Physical Origin of Temperature Induced Activation Energy Switching in Electrically Conductive Cement

Electrically conductive cement (CEMe), enabled by percolative networks of conductive fillers, presents a promising future for multifunctional cementitious composites in next-generation sustainable infrastructure. However, the mechanisms governing temperature-dependent charge transport, particularly the temperature-induced switching of Arrhenius activation energy, remain poorly understood. This study provides a rigorous investigation into the physical origin of variable activation energy behaviour in CEMe across different percolation regimes, a key factor for ensuring reliable multifunctional performance. It is demonstrated that activation energy switching arises from structural degradation within the biphasic conduction architecture: ionic transport through liquid-filled connected pore network and electronic conduction via conductive carbon fibre network. In contrast, the intrinsic non-Arrhenius behaviour of the pore solution and the Arrhenius behaviour of the carbon fibre have negligible influence on the overall activation energy switching behaviour. For the first time, Meyer-Neldel Rule (MNR) is observed in CEMe, attributed to the stable intrinsic conductivity (≈0.046 S m^-1) of calcium silicate hydrate (C─S─H) gel across the temperature range of 5-90 °C and carbon fibre contents of 0-1.5 vol%. These findings advance the fundamental understanding of charge transport in CEMe and biphasic conducting materials systems, establishing a robust scientific basis for designing intelligent, multifunctional materials that adapt to dynamic environments.