Feasibility of Industrial High-Titanium Heavy Slag for Thermally Induced Self-Healing Asphalt Pavement Materials: Road Performance and Thermal Conductivity Analysis

Thermally induced self-healing technology is regarded as an effective approach to mitigating the frequent occurrence of asphalt pavement distresses. Its efficiency, however, is highly dependent on the thermal conductivity of asphalt mixtures, which conventional aggregates can hardly satisfy. Meanwhile, high-titanium heavy slag (HTHS), an industrial solid waste rich in TiO2, has been stockpiled in large quantities, and its large-scale resource utilization remains a critical challenge. Against this background, HTHS was employed in this study to replace limestone at equal mass ratios for the preparation of seven asphalt mastics (replacement rates of 0%, 20%, 40%, 60%, 80%, 100%, and neat asphalt) and four types of asphalt mixtures differentiated by coarse and fine aggregate compositions. The results indicate that with increasing HTHS content, the proportion of structural asphalt in the mastic increased markedly, leading to significant improvements in temperature susceptibility, high-temperature stability, and rutting resistance. Compared with the 100% limestone system, the penetration index (PI) of the 100% HTHS mastic increased by 8.4%, the softening point rose by 18.0%, and the rutting resistance factor at five temperatures from 46 °C to 70 °C increased by 21.8%, 56.8%, 79.2%, 171.7%, and 169.6%, respectively. Although low-temperature ductility decreased by 21.3% due to the reduction in free asphalt, it remained within acceptable limits. Regarding asphalt mixture performance, both high-temperature stability and low-temperature cracking resistance improved progressively with increasing HTHS replacement, showing increases of 75.56% and 11.75%, respectively, at full replacement. Water stability decreased by approximately 9% owing to the porous and water-absorptive nature of the slag, yet still satisfied specification requirements. In addition, the incorporation of HTHS significantly enhanced the thermal conductivity of the system, with increases of 0.125 W/(m·K) for asphalt mastics and 0.666 W/(m·K) for asphalt mixtures, corresponding to improvements of 33.7% and 32.2%, respectively. This study confirms that HTHS can serve as a viable asphalt pavement material capable of meeting the thermal conductivity requirements of thermally induced self-healing technology, while simultaneously providing a promising pathway for its large-scale resource utilization.