## 3 Results
### Extrinsic Healing
#### 3.5.2. High Capsule Content SMA Mix  
In order to test the HealRoad capsules for induction heating in an asphalt mix, the amount of HealRoad capsules was increased to 5%, 10% and 20% (when capsule content is higher than 20%, the HealRoad capsules do not disperse evenly in the mix). The percentages of constituent material in each mix are summarized in Table 3. These mixtures were not investigated for standard mix performance, the aim was only to test whether the increased volume of HealRoad capsules had the capacity to initiate induction heating and self-heal. Figure 7 shows the images of 10 mm SMA mix containing varying percentages of HealRoad capsules, 0-20%. From the Figure 7c,d, it is evident that the mixes containing 10% and 20% of HealRoad capsules show evidence of corrosion. Another finding is that the mixes containing 20% of HealRoad capsules had fewer large aggregates in comparison to mixtures  
Figure 5: Wheel tracking results—resistance to rut deformation. Figure 6: Image of 10 mm SMA—mix 6 containing 1.45% capsules in the mix. without HealRoad capsules. This could be an issue for the material strength as large angular aggregates, which determine the load carrying performance of a mix, are replaced by softer, round HealRoad capsules. The specimens were subjected to the ITS test protocol described in Section 2.2.4 and test specimen healing was performed following the protocol described in Section 2.2.5. After the ITS test, the test specimens were tied with cable ties to join two test specimen parts and to allow test specimens without HealRoad capsules to heal. Figure 8 shows the tied test specimens. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Aggregate Type**} & \multicolumn{4}{c}{**Constituent Content in the Mix (\%)**} \\ \cline{2-5}  & **Mix 1 (Control Mix)** & **Mix 2** & **Mix 3** & **Mix 4** \\ \hline
14 & 4.02 & 4.01 & 3.79 & 3.34 \\
10 & 47.21 & 44.60 & 42.10 & 37.11 \\
6.3 & 7.55 & 7.14 & 6.74 & 5.92 \\ Dust & 32.10 & 30.33 & 28.63 & 25.23 \\ Filler & 3.30 & 3.12 & 2.95 & 2.60 \\ Capsules & 0.00 & 5.00 & 10.00 & 20.0 \\ Binder & & 5.8 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The 10 mm SMA mix designs. Figure 7: The 10 mm SMA mix containing varying amounts of capsules: (**a**) 0% capsules, (**b**) 5% capsules, (**c**) 10% capsules and (**d**) 20% capsules. The healing results show a positive response to induction heating with a test specimen temperature increase. As expected, test specimens containing higher amounts of HealRoad capsules were able to reach high temperatures, while test specimens containing 20% of HealRoad capsules reached a temperature of 80 \({}^{\circ}\)C. Figure 9 shows the temperature readings (measured using an infrared laser temperature gauge). Figure 10 shows the test samples after the ITS test and before healing. The damage in the mixture containing 20% of HealRoad capsules was significant. We believe that this was caused by the high proportion of capsules in the mix, which replaced larger aggregates. Large aggregates (angular, flaky and elongated aggregates) in an asphalt mix form a load carrying skeleton which is responsible for pavement strength and for resistance to rutting [26]. Figure 11 shows the images of the same samples after healing. It is evident that mixtures with a high HealRoad capsule content--Mix 3 with 10% of capsules and Mix 4 with 20% of capsules--more efficiently repaired the damage, i.e., closed the cracks, in comparison to the control mix--Mix 1 containing 0% of capsules and Mix 2 containing 5% of capsules. Figure 8: The 10 mm SMA test specimen containing 5% capsules ready for induction healing. Figure 9: Temperature reading of the induction healing. Figure 11: Images of test specimens after induction healing: (**a**) control mix—Mix 1, (**b**) Mix 2–5% capsules, (**c**) Mix 3–10% capsules and (**d**) Mix 4–20% capsules. Figure 10: Images of test specimens after ITS test: (**a**) control mix—Mix 1, (**b**) Mix 2–5% capsules, (**c**) Mix 3–10% capsules and (**d**) Mix 4–20% capsules.