• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.307-313
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• 2014

Recent interest in the increased structural performance and durability evaluation of this concrete structure in a salt damage environment is increasing. The most secure and reliable method of accelerated corrosion test is a method to carry out the rebar corrosion monitoring can be exposed directly to the marine test site exposure. However, long-term exposure testinghas the disadvantage that a long period is necessary. So, a lot of research on RC of salt damage environment have beenpromoted as alternatives to replace this. However, accelerated corrosion test, in the short term only is appropriate and is but an accelerated test method to evaluate the critical chlorine concentration, there is a difficult problem that you still get the answer. It is one of the correlation problems accelerated test correspond to a certain period of exposure environment. Therefore, in this study, to clarify the differences rebar corrosion beginning, through the actual corrosion accelerated test in corrosion time and laboratory test chamber of the structure of the marine environment results in both environments, it is an object of correlation coefficient derived.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.1015-1020
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• 2012

Antifungal cement mortar or microbiological calcium carbonate precipitation on cement surface has been investigated as functional concrete research. However, these research concepts have never been fused with each other. In this study, we introduced the antifungal calcite-forming bacteria (CFB) Bacillus aryabhattai KNUC205, isolated from an urban tunnel (Daegu, South Korea). The major fungal deteriogens in urban tunnel, Cladosporium sphaerospermum KNUC253, was used as a sensitive fungal strain. B. aryabhattai KNUC205 showed $CaCO_3$ precipitation on B4 medium. Cracked cement mortar pastes were made and neutralized by modified methods. Subsequently, the mixture of B. aryabhattai KNUC205, conidiospore of C. sphaerospermum KNUC253, and B4 agar was applied to cement cracks and incubated at $18^{\circ}C$ for 16 days. B. aryabhattai KNUC205 showed fungal growth inhibition against C. sphaerospermum. Furthermore, B. aryabhattai KNUC205 showed crack remediation ability and water permeability reduction of cement mortar pastes. Taken together, these results suggest that the $CaCO_3$ precipitation and antifungal properties of B. aryabhattai KNUC205 could be used as an effective sealing or coating material that can also prevent deteriorative fungal growth. This study is the first application and evaluation research that incorporates calcite formation with antifungal capabilities of microorganisms for an environment-friendly and more effective protection of cement materials. In this research, the conception of microbial construction materials was expanded.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.47-52
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• 2008

Deicer has been generally used for prevention of a road freezing in winter, and the usage amount is increasing every year. However, deicer may induce the decrease of bond strength, surface scaling, and environmental pollution. In this study, the field test was performed to investigate the deterioration of concrete road structures used for 17 years. And, the corrosion resistance characteristics were compared for the existing deicer and eco-friendly deicer. According to the field test results, the penetration depth of limit chloride amount was about 40mm, and the average concentration of chloride was $3.45kg/m^3$ at the surface of structures. On the contrary, the carbonation depth was slight. The penetration depth of eco-friendly deicer was less than the existing deicer, and the corrosion resistance of eco-friendly deicer was higher.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.148-155
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• 1992

For the enhancement of the concrete durability, we developed high - durable portland cement (ACTPC) by physical treatment of ordinary portland cement with asphalt and carbon black. In this research, the hydration reaction characteristics of ACTPC were studied by using SEM, X-Ray, Conduction Micro Calolimeter etc. When the ACTPC is mixed with water, it is believed the asphalt films on cement particles suppress the early stage of hydration reactions of cements, because the films hinder the contact with water and the elusion of soluble ions from particles. But the carbon blacks on the cement particles accelerated the hydration reactions of cement after a while, because the micro particles can be used as seed crystals in $CaO-SiO_2-H_2O$ gel formation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.32-39
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• 2018

Repairing timing and the extended service life with repairing are very important for cost estimation during operation. Conventionally used model for repair cost shows a step-shaped cost elevation without consideration of variability of extended service life due to repairing. In the work, RC(Reinforced Concrete) Column is considered for probabilistic evaluation of repairing number and cost. Two mix proportions are prepared and chloride behavior is evaluated with quantitative exterior conditions. The repairing frequency and cost are investigated with varying service life and the extended service life with repairing which were derived from the chloride behavior analysis. The effect of COV(Coefficient of Variation) on repairing frequency is small but the 1st repairing timing is shown to be major parameter. The probabilistic model for repairing cost is capable of reducing the number of repairing with changing the intended service life unlike deterministic model of repairing cost since it can provide continuous repair cost with time.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.219-225
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• 2017

The durability factors of concrete has been researched by many researchers. Among the chemical ingression by acid, alkali, or salt, specially the ingression by sulfate has been actively studied and reported. Generally, for the oil type chemical, it is reported to cause the excessive expansion of cement mortar and further to cause the collapse, while there was no enough research on influence of oil type, relationship with microstructure of mortar, and collapse pattern. Therefore, in this research, using the various oils from general market, the degradation properties of the mortar mixtures with various mix designs were evaluated. according to the experiment, Bio diesel damaged worst and the mix design with less cement content showed the worst damage against oils.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.597-604
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• 2006

Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.134-138
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• 2003

The purpose of this paper is to recycle the fly ash to the valuable resources and settle environment problems which was caused by the fly ash produced from the thermal power plant. Making the fly ash-cement matrix reused fly ash in large quantities, we looked into minutely the physical properties - the elastic modulus, the compressive strength - to increase the usefulness as the building materials for the structure widely. In this paper, the variables are the water-binder(39, 42, 45%), the fine aggregate ratio(37, 41, 45%). Because the fracture energy is influenced by the strength, it is showed to decrease with the increase of W/B and S/a. Besides, we will be able to know that basic properties of the fly ash-cement matrix are similar to that of concrete. But, it is needed to carry out durability experiment on the drying shrinkage, creep, freezing and thawing test to use structural materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.39-46
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• 2023

In this study, the dynamic behavior of friction bearings of PSC (Pre-Stressed Concrete) box train continuous bridge was numerically analyzed at 10 km/h intervals up to 600 km/h according to the increasing speed of the next-generation high-speed train. A frame model was generated targeting the 40-meter single-span and two-span continuous PSC box bridges in the Gyeongbu High-Speed Railway section. The interaction forces including the inertial mass vehicle model with 38 degrees of freedom and the irregularities of the bridge and track were considered. It was calculated the longitudinal displacement, cumulative sliding distance and displacement speed of the bridge bearings at each running speed so that compared with the dynamic behavior trend analysis of the bridge. In addition, long-term friction test standards were applied to evaluate the durability of friction plates.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.188-193
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• 2015

Blast Furnace Slag is good for enhancing the qualities of concrete such as reducing hydration heat increasing fluidity, long-term strength and durability, but it has some problems: construction time is increased or the rotation rate of form is decreased due to low development of early strength. In this study, an aqueous alkali solution for alkali activated reaction was obtained by the electrolysis using concentrated water discharged from seawater desalination process. Prepared aqueous alkali solution was applied to produce mortars using blast furnace slag. The results can be summarized as follows : For the mortar, compressive strength was decreased below 2% of NaOH and increased below 6% of NaOH. And compressive strength was increased gradually with increasing NaOCl contents. However, NaCl contents of mortars caused a decrease of 28days strength above early strength.