• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.4A
• /
• pp.365-371
• /
• 2009

It is time-consuming to estimate chloride diffusivity of concrete by concentration difference test. For the reason chloride diffusivity of concrete is mainly tested by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. In this study, portland cement concrete and concrete containing with ground granulated blast-furnace slag (40 and 60% of cement by weight) with water-cementitious material ratio 40, 45, 50 and 60% were manufactured. To compare with chloride diffusivity calculated from the electrically accelerated test and immersed test in artifical seawater, chloride diffusivity tests were conducted. From the results of regression analysis, regression equation between accelerated chloride diffusivity and immersed chloride diffusivity was linear function. And the determinant coefficient was 0.96 for linear equation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.617-620
• /
• 2008

When the RC structure repaired by patching repair method, which method refilles with patching repair material after removes degraded area, It is necessary to determine chloride ion's permeation from outside of the RC structure repaired by patching repair material. Therefore, in this study, damage from sea environment of structure was predicted, moreover, diffusion coefficient of concrete also determined to figure out rebar's corrosion and concentration of chloride ion. RCPT(Rapid Chloride Permeability Test) was used for ditermination of patching repair material's diffusion coefficient, also connection between material thickness and effect of chloride ion's permeation was examined in analytically. Results which derived by experimental test was used in FEM(Finite Element Method) and equation suggested by JSCE to predict concentration of chloride ion in different distance from surface.

• Journal of the Korea Concrete Institute
• /
• v.15 no.3
• /
• pp.400-408
• /
• 2003

Chloride ion inside concrete destroys the so-called passive film surrounding reinforcing bars inside concrete so that the so-called salt attack accelerates corrosion which is the most critical factor for durability as well as structural safety of reinforced concrete structures. Recently, as a solution of the salt attack, the ground granulated blast-furnace slag(GGBFS) have been used as binder or blended cement more extensively. In this paper, characteristics of chloride ion diffusion for the GGBFS concrete, which is known to possess better resistance to damage due to the chloride ion penetration than ordinary portland cement(OPC) concrete possesses, are analyzed and a chloride ion diffusion model for the GGBFS concrete is proposed by modifying an existing diffusion model for the OPC concrete. The proposed model is verified by comparing diffusion analysis results using the model accelerated chloride penetration test results for concrete specimens as well as field test results for an RC bridge pier. Then, an optimal resistance condition to chloride penetration for the GGBFS concrete is obtained according to degrees of fineness and replacement ratios of the GGBFS concrete. The result shows that the GGBFS concrete has better resistance to chloride ion penetration than OPC concrete has and the resistance is more affected by the replacement ratio than the degree of fineness of the GGBFS.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.9 no.2
• /
• pp.147-154
• /
• 2005

It is found that as contents of chloride ion and age increase, area of corrosion also increases. Inare increased to 1035 days from 730 days, slope of increase of corrosion area is greatest. Non-rust inhibitor specimens show corrosion area of 8~35 times more than rust inhibitor specimens and anticorrosive effects by application of rust inhibitor can be confirmed. When chloride ion is not contained, corrosion control effects of steel reinforcing according to increase of thickness are found, but specimens having chloride ion show no regular tend of thickness and corrosion due to complex problems such as reverse diffusion of chloride and test errors.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.6
• /
• pp.730-737
• /
• 2014

In this study, chloride content of marine concrete bridge at the south coast in 5~34years was calculated based on the measured data and the validity of the proposed value was evaluated. Also, correlation of existence of salt injury prevention coating, chloride content, carbonation depth and the compressive strength of marine concrete bridges were derived and relationship of the four was evaluated. According to the research results, surface chloride content value in the tidal zone proposed form KCI 2009 and value in the splash zone and atmospheric zone proposed form Cheong et al.(2005) was the most valid. Also, salt injury prevention coating of marine concrete bridges had the outstanding effect of preventing chloride content penetration, carbonation depth and reduction in the compressive strength. Compressive strength of concrete was reduced by the increase of carbonation depth and chloride content.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.513-516
• /
• 2008

In this study the prediction model of Chloride Ion progress rate of concrete using steel powder as an addition is developed, in which the reduction of not only the diffusion rate of $Cl^-$ but also the corrosion rate by replenishment of pore by corrosion products. The model is based on the diffusions of $Cl^-$ and its reaction with $Fe^{2+}$, in chloride attack progression region. The model can also explain the characteristics of chloride ion permeation resistance of concrete that the matrix is densified due to corrosion products. The prediction by the model agreed well the experimental data in which the concrete using steel powder, and it showed the lower rate in long-term age to Chloride Ion progress rate than the concrete without steel powder. Consequently the model can predict Chloride Ion progress rate of concrete exposed in the atmosphere regardless of the water-to-cement raito, the amount of the content of steel powder, etc.

• Journal of the Korea Concrete Institute
• /
• v.14 no.1
• /
• pp.100-109
• /
• 2002

Significant damage to concrete results from the intrusion of corrosive solutions, for example, dissolved chlorides corrode reinforcing steel and cause spatting. Effectively blocks the penetration of these solutions will eliminate or greatly reduce this damage and lead to increased durability. This study is to investigate the effects of pozzolanic admixtures, fly ash and silica fume, and a blast furnace slag on the chloride ion penetration of concretes. The main experimental variables wore the water-cementitious material ratios, the types and amount of admixtures, and the curing time. And it is tested for the porosity and pore size distributions of cement paste, chloride ion permeability based on electrical conductance, and 180-day ponding test for chloride intrusion. The results show that the resistance of concrete to the penetration of chloride ions increases as the w/c was decreased, and the increasing of curing time. Also, concrete with pozzolans exhibited higher resistance to chloride ion penetration than the plain concrete. The significant reduction in chloride ion permeability(charge passed) of concrete with pozzolans due to formation of a discontinuous macro-pore system which inhibits flow. It is shown that there is a relationship between chloride ion permeability and depth of chloride ion penetration of concrete, based on the pore structure (porosity and pore size distributions) of cement paste.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.3
• /
• pp.138-143
• /
• 2010

Recently, as many big marine concrete structures increase, it is necessary that chloride ion diffusion coefficient of concrete shall be evaluated but it will take a long time to evaluate chloride ion diffusion coefficient of concrete. Accordingly, many test methods are suggested to evaluate chloride ion diffusion coefficient in a short period time by the promotion in electro chemical ways but the systematic study for this is insufficient. Therefore, this study evaluates chloride ion penetration and diffusion features by three representative electric promotion tests targeting for three different cements whose ingredients are different and analyzes the correlationship between them. As a result, diffusion features of chloride ion varied according to the cement ingredients and three ingredients cement in which blast furnace slag powder and fly ash are mixed in constant ratio, which shows the most excellent cement diffusion properties. For diffusion properties of chloride ion, the correlationship between test methods are good.

• Journal of the Korea Concrete Institute
• /
• v.14 no.5
• /
• pp.789-795
• /
• 2002

To evaluate the bind rate and behavior of two types chloride ion-one is the chloride ion added in mixture when un-washed sea sand is used as fine aggregate, one is the chloride ion admitted in the new version of concrete standard specification, pore solution extracted in cement paste were analyzed. The results are follow. 1 As passing the time, the chloride concentration in the pore solution decreases with the Increase in the chloride content absorbed by the hydrate products. As compared with chloride contents in mixing water, the bound ratio of chloride at 49 days is 64∼90％. 2. The bound ratio of chloride in cement paste considering evaporable water as pore solution is obtained. In case of Pl∼P3(added chloride content wt of cement 0.046∼0.16 ％), the bound ratio of chloride is 91.8∼93.5 ％. P4(added chloride wt of cement 0.3％) is 89.1％, but P5(added chloride wt of cement 0.617％) bound is only 77％. 3. The bound ratio of chloride to wt of cement is 0.015∼0.475％ with adding chloride. In case chloride added over 0.091 ％ wt of cement, the bound chloride content increases 1.7∼1.8 times in spite of added chloride increase twice. The bound ratio of chloride to wt of cement decreased with the increase in the chloride content. 4. The more increase added chloride content, the more increase the bound ration of chloride. But the absolute value of chloride content in pore solution increased.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.4
• /
• pp.553-557
• /
• 2022

The present study evaluate the chloride extracion under electrochemical chloride extraction method. Chloride was penetrated into the concrete from external reservoir using a 4M NaCl solution, and an electrochemical chloride extraction method was applied after the curing period of 1 year. The current density was constantly kept 1000 mA/m² for coulostatic application with the variation in potential difference. The duration of the ECE treatment was 2, 4, 8 weeks, respectively. The residual chloride concentration at all depths decreased, and the chloride concentration decreased as the application period increased. After the application period of 8 weeks, 62.9 to 77.6 % of chloride extracted in the total chloride profile, and 77.7 to 99.5 % of chloride extracted in the free chloride profile. In particular, the concentration of free chloride at a depth of 7 mm or more from the concrete surface was 0.01 % or less by cement. In addition, it was confirmed that the bound chloride could be extracted by the electrochemical chloride extraction.