter is based on deterministic analyses involving the most influencing parameters such as distance of the concrete structure from the seaside, depth of steel concrete cover, ambient temperature, relative humidity and the water-cement ratio. However, a realistic corrosion initiation time cannot be estimated because of the uncertainties associated to the different parameters of the models. Therefore a reliability approach using FORM/SORM method has been applied to develop the proposed engineering models integrating a limit state function and a reliability index β. As a result, the corrosion initiation time is expressed by new exponential engineering models where the uncertainties are associated to the model parameters. The main emerging result is a realistic decision tool for corrosion planning inspection.

• Corrosion Science and Technology
• /
• v.21 no.3
• /
• pp.184-199
• /
• 2022

Steel was exposed in an atmospheric environment, and atmospheric environmental factors that include chloride, humidity, SO₂, NO₂ etc. induced the corrosion of steel. Corrosivity categories classified by SO₂ and chloride deposition rate were low, but those classified by TOW were high in the Korean Peninsula, and on these environmental categories, the corrosivity of atmospheres classified by corrosion rate in carbon steel was low medium, C2-C3, and medium, C3 for zinc, copper, and aluminum. This work performed the outdoor exposure test for 10 years at 14 areas in Korea and calculated the atmospheric corrosion rate of carbon steel. The atmospheric corrosion behavior of carbon steel is discussed based on the various corrosion factors. When the corrosion product forms on carbon steel by atmospheric corrosion, cracks may also be formed, and through these cracks, the environmental factors can penetrate into the interior of the product, detach some of the corrosion products and finally corrode locally. Thus, the maximum corrosion rate was about 7.3 times greater than the average corrosion rate. The color difference and glossiness of carbon steel by the 10 year-outdoor exposure tests are discussed based on the corrosion rate and the environmental factors.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.10
• /
• pp.883-887
• /
• 2016

This study aims to evaluate the corrosion behavior of a newly developed high-strength steel in marine environments. Metals used in seawater are easily deteriorated because of the presence of corrosive species such as chloride ions in it. Seawater causes much higher corrosion than fresh water. Thus, the corrosion of steel in marine environment has been recognized as a crucial problem in designing structures which cannot be cathodically protected. In this study, the corrosion resistance of a newly developed high-strength steel was evaluated. Four different specimens were tested to confirm the corrosion resistance. The exposure corrosion test was carried out by exposing the specimens to different marine environments such as atmospheric, tidal, splash, and submerged zones for two years. The specimens taken out from each location were cleaned ultrasonically and chemically prior to the evaluation of their corrosion resistance by the weight loss method. Finally, the pitting depth of the specimens was also measured to evaluate their pitting corrosion. The conditions used for the corrosion test were similar to the environmental conditions. The corrosion test results revealed that the corrosion rate and pitting corrosion of the newly developed high-strength steel was lower than that of the other carbon steels.