## 4 Discussion
The more uniform the pore profile the more homogeneous the materials, which is consistent with improved mechanical properties. Furthermore, the Gaussian deconvolution procedure of the GSH of all the mortar specimens examined in this work, showed that the minimum unhydrated cement phases (5%) were found in the case of the mortar-SAPs-1 specimens, whereas the corresponding phases in mortar-reference (36%) and mortar-SAPs-2 (35%) were almost identical (see Table 4). Firstly, this indicates that SAPs were more homogeneously dispersed in the cementitious matrix for the concentration of 1% bwoc thus allowing them to function as water reservoirs and cement hydration promoting agents and therefore led to denser and more durable cementitious structures. Secondly, it is safe to assume that even greater SAPs concentrations, if needed to render different functionalities to the mortars, will not compromise the mortar behavior. In mortars, apart from one single crack several other microcracks are formed and distributed in the bulk of the specimens, when they are subjected to compressive loads, which sometimes may not be easy to detect using conventional methods. On the contrary, by running a full 3D analysis via microCT, apart from crack healing, the 3D volume of the specimen was also be thoroughly evaluated. As mentioned earlier, the quantitative analysis of the self-healing progress in pre-cracked mortar specimens took place via microCT Analysis. More specifically, a morphological and an architectural parameter were calculated for all mortar specimens before and after eight days of healing treatment. These parameters were:  
* Morphometric parameter, \"Percent Object Volume\" (%) which shows the percent of the specimen volume variation during the healing treatment. The value of this parameter increases with healing time, since healing products that are formed cover progressively the crack volume in part, thus representing the healing progress with time [51; 57; 58]. * Architecture parameter, \"Connectivity Density\" (mm\({}^{-3}\)) comprising a sensitive indicator of the change in texture and complexity associated with the healing progression. More specifically Connectivity Density is an indicator of complex, very highly porous structures. The value of this parameter decreases with healing time, since crack healing provides denser structures within the crack volume [58; 60]. In order to estimate the relative self-healing enhancement of mortar/SAPs specimens versus the control specimens, the relative self-healing enhancement index \(h_{i}\) (%) was calculated [61], based on the results of Connectivity Density since this architecture parameter is very sensitive to texture and complexity changes. \[h_{i}(\%)=\left(1-\frac{CD_{i,n}}{CD_{i,0}}\right)\times 100, \tag{1}\]  
where:  
\(h_{i}\): relative self-healing enhancement index for specimen, \(i\)  
\(CD_{i,n}\): value of Connectivity Density for specimen, \(i\) after \(n\) days of self-healing treatment \(CD_{i,0}\): value of Connectivity Density for specimen, \(i\) before self-healing treatment (at 0 days)  
More specifically, when no self-healing is observed \(h_{i}\) value is \"0\", as the final and the initial value of connectivity density are the same. On the other hand, when self-healing is promoted, \(h_{i}\) values become higher and approach the value \"100\", since the ratio \(CD_{i,n}/CD_{i;0}\) approaches \"0\" as \(CD_{i,n}\) decreases. The corresponding values of \(h_{i}\) for the mortar/SAPs and control specimens are shown in Table 5 and it is revealed that the self-healing index was 84% and 31% for mortar-SAPs-1 and mortar-SAPs-2, respectively, while it was 20% for mortar-reference specimen. Comparatively, self-healing was enhanced by about 60% and 10% for mortar-SAPs-1 and mortar-SAPs-2, respectively compared to the mortar-reference specimen. These results reveal that healing efficiency was optimized for the specimen mortar-SAPs-1.