Thermal and mechanical performance of bio-concrete with phase change material-encapsulated lignocellulosic aggregates

This research presents a novel use of recycled wood residues as containers for bio-based phase change materials (PCMs). Beyond serving as a natural reservoir, wood’s inherent deformability enables it to absorb the stresses generated during PCM phase transitions, offering an innovative and sustainable solution for thermal energy storage. The aim of this work is to develop and evaluate a bio light-weighted concrete with thermal energy storage capacity, the innovation consists of using wood particles as phase change material (PCM) carriers. The bio-aggregates with thermal energy storage was made by phase change material (PCM) incorporation in lignocellulosic particles. To this study, the following materials were obtained, Pinus sp. and Ceiba sp. wood particles, Crodatherm 24 as commercial PCM, and coconut oil as a natural alternative, carboxylated styrene butadiene (XSBR) and carboxylated acrylonitrile butadiene (XNBR) rubbers, granite aggregates, sand and Brazilian CP-V ARI cement type. To develop the bio-aggregate, the particles wood from the different species were saturated by immersion in PCM using a vacuum pump and coated with rubber and sand. Also wood particles without PCM or coconut oil were coated. For a further understanding, different bio-aggregates were used. Finally, composites were produced and evaluated. The composites were subjected to thermal analysis according to the DKK (dynamische kugel kalorimetrie) methodology. Mechanical analysis was also carried out in accordance with EN-196, flexural and compression tests. The composites containing bio-aggregates with PCM resulted in approximately 4.3 and 5.8 % PCM mass for the Ceiba sp. and Pinus sp. woods, respectively. Thermal analysis revealed that composites containing wood bio-aggregates impregnated with PCM exhibited an effective thermal energy storage capacity, mitigating temperature rise during fusion and delaying cooling during crystallization. Among the tested bio-aggregates, those produced with Pinus wood demonstrated superior performance, showing approximately a 200% reduction in both heating and cooling rates compared with Ceiba-based aggregates. Furthermore, industrial PCMs outperformed coconut oil as thermal energy storage (TES) materials. In terms of mechanical characterization, however, a substantial decrease in strength properties was observed, around 60% in flexural strength and 85% in compressive strength relative to the reference composite. Despite this mechanical drawback, wood bio-aggregates show promising potential for use in lightweight concrete and non-structural construction elements, such as masonry blocks and partition panels, thereby contributing to sustainable and energy-efficient building solutions. • PCM composites increased TES capacity by up to 600% compared to coconut oil. • Bio-aggregates with PCM achieved mass incorporation of 4–6.5% in the final composite. • Pinus PCM composites delayed heating and cooling by up to 18 min. • Coconut oil proved to be efficient as a natural PCM in thermal energy storage. • Innovative and sustainable use of bio-aggregates with wood particles in construction.