• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.1-7
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• 2017

Concrete behavior in early-age is changing due to hydration reaction with time, and a resistance to chloride attack and strength development are different characterized. In the present work, changing strength and resistance to chloride attack are evaluated with ages from 28 days to 6 months. For the purpose, strength, diffusion coefficient, and passed charge are evaluated for normal concrete with 3 different mix proportions considering 28-day and 6-month curing conditions. With increasing concrete age, the changing ratio of strength falls on the level of 135.3~138.3%, while diffusion coefficient and passed charge shows 41.8%~51.1% and 53.6%~70.0%, respectively. The results of chloride diffusion coefficient and passed charge show relatively similar changing ratios since they are much dependent on the chloride migration velocity in electrical field. The changing ratios in chloride behaviors are evaluated to be much larger than those in compressive strength since the ion transport mechanism is proportional to not porosity but square of porosity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.10-16
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• 2020

Deterioration of reinforced concrete structure caused by chloride ingress is the main issue and regrading this, many studies have been investigated with both experiments and computational modelling. In addition to chloride diffusion, chloride sorption should be considered as a chloride transport mechanism in concrete structure and cracks formed in concrete structures are the main variable to evaluate the performance of the structures. In this study, after making two types of cracks width (0.1 and 0.3 mm) in reinforced concretes, chloride absorption tests were performed. Weight change and colour change using 0.1 AgNO3 solution from the samples were performed to measure chloride ingress. Image processing was also carried out to quantify range of colour change in carck face. From the result, it were confirmed that the amount of chloride absorption increases with exposure time and increasing crack width, and chlorides reached at steel depth within 1 hour. It would be possible that chloride can move through interface bewteen steel and concrete, thereby further study regarding this is required.

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

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.189-196
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• 2007

The purpose of this study was to analyze steel corrosion resistance of concrete containing copper slag. The specimens were made with normal portland cement and pozzolan materials with various replacement ratio and with W/B ratio ranging from 35% to 55%. Compressive strength, coefficient of chloride diffusion, corrosion area ratio and weight reduction ratio were determinated for the test. The results show that the concrete with pozzolan materials is superior resistant to chloride ions compared to the concrete without pozzolan materials. It was observed that blast furnace slag replacement ratio of 20% gives the best results with respect to chloride ion penetration and corrosion tests and observed that copper slag replacement ratio of 10% gives the seperior resistance compared to normal concrete.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.481-488
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• 2016

Concrete member has been subjected to dead and live loads in use, and the induced stress can affect not only structural but also durability behavior. In mass concrete construction, construction joint are required, however cold joint usually occur due to poor surface treatment and delayed concrete placing. The concrete with joint is vulnerable to both shear stress and chloride ingress. This paper presents a quantitative evaluation of cold joint and loading conditions on chloride diffusion behavior. With increasing tensile stress from 30% to 60%, chloride diffusion coefficient gradually increases, which shows no significant difference from result in the sound concrete. However chloride diffusion coefficient under 30% level of compressive stress significantly increases by 1.70 times compared with normal condition. Special attention should be paid for the enlarged diffusion behavior cold joint concrete under compressive stress.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.359-366
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• 2007

Recently, analysis researches on durability are focused on chloride attack and carbonation due to increased social and engineering significance. Generally, chloride penetration and carbonation occur simultaneously except for in submerged condition and chloride behavior in carbonated concrete is evaluated to be different from that in normal concrete. Furthermore, if unavoidable crack occurs in concrete, it influences not only single attack but also coupled deterioration more severely. This is a study on analysis technique with system dynamics for chloride penetration in concrete structures exposed to coupled chloride attack and carbonation through chloride diffusion, permeation, and carbonation reaction. For the purpose, a modeling for chloride behavior considering diffusion and permeation is performed through previous models for early-aged concrete such as MCHHM (multi component hydration heat model) and MPSFM (micro pore structure formation). Then model for combined deterioration is developed considering changed characteristics such as pore distribution, saturation and dissociation of bound chloride content under carbonation. The developed model is verified through comparison with previous experimental data. Additionally, simulation for combined deterioration in cracked concrete is carried out through utilizing previously developed models for chloride penetration and carbonation in cracked concrete. From the simulated results, CCTZ (chloride-carbonation transition zone) for evaluating combined deterioration is proposed. It is numerically verified that concrete with slag has better resistance to combined deterioration than concrete with OPC in sound and cracked concrete.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.299-306
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• 2017

In this research, it was examined chloride ion penetration resistance of slag-replaced concrete and cementless slag concrete considering marine environmental exposure conditions of splash zone, tidal zone and immersion zone. In the design strength of grade 24 MPa, the specimens were tested to determine their compressive strength, scanning electron microscopy images and chloride migration coefficient. Further, chloride ion penetration depth and carbonation depth of specimens exposed to marine environment were measured. Experimental results confirm that chloride migration coefficient of specimens tended to decrease with increasing the replacement ratio of ground granulated blast-furnace slag in accelerated laboratory test. In addition, the specimens exposed to the tidal zone were found to be the greatest chloride ion penetration depth compared to splash zone and immersion zone. On the other hand, the chloride ion penetration depth of the specimens exposed to splash zone tended to increase with increasing the replacement ratio of ground granulated blast-furnace slag in contrast with the results for the tidal zone and immersion zone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.66-74
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• 2016

The objective of this study is the investigation of the influence of carbonation on the penetration of chloride ions in reinforced concrete sections for different mix proportions and environmental conditions. A comprehensive numerical model based on the change of the pore structure and the chemical equilibrium was used for this combined action of carbonation and chloride ingress. The empirical formulae of some parameters in this model are estimated according to numerous experimental data. And, a set of data analysis is carried out to simplify the estimation of model variables to reduce the computational cost. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Then, the parametric analysis is given and the numerical results show that the effect of carbonation of the free chloride ingress is significant and depends on the binder types and concrete mix proportion.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.486-486
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• 2011

금속산화물을 제조하는 방법으로 수열반응은 wire, rod, needle, lamella, flower등 다양한 형상을 화학적으로 합성하는데 널리 이용된다. 또한 금속산화물의 특성은 구조와 형상에 의존하고, 구조와 형상에 따라 촉매, 기능성 첨가제, 초전도체등에 다양한 분야로 사용되어진다. 본 연구는 수열방법으로 각 물질의 염화물과 암모니아수를 출발물질로 사용하였고, ionization 제어를 위해 염화암모늄을 사용하여 각 물질의 전구체를 합성하였다. 형성된 각 물질의 전구체는 열분해를 통해 산화물로 제조하였다. 이들 입자의 형상 및 특성을 확인하기 위해 SEM, XRD, FT-IR, Raman을 사용하여 확인하였다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.125-132
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• 2012

The dehydration schemes of rare earth (La, Ce, Nd, Pr, Sm. Eu, Gd, Y) chloride hydrates was investigated by using a dehydration apparatus. To prevent the formation of the rare earth oxychlorides, the operation temperature was changed step by step ($80{\rightarrow}150{\rightarrow}230^{\circ}C$) based on the TGA (thermo-gravimetric analysis) results of the rare earth chloride hydrates. A vacuum pump and preheated Ar gas were used to effectively remove the evaporated moisture and maintain an inert condition in the dehydration apparatus. The dehydration temperature of the rare earth chloride hydrate was increased when the atomic number of the rare earth nuclide was increased. The content of the moisture in the rare earth chloride hydrate was decreased below 10% in the dehydration apparatus.