# Polysaccharides-Reinforced Bitumens: Specificities and Universality of Rheological Behavior
## 3 Results and Discussion
### \(G^{\prime}\)@50 \({}^{\circ}\)C and T\({}^{\star}\)
[3], who investigated the rheological effect of some additives. They found in that paper that some additives with almost apolar nature, like organosilane, oleic acid, and octadecylamine, are preferentially solubilized within the maltene phase, giving weak interactions with asphaltenes and their cluster, and consequently not being able to reinforce the overall structure. In this situation, T* decreases, as well as \(G^{\prime}\)@50 \({}^{\circ}\)C, which seemed correlated. On the contrary, a more polar additive like polyphosphoric acid was able to reinforce the structure, stiffening the bitumen, and increasing T*. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Additive** & \(G^{\prime}\)@50 \({}^{\circ}\)C (kPa) & \multicolumn{1}{c}{**T*** (\({}^{\circ}\)C)**} & \multicolumn{1}{c}{**Ea (kJ/mol)**} \\ \hline ref & 1.0 & 60.2 & 132 \\ Algae _euchemae_ & 13.0 & 75.0 & 130 \\ carobs & 10.5 & 72.0 & 139 \\ orange skin & 5.4 & 68.5 & 123 \\ flour 00 & 1.4 & 61.8 & 132 \\ agar & 1.9 & 63.2 & 132 \\ carragenine & 6.0 & 70.3 & 127 \\ carboxymethylcellulose & 7.8 & 70.5 & 140 \\ pectin & 1.7 & 62.7 & 139 \\ arabic gum & 1.4 & 62.2 & 131 \\ cellulose & 1.7 & 63.1 & 133 \\ Corn flour & 1.1 & 60.4 & 134 \\ starch & 1.6 & 62.6 & 131 \\ guar gum & 5.3 & 68.4 & 135 \\ xantam gum & 2.4 & 64.2 & 138 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: \(G^{\prime}\)@50 \({}^{\circ}\)C, T* and Ea values for bitumen modified with various additives. Figure 2: Correlation between the values of \(G^{\prime}\)@50 \({}^{\circ}\)C and T*. The dotted line is a guide for the eye. In our case, the additives are long molecules/polymers characterized by the presence of numerous polar groups. They would be able, in fact, to establish interactions with the asphaltene molecules and their clusters and this is confirmed by the fact that all additives tend to bring both \(G^{\prime}\)@50 \({}^{\circ}\)C and T\({}^{\star}\) to higher values. This can be ascribed by the presence of numerous polar groups that are able to establish interactions with the asphaltene molecules and their clusters. There are some differences among the various polysaccharides in the extent of \(G^{\prime}\)@50 \({}^{\circ}\)C and T\({}^{\star}\) increase: the most prominent effect is exerted by algae _euchemae_, followed by carob seeds flour, with the least effect by 00 and corn flours. These differences can be ascribed to their specific molecular structure. The most soluble additives, like those rich in starch, i.e., 00 and potato flours, have little influence on the bitumen properties. They can bind asphaltenes but are not of sufficient length or strength to connect the hierarchical structures made of asphaltenes clusters at longer length scales. Fibers instead, (recognizable by their lower solubility in water) like carboxymethylcellulose or algae _euchemae_, have the proper characteristics to do this. The remaining small differences among the various polysaccharides should be interpreted going deeper into their specific interactions with all the molecules involved in such complex systems, for which more challenging experiment would be required. The present data however, represent a good starting point for experimentalists and theoreticians.