Modeling of piezoresistivity of carbon black filled cement-based composites under multi-axial strain

A tunnel effect theory-based piezoresistivity model is proposed to predict the strain-sensing property of carbon black filled cement-based composite (CBCC1) whose CB concentration is near percolation threshold and the conductive mechanism is dominated by tunnel effect. The conductive network in CBCC is assumed to be composed of randomly distributed tunnel resistors which are formed by each adjacent CB particles. According to tunnel effect theory, tunnel resistance is an exponential function of tunnel width (distance between two adjacent CB particles). The width change of an individual tunnel resistor under external strain is first quantified to obtain the consequent resistance change. Then, the conductive network is modeled based on SEM imaging, enabling us to combine the change of individual tunnel resistances to obtain the macro-resistance behavior of a CBCC specimen. Comparative analysis on experimental and theoretical results indicates that the proposed model is able to predict the resistance behavior and strain gauge factors of CBCC under various loading and environmental conditions.