Discrete element modelling of electro-mechanical behaviour in modified cementitious materials

• Tunnelling theory is integrated into classic discrete element modelling (DEM). • Novel DEM electro-mechanical model captures piezoresistivity and damage mechanisms. • Micro-scale insights reveal electro-mechanical behaviour in complex cement scenarios. • Transition regions serve as early indicators of micro-cracks in self-sensing cement. • Crack numbers quantitatively link to electrical resistance changes. Carbon black nanoparticle (CBN) modified cementitious materials have intrinsic self-sensing ability owing to their enhanced electrical properties. The material has been gaining increasing attention for its potential in structural health monitoring; however, its sensing mechanisms rely on macroscopic observations, making it extremely difficult to predict and evaluate electro-mechanical behaviour. This limitation becomes especially significant when the material itself suffers internal damage. To improve the understanding of conductive mechanisms and quantitatively evaluate electrical resistance variations of such materials, this study proposes a novel approach by integrating the tunnelling effect-based mathematical model with the discrete element method (DEM) to simulate the electrical behaviour in CBN-modified cementitious materials. Compared to traditional analytical solutions, the proposed model shows comparable capability to describe the piezoresistivity behaviour in elastic regions. More importantly, in the plastic region where other solutions lose the niche due to crack development, this model is the first to demonstrate a good agreement between simulation and experiment data in terms of resistance changes caused by cracks. These results highlight that the proposed method can effectively capture the evolution of electrical resistance in both elastic and plastic regions, making it suitable for better understanding the mechanism of such materials for stress sensing and damage detection in practice.