• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.105-106
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• 2016

The study of the sandwich wall with the increasing interest in building energy consumption have been actively conducted. This study designed exposed sandwich wall in the light of energy saving design standard and thermal bridge of share connection. The heat insulating performance was analyzed U-fator using calculation program provided in passive houses association and KS F 2277 (method of measuring thermal insulation of construction component materials).

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.126-134
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• 2009

Generally, reinforced concrete structures exposed to the outside temperature are affected by freezing and thawing process during winter and early spring. These freeze-thawing process can lead to the reduction in durability of concrete as cracking or surface spalling. This paper is to study the flexural behavior of RC beams exposed to freeze-thawing environments. To compare the difference in flexural behavior of RC Beams, limited tests were conducted under different types of Longitudinal steel ratio and freeze-thawing cycles. For this purpose, fourteen small-scale RC beams ($100mm{\times} 100mm {\times}600mm$) were strengthened in monotonic and cyclic loadings, subjected to up to 150, 300 cycles freeze-thawing from $-18{\sim}4^{\circ}C$. It is thought that experimental results will be used as basic data to evaluate flexural behavior of RC beams exposed to freeze-thawing.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.698-707
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• 2002

A review is presented of experimental studies on the strength performance of concrete exposed at short-term and rapid heating as in a fire and after cooling. Emphasis is placed on concretes with high original compressive strengths, that is, high-strength concrete(HSC). The compressive strength-temperature relationships from the reviewed test programs are distinguished by the test methods used in obtaining the data(unstressed, unstressed residual strength, and stressed tests) and by the aggregate types(normal or lightweight), The compressive strength properties of HSC vary differently with temperature than those of NSC. HSC have higher rates of strength loss than lower strength concrete in the temperature range of between 20$^{\circ}C$ to about 400$^{\circ}C$. These difference become less significant at temperatures above 400$^{\circ}C$ compressive strengths of HSC at 800$^{\circ}C$ decrease to about 30 ％ of the original room temperature strength. A comparison of lest results with current code provisions on the effects of elevated temperatures on concrete compressive strength and elastic modulus shows that the CEN Eurocodes and the CEB provisions are unconservative.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.21-22
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• 2009

This paper presents the results of an experimental study on flexural behavior and cracking process of concrete beams subjected to cycles of freezing and thawing after patch-repaired with strain-hardening cement composites (SHCCs). The SHCCs were reinforced with hybrid 0.75% PVA and 0.75% PE fibers. Experimental testing of concrete beams patch-repaired with SHCCs revealed that the SHCC patch-repair system without freeze thaw (FT) exposure showed average 3.31 times increased load carrying capacity and for beams exposed to 300 FT cycles, load carrying capacity increased up to 2.42 times. Cracking damage of SHCC patch-repaired beams mitigated compared to plain concrete beams but this trend decreased under FT exposure.

• Explosives and Blasting
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• v.25 no.2
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• pp.1-10
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• 2007

In this paper, the 1/5 scale models of the reinforced concrete colunms were designed and fabricated. The influence of the number of blasting holes on the exposed length of steel bars and vertical load was investigated. The relation between the length of steel bar and the number of blasting holes was examined by performing the blast tests considering the vertical load on the scaled reinforced concrete columns. Weight of scaled column models by blasting and that of exposed was compared with the number of blasting holes. Finally, based on the exposed length of steel bars and vertical load, the number of blasting holes were calculated. Results shows that the number of blasting holes calculated in this study are suitable for scaled structure models test by blasting demolition.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.693-696
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• 2008

In order to assess time-dependent behaviors of the high-strength concrete that applied in actual FCM bridges with various curing environments, the shrinkages of air-dried, sealed, and moist 100${\times}$100${\times}$400 mm prism specimens were measured. And the compressive creep test of 3 and 28 days aged concrete in the tap water and 10% CaCl$_2$ solutions were carried out, then results were compared with traditional test results of air-dried and sealed specimens. Time-dependent behaviors of the concrete that according to curing circumstances between sealed and moist specimens show remarkable differences not only on the shrinkage but also on the creep. Hence there need some reconsiderations to the traditional creep test manners that predicting the creep and shrink age of actual concrete structures.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.419-424
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• 2021

This study investigated the possibility of early determination of frost damage on the concrete surface by using the rebound hardness method, widely used for estimation the compressive strength of concrete on the site. For this purpose, the surface damage of concrete was compared by measuring the rebound hardness and the relative dynamic modulus of the concrete for the multi-sided and single sided concrete surface exposed to freeze and thaw condition. Compared to the resonance vibration method, the rebound hardness method was able to show the frost damage 150 cycles quicker for the single-sided exposed concrete specimen and 50 cycles quicker for the multi-sided exposed concrete specimen. Therefore, it is considered that the rebound hardness method can determine the concrete surface damage more quickly than that of the resonance vibration method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.400-403
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• 2011

본 논문에서는 시차열중량분석법과 X-선 회절분석법을 이용한 원전콘크리트의 탄산화에 의한 열화도 평가를 진행하였으며 두 가지 정성적 분석방법을 이용한 반정량적 평가 방법을 개발하였다. 원자력발전소 건설에 사용된 동일한 콘크리트 배합을 사용한 시편을 촉진 탄산화 시험장치에 28, 56, 91, 180, 365일 기간에 걸쳐 노출시켜 탄산화를 진행하였으며 노출된 시편은 시차열중량분석법, X-선 회절분석법을 이용하여 탄산화에 따라 발생된 열화생성물의 양을 정성적으로 분석하였다. 그 결과, 탄산화로 인해 발생되는 Calcite의 양이 노출기간에 따라 점차적으로 증가되는 것이 확인되었으며, Calcite의 생성을 위해 이산화탄소와 반응하는 Portlandite의 양이 점차적으로 감소되는 것이 확인되었다. 본 논문에서는 위의 언급된 두 방법의 관계성을 통해 열화도 평가를 진행하였다.

• Magazine of the Korea Concrete Institute
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• v.13 no.4
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• pp.22-29
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• 2001

• Magazine of the Korea Concrete Institute
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• v.13 no.4
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• pp.30-37
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• 2001