A multi-layer inductive healing layer (ML-IHL) based on the magnetic field distribution characteristics was designed to solve gradient healing behaviors of conventional single-layer inductive healing layer (CSL-IHL). Two representative conductive metals, including waste steel shaving and steel wool fibers, were used to prepare two kinds of ML-IHL, which is a 2-layer system composed of asphalt mixtures with different conductive metal contents. Then infrared images of the temperature distribution of ML-IHLs and CSL-IHL were recorded to analyze the temperature changes at different depths. Subsequently, the temperature coefficient of variation and radar chart method was used to evaluate the temperature gradient. Results show that as the difference in the conductive metal contents between the two lays of the ML-IHL increases, the temperature gradient gradually decreases. Also, it is recommended that the optimum content in the upper layer containing waste steel shavings or steel wool fibers is 4% or 2%, and the optimum content in the lower layer is 8%. Finally, the inductive healing test of the optimal scheme shows that the healing effect of the upper and lower layers of both ML-IHL has been significantly improved, and the healing rate difference between the two layers is all less than 2%.

The asphalt pavement with heating cables (APHC) was widely used for snow/ice-melting. However, the adverse effects of heating cables on the interlaminar stability of APHC was neglected. Therefore, an evaluation method was developed to evaluate the interlaminar stability of APHC. Firstly, the shear fatigue life equations for APHC with different cable types were obtained through shear fatigue test results. Through the fatigue life equations, the damage model was established to describe the nonlinear shear damage characteristics of APHC, andthe safety range of cumulative strain (ϵ_N) was obtained as an evaluation index. Secondly, the actual shear fatigue life (N_Af) was proposed by axial-load conversion and the number of laboratory fatigue loading. Finally, an evaluation method was developed, which has a good agreement with the field validation data. The mentioned method evaluate the interlaminar stability of AHPC from two aspects. One is ϵ_N should be controlled within the safe range. Another is N_Af meets the number of standard axial load in transverse shear. .

Polyurethane grouting technology is widely employed to maintain critical transportation infrastructure, including pavements, airports, and railways. After injection, foamed polyurethane bonds with surrounding aggregates to form a polyurethane–aggregate composite material (PACM). The gradation of aggregates in PACM, stress levels, and loading frequencies significantly influence fatigue performance under cyclic traffic loading. This study investigates the fatigue behavior of three distinct PACM gradation types through three-point bending fatigue tests under varying stress levels and loading frequencies. Results reveal that the finer gradations of PACM tend to exhibit higher flexural stiffness and longer fatigue life but also greater sensitivity to stress levels. Conversely, coarser gradations show lower stiffness but improved energy dissipation characteristics. Additionally, the flexural stiffness modulus, fatigue life, and cumulative dissipated energy decrease with increasing stress levels, while they grow with higher loading frequencies. In contrast, the dissipated angle follows an opposite trend. Additionally, mathematical models were developed to describe the evolution of dissipated energy, uncovering a three-stage pattern dominated by a prolonged plateau phase accounting for over 80% of the fatigue process. Based on this characteristic plateau, fatigue life prediction models were established for each gradation type, achieving high prediction accuracy with relative errors below 10%. These findings not only highlight the significant impact of aggregate gradation on PACM fatigue performance but also provide practical tools for optimizing material design in pavement maintenance.

To reduce reflective cracking in asphalt pavements, gravel base layers are commonly employed to disperse stress and delay structural damage. However, the loose nature of gravel bases results in complex interlayer contact conditions, typically involving interlocking between gravel particles in the base and aggregates in the asphalt surface course. In order to accurately simulate this interaction and to improve the interlayer shear performance, a mesoscale finite element model was developed and combined with macroscopic tests. Effects due to the type and amount of binder material, type of asphalt surface layer, and external loading on shear strength were systematically analyzed. The results indicate that SBS (Styrene–Butadiene–Styrene)-modified asphalt provides the highest interlayer strength, followed by SBR (Styrene–Butadiene Rubber)-modified emulsified asphalt and unmodified base bitumen. SBS (Styrene–Butadiene–Styrene)-modified asphalt achieves optimal interlaminar shear strength at a coating rate of 0.9 L/m². Additionally, shear strength increases with applied load but decreases with increasing void ratio and the nominal maximum aggregate size of the surface course in the analyzed spectra. Based on simulation and experimental data, an equivalent macro–meso predictive model relating shear strength to key influencing factors was established. This model effectively bridges mesoscale mechanisms and practical engineering applications, providing theoretical support for the design and performance optimization of asphalt pavements with gravel bases.