• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.301-310
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• 2006

In this short paper, an elasto-plastic repair and retrofit element is developed for the investigation of the seismic performance of damaged reinforced concrete members. The developed element is capable of reflecting the increased characteristics due to both repair and retrofitting for degraded strength and stiffness of the members. The element having both birth and death time can freely be activated within the user-defined time intervals during static and dynamic time-history analysis. Comparative studies are conducted for reinforced concrete members being repaired and retrofitted. Analytical predictions including the developed element display reasonable correlation with experimental results. In short, it is concluded that the developed element is capable of providing salient features for the healthy assessment of seismic performance of RC members being repaired and retrofitted.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.88-93
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• 2004

The objective of this study was to investigate applicability of epoxy injection method to cracked RC beams and structural behavior of repaired RC beams considering pre-loading conditions. For this purpose, five test beams were fabricated under two experimental variables. The main variables of this experimental study were pre-loading conditions and repair methods. The two pre-loading conditions were selected as $70\%$ and $90\%$ of nominal strength and the repair methods were to repair the cracked RC beams under free loading after crack and sustained loading. The comparative study was executed to evaluate effects of pre-loading conditions on the structural behavior of the cracked RC beams after crack-repair. The strains of reinforcement and concrete and deflections of beams at each loading step were measured and evaluated. As the results of this study, repair methods have much influence on structural behavior of epoxy injected RC beams and epoxy injection method for cracks of RC structures is appeared to be efficient.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.462-469
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• 2003

This paper presents an experimental study on the potential durability enhancement of infrastructures repaired by a sprayed high ductile fiber-reinforced cementitious composite (ECC). For this study, a PVA-ECC which exhibits sprayable properties in the fresh state and tensile strain-hardening behavior in hardened state was sprayed and tested. The experimental results show that the sprayed ECC exhibits mechanical properties with strain capacity comparable to the cast ECC with the same mix design. During loading, the crack widths of ECC are tightly controlled with an average of 30${\mu}m$. It is also revealed that when sprayed ECC is used as a repair material, ductility represented by deformation capacity at peak load of repaired beams in flexure are obviously increased in comparison to those of commercial prepackaged mortar (PM) repaired beams. In addition to high delamination resistance, the significant enhancement of energy absorption capacity and crack width control in ECC repair system suggest that sprayed ECC can be effective in extending the service life of rehabilitated infrastructures.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.341-348
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• 2017

The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.226-234
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• 2011

The service life of concrete structures exposed to a marine environment can be extended by controlling the amount of chloride in cover concrete. Patching is one of the appropriate maintenance techniques for chloride contamination. Chloride-contaminated cover concrete is removed and replaced with sound one. It can provide less risk of corrosion of steel, so that the structure can be maintained for required service life. In this study, a quantitative assessment of the service life subjected to the chloride attack is proposed to determine the effective repair options such as repair depth, repair material and timing of repair. The Crank-Nicolson based finite difference formulation from Fick's second law is proposed to predict the profiles of chloride ion in a repaired concrete structure, considering ingress of chloride from outer and redistribution of residual chloride from the substrate concrete. Therefore, the repair application times and maintenance cost for the target service life can be estimated. Finally, the numerical examples are presented to ensure its applicability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.77-86
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• 2007

The repair technique utilizing surface impregnant is widely used due to its simple construction procedures and economical benefit. Surface protection through this reparing technique cannot increase the bearing capacity of concrete members much but increase the durability performance and service life efficiently. In this study, fundamental tests such as water suction and permeation are performed for concrete specimens with several organic/inorgarnic impregnant and suitable impregnant is selected on the basis of the results. Finally, durability tests such as carbonation, freezing and thawing, and chloride attack are carried out for the concrete specimens with selected impregnant and it is experimentally verified that they have good resistance to deteriorations.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.92-98
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• 1995

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.83-89
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• 1996

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.233-234
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• 2017

본 논문에서는 콘크리트 구조체의 단면 손실에 의한 내력 저하 및 보수용 모르타르에 의한 개선효과를 확인하고자 하였다. 이를 위하여, 모르타르와 콘크리트의 각종 강도 특성을 파악하여 비교 검토하여 연구하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.621-624
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• 2008

Repair materials which applied to the concrete structures may have different quality characteristics depending on the environmental factors. Evaluation on durability of domestic repair materials have not yet secured enough quality performance on durability, mainly due to the lack of test methods resulted from various environmental factors. In this study, we carried out the tests on freezing and thawing resistance of domestic repair materials with different environmental factors applied under BS EN 13687, and analyzed the results by comparing with Korea's national test standards(KS F 4716). The results indicate that after the repetition of dry and wet conditions and the test on freezing and thawing with salt immersion resistance bond strength might show great difference depending on the type of repair materials and the size of sample. For securing better quality performance of repair materials, it is required to establish various standards on the test methods of freezing and thawing resistance with different environmental factors applied.