Self-heating performance of phase change cementitious mortar with hybrid carbon-based nanomaterials

Abstract

Temperature fluctuations pose a critical challenge for infrastructure, necessitating functional concrete to protect structures and promote sustainability. Self-heating concrete and phase change material (PCM) concrete are closely linked to thermal energy, with the former focused on heat generation and the latter on heat storage. This study aims to explore the self-heating performance of modified PCM concrete. Carbon-based materials, chosen for their low electrical resistance and high thermal conductivity, are incorporated to enhance the PCM concrete. Carbon black (CB), carbon nanotubes (CNT), and carbon fibres (CF) with various dimensions and scales, are combined to achieve optimal performance. Materials below a threshold yield minimal change, as they fail to establish the crucial conductive circuit. The self-heating behaviour becomes pronounced with increased in materials, reaching an optimal temperature rise up to 31.2 °C in one hour. However, the group with the highest content of materials experiences a reduced final temperature of 23.9 °C and an increased electrical conductivity of 40 Ω. CB and CNT show different efficiency improvements, and the ideal combination is proposed as 0.3 % CNT and 0.75 % CB. Inorganic hydrated salt-based PCM reduces electrical conductivity by 12 % – 35 % in its liquid state due to free ions, potentially enhancing self-heating capability, though its impact is less significant compared to carbon materials. Overall, the optimum group demonstrates significant self-heating behaviour, high efficiency, and low material cost. Models and electrical impedance results validate these observations and provide novel insight into the self-heating performance of PCM mortar with hybrid carbon-based materials.