In order to study the extension behavior of dry shrinkage type reflective cracks in asphalt pavements, this paper uses the differential equation theory to derive the calculation formula for the inhomogeneous gradient distribution of dry shrinkage stress in the subgrade. Meanwhile, based on the traction separation rule and damage behavior equation, the extended finite element method is applied to simulate the extension path and tip stress response of dry shrinkage type reflection crack, and then analyze the influence of Semi-rigid subgrade structure and material parameters on the extension behavior of dry shrinkage type cracks. The results show that the dry shrinkage stress of Semi-rigid type base is related to the elastic modulus of base course material, dry shrinkage coefficient, uniform variation of moisture content, horizontal deformation resistance coefficient, and structural dimensions of Semi-rigid type base. Micro cracks in the Semi-rigid type base under the action of dry shrinkage stress will occur two-way extension behavior, one is to continue cracking below the base course, and the other one is the reflection extension into into the surface layer, in addition, the extension speed of the reflected cracks in the surface layer is much larger than the crack cracking speed in the base course. Reducing the modulus of the base course, increasing the thickness of the base course and controlling the variation of the moisture content of the base course within the limit value can effectively retard the emergence and extension rate of reflection cracks.

This study investigates the composition–property relationships in ternary engineered geopolymer composites (EGCs) using a simplex centroid design method to optimize the synergy between ground granulated blast furnace slag (GGBS), fly ash (FA), and metakaolin (MK). Mechanical testing revealed that compressive strength (>85 MPa) peaked at 75% GGBS/25% MK, demonstrating MK’s dominant role in enhancing densification, while flexural strength showed a negative correlation with GGBS content but consistent improvement with MK addition. Strain-hardening behavior was most pronounced in 75% GGBS/25% MK and 83% GGBS/8% FA/8% MK mixtures, with the latter achieving optimal precursor synergy. Fiber dispersion uniformity showed a strong linear correlation (R² = 0.98) with tensile strain capacity, confirming its critical role in strain-hardening performance. Mercury intrusion porosimetry analysis demonstrated that the G83F8M8 mixture exhibited the lowest porosity (<10%) and finest pore size distribution (50–100 nm dominant), directly linking pore refinement to superior mechanical properties.

In order to reveal the nature of the Ultraviolet aging(UV-aging) behavior of asphalt molecules, simulation by Materials Studio software. The effect of UV aging on the transformation, aggregation and motion state of asphalt microstructure is analyzed by the changes in energy, density of dispersive phase, glass transition temperature and viscosity of the asphalt molecular system. The results show that UV aging enhances the bonding degree of asphalt molecules by increasing the heavy components in the asphalt molecules and increasing the distribution width between the asphalt molecule components, which improves the high-temperature resistance of asphalt. At the meantime, the UV aging causes the asphalt molecular movement state to solidify at low temperature so that the rheological behavior is difficult to occur by reducing the lightweight component and free volume of the asphalt molecule and increasing the glass transition temperature, which reduces the low-temperature resistance of asphalt. In addition, among the factors affecting the viscosity of asphalt molecular, the degree of influence of the molecular structure and molecular weight is significantly greater than the molecular activity. The addition of short branched chain hydrocarbon molecules to the UV-aged asphalt molecules could effectively reduce the viscosity of the asphalt molecules and improve the flowability of the asphalt molecules. The results of the study contribute to the understanding of the characteristics of changes in the microstructural pattern and dynamic behavior of asphalt molecules during UV aging, and achieve interpretation and prediction of changes in asphalt properties at the microscopic level.