Thermal and mechanical performance of earth composites with rice husk shape-stabilised PCM

Phase change materials (PCM) can enhance energy efficiency by storing and releasing latent heat, thereby moderating temperature fluctuations. This study examines the thermal behaviour and compressive strength of earth–cement composites incorporating shape-stabilised PCM, with potential application in façade elements. A bio-based PCM with a melting point of 29°C was embedded into rice husk (RH) to produce bio-aggregates through a shape-stabilisation process. Composites were prepared with volumetric contents of 8% and 40% bio-aggregate, using raw RH and RH-PCM separately. Compressive strength and thermal response were evaluated, the latter using dynamic sphere calorimetry (Dynamische Kugel-Kalorimetrie test). PCM incorporation reduced the water absorption of RH by approximately 65%, indicating partial filling of its porous structure. The inclusion of bio-aggregates reduced compressive strength; however, RH-PCM mixtures performed better than those with equivalent contents of raw RH. Thermal analyses showed that the composite with 40% RH-PCM exhibited a temperature plateau near the PCM melting point and maintained a core temperature 1°C lower than the reference mixture after 3 h of heating. This confirms latent heat storage during phase transition and demonstrates the potential of these composites to enhance thermal regulation in façade applications.