• Journal of the Korean Wood Science and Technology
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• 제32권3호
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• pp.33-41
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• 2004

In ancient wooden structures, the mechanical properties of the structural members have been reduced by time-dependent degradations such as fatigue or creep. Also, the external and internal deterioration was caused by environmental condition, fungi, bacteria, or insect, and then reduced the quality of structural members. However, the previous methods for evaluating the deterioration have been mainly depended on the visual inspection. In this study, therefore, ultrasonic stress wave test, accelerometer stress wave test were used to evaluate the deterioration of structural wood members in ancient wooden structures. Based on the results, the quantitative criteria of stress wave transmitted velocity were proposed to evaluate the deterioration of structural member. The proposed criteria were related to the degree of deterioration. In accelerometer stress wave, the criteria of deterioration of wave reciprocal velocity was below 1800 ㎲/m at incipient deterioration (below 12% ratio of deterioration), between 1800 and 2200 ㎲/m at moderate deterioration (12~17%) and above 2200 ㎲/m at severe deterioration (above 17%). The ultrasonic stress wave, the criteria of deterioration were 800 and 950 ㎲/m at below 8% and above 15% of the degree of deterioration respectively.

• Corrosion Science and Technology
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• 제8권2호
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• pp.53-61
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• 2009

본 연구에서는 강교 도장재료로 사용될 수 있는 에폭시 하도 도료를 도포한 시험편을 촉진시험을 통해 열화시킨 후 도막의 외관 평가 및 EIS에 의한 평가를 실시하고, 그 2가지 방법에 대한 비교 분석을 실시하였다. 화상처리 기법에 의해 구한 총 열화 면적율과 열화도 평점 산정 결과를 상호 비교해 본 결과 녹이 발생한 경우가 그렇지 않은 경우보다 열화도 평점이 높게 나타났다. 이는 강교 도장의 열화도 평가 기준에서 단위 열화 면적율당 부여하는 열화도 평점이 박리의 경우보다 녹의 경우가 더 크기 때문이다. 열화 면적율과 EIS 측정 데이터를 비교해 본 결과 녹의 면적율 약 0.1% 이상, 블리스터링의 면적율 약 3% 이상만 되어도 도막의 임피던스는 약 $10^4{\Omega}{\cdot}cm^2$ 혹은 그 이하로 크게 저하되었다. 2개의 시험편을 제외한 모든 시험편에 대해 전하전달저항(charge transfer resistance, $R_{ct}$)과 이중층 정전용량(double layer capacitance, $C_{dl}$) 값이 나타났으며, 이 결과로부터 이들 시험편들은 도막과 강재 계면에 수분이 축적되어 부식이 진행되고 있음을 알 수 있었다. 열화도 평점과 EIS 측정결과를 상호 비교해 본 결과 저주파수(10 mHz)에서의 임피던스 값이 $10^6{\Omega}{\cdot}cm^2$ 이하로 떨어진 경우는 모두 열화도 평점이 10점 이상으로 나타났으며, NORSOK cyclic test 과정에 의해 열화시킨 경우 열화도 평점이 높지 않음에도 불구하고 임피던스는 가장 낮게 나타났다. 이것은 도장계와 열화조건이 주 시험편과 다르기 때문인 것으로 판단되며, 열화조건이 더 가혹하거나 복합적일 경우 외관 상태에 비해 도막의 저항이 더 크게 저하될 가능성이 있다고 생각된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.727-730
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• 2003

The objective of this work is to understand the deterioration mode of ordinary portland cement pastes and mortars immersed in 5% sodium sulfate solution for 510 days. In order to achieve the goal, x-ray diffraction (XRD) and scanning electron microscopy (SEM) are presented in this experimental work. Strength deterioration (SDF) and length change of the mortars were also measured to evaluate resistances to the attacking solution. The mortars were prepared by using water-cement ratio of 35%, 45% and 55%, respectively, and the water-cement ratio of pastes was fixed at 45%. Conclusively, the deterioration by sodium sulfate attack was primarily due to the formation of ettringite and thaumasite. This process of deterioration may submit the reasonable understanding on the sulfate attack mechanism of hardened cement pastes, mortars, and concretes.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.623-631
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• 2018

공용중인 콘크리트 구조물의 내구성 연구는 한 가지 원인에 대한 단독열화 연구를 주로 연구하였지만 실제 구조물의 공용시기에는 두 가지 이상의 환경에 노출되어 있어 이러한 복합열화에 대한 관심이 최근 증가하고 있는 실정이다. 복합열화에 대해 일반적으로 염해와 동결융해에 대해서는 일부 연구가 진행되어 있지만 콘크리트의 양생 직후부터 발생하는 탄산화와 다른 내구성능저하에 대한 복합열화 연구는 매우 미흡한 실정이다. 특히, 탄산화를 중심으로 하는 복합열화는 탄산화의 경우 탄산화 진행시 콘크리트 조직이 치밀해진다는 문헌고찰에 따라 조직의 치밀해지는 이유로 연구가 미흡하다. 본 연구에서는 콘크리트의 탄산화 및 동결융해에 대한 복합열화를 평가 분석한 결과이다. 평가를 위하여 탄산화된 콘크리트를 동결융해 300싸이클까지 복합열화 시험을 실시하여 동탄성계수와 압축강도를 측정하였다. 그 결과 물-결합재비에 대한 영향 평가에서 35 %의 콘크리트가 55 %의 콘크리트에 비해 복합열화 성능이 낮은 것을 확인하였고, 광물질혼화재료를 사용한 경우 플라이애시와 고로슬래그미분말을 사용한 경우 동일 물-결합재비에서 보통포틀랜드 시멘트 사용 콘크리트보다 복합열화에 대한 성능이 개선되는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.101-102
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• 2023

This study aims to mix the base concrete by mixing latex to improve the durability performance to reduce the composite deterioration of the base concrete. Latex fiber has high resistance to freezing and thawing, adhesion, and deicing agent (calcium chloride), and it is used to secure long-term durability to reduce cracking and compound deterioration of concrete. In addition, through experiments, we are trying to find ways to improve the strength of concrete by studying the mixing of the appropriate mixing ratio of latex.

• 한국도로학회논문집
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• 제20권3호
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• pp.11-18
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• 2018

PURPOSES : Durability of concrete is traditionally based on evaluating the effect of a single deterioration mechanism such as freezing & thawing action, chloride attack, carbonation and chemical attack. In reality, however, concrete structures are subjected to varying environmental exposure conditions which often results in multi-deterioration mechanism occurring. This study presents the experimental results on the durability of concrete incorporating air-cooled slag(AS) and/or water-cooled slag(WS) exposed to multi-deterioration environments of chloride attack and freezing & thawing action. METHODS : In order to evaluate durable performance of concretes exposed to single- and multi-deterioration, relative dynamic modulus of elasticity, mass ratio and compressive strength measurements were performed. RESULTS :It was observed that multi-deterioration severely affected durability of concrete compared with single deterioration irrespective of concrete types. Additionally, the replacement of cement by AS and WS showed a beneficial effect on enhancement of concrete durability. CONCLUSIONS : It is concluded that resistance to single- and/or multi-deterioration of concrete is highly dependent on the types of binder used in the concrete. Showing the a good resistance to multi-deterioration with concrete incorporating AS, it is also concluded that the AS possibly is an option for concrete materials, especially under severe environments.

• 한국구조물진단유지관리공학회 논문집
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• 제2권4호
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• pp.186-193
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• 1998

The purpose of this research is to seek properties of flowing light-weight aggregate concrete and possibility of application. The experimental analysis results by using light-weight aggregate and industrial waste such flyash, furnace slag are as follow. 1) The research shows that flowing light-weight aggregate concrete of slump 23~27cm, slump flow 58~69 cm is possible, but material segregation is appeared above slump 26.5cm and slump flow 65 cm. 2) If mixing ratio of flyash is increase, strength deterioration is about 25 % in early age. It showed that effectiveness of long time strength improvement because strength manifestation ratio is above 95% in a long term. 3) This research showed possibility of substitution of blast furnace slag because strength deterioration by using mixing of furnace slag was appeared small deterioration range as below 10 %. 4) Each experimental compressive strength ratios were 77 %(1st week), 86 %(2nd week), 109 %(8th week), 115 %(13th week), 125 % (26th week) on the basis of 28 days. If mixing ratio of flyash is increase, long term strength increase ratio is improved.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.169-174
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• 1996

It have been announced that concrete subjected to freezing and thawing cause deterioration by expanded inside water and contracted at thawing. However, this study descrebe the deterioration mechanism of concrete by freezing and thawing test. Embeded strain gauges were used to measure the inside restrict strain due to the temperature differenct inside and outside the concrete test specimens. Test results showed that using the air entrained admixture and expanded poly-styrene was developed durability of concrete by decreasing inside retrict strain ratio.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.53-58
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• 2003

Concrete structures move wholly with concrete and rebar, so they endure external force, but recently the embedded rebar in concrete has been corroded by environmental, physical and chemical factors, the embedded rebar corrosion influences concrete structure to deteriorate structure capacity. To revaluate effect to deterioration of concrete structure according to corrosion of rebar, the researcher mostly examined into corrosion rebar and complex relation of concrete. In that there are flexural strength deterioration of corrosion concrete structure and the bond strength of concrete. But It has not sufficiently studied about physical characteristic of corrosion rebar itself. In this study I will compare specification of rebar through corrosion experiment with corrosion ratio of rebar according to diameter and revaluate. And will investigate the effect to strength characteristic of rebar according to corrosion ratio.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.53-58
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• 2003

Concrete structures move wholly with concrete and rebar, so they endure external force, but recently the embedded rebar in concrete has been corroded by environmental, physical and chemical factors. the embedded rebar corrosion influences concrete structure to deteriorate structure capacity. To revaluate effect to deterioration of concrete structure according to corrosion of rebar, the researcher mostly examined into corrosion rebar and complex relation of concrete. In that there are flexural strength deterioration of corrosion concrete structure and the bond strength of concrete. But It has not sufficiently studied about physical characteristic of corrosion rebar itself. In this study I will compare specification of rebar through corrosion experiment with corrosion ratio of rebar according to diameter and revaluate. And I will investigate the effect to strength characteristic of rebar according to corrosion ratio.