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    Öğe
    Investigation of Properties of Engineered Cementitious Composites Incorporating High Volumes of Fly Ash and Metakaolin
    (Amer Concrete Inst, 2012) Ozbay, E.; Karahan, O.; Lachemi, M.; Hossain, K. M. A.; Atis, C. Duran
    This study was carried out to develop engineered cementitious composites (ECCs) incorporating binary blends of high volumes of fly ash (FA) and metakaolin (MK) for the purpose of achieving low drying shrinkage and high composite strength with adequate ductility and improved durability. ECC, an ultra-ductile cement-based composite reinforced with short random fibers, exhibits strain-hardening and multiple-cracking behavior in uniaxial tension and bending. Standard (M45) and high-volume FA ECC mixtures are typically produced by replacing portland cement (PC) with 55% and 70% of FA, respectively (FA-to-cement ratio of 1.2 and 2.2 by weight). In this study, the (FA + MK)/PC ratio was maintained at 1.2 and 2.2 and the FA/MK ratio was maintained at 4.5. Two replacement levels of MK with FA were adopted. The investigation used 10% and 12.5% MK by weight of total binder content, respectively. For the purposes of comparison, standard and high-volume FA ECCs were also studied. To determine the effect of binary blends of FA and MK on the properties of ECC, this study focused on the evaluation of free drying shrinkage, flexural and compressive strengths, porosity and water absorption (WA), sorptivity, and chloride-ion permeability. The experimental results showed that the drying shrinkage, porosity, absorption, sorptivity, and chloride-ion permeability properties were significantly reduced with the use of binary blends of FA and MK, while ECC's ultra-high ductility and strain-hardening properties were preserved at an adequate level.
  • Küçük Resim
    Öğe
    Metamaterial Absorber Based Multifunctional Sensor Application
    (Iop Publishing Ltd, 2017) Ozer, Z.; Mamedov, A. M.; Ozbay, E.
    In this study metamaterial based (MA) absorber sensor, integrated with an X-band waveguide, is numerically and experimentally suggested for important application including pressure, density sensing and marble type detecting applications based on rectangular split ring resonator, sensor layer and absorber layer that measures of changing in the dielectric constant and/or the thickness of a sensor layer. Changing of physical, chemical or biological parameters in the sensor layer can be detected by measuring the resonant frequency shifting of metamaterial absorber based sensor. Suggested MA based absorber sensor can be used for medical, biological, agricultural and chemical detecting applications in microwave frequency band. We compare the simulation and experimentally obtained results from the fabricated sample which are good agreement. Simulation results show that the proposed structure can detect the changing of the refractive indexes of different materials via special resonance frequencies, thus it could be said that the MA-based sensors have high sensitivity. Additionally due to the simple and tiny structures it could be adapted to other electronic devices in different sizes.