Piezoresistive performance of self-sensing bitumen emulsion-cement mortar with multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes (MWCNTs) were incorporated as functional fillers into bitumen emulsion, along with self-sensing cementitious sensors, to investigate their internal curing and ion conduction. The mechanical properties, piezoresistivity, moisture content, and internal curing of cementitious sensors were analysed under different MWCNTs and water contents. Isothermal Calorimetry (IC), Nuclear Magnetic Resonance (NMR), Thermogravimetric Analysis (TGA), and Inductively Coupled Plasma (ICP) methods were employed to supplement the findings and unveil the mechanism. The compressive strength of bitumen-cement mortars was found to be comparable to that of the counterpart cement mortars. The results confirmed that bitumen emulsion improved the piezoresistivity due to the increased water content in the mortars and the influence of micro-holes. Additionally, the bitumen emulsion limited the moisture loss, leading to improved internal curing. The piezoresistivity was observed to be affected by ion conduction, which in return was influenced by water content. Moreover, as water content of self-sensing mortar decreased, the piezoresistivity initially increased and then decreased, flowing the moisture loss rate. These outcomes can offer insights into the performance of self-sensing bitumen cementitious sensors and their potential application in traffic condition detection and road health monitoring.