# Stability of Bituminous Emulsion Induced by Waste Based Bio-Surfactant
## 3 Results and Discussion  
Before examining the chemical composition of the bitumen, we calculated the acid number of each sample correlating the values obtained to the emulsionability of each bitumen. A relatively simple method known as Catalytic Thermometric Titration (as described in Section 2.5) was used to determine the acid number of the bitumen samples used for this study. The main advantage of this method is that it is relatively easy to carry out and this method can be adopted by industries who need to determine if a certain bitumen to be used for the production of emulsions is up to emulsionable standards. As mentioned earlier, this procedure can be carried out in any laboratory and by any technician who understands the basic principle of titration. As per instrumentation, only basic titration apparatus and a temperature measuring probe are needed. In Table 2, we show the results obtained. As expected, making the emulsion as indicated in Section 2.2, we observed that the Cimar bitumen is the only one among the three analyzed bitumen samples to be emulsionable. The high acidity of Cimar bitumen (the only emulsionable one) helps us to understand how this parameter could govern the process of bituminous emulsion formation. Hence, the acidity can be used as a key role to evaluate the tendency of a generic bitumen sample to produce a stable emulsion. We proceeded with the characterization of all samples with the aim of identifying the ideal additives which will make the non-emulsionable bitumen samples emulsionable. Time cure curves (Figure 1) acquired for the three neat bitumens show that, as expected, the two bitumen samples with the same 70/100 penetration grade have very similar rheological behaviors, while Adriatica bitumen has a lower sol-gel transition temperature of about 10 \({}^{\circ}\)C.  
In Table 3, the transition temperature and percentage asphaltene of all the bitumen samples are reported. The asphaltene content could play a role in the stability of emulsions; in fact, asphaltenes show an important interfacial activity [20]. Adriatica bitumen shows a different rheological behavior but similar asphaltene concentration to the reference bitumen. Therefore, in order to obtain a mechanical behavior similar to that of the reference bitumen, only the Adriatica bitumen was treated with several modifier additives. On the market, there are several types of modifying additives \begin{table}
\begin{tabular}{c c} \hline
**Bitumen** & **Acid Number (mg/g KOH)** \\ \hline Cimar & 22.7 \\ Alma & 13.5 \\ Adriatica & 14.7 \\ \hline \end{tabular}
\end{table} 
Table 2: Acid number for each sample. Figure 1: (**a**) Time cure test for Cimar 70–100 (blue); Alma 70–100 (red) and Adriatica 170–210. (**b**) Comparison between the time cure test for Cimar and modified Adriatica with 1.5% SASOBIT. \begin{table}
\begin{tabular}{c c c} \hline
**Bitumen** & **Transition Temperature \(\pm\) 0.1 (\({}^{\circ}\)C)** & **Asphaltene \(\pm\) 1 (\%)** \\ \hline Cimar & 64.1 & 17 \\ Alma & 64.4 & 31 \\ Adriatica & 52.4 & 19 \\ \hline \end{tabular}
\end{table} 
Table 3: Transition temperature and percentage asphaltene of all bitumen samples. with only some of them chemically interacting with the bitumen [21; 22; 23; 24; 25]; others simply impart their own chemico-physical properties to it [26; 27; 28; 29; 30; 31; 32; 33]. The criteria on which the additive was chosen was its ability to increase the transition temperature without increasing the viscosity of the binder at high temperatures [34; 35; 36]. This commercial additive is a wax-based additive called SASOBIT. In fact, at temperatures above 100 \({}^{\circ}\)C it acts as a fluxing agent, lowering the viscosity of the binder thus favoring the emulsion process. This additive was added to the Adriatica bitumen in different dosages. In Figure 1b, we reported only the time cure of the best sample obtained with 1.5% additive. This modified bitumen was treated according to the reference experimental conditions for emulsion production.