• Tuberculosis and Respiratory Diseases
• /
• 제59권6호
• /
• pp.684-689
• /
• 2005

규폐증은 유리규산에 노출될 수 있는 다양한 작업장에서 발생할 수 있는 질환으로 호흡성 분진의 축적에 의한 폐실질의 병리학적 변화를 가져오는 대부분 만성적인 경과를 보이는 질환이다. 하지만 드문 경우에 노출된 분진의 강도와 노출기간에 따라 임상양상이 급격하게 진행되는 경우가 있을 수 있다. 저자들은 진폐증으로 진단하였던 환자가 약 2개월 동안의 급격한 방사선학적 소견의 진행을 보여, 속립성 결핵과의 감별을 위해 시행한 경기관지 폐생검을 통하여 진단하였던 가속형 규폐증 1례를 경험하였기에 문헌고찰과 함께 보고하는 바이다.

• 한국건설순환자원학회논문집
• /
• 제7권2호
• /
• pp.109-115
• /
• 2019

콘크리트에 균열이 발생하는 경우 균열부로의 열화 이온의 침투가 확산되어 철근콘크리트 구조물에 구조적 내구적 문제를 야기한다. 본 연구에서는 보통 및 고강도 플라이애시 콘크리트를 대상으로 재령 56일에 최대 1.0mm까지 다양한 균열 폭을 유도한 후 재령 2년의 정상상태 촉진 염화물 확산계수를 평가하였다. 균열 효과를 선형회귀분석을 통해 고려하면 고강도 콘크리트는 보통 강도 콘크리트 보다 균열 폭에 의한 확산계수 증가가 다소 적었으며 균열 폭이 증가함에 따라 확산계수가 비선형적으로 증가하였다. 또한 두 가지 배합에서 재령이 증가할수록 균열에 의한 영향이 감소하였다. 지수함수 형태를 사용하여 균열 및 재령 효과를 정량화하는 경우, 선형회귀분석을 통한 경우보다 더 높은 결정계수를 나타내었다. 정상상태에서는 균열 효과와 재령의 영향 간의 상관성이 크지 않은 것으로 보이며 두 가지 독립영향을 고려하는 경우 합리적인 균열부 콘크리트 확산성 예측식을 제안할 수 있다고 사료된다.

• 한국건설순환자원학회논문집
• /
• 제6권3호
• /
• pp.53-60
• /
• 2011

건설폐기물이 매년 증가함에 따라 제도적으로 건설폐기물을 재활용한 순환골재의 사용을 촉진하게 되었고, 이에 따라 현장에 순환골재의 사용이 증가되었다. 그러나 순환골재의 알카리수 용출에 의한 환경적 문제가 발생하게 되었고, 이를 저감시킬 방안에 대한 연구가 요구되었다. 본 연구는 순환골재의 알카리저감을 위한 방안으로 촉진탄산화 반응을 이용한 알카리 저감장치를 제작하여 순환골재 생산현장에 설치하고, 대량의 순환골재를 대상으로 알카리저감효과 및 품질의 영향을 분석하였다. 그 결과, 탄산화 반응시간 30초, 반응압력 -50 kPa에서 100 kPa까지 3싸이클의 압력변화를 주는 조건에서, 순환골재 pH는 9.33에서 9.8의 범위 내를 유지하였다. 또한 순환골재의 물리적 품질은 탄산화 반응 전보다 반응 후의 소성지수, 수정 CBR, 마모감량, 모래당량, 액성한계, 입도분포, 밀도 및 흡수율이 개선되는 것으로 나타났다.

• Corrosion Science and Technology
• /
• 제6권4호
• /
• pp.186-192
• /
• 2007

Carbonation is one of the most important factors causing the corrosion of reinforcement concrete. Nevertheless, experimental studies on the concrete carbonation have not been carried out sufficiently because of the slow process of carbonation process. Therefore, this study adopts an experimental system exploiting a vacuum instrument that has been recently developed to accelerate carbonation instead of existing experimental system to conduct rapid carbonation tests on Portland cement and fly-ash cement concretes. Test results revealed that, compared to water-cement ratio of 40%, the carbonation depth increases from 103% to 138% for an increase of water-cement ratio from 45% to 60%. These results are larger than the carbonation depths obtained by mathematical model, and such difference is increasing with larger water-cement ratios. The results also indicated that larger fly-ash contents lead to sharp increase of the carbonation depth, which is in agreement with previous experimental researches. The adoption of the new accelerated carbonation test system enabled to shorten effectively the time required to produce experimental data compared to the existing carbonation test method. The experimental data obtained in this study together with ongoing acquisition of data using the new carbonation test method are expected to contribute in the understanding of the carbonation process of concrete structures in Korea.

• 한국건축시공학회지
• /
• 제5권3호
• /
• pp.101-107
• /
• 2005

This paper reports the contribution of Shrinkage reducing admixture(SRA) to the physical properties and drying shrinkage of concrete. Dosage of SRA is varied with. For the properties of fresh concrete, an increase in SRA dosage results in a decrease in fluidity and air content, while setting time is accelerated. For the properties of hardened concrete, the incorporation of mineral admixture leads to a decrease in compressive strength at early age, whereas after 28 days, the incorporation of fly ash(FA) and blast furnace slag(BS) has greater compressive strength than conventional concrete without admixture. The use of SRA results in a decrease in compressive strength. The incorporation of SRA with every $1\%$ increase causes the decrease of compressive strength by as much as $3\~6\%$. For drying shrinkage properties, the incorporation of FA and BS reduces drying shrinkage slightly. The use of SRA also decreases drying shrinkage. Every $1\%$ of increase in SRA dosage can reduce drying shrinkage by as much as $10\~15\%$

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2004년도 학술.기술논문발표회
• /
• pp.41-44
• /
• 2004

Recently, in the case of domestic, for all that the deterioration environment about the carbonation of reinforced concrete structures is accelerated, systematic diagnosis and researches are not completed. And the selection techniques of repair material and method used under the situation that the indicator and the performance evaluation method are nor established are dependant on existing experience. Therefore, the purpose of this study is intend to present fundamental data for the reasonable selection of repair material and method. durability design and longevity on the deteriorated reinforced concrete structures, through computing the carbonation depth and velocity coefficient by accelerating carbonation test under various accelerating conditions and investigating the application of carbonation evaluation method. The results of this study are as follow; The resistances to carbonation are increased when the W/C ratio if lower and the treatment of surface coating is executed. And the carbonation depth and velocity coefficient according to accelerating carbonation test conditions are increased when the conditions of temperature, relative humidity and $CO_2$density are higher individually.

• 한국건축시공학회지
• /
• 제6권3호
• /
• pp.99-105
• /
• 2006

In this paper, the estimation of compressive strength of concrete incorporating fly ash subjected to high temperature is discussed. Ordinary Portland cement and fly ash cement(30% of fly ash) were used, respectively. Water to binder ration ranging from 30% to 60% and curing temperature ranging from $20^{\circ}C{\sim}65^{\circ}C$ were also adopted for the experimental parameters. According to results, at the high temperature, FAC had higher strength development at early age than OPC concrete and it kept its high strength development at later age due to accelerated pozzolanic reaction subjected to high temperature. For strength estimation, Logistic model based on maturity equation and Carino model based on equivalent age were applied to verify the availability of estimation model. It shows that fair agreements between calculated values and measured values were obtained evaluating compressive strength with logistic curve. The application of logistic model at high temperature had remarkable deviations in the same maturity. Whereas, the application of Carino model showed good agreements between calculated values and measured ones regardless of type of cement and W/B. However, some correction factors should be considered to enhance the accuracy of strength estimation of concrete.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 추계 학술논문 발표대회
• /
• pp.57-58
• /
• 2015

In this research the processing method of Desulfurized Plaster is changed to cyclotomy, 0.3mm sieve analysis and 500℃ heat exposure, and by changing the mix rate of the binding agent to 0~20%, it was applied to mortar that used cyclic aggregate and blast furnace slag for testing. The test results showed that the flow decreased in the order of cyclotomy, high heat exposure, and sieve analysis according to the mix rate of FGD, and while the air volume decreased for cyclotomy, it was shown to have almost no effect on sieve analysis and high heat exposure. The setting time accelerated as the mixing rate of FGD increased, and the compression strength increased as the mixing rate of FGD increased and especially showed a high trend with cyclotomy and sieve analysis.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 추계 학술논문 발표대회
• /
• pp.55-56
• /
• 2015

In this research the processing method of Desulfurized Plaster is changed to cyclotomy, 0.3mm sieve analysis and 500℃ heat exposure, and by changing the mix rate of the binding agent to 0~20%, it was applied to mortar that used natural aggregate and blast furnace slag for testing. The test results showed that the sieve analysis and high heat exposure of the flow and air volume increased according to the increase of mixing rate of FGD while the cyclotomy decreased. The setting time accelerated as the mixing rate of FGD increased, and the compression strength increased to its maximum when the mixing rate of FGD was right around 10%, and especially showed a high trend with cyclotomy and sieve analysis.

• Nuclear Engineering and Technology
• /
• 제52권9호
• /
• pp.2119-2129
• /
• 2020

Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDIE), cavitation and flashing can cause continuous wall-thinning in nuclear secondary pipes. In order to prevent pipe rupture events resulting from the wall-thinning, most NPPs (nuclear power plants) implement their management programs, which include periodic thickness inspection using UT (ultrasonic test). Meanwhile, it is well known in field experiences that the thickness measurement errors (or deviations) are often comparable with the amount of thickness reduction. Because of these errors, it is difficult to estimate wall-thinning exactly whether the significant thinning has occurred in the inspected components or not. In the previous study, the authors presented an approximate estimation procedure as the first step for thickness measurement deviations at each inspected component and the statistical & quantitative characteristics of the measurement deviations using plant experience data. In this study, statistical significance was quantified for the current methods used for wall-thinning determination. Also, the authors proposed new estimation procedures for determining local wall-thinning to overcome the weakness of the current methods, in which the proposed procedure is based on analysis of variance (ANOVA) method using subgrouping of measured thinning values at all measurement grids. The new procedures were also quantified for their statistical significance. As the results, it is confirmed that the new methods have better estimation confidence than the methods having used until now.