## 8 Structural Tests for Self-Repairing Efficacy Evaluation
### Macrostructures Evaluation  
Multiple assessments at the macro-level were carried out to ascertain the self-healing effectiveness of concrete. The extent of flexural and CS, as well as other mechanical properties, recovery was tested and assessed (Table 2). Toughness and split TS assessments form a part of these tests [85; 86; 87]. Various studies reported that UPV and water permeability assessments form a part of these tests [88; 89]. Encapsulated tetraethyl orthosilicate, colloidal silica, sodium silicate and their respective effectiveness in autonomously healing were evaluated using the gas permeability and sorptivity tests [90]. These assessments revealed about an 18% and 69% decrease in the sorptivity and gas permeability, respectively. The healed material's performance was measured using the stiffness test [91]. The control specimen was found to have 50% less FS than the healed concrete [51]. In the crack sites, a white deposited material was identified, and thermo-gravimetric analysis was performed [47]. Table 2 shows the oxygen profile, chloride penetration depth, pore size distribution and porosity results obtained using different tests. Through the autonomous healing, up to 60% of the CS was recovered. Thus, the biological self-healing technique may be suitable for the durability criterion over a prolonged time, wherein the concrete infrastructures and their life span can be prolonged by such an approach. Nonetheless, some evaluations, such as permeability, stress-strain relationship, and bond strengths amid concrete and deposited agents in the formed cracks are seldom made. Hence, multiple techniques must be used to accurately assess the development of the autonomously healing concrete. In short, the suitability with the concrete composition and bonding ability of the deposited material in the formed cracks must be compared more effectively.  
\begin{table}
\begin{tabular}{l l l} \hline \hline
**No.** & **Test** & **Dependent Variable.** \\ \hline
1 & Strength properties & CS, FS and splitting TS. \\ \hline
2 & Permeability & UPV, chloride penetration, gas permeability. \\ \hline
3 & Scanning electronic microscopy (SEM). & Fabric of nanostructures of concrete. \\ \hline
4 & Nanostructures’ measurements & Nanomechanical properties. \\ \hline \hline \end{tabular}
\end{table}
Table 4: Structural analyses for self-repairing efficacy evaluation.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**No.** & **Control Variables** & **Methods** & **Results** \\ \hline
1 & Immobilized organism & Optical density & Higher urecolitic activity with immobilized samples for prolonged duration \\ \hline
2 & Laboratory condition & Optical density & More self-repairing at optimal contents \\ \hline
3 & Microfibers & Weight present & Completely plugged the cracks up to size of 138 \(\upmu\)m \\ \hline
4 & Medium cultures & Liner methods & Mixed bacterial cultures could plug cracks without appreciably regaining the CS \\ \hline
5 & Ambient conditions & Particle sizes analyses & Higher self-repairing with microcapsules of size 230 \(\upmu\)m \\ \hline \hline \end{tabular}
\end{table}
Table 3: Control variables and methods for self-healing materials.