Engineering shape-stabilized pomegranate peel-derived Biochar-PCM incorporating cement mortars for passive thermal regulation in sustainable buildings

Abstract

This study proposes a novel bio-derived, sustainable, and shape stabilized composite phase change material (PCM) and evaluates its performance within cement mortars. The PCM composite was produced by impregnating an organic PCM into activated carbon (AC) obtained from pomegranate peel waste (PPW). The micro and mesoporous structure of the AC was used as physical host for the PCM. To evaluate the performance of PCM composite, characterization tests and analyses were performed to verify structural stability, chemical compatibility, and thermal reliability. The optimum PCM loading was found to be 45 wt% to achieve high latent heat storage capacity, negligible or no leakage, and robust cycling stability. Subsequently, mortar specimens incorporating the biochar shape-stabilized PCM (AC-PCM) composite were prepared and tested for compressive strength, porosity, water absorption, thermal conductivity, and thermoregulation under realistic conditions. The PCM composite has a melting temperature of 26.32 °C and an enthalpy of 116.8 J/g that confirms its applicability for low-temperature thermal storage in build environments. Mortars with 20 vol% composite achieved a 28-day compressive strength of 33.44 MPa. While this represents a 43.5% decrease compared to the control mix, the mechanical performance remained within acceptable limits. Open field thermoregulation tests revealed that the PCM-enhanced mortar reduced peak indoor temperatures by 8.9 °C. Hence, the Bio-AC–PCM incorporated mortar offers an eco-friendly and mechanically viable approach to climate-resilient and energy-efficient construction materials. © 2026 Elsevier Ltd