**2. Experiment and Methods**

#### *2.1. Materials*

Neat binder produced from Suizhong crude oil was adopted for modification, and its penetration grade was 80/100 according to the ASTM standard. Its basic specifications are presented in Table 2. PPA was supplied by Macklin in China. The phosphorous pentoxide (P2O5) concentration was greater than 85 wt.% and the density was 2.05 g/cm3. The APAO-828 compound applied in this study was manufactured by Evonik Degussa of Germany. The key parameters of APAO-828 are summarized in Table 3.

#### **Table 2.** Physical properties of neat binder.


**Table 3.** Physical properties of APAO.

