• KSBB Journal
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• v.29 no.3
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• pp.188-192
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• 2014

Calcite forming bacteria (CFB) have been received increasing attention as a novel and environmental friendly strategy for the healing of concrete crack. Among the CFB, spore forming bacteria were proposed to overcome concrete condition (high pH, hydration heat, deicer). In this study, Lysinibaclillus sphaericus WJ-8 (WJ-8) isolated from concrete pavement was characterized. The WJ-8 was able to precipitate calcite at 10 mg/mL. When observed by scanning electron microscopy, WJ-8 showed spore formation and maximum spore yield was approximately 97.9%. Also response of spores against various environment stresses was examined. Approximately 83~97% of spores maintained their survivability at each three conditions ($60^{\circ}C$, 3 M NaCl and pH 12).

• KIEAE Journal
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• v.11 no.1
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• pp.9-14
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• 2011

Currently, the multi-residential apartments used in Korea are mostly bearing wall apartments which don't satisfy consumers for the lack of architectural plan flexibility. And due to remodelling-incompatible, bearing wall apartments have to be reconstructed. It is, thus, necessary to develop multi-residential apartments utilizing composite beam that can replace the conventional bearing wall-type apartment buildings. Composite beams proposed in this paper ensure modification of space and quality control, while the floor heights are maintained at the same floor height as in bearing wall structures. This study analyzes the experimental behavior of composite beams with proper combination of structural steel, reinforced concrete, and precast concrete. By comparing with the theoretical analysis and experimental results, the accuracy of flexural moment capacity and neutral axis was evaluated. The experiments were performed by two simply-supported specimens using loading and unloading. When the analysis results were compared with the experimental results, the flexural moment capacity of the composite beam was shown with an error of approximately -0.5 to 0.1% at the maximum load limit state.

• KIEAE Journal
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• v.7 no.4
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• pp.113-118
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• 2007

From the construction material the cement and the concrete which will reach to 90% are used to construction. But the cement occurrence (from the whole industry 4.4% of carbon dioxide exhaust quantity) makes the carbon dioxide of manufacture hour and anti- the recognition which is an environment industry. The cement absorbs the carbon dioxide during life period of the life time. It calls carbonation. In this study in order to evaluate the carbon dioxide absorption of the cement test produced the mortar specimens which it follows in the W/C. And carbonatable material of mortar specimens (calcium hydroxide) the quantitly it measured, reference study it led and absorption of carbon dioxide quantity it produced. Finally two result comparisons leads and it is a fundamental study which does the test evaluation possibility and a propriety investigation of carbon dioxide absorption quantity in objective.

• KIEAE Journal
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• v.7 no.4
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• pp.141-146
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• 2007

It is necessary to guarantee the safety, serviceability and durability of reinforced concrete structures over their service life. However, concrete structures represent a decrease in their durability due to the effects of external environments according to the passage of time, and such degradation in durability can cause structural degradation in materials. In concrete structures, some degradations in durability increase the corrosion of embedded rebars and also decrease the structural performance of materials. Thus, the structural condition assessment of RC materials damaged by corrosion of rebars becomes an important factor that judges needs to apply restoration. In order to detect the damage of reinforced concrete structures, a visual inspection, a nondestructive evaluation method(NDE) and a specific loading test have been employed. However, obscurities for visual inspection and inaccessible members raise difficulty in evaluating structure condition. For these reasons, detection of location and quantification of the damage in structures via structural response have been one of the very important topics in system identification research. The main objective of this project is to develope a methodologies for the damage identification via static responses of the members damaged by durability. Six reinforced concrete beams with variables of corrosion position and corrosion width were fabricated and the damage detections of corroded RC beams were performed by the optimization and the conjugate beam methods using static deflection. In results it is proved that the conjugate beam method could predict the damage of RC members practically.

• Explosives and Blasting
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• v.14 no.1
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• pp.49-63
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• 1996

Blasting is a work that destruct an object by use of explosive. Its use covers a wid range, and it is applicable to blast the rocks, minerals, coal, steel and concrete structures, bridges, etc. To execute the blast plan most effectively, the properties of the object and the explosives should be well understood, and all the other conditions must ve incorporated in its design and plan. A safe blasting pattern and procedure should be selected considering the envirinmental effects and dther conditions. At the same time, a protective protective pricedures should be utilized to prevent the safety hazards such as the excessive blast vubration, air pressure, and the flying fragments. This study reviews the controlled blasting techniques in these regards.

• International Journal of Highway Engineering
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• v.19 no.3
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• pp.1-10
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• 2017

PURPOSES : This paper focuses on strength development according to the mix design with cement type and mineral admixture from laboratory and field tests in cool weather. METHODS : Two methods evaluated the mix design of concrete pavement in cool weather. Firstly, laboratory tests including slump, air contents, setting time, strength, maturity, and freezing-thawing test were conducted. Three alternatives were selected based on the tests. Secondly, a field test was conducted and the optimum mix design in cool weather was suggested. RESULTS : It is an evident from the laboratory test that a mix with type III cement showed better performance than the one with type I cement. There was a delay in strength development of a mix with mineral admixture compared to mix design without any mineral admixture. In the field test, type III cement+flyash 20% mix design proved the best performance. CONCLUSIONS : For concrete pavement in cool weather, mix design using type III cement could overcome the strength delay due to mineral admixture. Moreover, it is possible to make sure of durability of pavement. Therefore, strength and durability problems due to cool weather would decrease.

• International Journal of Highway Engineering
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• v.19 no.3
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• pp.11-18
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• 2017

PURPOSES : This study investigates the effect on concrete pavement accordance with the curing methods in cool weather and supports the best method in the field. METHODS : Two field tests evaluated the curing methods of concrete pavement in cool weather. Firstly, five curing methods were tested, including normal curing compound, black curing compound, bubble sheet, curing mat, and curing mat covered with vinyl. Concrete maturity was compared from temperature data. Secondly, normal curing compound and curing mat with vinyl, which showed the best performance, were compared in terms of maturity and join condition index. RESULTS:From the field tests, it is an evident that curing mat with vinyl accelerated the concrete strength. Therefore, it is possible to conduct saw-cut works in cool weather, which minimizes damage on concrete at joint. CONCLUSIONS : For concrete pavement in cool weather, using curing mat with vinyl as the curing method could overcome the strength delay. Therefore, strength and durability problems on concrete at joint due to cool weather would be fewer in the future.

• Journal of the Korean Society of Safety
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• v.30 no.6
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• pp.102-109
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• 2015

In this study, on the basis of the results of the field survey and the theoretical consideration for Korean Standard Specification for concrete durability and maintenance, the following conclusions are derived. From the survey, the prediction equation of carbonation depth for the southwest region in Korea is experimentally proposed, $y_p=5.865{\sqrt{t}}$, which predicts about 60mm of the carbonation depth for the concrete structures of 100 years, a 1st class of target endurance period, under a combined deterioration environment like a marine environment. Considering that the marginal value for a carbonation depth limitation under very severely marine environment is 25mm, in accordance with the Specification, it is found that the predicting carbonation depth for the concrete cover depths, 100mm and 60mm are 63mm and 29.4mm, respectively. In conclusion, according to the equation and the Specification, it is strongly required that the reinforced concrete structures with the cover depth under 100mm have to make a protection from combined deterioration factors by any methods like a surface coating, an increment of cover depth or an application of a special concrete.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.100-104
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• 2009

In this study, the space gamma dose rates in the apartments structured with concrete were measured in accordance with construction year. In addition, the environmental radiation rates coming from the subway platforms and the road tunnels were analyzed in the equivalent dose by multiplying the absorbed dose with the radiation weighting factors. The space gamma dose rates measured in apartments were higher than those of outdoor which was $0.08{\sim}0.11uSv/h$ in the natural conditions. Especially, the older construction year is, the higher becomes space gamma dose rate. The average gamma dose rates in the subway platforms were measured. In the case of Busan and Daegu subway, the earlier the opening year is, the higher becomes dose rate. However, the dose rates of Seoul subway Lines were high overall, regardless of opening year. Seoul subway Line 6 showed the highest value of 0.21uSv/h. The gamma dose rate in road tunnels was higher than one of the outdoor and increased with opening year like as apartment. In dose rate comparison of the concrete structures with the outdoor, therefore, the space gamma dose rate of indoor is higher than one of the outdoor and the older structures have a higher dose rate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.132-133
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• 2016

This research team has developed single silk white bubble sheets to be used as surface sheath curing material for spring, summer, and autumn. But though its effects for spring and autumn temperature conditions have been proved, there haven't been any studies for summer temperature conditions. Therefore in this study, single silk white bubble sheets and single silk transparent bubble sheets as well as aluminum metalizing single silk bubble sheets have been applied to actual box-frame apartment slabs in construction, in order to compare temperature backgrounds of the concrete and other qualities. Upon application, the temperature of concrete cured in summer temperature conditions showed excellent scores, being the lowest for aluminum metalizing single silk white bubble sheets, then single silk transparent bubble sheets. But the aluminum metalizing single silk bubble sheet gave off a harmful glare, so for actual use, white single silk bubble sheets are recommended.