# Stability of Bituminous Emulsion Induced by Waste Based Bio-Surfactant
## 3 Results and Discussion
Nevertheless, even in this case, no stable emulsion was obtained proving that the mechanical behavior does not play a decisive role in the formation of bituminous emulsions. Therefore, having established that the mechanical properties do not significantly affect the emulsifiability of the bitumen, a new approach based on the chemical composition of the bitumen was undertaken. Still using Cimar bitumen as reference, NMR analyses were carried out to obtain more information on the chemical composition of all three bitumens analyzed [18; 37; 38; 39]. The acquisition of the proton NMR spectra (Figure 2) allowed the characterization of the bitumen under examination from a chemical point of view. Table 4 shows the fractional proton distribution obtained from the normalization and integration of the peaks. By comparing the distribution of the protons of the bitumens analyzed, it emerges that the Cimar bitumen has a similar aromatic character (3.88%) to the Adriatica one (4.17%) while the Alma bitumen has greater aromatic character (5.75) in comparison with the other bitumens. Furthermore, Cimar bitumen is characterized: (i) by having the highest percentage of hydrogens in \(\beta\) compared to the aromatic ring (56.95% against 55.52% and 53.50%); (ii) having a percentage of hydrogens in \(\alpha\) (12.26%) in the aromatic ring comparable to that of Adriatica bitumen (12.46%) but lower than that of Alma bitumen (14.46%); (iii) finally, the percentage of methyl hydrogens is intermediate between the percentages of the other two bitumens (26.91% against 24.26% and 29.87%). The major differences correspond to methylene hydrogens in \(\beta\) to the aromatic ring and methyl protons in the \(\gamma\) position. From the information obtained by NMR spectroscopy, it was possible to identify any surfactants that could compensate for the chemical differences between the bitumens. Adriatica bitumen has a different rheological profile from the reference bitumen, however it has a similar value of percentage asphaltenes and shows values of aromatic components very close to it. This data pointed towards the choice of an additive capable of making the bitumen more acidic without altering the aromatic components, which is an acid aliphatic/aromatic surfactant. In light of this, the commercial additive called \"AS\" was chosen. This additive is a Bronsted acid surfactant [40; 41], consisting of an acid group (polar head), as a substituent of an aromatic ring, and a long hydrophobic chain (lipophilic tail) [42; 43]. Thanks to these characteristics, the AS additive has been able to balance both the aromatic and aliphatic components to compensate for the differences with Cimar bitumen. In fact, once the Adriatica bitumen was modified with AS at different dosages (2.5 to 7.5%), it was possible to proceed with the preparation of the emulsion in accordance with what was done for the emulsion obtained with the Cimar bitumen. This modified bitumen was able to produce stable emulsions and the best emulsion was obtained after modification with 2.5% AS (see Figure 3). Figure 3: Pictorial representation of Adriatica bitumen emulsions obtained with aliphatic/aromatic acid surfactant (AS) additive (**a**), and without AS additive (**b**). Alma bitumen has a rheological profile very similar to Cimar bitumen (Figure 1a) but has a different percentage of asphaltenes (almost double, see Table 2) [44]. Above all, based on the data obtained by NMR measurements, it is observed that it has a higher aromatic component. Consequently, the function of the additive to be used to make this bitumen more similar to the reference bitumen must be to integrate the maltene part, thus decreasing the asphaltene percentage, lowering the percentage of the aromatic components and also increasing the total acidity of the bitumen with additives. The latter is in fact a central component in the realization of anionic emulsions. The methodological approach used shows how fundamentally important the chemical nature of bitumen is for the realization of bituminous emulsions.