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    Properties of 3D printed concrete (3DPC) containing microencapsulated phase change material (PCM)
    (Elsevier Ltd, 2025) Gençel, Osman Serden; Nodehi, Mehrab; Subaşı, Serkan; Ustaoglu, Abid; Sarı, Ahmet; Bozkurt, Ahmet; Hekimoğlu, Gökhan
    3D printing of cementitious materials is a novel approach to fabricating structural components with many applications, including rapid structural recovery in remote areas since it can function almost autonomously. However, since the newly built components are instantly exposed to the outside environment, their thermal properties can have major impact on their energy efficiency and the long-term operating costs for heating, ventilation, and air conditioning (HVAC) systems. To address this challenge, and for the first time, this study combines an outdoor thermal monitoring system with a detailed material performance evaluation for 3D printed concrete (3DPC) containing melamine–formaldehyde-based phase change materials (PCMs). To uncover the impact of PCMs in 3DPC sections, a series of standardized and advanced tests, including nano-indentation, µCT scanning, SEM, and thermal efficiency measurements, were performed. Results show that the inclusion of PCM increased total porosity from 14.44 % to 21.49 % and water absorption from 8.57 % to 11.20 %. Surface hardness decreased from 1296.11 MPa to 764.58 MPa, accompanied by a higher variability (standard deviation rising from 256.60 MPa to 414.55 MPa) for PCM-containing samples, as compared to the reference 3DPC samples. The addition of PCMs also reduced thermal conductivity by ∼10%, while it also remained stable after 100 cycles of freeze-thawing. The results of the study are found to be significant and contribute to the development of energy-efficient and resilient materials. © 2025 Elsevier B.V., All rights reserved.
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    Transforming industrial byproduct to eco-friendly functional material: Ground-granulated blast furnace slag reinforced paper for renewable energy storage
    (Elsevier B.V., 2024) Gençel, Osman Serden; Musatat, Ahmad Badreddin; Demir, Ahmet; Tozluoǧlu, Ayhan; Tutuş, Ahmet; Kıllı, Ufuk; Fidan, Hakan
    This study pioneered an eco-friendly approach for reutilizing Ground-granulated blast furnace slag (GGBFS) in paper production. This investigation is the first study focusing on the usage of paper production that presents both a new usage area of GGBFS and also a new sight. So, it can contribute to save the trees. Also, GGBFS gains economical value in paper production. 15–25 % integrated slag led to markedly enhanced brightness, density and smoothness accompanied by only minor mechanical strength decreases versus pure pulp. Significantly, the electrical analysis revealed a higher conductivity at higher frequency region reaching almost S value near to 1 which might be a good choice for electromagnetic shielding, thus; higher conductivity with increasing slag contents from pure paper's 10−11 S/cm up to 10−6 S/cm for 25 % addition which confirms the modified paper's usefulness as conductive slag agent. Although the higher addition of GGBFS has led to rising in relaxation time basically from 1.77e−4 to 2.95e−3 and based on Debye relaxation, the rising time in relaxation which was observed after the addition of GGBFS reveals better polarizability values 0.29–0.35 compared to control sample 0.26 by which both longer relaxation time and higher polarizability contribute to the ability of energy storage of modified papers. The conductive characteristics and improved qualities demonstrate these recyclable slag-modified papers present unique opportunities for emerging flexible, eco-friendly electronics, capacitors, electromagnetic shielding, and renewable energy storage applications. Overall, novel integration and characterization of slag waste for enhanced sustainable paper products pioneers an unexplored territory. © 2024 Elsevier B.V., All rights reserved.