# An Evaluation of the Efficiency of Compartmented
## 4 Discussion & Conclusions  
The healing capacity of the compartmented alginate fibres encapsulating a rejuvenator as a self healing system for Porous Asphalt (PA) mix was evaluated in this study, by comparing the performance of asphalt mixtures with and without healing systems. By carrying out the parallel tests programme, the control mixture (without a healing system) can be used to ascertain whether the self healing asphalt mix design is suitable for standard testing. The test results can be compared to the historical data sets of standard asphalt mixtures. The results further demonstrated the value of such comparisons, as in some cases, mixtures without the healing system outperformed mixtures with the healing system. This approach gives researchers the opportunity to further investigate and correct self healing system design or asphalt pavement mix design. The healing time adopted in this study was 20 h at 20 \({}^{\circ}\)C, and this healing time was shown to be sufficient for this particular healing system, which employs a rejuvenator as the healing agent. However, the healing time can be reduced and the temperatures increased, but if the temperature is decreased, the healing time needs to be increased. This is due to the time that it takes for the rejuvenator to diffuse into the aged binder. The key aim of this study was to assess test methods for the evaluation of the asphalt healing performance. Specifically, the ITS, SCB, and 4 PB test methods were used to evaluate the healing performance of asphalt mixtures containing compartmented fibres as a self healing system. The results from the ITS and SCB tests showed that the initial strength of the control mix is higher than that of the mixtures containing fibres. This was an unexpected result as research had previously suggested that fibres can reinforce and strengthen asphalt mixtures [14; 15]. It is believed that the reduction in the material initial strength was caused by the test specimen machining process; during the test specimen production process, fibre compartments were damaged, which caused the release of the rejuvenator and the premature triggering of the healing process, i.e., rejuvenation. In addition, the results from the SCB test showed that the crack propagation speed for asphalt mixtures containing fibres is lower than that for the control asphalt mix. This is due to aged binder rejuvenation, binder softening, caused  
Figure 11: 4 PBT results – healing efficiency of the fibre asphalt mix vs. control asphalt mix, (**a**) initial test results; (**b**) test results after 20 h healing at 20 \({}^{\circ}\)C.  
by the release of the rejuvenator into the asphalt mix. In general, the observations from the ITS and SCB tests demonstrated that full loading-full failure causes large deformations of the test specimens, significantly deforming the shape of the test specimen. These deformations are difficult to repair, thus making test specimens unusable for repeated tests after healing and these tests unsuitable for an evaluation of the asphalt healing. On the other hand, the 4 PB Fatigue test, as it is strain controlled (deflection controlled), controls the damage to the test specimen and the minor damage caused presents as micro cracks, which are common on-site. Therefore, the most suitable and convenient test method for the evaluation of the self-healing asphalt mix performance is the 4 PB Fatigue test method. The results from these tests showed that the compartmented alginate fibres encapsulating a rejuvenator have a better stiffness recovering ability in comparison to the control asphalt mix (without fibres). These results confirm the potential of the compartmented alginate fibres encapsulating a rejuvenator as an asphalt healing system. However, the development of the healing system is still in its infancy and requires further development, such as: modifying the fibre composition in order to improve its mechanical and the thermal strength of the fibres.