## 3 Results and Discussion
### Moisture Sensitivity and Ageing Effect  
The ITSR of AC mixtures is an indicator of their resistance to moisture susceptibility. However, before presenting ITSR results, average ITS values for each case (AC mixture, dry vs wet, and unaged vs TEAGE aged) are presented in Table 1, depicted in Figure 6 and then discussed. Figure 5: Bulk density and air voids content results for each AC mixture and set of specimens (dry/wet and unaged/aged). Figure 6: Indirect tensile strength (ITS) results. From Figure 6, it is possible to observe the following:  
* All the AC mixtures showed high ITS values even in wet specimens. It can be justified by the reduced air voids content of the samples that minimizes the moisture damage of the mixture [23], and by the bitumen grade used (low penetration grade) [21]. * Notwithstanding the slightly higher air voids content, both modified AC mixtures presented an increase in the conventional ITS (unaged and dry conditions). Compared with the ITS of the control AC mixture, the plastic modified AC mixture presented an increase of 12%, and the plastic and nanoclay-modified AC mixture presented an increase of 5%. * In general, ITS values of wet specimens (where moisture damage is present) are lower than the dry ones (no moisture damage). * Ageing tends to increase ITS values as bitumen became stiffener during the ageing process [29; 50]. The exception, on average, was the dry set of specimens of the plastic modified-AC mixture, which is more a verification of the fact for this set of tests than a documented trend, once the variability of the samples could induce some \"not normal\" results as can be understood by the interval of results found in Figure 6.
* The outcome of the ageing effect in the plastic modified-AC mixture is not obvious. The TEAGE aged dry specimens presented lower values (5%) than the unaged ones, and the TEAGE aged wet specimens presented higher values (8%) than the TEAGE aged dry ones. * Nanoclay addition improved the resistance of plastic modified-AC mixture to moisture damage. The ITS values were similar in dry and wet specimens. The ageing effect on the plastic and nanoclay-modified AC mixture was less pronounced than in the other specimens. A two-way analysis of variance (ANOVA) with interaction on the obtained ITS values was conducted. The response variable was ITS (dry and wet) and the influence factors were AC mixture and ageing. The ANOVA results are shown in Table 2. From the \"\(p\)-value\" column, which presents the statistical significance level of the two-way ANOVA. It is observed that the \(p\)-values of the influence of ageing, AC mixture, and ageing-AC mixture interaction (AB) are higher than the threshold value of 0.05. Therefore, those factors do not have a significant effect on results. Only for wet specimens, the ageing effect was pronounced (\(p\)-value equal to 0.075). After carrying out a one-way ANOVA to evaluate only the ageing effect (Table 3), it is observed that it was only significant for the plastic-modified mixture (\(p\)-value equal to 0.008). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**ITS Values**} & \multicolumn{4}{c}{**Control**} & \multicolumn{4}{c}{**Plastic**} & \multicolumn{4}{c}{**Plastic \& Nano**} \\ \cline{2-13}  & \multicolumn{2}{c}{**Unaged**} & \multicolumn{2}{c}{**TEAGE Aged**} & \multicolumn{2}{c}{**Unaged**} & \multicolumn{2}{c}{**TEAGE Aged**} & \multicolumn{2}{c}{**Unaged**} & \multicolumn{2}{c}{**TEAGE Aged**} \\ \cline{2-13}  & **Dry** & **Wet** & **Dry** & **Wet** & **Dry** & **Wet** & **Dry** & **Wet** & **Dry** & **Wet** & **Dry** & **Wet** \\ \hline in kPa & 1845 & 1790 & 1956 & 1867 & 2065 & 1808 & 1957 & 2118 & 1936 & 1926 & 2013 & 2007 \\ in psi & 268 & 260 & 284 & 271 & 300 & 262 & 284 & 307 & 281 & 279 & 292 & 291 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Indirect tensile strength (ITS) values.