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Using Recycled Asphalt Materials as an Alternative Material Source in Asphalt Pavements
문기훈,Augusto Cannone Falchetto,Mihai Marasteanu,Mugurel Turos 대한토목학회 2014 KSCE Journal of Civil Engineering Vol.18 No.1
Using recycled materials in pavement applications is a viable option to reduce costs and limit the environmental impact of road construction. During the past decades, many agencies in the U.S. have investigated the effect on pavement performance of adding Reclaimed Asphalt Pavement (RAP), and, more recently, Recycled Asphalt Shingles (RAS) to asphalt mixtures, and limits were proposed on the amount of recycled materials which can be used. This paper investigates the effect of adding both RAP and RAS to virgin asphalt mixtures by means of a simple low temperature creep test performed on asphalt mixture beams. From the experimental work, creep stiffness, m-value, thermal stress and critical cracking temperature are calculated and compared statistically and graphically. Based on the results, it is concluded that most of the mixtures prepared with combinations of RAP and RAS perform similarly to standard mixtures at low temperature. For a limited number of mixtures, a negative effect is observed.
문기훈,한상환,조한철,이강석 한국지진공학회 2011 한국지진공학회논문집 Vol.15 No.6
본 연구의 목적은 마찰 감쇠기를 사용한 기존 구조물의 제진보강 설계절차를 제시하는 것이다. 보강된 구조물의 목표 지붕층 변위는 기존 구조물이 급격한 강도의 저감없이 보유내력을 발휘할 수 있는 최대변위를 초과하지 않도록 결정하였다. 보강 구조물의 변위는 비탄성 변위비 제안식을 이용하여 예측하였다. 제안된 방법의 유효성을 검증하기 위하여 80개의 지반운동 데이터를 사용하여 비선형 동적해석을 수행하였다. 해석결과 제안된 방법은 보강 구조물의 지붕층 변위를 정확히 예측할 수 있는 것으로 나타났다. The purpose of this study was to propose a design procedure for a damped structure with a friction damper for an existing structure. The target displacement of the damped structure was determined using the maximum displacement of the existing structure. The displacement of the damped structures was predicted using a proposed equation for the inelastic displacement ratio. For this study, we conducted a nonlinear response history analysis using 80 earthquake ground motions to verify the validity of the proposed design procedure by comparing the responses of the damped and undamped structures. Based on the dynamic analysis results, it was concluded that the predicted displacement of the damped structure using the proposed design procedure matched well with the analysis results.
Investigation of Limiting Criteria for Low Temperature Cracking of Asphalt Mixture
문기훈,Augusto Cannone Falchetto,Mihai O. Marasteanu 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.1
This paper investigates the possibility of developing low temperature limit criteria for asphalt mixtures, similarly to what is currently available in the standard specification for asphalt binder. The investigation is based on extensive experimental work that includes Bending Beam Rheometer (BBR) creep tests on asphalt binders and asphalt mixtures at low temperature and on semiempirical Hirsch model, and on the rheological model proposed by Christensen, Anderson and Marasteanu (CAM). Limiting asphalt mixture creep stiffness values are predicted from Pressure Aging Vessel (PAV; Long term aging) binder creep stiffness data and are next compared with results available in literature. Then, BBR creep data for Rolling Thin-Film Oven Test (RTFOT; Short term aging)asphalt binder are used to predict creep stiffness of the corresponding short term aged asphalt mixtures. Based on these results, a range of limiting stiffness values is obtained. Due to large variations in the calculated slopes of the mixture creep stiffness curves, a limiting value for the relaxation parameter m-value could not be recommended.
$Fe_2O_3$몰비 및 B\ulcorner첨가가 Sr-Ferrite 특성에 미치는 영향
문기훈,심영재,조성걸 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.5
Sr-ferrite having magnetoplumbite structure is similar to Ba-ferrite in magnetic characteristics, but better magnetic characteristics for using motor application. To improve remanence magnetic flux density(Br) and coercive force(iHc), it is necessary that sintered ferrites must have high density and grain size less than 1 $\mu$m. By varying n values in SrO.nFe2O3 basic composition, calcination temperature, and BaO addition, Sr-ferrite powder and sintered specimen was prepared. The n values, calcination temperature, and BaO addition affected secondary phase formation, particle size, and particle shape. BaO addition enhanced Fe2O3 secondary phase and hexagonal shape particle. Fe2O3 phase reduced sintered density which greatly decreased Br.
Electric Arc Furnace (EAF) Steel Slag의 아스팔트 포장 혼합물 내 대체 골재로서 적용 가능성에 대한 고찰
문기훈 한국도로학회 2015 한국도로학회논문집 Vol.17 No.1
PURPOSES: This paper, presents the results of a laboratory study aimed to verify the suitability of a particular type of Electric Arc Furnace (EAF) steel slag to be recycled in the lithic skeleton of both dense graded and porous asphalt mixtures for flexible pavements. METHODS : Cyclic creep and stiffness modulus tests were performed to evaluate the mechanical performance of three different asphalt mixtures (dense graded, porous asphalt, and stone mastic) prepared with two types of EAF steel slag. For comparison purposes, the same three mixtures were also designed with conventional aggregates (basalt and limestone). RESULTS : All the asphalt mixtures prepared with EAF steel slag satisfied the current requirements of the European standards, which support EAF steel slag as a suitable material for flexible pavement construction. CONCLUSIONS : Based on the experimental work, the use of waste material obtained from steel production (e.g. EAF steel slag) as an alternative in the lithic skeleton of asphalt mixtures can be a satisfactory and reasonable choice that fulfills the “Zero Waste”objective that many iron and steel industries have pursued in the past decades.
Microstructural Investigation of Hot Mix Asphalt (HMA) Mixtures using Digital Image Processing (DIP)
문기훈,Augusto Cannone Falchetto 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.6
It is well known that Nominal Maximum Aggregate Size (NMAS) significantly affects several mechanical properties of asphalt pavement layers both at low and high temperatures. Two different aggregate NMAS, 9.5 mm and 12.5 mm, are commonly used for surface layer mixture. Most of the past research studies investigated the effect of different aggregate NMAS on asphalt mixture properties through experimental testing, while the impact of NMAS on asphalt mixtures microstructure has received little attention. In this paper, asphalt mixtures with two NMAS, 9.5 mm or 12.5 mm, two air voids percentages, 4% and 7%, and two binder contents, 4% and 7%, were prepared. Then, the effect of aggregate NMAS on materials properties was investigated by performing low temperature creep test of asphalt mixture through the Bending Beam Rheometer (BBR) and advanced Digital Image Processing (DIP) analysis of two-dimensional images of asphalt mixture combined with numerical evaluations of 2- and 3- point correlation functions. As a result, asphalt mixtures containing smaller NMAS showed higher stiffness compared to those prepared with larger aggregates at low temperature. The spatial distributions of aggregates, asphalt mastic, and air voids were not significantly affected by the addition of aggregates with different NMAS. However, an increase in Auto Correlation Length (ACL) was observed for asphalt mixtures having smaller NMAS, which suggests that low temperature creep properties are associated to ACL.