*2.2. Specimen Preparation*

The compound modified binders were prepared by a high-speed stirring approach without a stabilizer. First, the neat binder was preheated to 165 ◦C in an iron cylinder and then APAO was slowly added. The temperature of the iron cylinder was maintained at 165 ◦C and the blend was stirred at 2000 rpm for 30 min. Then, PPA was poured into this cylinder and stirred for another 30 min. Subsequently, the prepared samples were subjected to analysis. Different contents of APAO and PPA were mixed together to prepare different modified binders. Four percentages of APAO (0 wt.%, 2 wt.%, 4 wt.% and 6 wt.%) and PPA (0 wt.%, 1.0 wt.%, 1.5 wt.% and 2.0 wt.%) (by the weight of neat binder) were employed in this research. For simplicity, the modified binders with various concentrations of APAO and PPA are labeled. The composition and corresponding abbreviations of all modified binders are listed in Table 4. The detailed technical flowchart of this study is shown in Figure 1.


**Table 4.** The composition and corresponding abbreviations of all modified binders.

**Figure 1.** Flowchart of the experimental program.
