## 3 Results and Discussion  
### Physical-Mechanical Properties of the Synthesised Capsules  
Figure 3 presents the main results of experimental characterisation of the WCO capsules. Statistical size analysis of 100 individual WCO capsules registered an average size of 1.649 mm (SD = 0.145 mm), with a spherical and uniform geometry (Figure 3a). These capsules presented an encapsulation efficiency of WCO close to 90%. SEM-EDS observations (Figure 3d) proved that WCO capsules reveal a polynuclear structure on their  
Figure 2: Representation of the procedure to synthetise polynuclear capsules containing WCO as rejuvenator. **(a)** First, an alginate-based O/W emulsion containing WCO is extruded by using a syringe pressure pump. **(b)** The alginate biopolymer present in the emulsion possesses Guluronic-Guluronic (G-G) molecular blocks structures with the capacity to crosslink in the presence of divalent Ca\({}^{2+}\) ions. Thus, when the extruded O/W emulsion drop into a CaCl\({}_{2}\) bath **(c)** the ionic gelation process take place by exchanging the Na\({}^{+}\) ions from carboxylic acids in the G-G blocks with Ca\({}^{2+}\) ions, resulting in **(d)** the well-known “egg-box” crosslinked complex. In the end, **(e)** capsules are formed, where the Ca-alginate complex encapsulate the WCO in multiple cavities. Figure inspired on [PERSON] et al. [9].  
surface (Figure 3b,c) with an elemental composition of Ca (73%) and Na (27%), which is consistent with the materials used for the synthesis of the porous Ca-alginate matrix structure in the presence of divalent calcium cations (Ca\({}^{2+}\)) allowing that the oil-in-alginate can be cross-linked.  
The size distribution of WCO capsules is shown by the frequency histogram in Figure 3e, proving that the capsule size can be fitted to the normal probability distribution (\(p\)-value 0.405 given by A-D test). Conversely, Figure 3f shows the pore size distribution of the internal multicavity of the WCO capsules. The frequency histogram proves that the capsule pore size can be fitted to the log-normal probability distribution function (\(p\)-value 0.159 given by A-D test). This Figure revealed that the internal structure of the capsules was characterised by micropores with areas \(<\) 120 um\({}^{2}\) and with an occurrence probability of 75%. Thus, the WCO was majorly encapsulated into small internal pores, contributing to homogeneously distribute the oil into the overall volume of the capsule.  
Additionally, Figure 3h,i show SEM images of an individual capsule and the fracture type on a capsule broken by effect of a compression test, respectively. This result proves that WCO capsules can break and partially release the encapsulated WCO by effect of an external trigger. Biopolymeric matrix presented an elastic-plastic mechanical behaviour with breakage in plastic deformation around the propagating cracks, see Figure 3i,j. WCO capsules registered an average maximum compressive force of 11.6 N (SD = 2.3 N) at an average maximum deformation of 0.7 mm (SD = 0.1 mm), Figure 3k. This result suggests that polynuclear WCO capsules can resist the asphalt manufacturing process (i.e., mixing and compaction) based on the results published by [PERSON] et al. [4] and [PERSON] et al. [8] (minimum compressive force of 10 N); hence, WCO capsules can be used as a resistant encapsulated rejuvenator for asphalt mixture self-healing.