Przeglądaj wg Autor "Chougan, Mehdi"

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  • Miniatura
    PozycjaOpen Access
    Development of 3D printed heavyweight concrete (3DPHWC) containing magnetite aggregate
    (Elsevier BV, 2023) Federowicz, Karol; Techman, Mateusz; Skibicki, Szymon; Chougan, Mehdi; El-Khayatt, Ahmed M.; Saudi, H.A.; Błyszko, Jarosław; Abd Elrahman, Mohamed; Chung, Sang-Yeop; Sikora, Pawel; Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, Poland; Department of Civil and Environmental Engineering, Brunel University London, Uxbridge UB8 3PH, UK; Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University, (IMSIU), Riyadh, Saudi Arabia; Reactor Physics Department, Nuclear Research Centre, Atomic Energy Authority, 13759 Cairo, Egypt; Department of Physics, Faculty of Science, Al-Azhar University, Women Branch, Nasr City, Cairo, Egypt; Structural Engineering Department, Mansoura University, Mansoura City 35516, Egypt; Department of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea
    The main objective of this study is to develop 3D printed heavyweight concrete (3DPHWC) to produce elements with a dry density of up to 3500 kg/m3 by replacing natural aggregate (SA) with magnetite aggregate (MA) up to 100%. A comprehensive systematic study was conducted to thoroughly assess mixtures' mechanical properties, physical proficiency, fresh properties, and printing qualities. The inclusion of MA exhibited the desired fresh properties required for 3D printing and promising physical and mechanical properties. Evaluation of the mechanical properties of designed 3DPHWC indicates that replacing SA with MA increases both cast and printed samples' strengths. The 3D printed M100 sample achieved higher 28 days flexural and compressive strengths by 18 % and 20 %, respectively, compared to printed control mix (M0). Micro-CT study correspondingly demonstrated improvements in the composites' porosity, pore size, and pore morphologies. The linear attenuation coefficients (LACs) and half-value layer (HVLs) for slow neutron and gamma-ray were measured to assess radiation shielding characteristics. A significant performance improvement was obtained for slow neutrons by introducing the magnetite aggregate. Unlike slow neutrons, no significant difference was observed between cast and printed samples against γ-rays. Moreover, the effect of porosity on the shielding performance was discussed.
  • Miniatura
    PozycjaOpen Access
    Enhancing the Fresh and Early Age Performances of Portland Cement Pastes via Sol-Gel Silica Coating of Metal Oxides (Bi2O3 and Gd2O3)
    (MDPI, 2023) Cendrowski, Krzysztof; Federowicz, Karol; Techman, Mateusz; Chougan, Mehdi; Kędzierski, Tomasz; Sanytsky, Myroslav; Mijowska, Ewa; Sikora, Paweł; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering, Poland; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering, Poland; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering, Poland; Brunel University London. Department of Civil and Environmental Engineering,UK; West Pomeranian University of Technology. Faculty of Chemical Technology and Engineering. Poland; Lviv Polytechnic National University. Department of Building Production; West Pomeranian University of Technology. Faculty of Chemical Technology and Engineering,; West Pomeranian University of Technology in Szczecin. Faculty of Civil and Environmental Engineering, Poland
    Incorporating metal oxide nanoparticles into cement-based composites delays the hydration process and strength gain of cementitious composites. This study presents an approach toward improving the performance of bismuth oxide (Bi2O3) and gadolinium oxide (Gd2O3) particles in cementitious systems by synthesizing core–shell structures via a sol-gel process. Two types of silica coatings on cementitious pastes with 5% and 10% substitution levels were proposed. The rheology, hydration, and mechanical properties of the pastes were analyzed to determine the relationship between the coating type and nanoparticle concentration. The results indicate that despite the significant disparities in the performance of the resulting material, both methods are appropriate for cement technology applications. Bi2O3’s silica coatings accelerate the hydration process, leading to early strength development in the cement paste. However, due to the coarse particle size of Gd2O3, silica coatings exhibited negligible effects on the early age characteristics of cement pastes.
  • Miniatura
    PozycjaOpen Access
    Functional Bi2O3/Gd2O3 Silica-Coated Structures for Improvement of Early Age and Radiation Shielding Performance of Cement Paste
    (MDPI, 2024-01-12) Cendrowski, Krzysztof; Federowicz, Karol; Techman, Mateusz; Chougan, Mehdi; El-Khayatt, Ahmed M.; Saudi, H.A.; Kędzierski, Tomasz; Mijowska, Ewa; Strzałkowski, Jarosław; Sibera, Daniel; Abd Elrahman, Mohamed; Sikora, Pawel; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; Imam Mohammad Ibn Saud Islamic University, Department of Physics, College of Science; Brunel University London, Department of Civil and Environmental Engineering; Atomic Energy Authority, Cairo, Nuclear Research Centre, Reactor Physics Department; Al-Azhar University, Women Branch, Nasr City Faculty of Science. Department of Physics,; West Pomeranian University of Technology in Szczecin. Faculty of Chemical Technology and Engineering. Department of Nanomaterials Physicochemistry.; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; West Pomeranian University of Technology in Szczecin. Faculty of Chemical Technology and Engineering. Department of Nanomaterials Physicochemistry.; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering; Mansoura University, Mansoura City. Structural Engineering Department; West Pomeranian University of Technology in Szczecin, Faculty of Civil and Environmental Engineering
    This study presents a new approach towards the production of sol-gel silica-coated Bi2O3/Gd2O3 cement additives towards the improvement of early mechanical performance and radiation attenuation. Two types of silica coatings, which varied in synthesis method and morphology, were used to coat Bi2O3/Gd2O3 structures and evaluated as a cement filler in Portland cement pastes. Isothermal calorimetry studies and early strength evaluations confirmed that both proposed coating types can overcome retarded cement hydration process, attributed to Bi2O3 presence, resulting in improved one day compressive strength by 300% and 251% (depending on coating method) when compared to paste containing pristine Bi2O3 and Gd2O3 particles. Moreover, depending on the type of chosen coating type, various rheological performances of cement pastes can be achieved. Thanks to the proposed combination of materials, both gamma-rays and slow neutron attenuation in cement pastes can be simultaneously improved. The introduction of silica coating resulted in an increment of the gamma-ray and neutron shielding thanks to the increased probability of radiation interaction. Along with the positive early age effects of the synthesized structures, the 28 day mechanical performance of cement pastes was not suppressed, and was found to be comparable to that of the control specimen. As an outcome, silica-coated structures can be successfully used in radiation-shielding cement-based composites, e.g. with demanding early age performances.
  • Miniatura
    PozycjaOpen Access
    A systematic experimental study on biochar-cementitious composites: Towards carbon sequestration
    (Elsevier BV, 2022-05-26) Sikora, Paweł; Woliński, Paweł; Chougan, Mehdi; Madraszewski, Szymon; Węgrzyński, Wojciech; Papis, Bartłomiej K.; Federowicz, Karol; Ghaffar, Seyed Hamidreza; Stephan, Dietmar; Department of Civil Engineering, Technische Universität Berlin, Berlin 13355, Germany; Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, 70-311 Szczecin, Poland; Faculty of Applied Sciences, Collegium Mazovia Innovative School, 08-110 Siedlce, Poland; Department of Civil and Environmental Engineering, Brunel University London, Uxbridge UB8 3PH, UK; Building Research Institute (ITB), 00-611 Warsaw, Poland
    The utilisation of biochar, the carbon negative product of pyrolysis, reduces the carbon footprint of the cementitious composites as it possesses the potential to replace the consumption of Portland cement. In a systematic investigation, biochar was used as a partial cement replacement for up to 20 wt% in both cement pastes and mortars. A comprehensive experimental framework was conducted to evaluate the impact of biochar replacement on the performance of (i) cement paste in terms of hydration kinetics, rheology, strength development, porosity, and (ii) mortars in terms of mechanical, thermal, and transport properties. In addition, the durability of developed mortars, including freezing and thawing resistance, thermal resistance, acid (corrosion) resistance, flammability, and smoke production, were examined. The results revealed that lower replacement rates of cement with biochar (up to 5 wt%) do not substantially change the performance of cementitious composites. However, incorporating biochar in higher dosages (i.e., 20 wt%) influenced the hydration process, reduced flexural and compressive strengths by 49% and 29%, respectively, and increased the water absorption coefficient by 60% compared to control specimens. The same cement mortar demonstrated the most promising freeze-thaw (i.e., 98% relative residual compressive strength), acid resistance as well as considerably lower thermal conductivity. In addition, regardless of biochar content, mortars did not exhibit flammability. Therefore, this study demonstrated that despite specific technical issues, biochar can be successfully incorporated into high dosage to cementitious composite as an alternative binder with minimum environmental impacts to improve durability and insulating performance of mortars.