Application of intrinsic cement-based sensor for traffic detections of human motion and vehicle speed

• Microstructures implied that CNF as conductive fillers can be well-dispersed in cementitious composites. • Microcharacterizations on the ITZs of cement-based sensors and mortar slab showed excellent connections. • FCR showed a peak at feet down and then returned to the initial values at feet up to detect human traffic. • Exact vehicle speed can be calculated based on the two peaks induced by the front and back wheels. • FCR peaks can adjust the vehicle speed, to determine the vehicle speed with speed higher than 40 km/h. To develop smart concrete pavement for intelligent infrastructure, the self-sensing performance of smart pavement with embedded cement-based sensors was experimentally investigated in this study. The self-sensing behaviors of mortar pavement is evaluated by the self-sensing of compression force, human motion detection, and vehicle speed monitoring. Because of the well-dispersed carbon nanofiber (CNF), the developed cement-based sensors intrinsically showed excellent piezoresistivity. The cement-based sensors connected in series were well bonded within the mortar slab, which indicates effective force transmission from the mortar slab to the cement-based sensors. The results showed that the smart mortar slab exhibited linear and repeatable fractional changes of resistivity (FCR) in response to cyclic compression force. With the cement-based sensors embedded, the smart mortar slab could monitor the human motions, such as ‘up-down’ feet or jumping movements. Moreover, the smart mortar slab could detect the exact vehicle speed with high accuracy for the traffic detection. The characterization on the interfaces between cement-based sensors and mortar slab demonstrated the excellent connections, which confirmed the smooth force transmission from the mortar slab to the cement-based sensors due to the excellent interfacial bonding between them. Moreover, the FCR value presented a firm relationship to the vehicle speed, with a decreasing trend with the increase of vehicle speed. The results will promote the practical applications of cement-based sensors, especially in the field of concrete pavement or road, to achieve smart concrete infrastructures.