2.2.2. Asphalt Regeneration

The regeneration agent was similar to asphalt in chemical properties, and they had good compatibility. The aged asphalt was heated to the flowing state, and the regeneration agent with doses of 0%, 2%, 4%, and 6% were added and stirred for 30 min at 140 ◦C and 1000 rad/min using a high-speed shear to produce the regenerated asphalt. The preparation process referred to the literature [14]. For the convenience of presentation, the regenerated asphalts with the regeneration agent doping of 0%, 2%, 4%, and 6% was recorded as RA0, RA2, RA4, and RA6, respectively, and the 70# matrix asphalt was recorded as MA, as shown in Table 3.


**Table 3.** Sample descriptions.

#### 2.2.3. Physical Properties Test

JTG E20-2011 "Highway Engineering Asphalt and Asphalt Mixture Experimental Procedure" [15] was used to determine the physical properties of the regenerated asphalt, including the softening point (T0606-2011), the ductility at 15 ◦C (T0605-2011), and needle penetration at 25 ◦C (T0604-2011).

#### 2.2.4. Viscosity Test

A Brookfield viscometer with a temperature control device was selected to determine the viscosities of various asphalts. Due to the low viscosity of the target asphalt, we measured the viscosities of 120 ◦C, 135 ◦C, and 150 ◦C at 20 rad/min according to T0625-2011. To further analyze the change of the asphalt viscosity, we chose activation energy to analyze the change of the viscosity of the regenerated asphalt. Activation energy is the minimum energy required for molecules to reach the activation molecule to do work [16]. Activation

energy can reflect the difficulty of the asphalt material to reach the flow state; the lower the activation energy, the better the construction and ease. The Arrhenius equation was described as:

$$L\mathbf{n}\,\eta = \frac{\mathbf{E}\_{\eta}}{RT} + L\mathbf{n}A\tag{1}$$

where *η* is the viscosity of asphalt (Pa·s); *T* is the absolute temperature (K); *A* is a constant; <sup>E</sup>*<sup>η</sup>* is the activation energy of asphalt when it undergoes change (kJ·mol−1); *<sup>R</sup>* is the universal gas constant with a magnitude of 8.314 J·mol−<sup>1</sup> <sup>K</sup><sup>−</sup>1. The study used the Brinell viscosity to derive the activation energy of the regenerated asphalt, which was utilized to analyze the construction and ease of regenerated asphalt [17].
