• Computers and Concrete
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• v.15 no.4
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• pp.643-671
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• 2015

Chloride induced reinforcement corrosion is widely accepted to be the most frequent mechanism causing premature degradation of reinforced concrete members, whose economic and social consequences are growing up continuously. Prevention of these phenomena has a great importance in structural design, and modern Codes and Standards impose prescriptions concerning design details and concrete mix proportion for structures exposed to different external aggressive conditions, grouped in environmental classes. This paper focuses on reinforced concrete column section load carrying capacity degradation over time due to chloride induced steel pitting corrosion. The structural element is considered to be exposed to marine environment and the effects of corrosion are described by the time degradation of the axial-bending interaction diagram. Because chlorides ingress and consequent pitting corrosion propagation are both time-dependent mechanisms, the study adopts a time-variant predictive approach to evaluate residual strength of corroded reinforced concrete columns at different lifetimes. Corrosion initiation and propagation process is modelled by taking into account all the parameters, such as external environmental conditions, concrete mix proportion, concrete cover and so on, which influence the time evolution of the corrosion phenomenon and its effects on the residual strength of reinforced concrete columns sections.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.45-48
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• 2005

The purpose of this study is to investigate evaluation technique of damaged depth of concrete exposed at high temperature. In order to evaluate damaged depth of core picked at member under fire, the 12 specimens have been made with variables of concrete strength(20Mpa, 40Mpa, 60Mpa). Water absorption after heating has been measured and split tensile stress test was performed. The results show that the deeper of the depth from heating face, water absorption ratio is smaller and tensile failure stress is larger. Using this technique at damage evaluation of fired structure, We evaluate damaged depth of member under fire and determine the reasonable strengthening range.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.85-88
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• 2000

This paper is dealt with the ways of the improvement of the surface glossing of exposed concrete through the construction field test. The field applied in this test is located at Daechon, Chungnam province where the service training institute of Chongju university has been built. The flowing method is applied. According to the test results, as water to cement ratio, or slump increase after flowed, surface glossing tends to be improved. As for the effects of the forms typer, following orders, which is shown to be better surface glossing values, are given; Acryle > fancy wood forms > steel forms > plywood forms.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.259-266
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• 2003

Recently, the premature corrosion for reinforced concrete structure exposed to chloride bring about a serious problem in concrete structures. Specially, the concrete structures of sea coast are exposed much to chloride which make rapid corrosion. Thus, construction activities and maintenances for marine facilities are more demanded than those for land structures. The results of this study have been analysed to identify the extent of chloride content and incidence of carbonation for construction age. After measuring chloride content in concrete, it was conclued that about 90% of all tests on concrete samples exceed the acceptable maximum limit to risk of chloride-induced carbonation. The carbonation rate coffnient by age of train structures in the east eatimated 6. 55, 4.76 grater than 3. 727. In the basis of this result, it is necessary to maintenance for the important train facilities with the regular tests of chloride and carbonation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.589-594
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• 2007

This paper is shown new method for durability assesment and design have been noticed to be very valuable has been successfully applied to predict concrete structures. This paper provides that a new approach for predicting the corrosion durability of reinforced concrete structures exposed to chloride attack. In this method, the prediction can be updated successive1y by the Bayesian theory when additional data are available. The stochastic properties of model parameters are explicitly taken into account into the model the probability of the durability limit is determined from the samples obtained from the Latin hypercube sampling technique. The new method may be very useful in designing important concrete structures and help to predict the remaining service life of existing concrete structures under chloride attack environments.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.151-152
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• 2018

The purpose of this study was to find out harmful effects of concrete, an essential material in modern architecture, on the human body. Based on the results from animal testing, we can consider the effects on the human body. The results of this study were as follows; Experimental Mouses in concrete have low body temperature due to cold radiation and more aggressive due to cold stress. Therefore, Cold radiation, a property of concrete, makes body temperature lower and affect the body's immune function.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.16-17
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• 2018

A few years ago, the rapid degradation of domestic air quality has led to the efforts of exhaust gas policy and fine dust mask, but it is not a fundamental measure. In Korea, photocatalyst will be applied to residential and multi-use facilites to purify indoor and outdoor air. Also, in this study, it is tried to produce exposed concrete that is aesthetically pleasing as well as air purification of indoor by combining with light transparent concrete according to the increasing interest in human indoor living environment. For this purpose, we have developed a block formwork for photocatalysis light transparent concrete and established a suitable manufacturing method for on-site construction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.3-4
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• 2014

There is high probability of steel corrosion on the reinforced concrete exposed to marine environment by penetration of chloride ion. When making concrete structure with slag as admixture in marine environment, salt damage can be prevented. Therefore, this paper presents experimental results of steel corrosion resistance of slag concrete considering marine environment through half-cell potential method which is one of the nondestructive test. As a result of half-cell potential experiment, it was assumed that every specimen exposed to marine environment was not corroded, and as a result of destroying specimens, it was confirmed that there was no corrosion in specimens.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.585-593
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• 2007

This paper presents a model for durability evaluation of concrete structures exposed to marine environment, considering mainly a build-up of surface chloride $(C_s)$ as well as diffusion coefficient (D) and chloride threshold level $(C_{lim})$. In this study, time dependency of $C_s$ and D were extensively studied for more accurate evaluation of service life of concrete structures. An analytical solution to the Fick's second law was presented for prediction of chloride ingress for time varying $C_s$. For the time varying $C_s$, a refined model using a logarithm function for time dependent $C_s$ was proposed by the regression analysis, and averaging integrated values of the D with time over exposed duration were calculated and then used for prediction of the chloride ingress to consider time dependency of D. Durability design was also carried out for railway concrete structures exposed to marine environment to ensure 100 years of service life by using the proposed models along with the standard specification on durability in Korea. The proposed model was verified by the so-called performance-based durability design, which is widely used in Europe. Results show that the standard specification underestimates durability performances of concrete structures exposed to marine environment, so the cover depth design using current durability evaluation in the standard specifications is very much conservative. Therefore, it is found that utilizing proposed models considering time dependent characteristics of $C_s$ and D can evaluate service lift of concrete structures in marine environment more accurately.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.22-33
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• 2015

Chloride ions in RC (Reinforced Concrete) structures can cause very severe corrosion in reinforcement steel. It is generally informed that chloride penetration can be considerably accelerated by enlarged chloride diffusion due to cracks. These cracks play a role in main routes through which chloride ions penetrate into the concrete, and also lead to steel corrosion in RC structures exposed to chloride attack, such as port and ocean structures. In this paper, field survey including evaluation of crack and chloride concentration distribution in concrete is performed to investigate an effect of crack on chloride diffusion. The service life of cracked concrete exposed to the marine environmental condition is estimated considering the crack effect on chloride diffusion. For this purpose, diffusion coefficients in cracked concrete are obtained based on the field survey. Using the relationship between diffusion coefficients in the cracked concrete and the crack widths, service life of the cracked concrete is predicted in a probabilistic framework. A bimodal distribution with two peaks, consisting of a weighted sum of two normal distributions is introduced to describe chloride diffusion of the concrete wharf with crack.