## 4 Conclusions  
A comparative investigation of the mechanical responses manifested by bitumen modified with three non-polymeric additives was performed at 25 \({}^{\circ}\)C, after the corresponding specimens were subjected to different cooling rates in the range 1-10 \({}^{\circ}\)C/min. The selected range of cooling ramps  
Figure 3: Dependence on the cooling rate of both \(z\) coordination number (upper plot) and interaction strength A (lower plot) for neat bitumen (diamonds) and bitumens modified by addition of 2% P2 KA (circles), LCS (squares) and PPA (triangles), respectively.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Cooling Rate (\({}^{\circ}\)C/min)** & **1** & **5** & **10** \\ \hline _Sample_ & \(A\times 10^{-6}\) & \(A\times 10^{-6}\) & \(A\times 10^{-6}\) \\ Bitumen & 0.68 \(\pm\) 0.01 & \(0.558\pm 1\times 10^{-3}\) & 1.14 \(\pm\) 0.01 \\ Bitumen + P2 KA 2\% & 1.22 \(\pm\) 0.01 & \(0.563\pm 3\times 10^{-3}\) & 0.518 \(\pm\) 2 \(\times\) 10\({}^{-3}\) \\ Bitumen + LCS 2\% & 0.530 \(\pm\) 3 \(\times\) 10\({}^{-3}\) & 0.479 \(\pm\) 2 \(\times\) 10\({}^{-3}\) & 0.675 \(\pm\) 2 \(\times\) 10\({}^{-3}\) \\ Bitumen + PPA 2\% & 1.06 \(\pm\) 0.01 & \(0.511\pm 1\times 10^{-3}\) & 1.42 \(\pm\) 0.03 \\ \hline \end{tabular}
\end{table}
Table 3: Dependence of the “interaction strength” \(A\) on the cooling rate, calculated as a fitting parameter in Equation (1) adapted to experimental oscillatory rheological data, 1 G*! vs. frequency, for neat bitumen and bitumens modified with additives.  
represented a good compromise between suitable experimental conditions performed at lab-scale and hypothetical cooling events that might occur in realistic environmental conditions.  
Aimed at searching for microstructural differences between various types of modified bitumens when they have undergone the action of several thermal ramps, a parallel morphological investigation was also carried out by using Atomic Force Microscopy (AFM). The correspondent rheological response was interpreted under the framework of the \"weak gel\" model whose analysis revealed the presence of lightly entangled networks with the exception of PPA-modified bitumen. A striking result was recorded from bitumen incorporating a raw mixture of natural phospholipids (2% LCS additive), which was able to leave the asphaltene aggregates fairly unaltered after the hot material was either slowly (1 \({}^{\circ}\)C/min) or rapidly (10 \({}^{\circ}\)C/min) cooled to the final reference temperature of 25 \({}^{\circ}\)C. The complex modulus of the correspondent LCS-modified bitumen was found almost independent of the cooling rate as well. The addition of LCS to bitumen should prove extremely fruitful in increasing the mechanical resistance of bitumen to thermal shocks and provide an attempt to substitute polymer-based rheology modifiers with additives derived from renewable bio-resources.  
This work was financially supported by KimiCal s.r.l. (Rende, Italy). Authors were very grateful to Loprete SRL for the support offered (supply of bitumen) and Ing. [PERSON] who stimulated the need to undertake the present study with strong applicative implications.  
[PERSON] and [PERSON] conceived and designed the experiments; [PERSON] performed the AFM experiments; [PERSON] prepared the samples and performed the rheological experiments; [PERSON] analyzed the data.  
The authors declare no conflict of interest