## 7 Conclusions  
The present paper aims to analyse the effectiveness of various chemical additives used to manufacture asphalt mixtures at lower temperatures, to determine whether a cleaner technology can be employed for the production of asphalt mixtures with appropriate mechanical behaviour for application in pavements for roads. To this end, this study focused on determining the optimal design parameters of a WMA by examining its use in a real asphalt plant and applying the mixture in a trial section, as well as assessing its mechanical properties through the use of laboratory tests. On the basis of the results obtained in this study, the following conclusions can be drawn:  
1. The manufacturing and compaction temperature has a strong impact on the behaviour of the mixture, obtaining better results when the manufacturing temperature is around 145 \({}^{\circ}\)C. Nonetheless, the behaviour of mixtures with the A1 and A2 additives appeared to be less susceptible to the effects of temperature than the material produced with A3 additives. 2. For mixtures manufactured at 145 \({}^{\circ}\)C, the results showed that the use of certain additives even allowed for an improvement in mixture workability, tensile strength, and water susceptibility in comparison with conventional HMA. 3. The results reveal that the use of certain chemical additives in WMA leads to lower stiffness modulus, without reducing the resistance to plastic deformations in reference to HMA. This \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Mix**} & **Density** & **Air Void** & \multicolumn{2}{c}{**Water Susceptibility**} & \multicolumn{2}{c}{**Stiffness Modulus**} & \multicolumn{2}{c}{**Triaxial**} \\ \cline{3-6}  & **(Mg/m3)** & **Content (\%)** & **ITS Dry (kPa)** & **ITSR (\%)** & **at 20 \({}^{\circ}\)C (MPa)** & **P. def. (\%)** & **Creep Ratio** \\ \hline WMA & 2.451 & 5.7 & 1530.2 & 96.0 & 6626.3 & 2.76 & 1.1 \\ HMA & 2.471 & 5.0 & 1569.6 & 91.4 & 7371.2 & 1.71 & 0.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results recorded for the HMA and WMA manufactured in a real asphalt plant. Figure 9: Visual appearance of the process for manufacturing the WMA with the chemical additive. (**A**) incorporation of additive to bitumen; (**B**) aggregates temperature; (**C**) WMA temperature; (**D**) spreading and compaction of the WMA. indicates the possibility of obtaining more flexible mixtures without reducing strength, which could result in greater longevity of the mixtures. Nonetheless, there is a need for more in-depth studies on this topic. 4. The A2 additive was identified as the most appropriate in this study on the basis of the laboratory results, and it was shown that using a lower dosage (0.05% over the bitumen mass, instead of 0.5% that is commonly used with chemical additives) allowed for lower susceptibility to the manufacturing temperature, whilst better mechanical performance was recorded. This fact could be associated with the nano-composition of this additive, which acts at the microscopic aggregate/bitumen interface. 5. This study indicates that WMA can be produced in a conventional discontinuous plant without incorporating any significant changes to the equipment and manufacturing process. 6. Moreover, the WMA presented appropriate density and air void values when compared to the HMA, whilst comparable tensile strength and water sensitivity was also recorded. Nonetheless, in this case, the reduction in stiffness modulus of the WMA produced a decrease in resistance to plastic deformations, which should be considered in further studies focusing on its application in bituminous pavements. Taken together, the results obtained in this study suggest that, at least when using tensoactive additives, it is possible to manufacture cleaner asphalt mixtures at lower temperatures (WMA), with the material showing comparable mechanical behaviours to that recorded for conventional hot mixtures.