• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.31-38
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• 2018

The effects of polymer-binder ratio and metakaolin content on the properties of ultrarapid-hardening polymer-modified concretes using metakaolin are examined. As a result, regardless of the metakaolin content, the flexural, compressive and adhesion in tension strength of the ultrarapid-hardening polymer-modified concretes tend to increase with increasing polymer-binder ratio. Regardless of the polymer-binder ratio, the strengths of the ultrarapid-hardening polymer-modified concretes increase with increasing metakaolin content, and reaches a maximum at metakaolin content of 5%. The water absorption, carbonation depth and resistance of chloride ion penetration of the ultrarapid-hardening polymer-modified concretes decrease with increasing polymer-binder ratio. The resistance of freezing and thawing improvement is attributed to the improved bond between cement hydrates and aggregates because of the incorporation of polymer dispersion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.16-22
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• 2023

In this study, a salt water immersion test was performed on concrete specimens simulating the concrete mix design of the nuclear power plant, and the correlation between the amount of chloride and the XRF component according to the depth of the concrete was analyzed. The amount of chloride on the surface of the nuclear power plant concrete increased slightly with increasing immersion time in salt water, but the amount of chloride in the depth of 5.5 mm or more showed a clear tendency to increase with increasing immersion time in salt water. As a result of analyzing the correlation between the amount of chloride in concrete and the XRF component, the concrete with 20% FA substitution compared with the OPC concrete showed a very high correlation between the composition ratio of Cl ions and the evaluation result of salt damage resistance by XRF component analysis. Accordingly, it was confirmed that chlorine ion analysis and salt damage resistance performance evaluation by XRF component analysis were possible through repeated data accumulation in the nuclear power plant concrete mix with 20% fly ash replacement.

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

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.111-112
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• 2015

There is high possibility of steel corrosion on the reinforced concrete exposed to marine environment by chloride ion penetration. And it show a big difference of concrete durability under conditions of splash zone, tidal zone, and immersion zone. Therefore, in this paper, half-cell potential and chloride ion penetration depth was measured to evaluate the durability of slag concrete by marine exposure experiment. As a result, SC70 specimen showed no steel corrosion, regardless of the marine exposed conditions. Also, a deterrent effect on chloride ion penetration by replacement of slag in tidal zone and immersion zone could be confirmed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.214-221
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• 2024

The present study concerns the resistance of calcium aluminate cement (CAC) to steel corrosion. The corrosion behavior of steel, chloride binding/buffering and chloride transport were evaluated in order to predict the risk of steel corrosion. The CAC mortar exhibited no corrosion on steel, irrespective of the curing temperature and CAC types, whereas ordinary Portland cement (OPC) showed a severe corrosion on the steel surface. The chloride binding capacity of CAC found to be was lower than that of OPC, yet buffering capacity against pH decrease was found to be significantly higher in the CAC paste. Furthermore, chloride ingress at all depths was found to be reduced in CAC, thereby reducing the risk of corrosion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.83-91
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• 2015

With varying conditions of concrete surface, induced chloride contents are changed and this is a key parameter for steel corrosion and service life in RC (Reinforced Concrete) structures. Many surface enhancement techniques using impregnation have been developed, however the evaluation techniques for chloride behavior through doubly layered media and time-dependent diffusion are rarely proposed. This paper presents an analysis technique considering double-layer concrete and time-dependent diffusion behavior, and the results are compared with those from the previous test results through reverse analysis. The chloride profiles from the surface-impregnated concrete exposed to atmospheric, tidal, submerged zone for 2 years are adopted. Furthermore surface chloride contents and diffusion coefficients are obtained, and are compared with those from Life365. Through consideration of time effect, the relative error decreases from 0.28 to 0.20 in atmospheric, 0.29 to 0.11 in tidal, and 0.54 to 0.40 in submerged zone, respectively, which shows more reasonable results. Utilizing the diffusion coefficients from Life365, relative errors increases and it needs deeper penetration depth (e) and lower diffusion coefficient ratio ($D_1/D_2$) due to higher diffusion coefficient.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.295-301
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• 2019

Currently, the most commonly used decontamination agent in the country is calcium chloride, and the use of decontamination agents nationwide is on the rise due to climate change in the country. The deicing agent, aimed at deicing snow, is sprayed and the chloride is frozen and thawed by the dissolved surface water, causing various damages such as deterioration to the concrete. Therefore, in this study, the reactive urethane polymer was manufactured to coat concrete surface protection material, which is a method that prevents moisture from externally penetrating by applying to concrete surfaces, and the mixing agent was selected through the size control of molecules and surface modification, and the properties of penetrant stiffening agents and the application method of concrete was evaluated.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.48-55
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• 2022

This study uses the recovered water as mixing water and artificial lightweight aggregate pre-wetting water as part of a study to increase the recycling rate and reduce greenhouse gas of the ready-mixed concrete recovered during the concrete transport process, and cement fine powder of blast furnace slag(BFS) and fly ash(FA). The engineering characteristics of the three-component lightweight aggregate mortar used as a substitute were reviewed. For this purpose, the flow, dry unit mass, compressive strength, drying shrinkage, neutralization depth, and chloride ion penetration resistance of the three-component lightweight aggregate mortar were measured. When used together with the formulation, when 15 % of BFS and 5 % of FA were used, it was found to be positive in improving the compressive strength and durability of the mortar.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.548-555
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• 2015

This paper aims to estimate the service life of the target bridge structures subjected to chloride ingress from de-icer, which is used for safety of vehicles in winter, by investigating the chloride ingress into concrete. In this study, the 10-year-old bridge structures were investigated by measuring the chloride along the depth from the exposed surface to derive the surface chloride concentration and the diffusion coefficient for the prediction of service life. The service life of each measured point on the structures were estimated with the surface chloride concentration and the diffusion coefficient by using Life-365 software. As a result, it was estimated for all measured points to have over 100-year service life. Furthermore, the diffusion coefficient and the service life from the measured data were compared to another method calculated with the concrete mix, considering the time dependency of diffusion coefficient.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.2
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• pp.136-143
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• 2013

In the sewage structures and wastewater facilities, concrete is exposed to hydrogen sulfide ($H_2S$) which acts as an acid material in a solution, and a strongly acidic sulfate ion ($SO{_4}^{-2}$) is generated by a sulfuric bacteria. Hence, a degradation of concrete with biochemical corrosion would be accelerated. Finally, durability of concrete and concrete structures may be greatly reduced. In this study, in order to remove the hydrogen sulfide which is used by the sulfuric bacteria organic-biologically, the antibiotic metal and metallic salt powders were mixed to concrete, and a suppressing performance of the sulfate ion was assessed. For the sulfuric acid bacteria, a comparative evaluation of antimicrobial performance on neutralized concrete specimens were carried out, also by a rapid chloride penetration test, chloride penetration depths and diffusion coefficients were measured for antibiotic concrete in accordance with the amount of metal and metallic salt-based antibacterial agents. Eventually, by an observation of the biochemical state of the surface of concrete specimens exposed outdoors, the performance and applicability of antibiotic concrete were confirmed.