• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.135-136
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• 2017

This paper examines the efficiency of the application of conventional and insulated gang forms for curing and protection of concrete by comparing the amount of electric energy required therefor. In addition, a thermal vision camera was used to identify heat loss from surfaces of the gang forms after each placement of concrete. Experimental results, show that the heat loss at the submerged temperature was large at the submerged surface due to the large calorific value at the surface of the mold. The insulated gang form had some heat loss in the horizontal bars. In the case of adiabatic reforming, the pattern shows a constant calorific value over time. In conclusion, the insulation performance is better than that of general gang form.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.168-169
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• 2013

In this study, the chemical resistance of polyurea resin waterproofing and anti-corrosion materials that is applied to the social infrastructure was analyzed. The result in this study will be utilizing as a basic data for establishing the quality standards which are able to judge the chemically resistant characteristic of polyurea resin waterproofing and anti-corrosion materials.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.235-236
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• 2019

Waterproofing materials and construction methods have been developed and applied to various construction sites since the past. However, there many cases where the waterproofing performance is not satisfactory, leading to continuous water leakage. It has been observed that a key reason for this is because waterproofing method and material selection is not optimized in terms of the appropriate application area and environmental degradation factors. This paper proposes that future selection of waterproofing methods should consider the following evaluation criteria; 1) waterproof performance evaluation according to site conditions, 2) evaluation of construction method, 3) manufacturing and maintenance of waterproofing systems.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.41-47
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• 2010

It has been continuously noted that many sewage treatment concrete structures have deteriorated due to sulfur-oxidizing bacteria. There have been many reports on approaches to protecting concrete from this bacteria corrosion. The purpose of this study is to evaluate the inhibition of growth of a sulfur-oxidizing bacterium by a antifungal agent such as $NiSO_4{\cdot}6H_2O$, and the characteristics of polymer cement mortar using nickel type antifungal agent. First, we developed antifungal agents using metal nickel and $NiSO_4{\cdot}6H_2O$ to inhibit the growth of thiobacillus novellus, which is the sulfur-oxidizing bacteria in concrete. Then, ordinary cement mortar and polymer cement mortar using nickel type antifungal agent with various polymer-cement ratios, and antifungal agent content were prepared, and were tested for the antifungal adding effect, compressive and flexural strengths, expansion and leaching of nickel ion. From the test results, it was confirmed that the adding of an antifungal agent has an inhibition effect on the growth of sulfur-oxidizing bacteria at antifungal agent contents of 20 mM or more. In addition, the strengths and expansion of polymer cement mortars are not significantly changed by the addition of an antifungal agent. Therefore, the nickel-type antifungal agent developed in this study can be used to improve the durability of reinforced concrete hume pipe in the construction industry.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.613-621
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• 2012

Steel corrosion is one of the most critical deteriorations in concrete structures due to the problems associated with both durability and structural safety issues. For protection of steel against corrosion problems, researches to improve concrete durability and steel corrosion protection such as rebar coating by hot-dip galvanizing steel have been carried out. This study was performed to quantitatively evaluate anti-corrosion and structural performance of concrete structures reinforced with hot-dip galvanizing steel rebar. Preliminary tests for several metal coatings such as zinc, aluminum, and their alloy (Zn 45% + AL 55%) were performed. After evaluation of corrosive characteristics, Zn was selected for the coating material and the corrosion behaviors in Zn-coated steel were evaluated in various conditions. Furthermore, tensile and adhesive strengths were evaluated for the normal and the hot-dip galvanized steel. The crack patterns and structural behaviors of RC specimens with the normal and coated steel were investigated. Also, corrosion characteristics including corrosion in various coating metal and potential change in metal with notch were evaluated. Structural performances of tensile and adhesive strengths as well as RC beam behavior under flexural/shear loading were evaluated. The test and evaluation results showed that the applicability of hot-dip galvanized steel rebar can be used as corrosion resistant reinforcements for RC structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.117-125
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• 2017

The role of fly ash in concrete become impotent with finding the characteristics of fly ash in which it is used as cement replacement material. In this paper, corrosion test results obtained by two test methods such as the long-term exposure corrosion test and the accelerated corrosion test method, were compared to investigated the corrosion resistance between fly ash concrete and normal concrete. Corrosion initiation time was measured in two types of concrete, i.e., one mixed with fly ash(FA) and the other without admixture(OPC). The accelerated corrosion test was carried out by four case, i.e., two samples is a cyclic drying-wetting method combined without carbonation(case 1) and combined with carbonation(case 2), and the other two samples is a artificial seawater ponding test method combined without carbonation(case 3) and combined with carbonation(case 4). Whether corrosion occurs, it was measures using half-cell potential method. The ponding test combined without carbonation was most effective in accelerating corrosion time of steel bars. The results indicated that the corrosion of rebar embedded in concrete occurred according to the order of OPC, FA. The delay relative ratio of corrosion obtained by corrosion initiation time between FA and OPC is 1.04 to 1.27. Consequently, fly ash concrete as the age increases its corrosion resistance was improved compared with OPC concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.39-46
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• 2020

Carbonation is a deterioration which degrades structural and material performance by permitting CO₂ and corrosion of embedded steel. Service life evaluation through deterministic method is conventional, however the researches with probabilistic approach on service life considering loading and cold joint effect on carbonation have been performed very limitedly. In this study, probabilistic service life evaluation was carried out through MCS (Monte Carlo Simulation) which adopted random variables such as cover depth, CO₂ diffusion coefficient, exterior CO₂ concentration, and internal carbonatable materials. Probabilistic service life was derived by changing mean value and COV (Coefficient of variation) from 100 % to 300 % and 0.1 ~ 0.2, respectively. From the analysis, maximum reduction ratio (47.7%) and minimum reduction ratio (11.4%) of service life were obtained in cover depth and diffusion coefficient, respectively. In the loading conditions of 30~60% for compressive and tensile stress, GGBFS concrete was effective to reduce cold joint effect on carbonation. In the tensile condition, service life decreased linearly regardless of material types. Additionally service life rapidly decreased due to micro crack propagation in the all cases when 60% loading was considered in compressive condition.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.105-111
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• 2020

The present study examined the effect of the silica-based accelerating agents on the setting time and compressive strength gain of biomimetic glycocalix coating materials that has been developed for protecting the substrate of concrete exposed to chemical and microbiological attacks. The accelerating agent contents varied from 10mL/L to 40mL/L in the mixtures of glycocalix coating materials determined for shotcrete and lining techniques. Test results showed that the setting time of coating materials containing accelerating agents was affected by the contents of the bacteria carrier. When the accelerating agent content was 40mL/L, the final setting time was 80 minutes for shotcrete mixtures and 318 minutes for lining mixtures. Meanwhile, the compressive strength gain of coating materials with accelerating agents tended to be lower than that of counterpart materials without accelerating agents.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.99-104
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• 2006

In this paper, the conventional 2 dimensional metamaterial structure has degeneration of shielding characteristic in cross polarization effect. The proposed 3-D resonator is designed for reduction of cross polarization effect. The proposed 3-D resonator using LTCC consists of 2-D parallel resonators on X-axis, Y-axis and Z-axis. The 2-D parallel resonator consists of two plate and one via. When the co-polarization electric filed is excited, the resonance frequency of 3-D resonator is 5.024GHz. The stop bandwidth is 19MHz. When the cross-polarization electric field is excited, the resonance frequency of 3-D resonator is 4.825GHz. The stop bandwidth is 19MHz. The proposed 3-D resonator achieve reduction of cross-polarization effect. The concrete consists of proposed 3-D resonator and absorbtion materials. The concrete will be applied for reduction or interference signal of ETCS(Electric Toll collection system).