Przeglądaj wg Autor "Abd Elrahman, Mohamed"

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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
    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
    Insight into the microstructural and durability characteristics of 3D printed concrete: Cast versus printed specimens
    (Elsevier BV, 2022-07-16) Sikora, Pawel; Techman, Mateusz; Federowicz, Karol; El-Khayatt, Ahmed M.; Saudi, H.A.; Abd Elrahman, Mohamed; Hoffmann, Marcin; Stephan, Dietmar; Chung, Sang-Yeop; Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, Poland; 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; Faculty of Mechanical Engineering and Mechatronics, West Pomeranian University of Technology in Szczecin, Poland; Building Materials and Construction Chemistry, Technische Universität Berlin, Germany; Department of Civil and Environmental Engineering, Sejong University, Seoul 05006, Republic of Korea
    This study presents the comparison of microstructural and durability characteristics of 3D printed concrete (3DPC) depending on its production method (printing or casting). Printed samples with different numbers of layers, as well as a cast specimen with an identical mix composition, were produced and compared, with their microstructural pore and solid characteristics quantitatively and qualitatively investigated. For this purpose, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray micro-computed tomography (micro-CT) were utilized to evaluate the microstructures of the 3DPC. In particular, quantitative approaches using micro-CT data were newly proposed for a better understanding of the microstructural characteristics of 3DPC. Moreover, their durability-related characteristics and transport properties, including freeze-thaw and thermal resistance, were examined and compared. Despite noticeable differences between the microstructures of the printed and cast specimens, including their anisotropic and inter-layer porosity and heterogeneity, confirmed by MIP, SEM and micro-CT, no significant differences in the transport (capillary water porosity and water sorptivity) or durability-related properties (frost and thermal attack) were found. This was due to the dense and homogenous microstructure of 3DPC, which is attributable to the high binder content and low w/b of the mixture. Moreover, the newly proposed evaluation provided reasonable quantitative and qualitative characteristics, which can be used to demonstrate and predict the material properties of 3DPC.
  • Miniatura
    PozycjaOpen Access
    Rheological, Mechanical, Microstructural and Radiation Shielding Properties of Cement Pastes Containing Magnetite (Fe3O4) Nanoparticles
    (Springer Nature, 2023-01) Sikora, Pawel; El-Khayatt, Ahmed M.; Saudi, H.A.; Liard, Maxime; Lootens, Didier; Chung, Sang-Yeop; Woliński, Paweł; Abd Elrahman, Mohamed; Faculty of Civil and Environmental Engineering, West Pomeranian University of Technology in Szczecin, Poland; Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University, (IMSIU), Riyadh, Saudi Arabia; Department of Physics, Faculty of Science, Al-Azhar University, Women Branch, Nasr City, Cairo, Egypt; Sika AG, Switzerland; Department of Civil and Environmental Engineering, Sejong University, Seoul 05006, Republic of Korea; Faculty of Applied Sciences, Collegium Mazovia Innovative School, 08-110 Siedlce, Poland; Structural Engineering Department, Mansoura University, Mansoura City 35516, Egypt
    This work examines the influence of iron oxide nanoparticles (Fe3O4 NPs) on neutron and gamma-ray radiation shielding characteristics of Portland cement paste. Experimental evaluations were supplemented with theoretical studies using NXCom program. Portland cement pastes with 5, 10, 15, 20, and 30 wt% of nanomagnetite cement replacement were produced. Moreover, rheological, early strength development, compressive strength, and mercury intrusion porosimetry (MIP) tests were performed. The results showed that increasing the amount of Fe3O4 NPs in a mix leads to a gradual increment in measured viscosity and yield stress. High nano-Fe3O4 content substantially impeded the early strength development process and led to a decrement in the 7- and 28-day compressive strength of cement paste. The MIP studies exhibited a gradual increment in total porosity, and average pore volume, as nano-Fe3O4 content was increased. All the macroscopic cross-sections of slow, fast and thermal neutrons constantly increased as a result of the addition of magnetite nanoparticles, with their variations being markedly linear. Similarly, gamma attenuation test results indicated that the addition of Fe3O4 powder enhances the shielding capability of paste in the energy range of interest (0.08–2.614 MeV). In conclusion, Fe3O4 nanoparticles can be successfully used in producing lead-free cementitious composites with improved gamma-ray and neutron shielding properties. However, certain drawbacks related to an increment in matrix porosity and thus a decrement in mechanical performance should be taken into account.
  • Miniatura
    PozycjaOpen Access
    Seawater-Mixed Lightweight Aggregate Concretes with Dune Sand, Waste Glass and Nanosilica: Experimental and Life Cycle Analysis
    (Springer Nature, 2023-08-01) Sikora, Pawel; Afsar, Levent; Rathnarajan, Sundar; Nikravan, Morteza; Chung, Sang-Yeop; Stephan, Dietmar; Abd Elrahman, Mohamed; Technische Universität Berlin, Germany; West Pomeranian University of Technology in Szczecin, Poland; Technische Universität Berlin, Germany; West Pomeranian University of Technology in Szczecin, Poland; Technische Universität Berlin, Germany; Yonsei University, Seoul, South Korea; Technische Universität Berlin, Germany; Mansoura University, Mansoura, Egypt
    The use of alternative and locally available materials is encouraged in the construction industry to improve its sustainability. Desert regions with shortages in freshwater and river sand as fine aggregates in concrete have to search for alternative materials such as seawater, dune sand, and waste glass powder to produce lightweight concretes. The potential negative effects of adding these alternative materials can be reduced by adding nanosilica to the cementitious system at very low quantities. This study evaluates the feasibility of using these alternative materials and nanosilica (NS) in producing lightweight aggregate concretes (LWACs). A systematic study was carried out to understand the synergistic effect of nanosilica and seawater in improving the hydration characteristics of the developed cementitious systems. Also, the effect of these alternative materials on the fresh properties of the cementitious system was assessed by slump flow tests. The evolution of compressive strength at early ages was investigated after 2, 7, and 28 days of moist curing and an improvement in the strength development in concretes with seawater was observed. Furthermore, the integrity of the developed LWACs was analyzed using oven-dry density, thermal conductivity, water porosity and shrinkage measurements. Moreover, the capillary porosity and sorptivity measurements revealed the denser microstructure in the nano-modified seawater lightweight concretes. In the end, the life-cycle assessment study calculated the benefit of alternative materials in terms of carbon footprint and water consumption. As an outcome, a sustainable solution for producing LWACs containing seawater, dune sand or glass powder was proposed.