## 6 Conclusions
### The Effect on the Self-Healing Performance  
The strength recovery results showed that the modified PS capsule enhanced the strength recovery of the paste compared to the mixtures without capsule (at 12.5% and 15% for 100%OPC and 95%OPC + 5%SF, respectively). However, the result found that the variation in PS capsule surface treatment did not significantly influence the strength recovery performance. Thus, the roughened surface treatment is the best approach for the PS capsule application in cement-based composites. The microstructural studies, SEM and EDX, revealed the dispersion of sodium silicate solution on the crack area and the healing agent promoted the healing process by the formation of new CSH gel. The elemental compositions of Ca/Si ratio for 100%OPC and 95%OPC + 5%SF were at 1.35 and 1.18, respectively. The lower value of the ratio indicated the high amount of healing products that are responsible for strength recovery. Furthermore, the study also found a promising strength recovery obtained by 95%OPC + 5%SF with a modified capsule, where the strength recovery was increased about 20% compared to those of 100%OPC (without capsule). Thus, the finding confirmed that the autogenous self-healing could be enhanced by the synergic effect between the encapsulation technique and blended cement. However, these results need to be validated with other pozzolan blended cementitious composites.  
PS capsules are known due to its brittleness characteristic, good chemical resistance, and cheap material. Although the PS capsule brittleness characteristic is better than the glass capsule, the bonding strength between the capsule and cement matrix is a major concern. This study shows the PS capsule can be used successfully by treating its outer surface texture. In conclusion, the findings suggest that the most practical surface treatment of the PS capsule is by roughening the capsule surface. Although the PS capsules may  
Figure 14: EDX analysis for healing compounds at 28 days for 100%OPC (up) and 95%OPC + 5%SF (down) (**a**) 100%OPC without capsules, (**b**) 100%OPC with capsules, (**c**) 95%OPC + 5%SF without capsule, (**d**) 95%OPC + 5%SF with capsule.  
not survive during mixing, the PS capsules can be placed in the molds during casting. Furthermore, the capsules' placement can be focused on the area that is expected to defect. The use of silica fume with capsule surface treatment demonstrated a better improvement in the bonding strength of PS capsules. Furthermore, a promising healing performance was also observed on the silica fume blended cement with the incorporation of encapsulated sodium silicate. Thus, the use of pozzolan in the OPC system with encapsulated sodium silicate improves the autogenous self-healing ability of cementitious composites.  
Conceptualization, N.A.M.N. and N.A.S.; methodology, N.A.M.N. and A.I.M.; formal analysis, N.A.M.N., A.I.M. and A.A.A.B.R.; investigation, A.I.M. and A.A.A.B.R.; resources, N.A.M.N.; writing--original draft preparation, N.A.M.N. and A.I.M.; writing--review and editing, N.A.B. All authors have read and agreed to the published version of the manuscript.  
This work is financially supported University Putra Malaysia (UPM) through the research grant GP-IPS/2019/9672700.  
Not applicable.  
The authors would like to thank and express their deepest gratitude and appreciation for the technical and financial aid provided by the Civil Engineering Department, Engineering Faculty, Universiti Putra Malaysia (UPM).  
The authors declare no conflict of interest.