• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.793-796
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• 2004

In domestic, various repair materials and method systems to keep up with these reinforced concrete deteriorated due to salt damage, carbonation. chemical decay et. being developed and applied. However, present polymer cement mortar applied to section restoration system cause the problem of long-term working and economica] efficiency. because that is divided into two process of liquid corrosion prevention agent and polymer cement mortar. In this background, accelerated test with due regard to $3\%$ NaCl soaking and autoclave cure was performed to confirm steel bar corrosion prevention properties of polymer cement mortar mixed with corrosion prevention agent of powdered type. In conclusion. we confirmed application possibility and excellency of steel bar corrosion prevention properties of polymer cement mortar mixed with corrosion prevention agent of powdered type comparing general polymer cement mortar applied to section restoration system of present study.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.49-50
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• 2021

However, in the case of concrete, there is a concern that carbonation may proceed due to environmental factors. However, in the case of concrete, there is a concern that carbonation may proceed due to environmental factors. Research is steadily underway to prevent carbonation because carbonation decreases durability and increases the risk from disasters. However, there are many cases in which studies related to carbonation have been conducted only with materials in the same space. Therefore, in this study, FT-IR was used to analyze the difference in carbonation components by structural parts of old buildings. As a result, it was confirmed that there was a difference in peak values for each structural part of the building. The difference in peak values was determined to indicate differences in components, so the level of carbonation progress was different, and it is believed that differentiated repair and reinforcement methods will be needed depending on the structure.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.167-175
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• 1999

Many composite girder bridges have been constructed for about thirty five years. Nowadays they are aged or deteriorated because of the increase in traffic and vehicle loads. In this study, the effect of strengthening with glass fiber sheet is investigated to estimate the possibility for applying to damaged prestressed concrete bridges. One normal and eight cracked specimens which had been preloaded were tested. The cracked specimens were strengthened with either external prestressing or bonding glass fiber sheet, or using both methods. The results showed that the maximum loads are almost same for both methods. So it seems that the strengthening with glass fiber sheet can be used for strengthening damaged prestressed concrete girders. It is important that proper devices should be selected to prevent glass fiber sheet from premature bonding failure below its maximum load, which is similar to end anchorage problem in external prestressing method. It is proved that the devices proposed in this paper have sufficient anchoring capability to increase load carrying capacity.

• Magazine of the Korea Concrete Institute
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• v.2 no.4
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• pp.91-98
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the constuction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have been deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechan¬ism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical pro¬gram is developed using these joint models. Using this numerical model as an analysis tool, the effects of joint parameters on the behavior of pavements are investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.661-664
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• 2008

The structure which is located in special surroundings like ocean-environment is physically and chemically eroded by seawater or salt damage, and then concrete-structure becomes deteriorated by iron corrosion and swelling pressure which leads to remarkably decline durability due to cracks and exploitation. As a measure against salt damage, it is actively being examined to use the blended cement that controls salt damage and fix chloride in the process of hydration. In this study, therefore, to examine the property of marine concrete added admixture, marine concrete is manufactured by adding high-strength admixture(omega2000) by 0, 5, 10, and 15% to low heat-blended cement. Then it shows that the compressive strength of manufactured marine cement tends to increase and chloride penetration resistance improves.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.377-385
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• 2003

Flexural characteristics of the R.C beams strengthened with newly-developed grid-type carbon fiber plastics(CFRP-GRIDS) were investigated. The tests were conducted under the four-points load to the failure to investigate the strengthening effects of CFRP-GRIDS on the beams. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly, the appropriate area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.213-220
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• 2005

Carbon fiber reinforced polymer (CFRP) sheets are becoming increasingly popular for strengthening deteriorated concrete bridges due to their excellent strength and stiffness-to-weight ratio, corrosion resistance, and convenience of construction work. The purpose of this study is to compare the performance of CFRP-strengthened reinforced concrete (RC) beams and to develop a new design formula. Simple beams with 3 m span length were tested to investigate the effect of reinforcing steel ratio and CFRP-reinforcing ratio on the flexural behavior of strengthened RC beams. The test results were analyzed with the special emphasis on the failure mode, the maximum load, and the strain distribution in the section. It is shown that the strain of the strengthened beams is not linearly distributed in the section. A new design formula based on the non-linear distribution of the strain has been derived and showed that it has a good agreement with the various domestic and foreign test results.

• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.119-126
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• 2004

Generally, reinforced concrete is one of the most commonly used structural materials and it prevents corrosion of steel bar by high pH of interior, But, as time elapsed, reinforced concrete structure become deteriorated by many of combined deterioration factors and environmental conditions. And, there are large number of deteriorate mechanism of the reinforced concrete structure and it acts complexly. It is recognized that steel bar corrosion is the main distress behind the present concern regarding concrete durability. In this study, to institute combined deterioration environments, established acceleration condition and cycle for combined deterioration environments has a resemblance to environments which are real structures placed. After that to confirm corrosion properties of reinforced concrete due to permeability with covering depth and types of surface cover under combined deterioration environments, measured carbonation velocity coefficients, chloride ion diffusion coefficients, water absorption coefficients, air permeability coefficients and electric potential, corrosion area ratio, weight reduction, corrosion velocity of steel bar. The results showed that an increase in age also decrease carbonation velocity coefficients, increase Chloride ion diffusion coefficients and increases water absorption coefficients. As well, an increase in age also increases corrosion of steel bar. Data on the development of corrosion velocity of steel bar with types of surface cover made with none, organic B, organic A, inorganic B, and inorganic A is shown. As well, permeability and corrosion velocity of steel bar with covering depth is superior to 10mm than 20mm. And it is confirmed permeability and corrosion properties of steel bar are closely related.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.111-119
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• 2016

Rebound hammer test, SonReb method and concrete core test are most useful testing methods for estimate the concrete compressive strength of deteriorated concrete structures. But the accuracy of the NDE results on the existing structures could be reduced by the effects of the uncertainty of nondestructive test methods, material effects by aging and carbonation, and mechanical damage by drilling of core. In this study, empirical procedure for verifying the in-situ compressive strength of concrete is suggested through the probabilistic analysis on the 268 data of rebound and ultra-pulse velocity and core strengths obtained from 106 bridges. To enhance the accuracy of predicted concrete strength, the coefficients of core strength, and surface hardness caused by ageing or carbonation was adopted. From the results, the proposed equation by KISTEC and the estimation procedures proposed by authors is reliable than previously suggested equation and correction coefficient.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.221-228
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• 2010

External bonding of carbon fiber reinforced polymer (CFRP) sheets has been widely accepted as a popular method for strengthening of deteriorated RC structures. The long-term behavior of CFRP-strengthened RC structure is often affected by that of the interface between CFRP sheets and concrete. This study aims at applying a viscoelastic model to describe the creep behaviour of the adhesive layer bonding CFRP sheet to concrete, the CFRP-concrete interface. Reviews of available models on concrete creep behavior have been first carried out and then new FE analysis model is proposed. The proposed FE analysis model based on the maxwell model has been verified by previous experimental results. It is shown that the creep effect of interfacial adhesive layer is very important on the long-term behavior of concrete structures strengthened with CFRP.