## 9 Effect of Parameters on Performance of Cementitious Self-Healing Agents
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Ref.** & **Method** & **Test** & **Major Findings** \\ \hline
[101] & Encapsulation & Three-point bending and splitting TS & FS and TS values were increased from 52 to 62\% and 40 to 64\%, respectively when polyurethane was incorporated into the tubes. \\ \hline
[53] & Vascular & CS & For SAPs, the CS was reduced to 18\% and cracks of width up to 50 to 250 mm were healed due to swelling of SAPs. \\ \hline
[85] & Encapsulation & CS and FS & The CS and FS values were 1.9 and 1.3 times higher than the normal concrete, respectively. \\ \hline
[105] & Encapsulation & Three-point bending & FS was increased by 35\%. \\ \hline
[48] & Direct & Ultrasonic pulse & The healing rates were appreciably increased depending on the polymers’ dosages. The repairing efficacy depended on the age of the damages in both mixes designed without or with polymers. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Polymers based self-healing cementitious materials. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Bacteria Used** & **Best Results** & **Bacterial Concentration** \\ \hline _Bacillus_ sp. CT-5 & CS vale was 40\% above the control specimen & 5 \(\times\) 10\({}^{7}\) cells/mm\({}^{3}\) \\ \hline _Bacillus megaterium_ & Maximum rate of strength development was 24\% (50 MPa) & 30 \(\times\) 10\({}^{5}\) cfu/mL \\ \hline _Bacillus subtilis_ & CS was increased by 12\% higher than control sample & 2.8 \(\times\) 10\({}^{8}\) cells/m \\ \hline _Bacillus aerius_ & CS was increased by 11.8\% in bacteria-added concrete than control sample made with 10\% rice husk ash. & 10\({}^{5}\) cells/mL \\ \hline _Sporosarcina pasteurii_ & CS was 35\% more than the control specimen & 10\({}^{5}\) cells/mL \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Obtained CS values of different kind of bacteria. in the mechanical properties of the concrete occur because of the fiber's incorporation. The cracks filling efficacy of various types of fibers as healing agents within concrete has widely been explored. The ability of the fiber-reinforced cementitious materials to seal the formed cracks was examined in detail [107]. Steel fibers, wollastonite, antifoaming agents, silica fume cement, and super-plasticizer were among the materials used in this study. When immersed in water, numerous cracks formed in the close proximity within the concrete were more effectively healed by the proposed materials. Surface cracks were examined via the microscopy and air permeability measurement. The autonomous healing procedure commenced with the immersion in water of the pre-cracked specimens. A decrease in the air permeability was observed while the cracks were filled by the precipitated crystalline particles emerged from the fiber-reinforced cementitious materials. The results indicated that the un-cracked samples had reduced air permeability compared to the cracked samples. Multiple synthetic fibers were utilized to ascertain the healing performance of the fiber-reinforced cementitious concrete (FRCC) [108]. Several distinct fibers such as polypropylene, ethylene-vinyl alcohol, poly-vinyl alcohol, and polyacetal were used. The primary materials consisted of polycarboxylic acid (super-plasticizer), silica fume, cement, and sand. The particles' diameters for cement-polypropylene (C-PP) and polypropylene (PP), polyvinyl alcohol (PVA)-I and II, ethylene vinyl alcohol (EVOH), and polyacetal (POM) were 18 mm, 11 mm, 37 mm, 14 mm, 15 mm, and 48 mm, respectively. The microscopic and air permeability of the samples were measured. The results revealed that the precipitates near the fibers led to a reduction in the water permeability. With PVA incorporation, a higher rate of calcium carbonate precipitation was observed in the high polarity of the fiber composites for cracks of width up to 0.3 mm. A reduction in the water permeability was found in the PVA II-included samples, while healing occurred within 72 h for the PVA-included specimen.