## 9 Effect of Parameters on Performance of Cementitious Self-Healing Agents
Table 6 shows that the FS and CS of normal concrete were 1.3 times and 1.9 times weaker, respectively, than that of the autonomously healing concrete. The efficacy of the superabsorbent polymers as self-recovery agents was examined [103] and ascertained via a water flow test. When exposed to water, the superabsorbent polymer showed an expansive trait and functioned as a cross-linked polymer. The widths of large cracks were significantly reduced through the self-healing procedure. The FS of the control concrete was 8% weaker compared to the self-healing concrete (Table 6). In addition, the autonomous healing capabilities of the cementitious composite materials were investigated [104], wherein the reaction rate was found to improve via the accelerator microencapsulating triethyl borane and methyl methacrylate monomers. A comprehensive mixing of the solution containing the microcapsules and methyl methacrylate occurred within the concrete. Three kinds of carbon microfiber-reinforced mortars were designed, and their mechanical performance was assessed. The first served as the control sample, the second was the sulfonated polystyrene modified mortars, and the third one was the autonomously healing mortar. The polymers-based self-healing cementitious materials designed using the encapsulation method showed significant improvement (Table 6) in their strength properties (CS, FS and TS). The strength of the healed crack in the concrete was examined after incorporating the flexible polymers as healing agents [105], wherein the encapsulation method enabled the incorporation of polymers into the concrete (Table 6). The TS of the autonomously healing concrete was evaluated using the split tensile tests, wherein the specimen was cured for 3 days at 20 \({}^{\circ}\)C. The FS of the concrete was found to improve by 35% after the healing of the crack by the flexible polymers. In a study, the concrete specimens were pre-cracked with the cracks' widths in the range of 100 to 400 \(\upmu\)m with the incorporation of SAP to determine the healing efficiency [106]. Specimens made with SAP showed 85% lower water flow than the normal concrete. In addition, a substantial reduction in the water flow was experienced by other mortars compared to the standard concrete. With regard to the cracks healing performance, the SAP was better than poly-acrylate. The results in Table 7 show more effective healing of the formed cracks in the concrete structures when the SAP particles were bigger. Various doses of the acrylic polymers and styrene-butadiene rubbers were mixed into the autonomously healing concrete [48]. The hydration process and healing time were evaluated via the thermogravimetric and UPV measurements. After nearly 3 weeks of curing, the rate of cracks healing was reduced. This was mainly due to the presence of styrene rubber in the concrete, wherein the cement particles were bonded with the polymer, indicating that the polymer dosage determined the healing time. Furthermore, the incorporation of styrene-butadiene rubber caused a reduction in the hydration process, while the healing time was prolonged by the polymer content. Most common kinds of fibers are the man-made and natural ones. The former is known as synthetic fibers, industrially fabricated, and include polyvinyl alcohol, polypropylene, vinyl alcohol, polyester, and polyethylene. Drying shrinkage and plastic induced cracks in concretes are regulated and prevented via the incorporation of synthetic fibers, which also enhance the toughness and TS of the concrete. Water penetration through pores is safeguarded as fibers enable to decrease the permeability of the concrete mix. Enhancements