Acrylamide with a double bond and amide group can not only copolymerize with macromolecules of crumb rubber but also react with acidic groups in asphalt, so it was selected as a modifier to activate crumb rubber through chemical graft action. The purpose is to improve the compatibility between crumb rubber and asphalt and thus improve the rheological properties and storage stability of rubber asphalt. Infrared spectroscopy (IR) and scanning electron microscopy (SEM) were used to characterize the crumb rubbers and their modified asphalt. It was found that the crumb rubber of grafting acrylamide had better compatibility in asphalt due to its larger specific surface area and chemical reaction with asphalt. In addition, the high temperature rheological test, low temperature creep test, and polymer separation test were carried out to study the effect of grafted activated crumb rubber on the properties of modified asphalt. The results showed that compared with modified asphalt with common crumb rubber (CRMA), the rheological properties and storage stability of modified asphalt with grafting activated crumb rubber (A–G–R) were improved significantly. The results of microscopic and macroscopic tests show that the activated rubber particles have a larger contact area with asphalt due to a rougher surface and the chemical cross-linking between rubber particles and asphalt further strengthens their interaction. Therefore, there is a relatively stable blend system formed in modified asphalt, and its performance of modified asphalt has been improved.

In order to reveal the changing law of the mechanical response of asphalt pavements under the action of vehicle load and provide references for the design of durable pavements, three typical asphalt pavement structures with flexible base (S1), combined base (S2), and semi-rigid base (S3) were selected to perform field strain tests under static and dynamic load using the fiber Bragg grating optical sensing technology. The changing characteristics of the strain field along the horizontal and depth directions of pavements were analyzed. The results indicate that the most unfavorable asphalt pavement layers were the upper-middle surface layer and the lower base layer. In addition, the most unfavorable loading positions on the surface layer and the base layer were the center of wheel load and the gap center between two wheels, respectively. The most unfavorable layer of the surface layers gradually moved from the lower layer to the upper layer with the increase of base layer modulus. The power function relationships between structural layer strain and vehicle speed were revealed. The semi-rigid base asphalt pavement was the most durable pavement type, since its strain value was the lowest compared to those of the other structures.

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