## 4 Experimental Results
Under these assumptions, \(d\) parameter was assumed to clarify the recovery aptitude because the recovered strain was almost achieved during the delay time; after the delay time, recovered deformation was quasi-negligible. The following Figure 7 helps to clarify the physical meaning of the parameters introduced. The calculated \(s\) and \(d\) are plotted in Figure 8 as a function of stress and temperature. Then, power and linear laws for \(s\) and \(d\) were used to reliably fit their trends over time according to Equations (6) and (7), respectively;  
\[s(T)=A\cdot T^{B} \tag{6}\]  
where, \(A\) is related to the curve position and \(B\) indicates its slope (power law coefficients). \[d(T)=m\cdot T+q \tag{7}\]  
Figure 7: Physical meaning of \(s\) and \(d\) parameters for a generic creep-recovery cycle. where, \(m\) is the slope and \(q\) is the intercept of the regression line. Table 6 reports the fitting parameter obtained for \(s\) and \(d\) evolution over time, at the different experimental temperatures and stress levels (the fitting reliability was demonstrated by high coefficients of determination \(R^{2}\)). Figure 8: Physical parameters describing creep-recovery strain evolution: \(s\) (**a**) and \(d\) (**b**) at 0.1 kPa; \(s\) (**c**) and \(d\) (**d**) at 3.2 kPa; \(s\) (**e**) and \(d\) (**f**) at 10 kPa. Generally, quasi-negligible fluctuations of 10-cycle data among the mean values were detected (see error bars in Figure 8). As far as \(s\) is concerned, \(A\) parameter (curve position) seemed to be inversely related to the material stiffness; as expected, lower creep slopes were found for the stiffer material; this means that the stiffer _MOR-S_ accumulate lower creep deformation at a given \(T\) and \(\tau\) with respect to other materials (lower creep slope at the fixed duration time of 1 s). On the other hand, \(B\) coefficient (curve slope) was quite similar for each material and stress level, suggesting a quite similar thermal and stress dependency of the creep slope. As far as the delay \(d\), the slope \(m\) (linear interpolation) was quite different depending on material and stress level. In general, the thermal dependency was reduced (lower \(m\)) when the material stiffness increased; on the contrary, the increase of stress led to amplified \(m\). It is worth noting that such an approach referring to \(s\) and \(d\) parameters allowed for discriminating among the selected materials, and was generally in accordance with the main findings from the \"traditional\" analysis. Moreover, it provided reasonable physical meaning in describing the high-temperature material's performance. Overall outcomes clearly indicated that an increased stiffness leads to a delayed development of the strain recovery (higher \(d\)), which can be in turn associated with a lower non-recoverable final strain; analogously, at lower test temperatures (i.e., when a predominant elastic behavior is expected), \(d\) was higher; then, fewer thermal-dependent behaviors were found for mastic and mortars due to the presence of aggregates that are not thermal-dependent. Finally, the stress level also decreased the materials' thermal dependency and generally reduced the time required to develop the main part of deformation recovery. Overall, such a comprehensive and innovative analysis of the rutting potential of fine mortars proved the suitability of steel slag in enhancing the anti-rutting properties of asphalt mixtures.