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In order to improve the high-temperature performance, antiaging performance, and storage stability of rubber asphalt, nano-organic montmorillonite (NOMMT) was mixed with rubber asphalt. Macroscopic influences of NOMMT on rubber asphalt were measured through penetration, softening point, ductility, rotational viscosity tests, dynamic shear rheology test, and bending beam rheology test at low temperature and were conducted on rubber asphalt with different contents of NOMMT. Then, the microscopic mechanism of NOMMT on the microscopic performance of rubber asphalt was studied through using scanning electron microscopy (SEM), infrared spectroscopy (IR), and differential scanning calorimetry (DSC). The results showed that the rubber particles were smoother, uniform, and dispersed after NOMMT was introduced, and the compatibility between NOMMT and crumbed rubber powder was good. Some stable structures were formed in the composite modified asphalt. The disappearance of alcohol phenol and the increase in related groups such as alkane, benzene, and hydrocarbon indicated that chemical reaction occurred between NOMMT and rubber asphalt, resulting in the changes of the performance of the composite modified system, so that high-temperature stability, antiaging properties, and storage stability were improved but its low-temperature performance was decreased.

To enhance the crack resistance of asphalt-treated base (ATB), a type of gapped and semiopened gradation ATB mixture, GSOG, was designed. Its design method was proposed based on the volume design method and performance tests. Firstly, several gradations were designed preliminarily in which middle particle sizes of coarse aggregates were partially or completely gapped according to the gradation specification. Secondly, their voids in coarse aggregates (VCA) were determined through dry rod compaction test on coarse aggregates, and then their theoretical voids were calculated. Gradations whose theoretical voids met the requirements were selected to fabricate specimens with Superpave Gyratory Compactor, and their voids were determined using vacuum sealing method and submerged weight in water method. Finally, gradations whose voids meet requirements were selected to fabricate different types of specimens for various performance tests, and the optimal gradation can be selected comprehensively considering their performances, especially focusing on their crack resistance. According to this gradation design method, the gradation of GSOG-25 was designed, and its performances, including high-temperature stability, water stability, fatigue, and antireflection crack resistance, were measured and compared to ordinary ATB-25. The results demonstrate that the performance of GSOG-25 is much better than that of ordinary ATB-25, especially in anticracking capacity.

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