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    Characteristics of cement-based thermo-concretes containing capric acid impregnated hemp for thermal energy storage and sound isolation in buildings
    (Pergamon-Elsevier Science Ltd, 2025) Gencel, Osman; Guler, Onur; Ustaoglu, Abid; Erdogmus, Ertugrul; Sari, Ahmet; Hekimoglu, Gokhan; Boztoprak, Yalcin
    Enhancing the lightweight structure, insulation, and thermal storage capacity of concrete is critical for energy efficiency and environmental impact reduction. The innovative application of using waste hemp shives as a phase change material (PCM) carrier in cementitious composites was performed in this study to enhance sustainable construction practices. Although previous studies have incorporated lightweight aggregates and PCMs, challenges such as PCM leakage and the reliance on synthetic materials have limited their effectiveness. This study utilized waste hemp shives as a natural porous support for capric acid (CA) PCM in diatomite-based lightweight concrete, offering an eco-friendly and leakage-resistant solution with improved thermal and acoustic performance. No leakage was observed in shape-stabilized hemp/CA composites with 45 wt% CA. The melting and solidification temperatures were determined as 30.6 degrees C and 28.7 degrees C, with corresponding enthalpy values of 80.9 and 80.8 J/g, respectively. Concrete composites containing hemp/PCM reduced indoor temperatures by up to 4 degrees C compared to control samples. Moreover, composites with 30 % hemp/PCM content achieved sound absorption coefficients up to 0.6 and transmission loss values exceeding 24 dB, demonstrating their dual functionality for thermal energy conservation and acoustic comfort in building applications.
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    Enhancing sustainability with waste hemp-shive and phase change material: Novel gypsum-based composites with advanced thermal energy storage properties
    (Elsevier Sci Ltd, 2024) Gencel, Osman; Guler, Onur; Ustaoglu, Abid; Erdogmus, Ertugrul; Sari, Ahmet; Hekimoglu, Gokhan; Boztoprak, Yalcin
    This study addresses the rising demand for sustainable construction by introducing composite materials from natural and renewable resources: gypsum, hemp, and phase change materials (PCMs). These materials cater to the growing preference for eco-friendly building solutions. Incorporating hemp enhances sustainability while integrating PCMs into the porous hemp structure ensures adequate thermal energy storage and release without leakage. Firstly, the agricultural waste hemp shives and lauryl alcohol (LA) PCM were mixed to create shapestabilized hemp/PCM composites. The highest PCM ratio was determined in shape-stabilized composites exhibiting non-leakage properties, which was 45 wt %. These composites were then incorporated into gypsum materials at loadings of 7.5 %, 15 %, 22.5 %, and 35 wt % to produce the final composites. Morphological, thermal, and chemical characteristics of shape-stabilized composites were examined using SEM, TGA, and DSC, while the solar thermoregulation tests assessed the gypsum matrix composites. The phase change temperature of PCM was determined as 20.24 degrees C with a melting enthalpy value of 224.4 J/g. The hemp/PCM shape-stabilized composites demonstrated an impressive melting enthalpy value of 100.2 J/g, with only a slight reduction to 99.5 J/g after 750 test cycles. When the ambient temperature exceeded 50 degrees C, the central temperature of the cabins containing PCM composites was found to be at least 4 degrees C cooler than those containing only gypsum. Conversely, when the ambient temperature dropped to around 20 degrees C, it was observed that the central temperature of the cabins with PCM composites was approximately 2 degrees C warmer than those with only gypsum. This study introduces a novel approach to creating environmentally friendly gypsum/hemp/PCM composites for thermal energy storage systems.