• Computers and Concrete
• /
• v.32 no.3
• /
• pp.287-302
• /
• 2023

Corrosion of reinforcing bars in reinforced concrete structures due to chloride attack in environments containing chloride ions is one of the most important factors in the destruction of concrete structures. According to the abundant reports that the corrosion rate around the repair area has increased due to the macro-cell current known as the incipient anode, it is necessary to understand the effective parameters. The main objective of this paper is to investigate the effect of the kinetic parameters of corrosion including the cathodic Tafel slope, exchange current density, and equilibrium potential in repair materials on the total corrosion rate and maximum corrosion rate in the patch repair system. With the numerical simulation of the patch repair system and concerning the effect of parameters such as electromotive force (substrate concrete activity level), length of repair area, and resistivity of substrate and repair concrete, and with constant other parameters, the sensitivity of the macro-cell current caused by changes in the kinetic parameters of corrosion of the repairing materials has been investigated. The results show that the maximum effect on the macro-cell current values occurred with the change of cathodic Tafel slope, and the effect change of exchange current density and the equilibrium potential is almost the same. In the low repair extant and low resistivity of the repairing materials, with the increase in the electromotive force (degree of substrate concrete activity) of the patch repair system, the sensitivity of the total corrosion current reduces with the reduction in the cathode Tafel slope. The overall corrosion current will be very sensitive to changes in the kinetic parameters of corrosion. The change in the cathodic Tafel slope from 0.16 to 0.12 V/dec and in 300 mV the electromotive force will translate into an increase of 200% of the total corrosion current. While the percentage of this change in currency density and equilibrium potential is 53 and 43 percent, respectively. Moreover, by increasing the electro-motive force, the sensitivity of the total corrosion current decreases or becomes constant. The maximum corrosion does not change significantly based on the modification of the corrosion kinetic parameters and the modification will not affect the maximum corrosion in the repair system. Given that the macro-cell current in addition to the repair geometry is influenced by the sections of reactions of cathodic, anodic, and ohmic drop in repair and base concrete materials, in different parameters depending on the dominance of each section, the sensitivity of the total current and maximum corrosion in each scenario will be different.

• KIEAE Journal
• /
• v.10 no.2
• /
• pp.3-8
• /
• 2010

Many countermeasures are presented to make excessive earth circumstance pollution better in the earth. A lot of researches are in progress to lessen $CO_2$ among the industries exhausting it. The industries manufacturing cement are making many countermeasures. Many concernments on ECO-friendly materials, rather than cement, are increased, and researches are in progress to develop them. Lime, material mostly used before Portland cement appeared, attracts the Occident as well as the Orient. In the Occident, lime mortar was used in common, for maintaining and repairing cultural properties, too. This study is aimed at offering basic materials for the modern use of lime, ECO-friendly material. This study measured the change of intensity and weight with lime, sand, and earth, basic materials of Samhoimool. As a result, at the beginning, hydrated lime displayed its density late, but as time was gone, density was promoted continuously. In addition, density was promoted, when it was given heat at the beginning. If heat-generation reaction of quicklime and water was used, density was promoted at the beginning, but liquidity showed a drop.

• Corrosion Science and Technology
• /
• v.5 no.1
• /
• pp.5-14
• /
• 2006

A lot of parts in FGD (Flue Gas Desulphurization) systems of fossil-fuel power plants show the environments in which are highly changeable and extremely acidic corrosive medium according to time and locations, e.g. in duct works, coolers and re-heaters etc.. These conditions are formed when system materials are immersed in fluid that flows on them or when exhausted gas is condensed into thin layered medium to contact materials of the system walls and roofs. The environments make troublesome corrosion and air pollution problems that are occurred from the leakage of the condensed solution. The frequent shut-down and repairing works of FGD systems also demand costs and low efficiencies of those facilities. In general, high corrosion resistant materials have been used to solve this problem. However, even the super alloys and Teflon linings sometimes have not been good enough to preventing corrosion. Further more, they are expensive and not easily repairable in short periods of operation stops. In this work, new technology that is effective, economical and easily repairable has proposed to solve the corrosion problems in FGD facilities. This technology contains cathodic protection, coatings and remote monitoring-controlling systems.

• Journal of the Korean institute of surface engineering
• /
• v.48 no.6
• /
• pp.275-282
• /
• 2015

The cost for maintenance (replacement cost) of Ni-superalloy components in plant industry is very expensive because of high unit price of INCONEL 718. A development of repairing technology using kinetic spray process can be very helpful for reducing the maintenance cost. However, it is very difficult to produce well-deposited INCONEL 718 layer showing high interfacial bond strength via kinetic spraying. Thus, INCONEL 718 was deposited on SCM 440 substrate and the interfacial properties were investigated, in order to elucidate the cause of hindrance to the bonding between INCONEL 718 layer and SCM 440 substrate. As a result, it was revealed that the dominant obstacle to the interfacial bonding was excessive compressive residual stress accumulated in the coating layer, resulting from low plastic-deformation susceptibility of INCONEL 718. Nevertheless, the bonding state was enhanced by the post heat-treatment through relieving the residual stress and generating a diffusion/metallurgical bonding between the INCONEL 718 deposit and SCM 440 substrate.

• Journal of the Korean Society of Safety
• /
• v.26 no.6
• /
• pp.45-53
• /
• 2011

This study was performed to develop repair and reinforcing materials in sewage drain pipe by using 40% of CAC(Calcium Aluminate Cement) and 4% of Polymer Powder. Regarding reinforcing materials to enhance load-bearing capacity, polyester textile and wire mesh were adopted and then they were evaluated by the measurement of deflection and Stress-strain Relationship. Two types of drain pipe made by concrete and PE were considered as plain specimens and then loading test were performed after repaired by CAC mortar impregnated reinforcing materials. As the test results of the load-bearing test on both drain pipe, there was higher load-bearing capacity on the specimen adopted wire mesh but debonding of repair mortar was found due to stiffness of wire mesh. By the way, repair system using CAC mortar impregnated polyster textile without wire mesh showed satisfactory results including bonding and load-bearing capacity regardless substrate, so this repair system using by mixture of CAC mortar and polyster textile is suggested as the reasonable repairing method within this experimental scope.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.5
• /
• pp.153-160
• /
• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Advances in nano research
• /
• v.15 no.3
• /
• pp.253-261
• /
• 2023

This study investigates the application of nano-composite materials in physical education, specifically focusing on improving the performance of sports hall flooring. The research centers on carbon nanotube reinforced polyvinyl chloride (PVC) composites, which offer enhanced mechanical properties and durability. The incorporation of carbon nanotubes as reinforcements in the PVC matrix provides notable benefits, including increased strength, improved thermal stability, electrical conductivity, and resistance to fatigue. The key parameters examined in this study are the weight percentage of carbon nanotubes and the temperature during the fabrication process. Through careful analysis, it is found that higher weight percentages of carbon nanotubes contribute to a more uniform dispersion within the PVC matrix, resulting in improved mechanical properties. Additionally, higher fabrication temperatures aid in repairing macroscopic defects, leading to enhanced overall performance. The findings of this study indicate that the utilization of carbon nanotube reinforced PVC composites can significantly enhance the strength and durability of sports hall flooring. By employing these advanced materials, the safety and suitability of physical education environments can be greatly improved. Furthermore, the insights gained from this research can contribute to the optimization of composite material design and fabrication techniques, not only in the field of physical education but also in various industries where composite materials find applications.

• Journal of Powder Materials
• /
• v.27 no.3
• /
• pp.219-225
• /
• 2020

The directed energy deposition (DED) process of metal 3D printing technologies has been treated as an effective method for welding, repairing, and even 3-dimensional building of machinery parts. In this study, stainless steel 316L (STS316L) and Inconel 625 (IN625) alloy powders are additively manufactured using the DED process, and the microstructure of the fabricated STS316L/IN625 sample is investigated. In particular, there are no secondary phases in the interface between STS316L and the IN625 alloy. The EDS and Vickers hardness results clearly show compositionally and mechanically transient layers a few tens of micrometers in thickness. Interestingly, several cracks are only observed in the STS 316L rather than in the IN625 alloy near the interface. In addition, small-sized voids 200-400 nm in diameter that look like trapped pores are present in both materials. The cracks present near the interface are formed by tensile stress in STS316L caused by the difference in the CTE (coefficient of thermal expansion) between the two materials during the DED process. These results can provide fundamental information for the fabrication of machinery parts that require joining of two materials, such as valves.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2002.11a
• /
• pp.43-48
• /
• 2002

Since the basement building like the communication hole and etc. is built under the ground where it is pressed by the water, the leakage happens due to the dried-shrinking crack, the sinking crack, the creation of the work-joint of the building and etc. caused by the character of the material and construction way of the reinforced concrete building. Especially, a lot of repair for the leakage cannot help but being taken in temporary way without any noticeable countermeasure. Therefore, this kind of repair is socially criticized many times that this is defective construction even if this costs a lot. The fundamental reason of the above mentioned symptoms can be found in the creation of the work-joint caused by the character of the concrete building, the limitation of the physical performance of the existing water-proof and repair material, the limitation of the construction, the limitation of the physical sustaining performance of the concrete building, the limitation(heat-injury, deterioration) of the constancy of the durability caused by aging and etc. Therefore, in this study, we would like to present the better understanding on the water-proof seal relating to the application at the spot and its test evaluation related data since the necessity of the establishment of the quality control standard and the performance testing way on the relevant water-proof seal is rising a lot to regulate the water-proof technology and the leakage repair technology in accordance with the growth of the demand on the facility.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.1 no.2
• /
• pp.51-58
• /
• 2010

This work examines the identification of stiffness reduction in damaged reinforced concrete bridges under moving loads, and carries out the performance assessment after repairing using advanced composite materials. In particular, the change of stiffness in each element before and after repairing, based on the Microgenetic algorithm as an advanced inverse analysis, is described and discussed by using a modified bivariate Gaussian distribution function. The proposed method in the study is more feasible than the conventional element-based method from computation efficiency point of view. The validity of the technique is numerically verified using a set of dynamic data obtained from a simulation of the actual bridge modeled with a three-dimensional solid element. The numerical examples show that the proposed technique is a feasible and practical method which can inspect the complex distribution of deteriorated stiffness although there is a difference between actual bridge and numerical model as well as uncertain noise occurred in the measured data.