• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.902-912
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• 2003

The most common deteriorating processes of concrete structures are carbonation and chloride ion ingress. Many concrete structures have been suffered from chloride ions diffusion or carbonation induced reinforcement corrosion damage and many studies have been done on it. However, those studies were confined mostly to the single deterioration of carbonation or chloride attack only, although actual environment is rather of combined conditions. In case of many in-situ concrete structures, deterioration happened more for the case of combined attack than the single case of carbonation or chloride attack. In this paper, chloride profiles of carbonated concrete is predicted by considering two layer composite model, which is based on Fick's 2nd law. From the experimental result on combined deterioration of chloride and carbonation, it was examined that high chloride concentration was built up to 3∼5 mm over depth from carbonation depth. The analytical modeling of chloride diffusion was suggested to depict the relative influence of the carbonation depth. The diffusion coefficients of carbonation concrete and uncarbonated concrete with elapsed time were considered in this modeling.

• Computers and Concrete
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• v.10 no.5
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• pp.523-539
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• 2012

Silica fume has long been used as a mineral admixture to improve the durability and produce high strength and high performance concrete. And in marine and coastal environments, penetration of chloride ions is one of the main mechanisms causing concrete reinforcement corrosion. In this paper, we proposed a numerical procedure to predict the chloride diffusion in a hydrating silica fume blended concrete. This numerical procedure includes two parts: a hydration model and a chloride diffusion model. The hydration model starts with mix proportions of silica fume blended concrete and considers Portland cement hydration and silica fume reaction respectively. By using the hydration model, the evolution of properties of silica fume blended concrete is predicted as a function of curing age and these properties are adopted as input parameters for the chloride penetration model. Furthermore, based on the modeling of physicochemical processes of diffusion of chloride ion into concrete, the chloride distribution in silica fume blended concrete is evaluated. The prediction results agree well with experiment results of chloride ion concentrations in the hydrating concrete incorporating silica fume.

• Computers and Concrete
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• v.11 no.4
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• pp.305-316
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• 2013

This paper aims to study the effect of measurement methods and cracking on chloride transport of concrete materials. Three kinds of measurement methods were carried out, including immersion test, rapid migration test and steady-state migration test. All of these measurements of chloride transport show that chloride ion diffusion coefficient decreased with the reduction of water to cement ratio. Results of the immersion test were less than that of rapid migration test and steady-state migration test. For the specimen of lower water to cement ratio, the external electrical field has little effect on chloride binding relatively. Compared with the results obtained by these different measurement methods, the lower water to cement ratio may cause smaller differences among these different methods. The external voltage can reduce chloride binding of concrete, and the higher electrical field made a strong impact on the chloride binding. Considering the effect of high voltage on the specimen, results indicate that results based on the steady-state migration test should be more reasonable. For cracked concrete, cracking can accelerate the chloride ion diffusion.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.34-39
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• 2014

The purpose of this experimental research is to evaluate the resistance of reinforcement corrosion and chloride ion penetration of high volume fly ash (HVFA) concrete. For this purpose, concrete test specimens were made for various strength level and replacement ratio of fly ash, and then compressive strength and diffusion coefficient for chloride ion of them were measured for 28, 91 and 182 days, respectively. Also, corrosion monitoring by half cell potential method was carried out for the made lollypop concrete test specimens to detect the time of corrosion initiation for reinforcement in concrete. As a result, it was observed from the test results that compressive strength of HVFA concrete was decreased with increasing replacement ratio of fly ash but long-term resistance against reinforcement corrosion and chloride ion penetration of that was increased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.160-168
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• 2010

Recently, there are a lot of researches related to the high-fluidity concrete (HFC) with field applications. However, most applications and studies are with concretes with high strength level so there are little studies about durability evaluations such as chloride ion penetration properties with normal strength concrete. Therefore, to evaluate the durability of HFC with normal strength level, this study performed the chloride ion penetration test and observed the micro pore distribution with normal strength HFC which contains limestone powder. Experimental results showed that most micro-pores have diameters between 0.005 to 0.05 ${\mu}m$ with HFCs using limestone powder and the average diameter becomes larger with the increase of limestone powder content. Also, it was shown that, with the increase of the limestone powder content, penetration depth and diffusion coefficient of chloride ion increased and diffusion coefficient had good relationships with compressive strength and average pore diameter with the coefficient of determination over 0.90.

• KSBB Journal
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• v.13 no.4
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• pp.404-410
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• 1998

Three types of adsorbents were developed by immobilizing synthetic zeolite, Philipsite-Gismonine, in alginate, cellulose acetate and dialysis membrane for the in situ removal of ammonium ion which inhibits growth and productivity of animal cells such as CHO cells producing tPA. Ammonium ion removal efficiency and cell growth promoting effect with various immobilized adsorbents were evaluated and the membrane type was selected as an optimal immobilized adsorbent. The experiments were then simulated by adding 8mM ammonium chloride and immobilized adsorbent in order to validate the removal effect under high density cell cultures. The results showed increase in maximum cell density by three times, in cell viability, and in tPA productivity by 40%. And it was found that the promoting effects were more significant in case of high ammonium ion concentration system. It was also found that the optimum addition time for immobilized adsorbents was 48 hr in the absence of ammonium chloride addition and 72 hr in the presence of ammonium chloride addition.

• Architectural research
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• v.7 no.1
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• pp.49-54
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• 2005

Conventional studies have focused on the reduction in the water-cement ratio, the use of various admixtures, etc., to ensure the durability of reinforced concrete structures against such deterioration factors as carbonation and chloride attack. However, improvement in the concrete quality alone is not considered sufficient or realistic for meeting the recent demand for a service life of over 100 years. This study intends to improve the durability of reinforced concrete structures by improvement in the reinforcing steel, which has remained untouched due to cost problems, through subtle adjustment of the steel components to keep the cost low. As a fundamental study on the performance of Cr-bearing rebars in steel reinforced concrete structures exposed to corrosive environments, The test specimens were made by installing 8 types of rebars in concretes with a chloride ion content of 0.3, 0.6, 1.2, 2.4 and $24kg/m^3$. Corrosion accelerated curing were then conducted with them. The corrosion resistance of Cr-bearing rebars was examined by measuring crack widths, half-cell potential, corrosion area and weight loss after 155 cycles of corrosion-accelerating curing. The results of the study showed that the corrosion resistance increased as the Cr content increased regardless of the content of chloride ions, and that the Cr-bearing rebars with a Cr content of 5% and 9% showed high corrosion resistance in concretes with a chloride ion content of 1.2 and $2.4kg/m^3$, respectively.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.829-839
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• 2003

Recently, the corrosion of reinforced concrete structures has received great attention related with the deterioration of sea-side structures, such as new airport, bridges, and nuclear power plants. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation to chloride attack in concrete structures. The test results indicate that the chloride penetration is more pronounced than the case of single chloride attack when the carbonation process is combined with the chloride attack. It is supposed that the chloride ion concentration of carbonation region is higher than the sound region because of the separation of fixed salts. Though the use of fly ash pronounces the chloride ion concentration in surface, amounts of chloride ion penetration into deep region decreases with the use of fly ash. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of both chlorides and carbonation but the future studies for combined environment will assure the precise assessment.

• Journal of the Korean Chemical Society
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• v.20 no.1
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• pp.48-55
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• 1976

The rate constants of the derivatives of N-(2,4-dinitrophenyl)-benzimidoyl chloride were determined at various pH and a rate equation which can be applied over wide pH range was obtained. The reaction mechanism of hydrolysis of N-(2,4-dinitrophenyl)-benzimidoyl chloride which has not been studied carefully earlier in acidic and basic solution can be fullly explained by the rate equation obtained. The rate equation reveals that, beow pH 7.00, the hydrolysis of benzimidoyl chloride proceeds through $S_N2$ reaction to form a carbonium ion intermediate.Above pH 8.5, however, the hydrolysis proceeds through the $S_N2$ type reaction which depends on hydroxide ion and imidoyl chloride concentration. At pH 7.0∼8.5, two reactions occur competitively.

• Journal of Navigation and Port Research
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• v.33 no.3
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• pp.235-240
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• 2009

Simulation method based on probability was developed to evaluate the durability of reinforced concrete structures about chloride attack. The effects of the probability parameters(surface chloride ion concentration, initial combined chloride ion concentration, the depth of cover thickness of concrete, and the chloride ion diffusion coefficient), probability distribution function and it's variation were calculated using the Monte Carlo method and Fick's 2nd law. From the durability design method proposed in this study, the following results were obtained. 1) The effects of the distance from the coast and the chloride ion diffusion coefficient to the corrosion probability were quite high. 2) The effect of the variation of each parameters was relatively low.