# Using Plastic Waste in a Circular Economy Approach to Improve the Properties of Bituminous Binders
## 3 Results and Discussion
### Dynamic Viscosity (\(\eta\))  
The dynamic viscosities (\(\eta\)) of the unmodified binders (10/20, 35/50, and 50/70) achieved in the rotational visometer identified in Section 2.2.4 are shown in Figure 9. This table also includes the results obtained from mixing wax into two types of paving-grade bitumen (10/20 and 35/50, which are referenced as \"10/20 + wax\" and \"35/50 + wax\"). \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Requirements** & **Parameters** & **Units** & **PMB** & **PMB** & **PMB** & **PMB** & **PMB** & **PMB** \\ \multicolumn{6}{l}{**Consistency:**} \\ At intermediate service temp. & Penetration @ 25 \({}^{\circ}\)C, \(P\) & 0.1 mm & 48 & 35 & 69.2 & 65.1 & 46.5 \\ At elevated service temp. & Softening point, \(t_{\text{R}ab}\) & “C & 71 & 90 & 67.7 & 89.1 & 94.7 \\ \multicolumn{6}{l}{**Additional property:**} \\ Thermal susceptibility & Penetration index, \(I_{p}\) & - & 2.9 & 4.7 & \(-\)0.245 & 0.0598 & 0.787 \\ \hline \hline \end{tabular}  
* It also includes functional additives; 2 in [17]; 3 in [17] for 3% of RPPW; 4 in [17] for 3% of FTW (FT wax).  
\end{table} 
Table 4: Consistency and thermal susceptibility of different PMB. Figure 8: Consistency and thermal susceptibility of the evaluated binders. Through the dynamic viscosity-temperature profiles evaluated in the viscometer, it was possible to verify that, on average, the addition of a pure wax (2% by wt. of binder) to the 10/20 bitumen reduced the viscosity, for example, by about 200 mPa-s and more than 250 mPa-s for the 35/50 bitumen (at \(\approx\)145 \({}^{\circ}\)C). These reductions are essential for manufacturing and applying bituminous mixtures that incorporate this additive. As with other wax from XLPE [6], this wax also has a high potential to be used in PMB with SBS as a viscosity-reducing additive. Such reductions are even superior to those promoted by the waxes used by [PERSON] et al. [17], blended with a 70 \(\times\) 0.1 mm penetration-grade bitumen and evaluated at 135 \({}^{\circ}\)C: when 3% of RPPW was added, the viscosity was reduced by 77 mPa-s, while with 3% FTW, it was lowered by only 18 mPa-s.  
Table 5 shows different temperatures recommended for hot mix asphalt (HMA) made with the traditional 35/50 neat bitumen and incorporating pure wax (without functional additives). In this case, dynamic viscosity can be considered approximately equal to the kinematics (\(\upmu\)), the one referred to in the European standard [42] (the difference is only a function of the specific weight of the binder, slightly higher than 1 g-cm\({}^{-3}\)). These results confirm the influence of this wax on the viscosity of the most used bituminous binder in the Iberian Peninsula, which can also contribute to a reduction in energy costs in manufacturing and applying HMA/WMA, especially at the current time of high prices. It was also possible to calculate other dynamic viscosity (complex) values from the test results in the DSR, respecting the European standard EN 14770 [55]. This calculation was a function of the complex shear modulus (G*), revealed in Section 3.5. This complex dynamic viscosity, \(\upeta\)* (Pa-s), was obtained in each of 12 to 15 iterations (for each test temperature), dividing G* (Pa) by the angular velocity, \(\omega\) (rad-s\({}^{-1}\)), for a strain amplitude (\(\gamma\)) ranging between \(\approx\)2% (1 st iteration) and \(\approx\)30% (15 th iteration). Figure 10 shows the average results calculated in this way for three binders (two traditional bitumens (35/50; PMB), and the PMB + wax) at each test temperature (for \(\omega\approx\) 1.6 Hz \(\approx\) 10 rad-s\({}^{-1}\) and test temperatures in the range of 46-88 \({}^{\circ}\)C). The \(\upeta\)* of PMB + wax (which also includes functional additives) at temperatures below 90 \({}^{\circ}\)C (essential for their mechanical performance in service), was the largest of the three binders.