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3종 혼합 잔골재를 사용한 굳지 않은 모르터의 성능 평가
유명열(Yu Myoung-Youl),이재용(Lee Jae-Yong),정철우(Chung Chul-Woo) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.1
The use recycled aggregate from the demolished concrete started to draw attention from concrete industry due to the economical and environmental concerns. The main use of recycled aggregate is to substitute for the coarse aggregate, but it is also used for the source of fine aggregate. However, the application of recycled fine aggregate to the concrete is still limited by the lack of the confidence in the quality of concrete. The available information from current research suggests the recycled fine aggregate to be substituted to natural fine aggregate for certain content, not recommended to use it by itself. Considering the lack of natural aggregate sources, the use of recycled fine aggregate needs to be promoted, for example, by blending it with other aggregates from various sources. To provide the guiding information for such applications, this research focuses on the investigation of mortar using fine aggregates from three different sources. The use of mortar is to remove the effect of coarse aggregate, and to efficiently evaluate the effect of blended fine aggregates to the properties of the mixture. Only fresh properties were investigated in this research, and the result indicated that the mortar flow was affected by the surface condition rather than the type of fine aggregate. The air content increased as the amount of porous recycled fine aggregate in the mixture increased. The unit weight was shown to be solely affected by the bulk specific densities of fine aggregates.
천연골재, 부순골재, 순환골재의 혼합비율에 따른 혼합 잔골재의 성능평가
유명열(Yu Myoung-Youl),이재용(Lee Jae-Yong),정철우(Chung Chul-Woo) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.11
The resources of natural fine aggregate started to decrease due to the increase in the amount of construction. In addition, it becomes more difficult and less economical to dispose used concrete structure because of the environmental concerns. The use recycled aggregate from the demolished concrete to produce new concrete, therefore, becomes an important issue in the concrete industry. Currently, the recycled aggregates are often used as a source of fine aggregate after some mechanical treatment, but the application to the concrete is limited by the lack of the confidence in the quality of recycled fine aggregate. In most cases, recycled fine aggregate is used as a source of blending fine aggregates, not by itself. Although the standard specification for quality evaluation of the blended aggregates is available, it is still difficult to use blended aggregates in the construction field due to absence of quality management procedure. Therefore, this research especially focuses on the estimation of the properties of the fine aggregate blended by 3 different aggregates. The estimation of properties based on the individual properties of each aggregates was performed using linear interpolation, and compared to the measured values from blended aggregates. The results indicate that the properties of blended fine aggregates can be successfully calculated based on their individual properties.
유명열(Yu Myoung-Youl),이재용(Lee Jae-Yong),최응규(Choi Eung-Kyoo),이현수(Lee Hyun-Soo) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.7
Carbonation does not cause deterioration of concrete but damage on durability of concrete because of corrosion of steel embedded in hydrating cement paste. In order to prevent reinforcing steel from corrosion, it is very important to maintain passivation by measurement of the depth of carbonation and repair. Laboratory techniques that can be used to determine the depth of carbonation are indicators, X-ray diffraction, infra-red spectroscopy and thermogravimetric analysis, etc. In those methods, phenolphthalein method is most useful in practical measurement because the method is easy and rapid to perform despite low reliability. Even though researches, which are carried out to improve the reliability of phenolphthalein method through standardization of usage, are being conducted, phenolphthalein method still has potential problems. 1) It is impossible to measure the degree of early carbonation and 2) the quantity of OH- with varying depth because the pink color indicates the presence of Ca(OH)2 in accordance with pH 8.9. In this study, many indicators are selected and applied to improve the reliability of phenolphthalein and solve the potential problems.
습식 생산된 재생 잔골재를 사용한 콘크리트의 특성에 관한 연구
심종우(Shim Jong-Woo),유명열(Yu Myoung-Youl),이세현(Lee Sea-Hyun) 대한건축학회 2004 大韓建築學會論文集 : 構造系 Vol.20 No.12
The recycled fine aggregate produced by a existing method is not recommended to use recycled fine aggregate for production of quality concrete, considering that it increases the water demand of fresh concrete and lower the strength and probably the durability of hardened concrete. But, the recycled fine aggregate is becoming increasingly important for alternative of natural fine aggregate faced shortage. Therefore, in this study, I proposed a production method which are able to produce recycled fine aggregates for quality concrete with a classifier, and analyzed the quality of the recycled fine aggregate and comprehended the properties of recycled aggregates mortar using the recycled fine aggregate to review whether it can be put to practical use for concrete. In the experiment, recycled fine aggregate is substituted for natural fine aggregate the rate of 0, 25, 50, 75 and 100% each. The results of the study are as follows.<br/> 1) The air content is increased irregularly according to the increasing of substitutive ratio<br/> 2) The slump and loss of slump with time since mixing are decreased irregularly according to the increasing of substitutive ratio<br/> 3) The compressive strength of the mortar using the recycled fine aggregate tends to be increase until 25~50% substitution ratio, and than reduced with the increase of the mixing ratio of recycled fine aggregate<br/> Based on the above results, it is concluded that the recycled fine aggregate through the wet production process can be used as fine aggregate on condition that the substitution ration is under 50%.
임중연(Lim Joong Yeon),유명열(Yu Myoung Youl),김종권(Jong-Kwon Kim),이현근(Hyun Geun Lee),김준석(Junseok Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In this presentation, we study numerically an optimization problem of a fire fighting robot cooling system. The governing equation for the system is the unsteady heat equation with source term. We use a multigrid method for numerical solutions in three-dimensional space. We investigated the effects of various parameters and the results will be presented.
봉파쇄기로 생산된 순환 굵은골재의 품질특성 및 이를 사용한 콘크리트의 기초적 특성
백대현(Baek Dae-Hyun),한동엽(Han Dong-Yeop),유명열(Yu Myoung-Youl),한천구(Han Cheon-Goo) 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.10
This paper presents the results of quality test of recycled coarse aggregate produced by the bar crusher and its effect on concrete properties. Recycled coarse aggregate by the bar crusher had larger density and shape index, and lower absorption ratio and loss due to abrasion than those of control recycled aggregate made by cone crusher and impact crusher due to improved peeling of mortar attached to the vicinity of aggregate and improved grain shape. For fresh properties, slump and air content had better results than those of concrete mased with recycled aggregate using existing crushing machine in order for bar crusher(S) > cone crusher(C)>impact crusher(I). For S, slump of concrete had favorable results with the increase of rotation speed, recycled aggregate contents and maximum size of aggregates. For compressive strength, the use recycled aggregates made with S and C had a favorable effect on the compressive strength of concrete except I. The variation of rotation speed of bar crusher led to reduction of compressive strength within 10%. At 500 rpm of rotation speed, compressive strength showed desirable values. An increase in recycled aggregates contents resulted in an increase in compressive strength. It is found that concrete with 40% of W/C had favorable compressive strength at 75% of recycled aggregates contents and with 60% of W/C, 50% of recycled aggregates.