• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.771-776
• /
• 2001

Test results on the deterioration process of concrete under single and combined attacks of chloride penetration have been obtained. After test period of 52 weeks, it is found that the internally penetrated chloride ion contents are less in the single attacks of chloride than the combined attacks of chloride and sulfate. Both the diffusion coefficients and surface chloride concentration derived form the chloride profiles showed a time dependence. Also the performance of fly ash-blended cements was observed to be better than plain cements in retarding chloride attack. However it should be needed that improved chloride diffusion model for the combined deterioration process.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.04a
• /
• pp.254-260
• /
• 1997

Chloride-induced corrosion of reinforcement is one of the main factors which cause the deterioration of concrete structures. Durability and service lives of the concrete sturctures should be predicted in order to minimize the risk of corrosion of reinforcement. The objective of this study is to suggest the basis of analytical methods of predicting the corrosion threhold time of concrete structures. Based on the chemistry and physics of chloride ion transport and corrosion process, chloride intrusion with various exposure conditions, variability of diffusivity and transport of pore water in concrete are taken into consideration in applying finite element formulation to the predicion of corrosion threhold time. The effects of main factors on the prediction of chloride intrusion and corrosion threhold time are examined. In addition, after chloride diffusivities of several mixture proportions with different parameters are measured by chloride diffusion test, the exemplary anayses of corrosion threhold time of those mixture proportions are carried out.

• International Journal of Concrete Structures and Materials
• /
• v.4 no.2
• /
• pp.71-75
• /
• 2010

The chloride ion attack on the passive iron oxide layer of reinforcement steel embedded in concrete under variable temperature environment is influenced by several parameters and some of them still need to be further investigated in more detail. Different school of thoughts exist between past researchers and the data is limited in the high temperature and high chloride concentration range which is necessary with regards to setting boundary conditions for enhancement of tafel diagram model presented in this research. The objective of this paper is to investigate the detrimental coupled effects of chloride and temperature on corrosion of reinforced concrete structures in the high range by incorporating classical Tafel diagram chloride induced corrosion model and laboratory controlled experimental non-linear effect of temperature on corrosion of rebar embedded in concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.1
• /
• pp.129-137
• /
• 2011

This study aims to evaluate the resistance to seawater attack of mortars and concretes incorporating limestone powder (0, 10, 20 and 30% of cement by mass). In order to achieve this goal, both chemical resistance by seawater and chloride ions penetration resistance of mortars or concretes were regularly monitored. From the test results, it was observed that the durability of cement matrix was greatly dependent on the replacement ratios of limestone powder. In other words, performance of cement matrix with 10% limestone powder was similar to that of OPC matrix. However, it was found that a high replacement ratio of limestone powder was ineffective to resist seawater attack.

• Journal of Navigation and Port Research
• /
• v.34 no.10
• /
• pp.787-792
• /
• 2010

It is necessary to predict the penetration of chloride ions for designing RC construction in marine environments. However, it takes a long time to obtain chloride migration coefficients. Therefore, the rapid chloride penetration test (RCPT) is generally used to shorten the test time. But there is a difference between chloride migration coefficients determined by rapid chloride penetration tests and those based on exposure in marine environments. In this study, we evaluated the effect on the chloride ion migration coefficient caused by a change in voltage and NaCl concentration. We also compared the relationship between the chloride ion migration coefficient by RCPT and that by exposure in marine environments. As a result of the experiments, we found that there is only a small change in the experimental factors based on changes in voltage and NaCl concentration and since they are so small, we can conclude that they are in the range of experimental error and test results from chloride ion migration coefficients by RCPT and exposure were very different from each other. In the exposure experiments, when the water-cement ratio was increased, the smaller fine air gaps in concrete affected the chloride ion migration coefficient.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.233-236
• /
• 2006

Chloride attack and carbonation induced corrosion of reinforcement are those of the main factors which cause the deterioration of concrete structures. The objective of this study is to suggest an analytic model for the prediction of chloride penetration into carbonated concrete, in order to make up for the current codes. Carbonation depth model considering the moisture effect is validated by being compared with the test data and the analytic model on chloride penetration into carbonated concrete is developed. Finally, the corrosion-initiation time has been predicted by the present model, being compared with that by the current code equation. The comparison shows that the current code equation can underestimate the chloride penetration into carbonated concrete in marine atmospheric conditions.

• Journal of the Korea Concrete Institute
• /
• v.26 no.1
• /
• pp.71-78
• /
• 2014

The long term integrity of concrete cask is very important for spent nuclear fuel dry storage system. However, there are serious concerns about early deterioration of concrete cask from creaking and corrosion of reinforcing steel by chloride ion because the cask is usually located in seaside, expecially by combined deterioration such as chloride ion and heat, carbonation. This study is to investigate the relation between temperature and chloride ion diffusion of concrete. Immersion tests using 3.5% NaCl solution that were controlled in four level of temperature, i.e. 20, 40, 65, and $90^{\circ}C$, were conducted for four months. The chloride ion diffusion coefficient of concrete was predicted based on the results of profiles of Cl- ion concentration with the depth direction of concrete specimens using the method of potentiometric titration by $AgNO_3$. Test results indicate that the diffusion coefficient of chloride ion increases remarkably with increasing temperature, and there was a linear relation between the natural logarithm values of the diffusion coefficients and the reciprocal of the temperature from the Arrhenius plots. Activation energy of concrete in this study was about 46.6 (W/C = 40%), 41.7 (W/C = 50%), 30.7 (W/C = 60%) kJ/mol under a temperature of up to $90^{\circ}C$, and concrete with lower water-cement ratio has a tendency towards having higher temperature dependency.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.05a
• /
• pp.136-137
• /
• 2018

The properties of concrete produced by ready mixed concrete company in Busan were measured. Because the concrete was mixed with blast furnace slag and fly ash etc., the compressive, tensile strength and chloride ion diffusion coefficient were lower than OPC concrete even though the specified concrete strength was same. If the durability about salt attack were satisfied, the concrete of lower specified concrete strength would be adopted to concrete mixing design. FEM analysis was carried out to predict the life time expectancy.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.782-785
• /
• 2004

Salt attack is one of the serious deterioration factor with respect to the durability of concrete structure. Especially, in case of exposed rebar concrete structure in marine environment, corrosion of rebar is accelerated by penetration of $Cl^-$ from exterior. Through this path, volume of corroded rebar is increased about two and half times due to increased inner pressure originated from rust. As a consequence, the overall deterioration of concrete structure, namely, cracks, reduction of adhesive strength and pop-out is followed. In this paper, the effect of structure treatment of concrete on chloride resistance has been investigated. At the same time, the relationship among several characteristics, such as resistance to chloride, water absorption coefficient and surface hardness of concrete has been investigated. It is believed that surface performance improvement by the application of penetrative hardening agent influences on positively water absorption coefficient, surface hardness of concrete and resistance to chloride ion penetration.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.433-436
• /
• 1999

Long-term durability of the reinforced concrete structures exposed to marine environment deteriorates seriously by the attack of the chloride ion from see water results in corrosion of steel reinforcement in concrete. Their coating effect is aluminum oxide-isocyanate-based coating material, resistance of chloride penetration, carbonation and freezing and thawing resistance were compared to acryl-based coating material and sealer type o waterproofing material. Aluminum oxide-isocyante-based and acryl-based coating material show higher resistance to chloride penetration and carbonation than the sealer type do waterproofing material and aluminum oxide-isocyanate-based coating resist about 99% of chloride penetration. Resultants to the accelerated test for freezing and thawing, coating concrete show higher resistance than non-coating concrete, respectively.