Electrically healing behavior and mechanism of asphalt mortar with carbon nanotube grafted basalt fibers

Self-healing functional pavement is the current hot spot of road engineering research, in which electrical healing plays a key role in enabling asphalt pavement to mend itself. To endow the asphalt mortar with conductive properties, a preparation process of carbon nanotubes grafted to basalt fibers (CNTs/BF) was proposed by using basalt fibers (BF) as the connecting matrix and carbon nanotubes (CNTs) as the conductive phase via a chemical grafting method. Characterization tests such as resistivity, micro-morphology, surface element and functional group changes were performed to determine the optimal grafting time of CNTs and BFs; Complex shear modulus and ductility electrical healing tests of CNTs/BF pastes were designed to analyze the energized healing effect of CNTs/BF pastes; Infrared thermography and digital image scattering deformation monitoring (DIC) were combined to analyze the electrical healing behavior of CNTs/BF pastes and reveal their healing mechanism. The results of the study show that: The resistivity of CNTs/BF at 3 h of grafting decreases by 6 orders of magnitude, the elemental mass fractions of C and the Si—O—Si peak area are increased by 23.96% and 60.54%, respectively, compared with the original sample BF, and 3 h is the optimal grafting time. The energized healing test shows that the healing indices of CNTs/BF pastes are higher than those of BF and CNTs pastes, and the complex shear modulus healing indices are improved by 14.7% and 18.6% and the ductility healing indices are improved by 22.43% and 16.76% at 0.3wt% doping compared with BF and CNTs pastes, respectively, and the optimal doping level is 0.3wt%. Infrared thermography shows that the temperature enhancement rates of CNTs/BF pastes are 123.53% and 533.53% higher compared to BF and CNTs pastes, respectively, indicating that CNTs/BF pastes have localized warming characteristics. DIC shows that CNTs/BF mastic have a healing height difference of 1.86 mm at the crack, which are 77.99% and 160.14% higher than that of BF and CNTs mastic, respectively, and the crack shows directional healing. Based on this, the energized healing mechanism of CNTs/BF mastic is revealed, and the research results provide an important reference for the application of CNTs/BF in road engineering.