## 4 Conclusions  
This study represents one of the largest trial campaigns on SAP concrete walls conducted in Europe to date. Two types of SAPs were studied, one commercially available and the other developed specifically for this study. The first SAP was used to facilitate internal curing of the concrete structure, thereby reducing the possibility of early-age shrinkage-induced cracking. The second SAP was designed to promote immediate crack sealing while improving the concrete's self-healing capabilities in the case of imminent crack formation. By combining the two SAPs, it was envisaged that an ideal concrete wall could be constructed, with active means of mitigating shrinkage and promoting self-sealing/crack healing. The internal curing promoted by SAPs had a positive impact, leading to a remarkable 55% reduction in shrinkage strain at 7 days compared with a reference mix without SAPs. As a result, the SAP-treated wall remained crack-free throughout the 24-month monitoring period. The reference walls without SAP, however, showed cracks as early as the first seven days after casting. With regard to corrosion initiation, no indication of corrosion potential was observed in the monitored areas of the SAP-treated wall. On the other hand, a drop in potential, indicating the start of corrosion, was noted in the reference wall near certain cracks 6 months after casting. Although there is no direct reported effect of SAPs on corrosion itself, the prevention of cracking by SAP-enhanced internal curing can be identified as the main factor responsible for the differences in corrosion potential  
Figure 19: Theoretical swelling of the SAP particles in the tested fluids. Dimensions expressed in \(\upmu\)m.  
between the two walls. This underlines the positive aspect of using SAPs not only for crack prevention but also for corrosion risk mitigation. The investigation of the effect of SAPs on (accelerated) carbonation and chloride ingress showed that the increased air void content and porosity expected with the inclusion of SAPs does not necessarily reduce the resistance to carbonation and chloride ingress. On the contrary, if the appropriate type of SAP is used (meaning an SAP with a well-controlled water release) and the correct amount of water is adopted to compensate for the loss in workability due to the absorption of SAPs, then the internal curing is effective, and the presence of the polymers might densify the matrix, thus slightly increasing the resistance to carbonation and chloride ingress. When cracked specimens are considered, there is a limited sealing effect against chloride ingress, which depends on the exposure regime (whether constantly submerged or in alternating wet/dry cycles), the size of the cracks in relation to the size of the SAP particles, and the swelling potential of the SAPs in the fresh concrete mix and in contact with the chloride solution. Furthermore, the use of SAPs also represents a more sustainable option by reducing (even avoiding) the need for repair work due to cracking and corrosion, extending the service life of the structure, and limiting the carbon footprint related to the maintenance and repair service commonly demanded for regular structures. Conceptualization, J.R.T.F., N.D.B. and D.S. ; methodology, J.R.T.F. and D.S. ; validation, J.R.T.F. and D.S. ; formal analysis, J.R.T.F. ; investigation, J.R.T.F. ; resources, N.D.B. and D.S. ; data curation, J.R.T.F., N.D.B. and D.S. ; writing--original draft preparation, J.R.T.F. and D.S. ; writing--review and editing, N.D.B. and D.S. ; visualization, J.R.T.F. ; supervision, N.D.B. and D.S. ; project administration, D.S. ; funding acquisition, N.D.B. and D.S. All authors have read and agreed to the published version of the manuscript. This work has been financed by the SIM program SHE (Engineered Self-Healing Materials) within the ICON project iSAP (Innovative SuperAbsorbent Polymers for crack mitigation and increased service life of concrete structures). Not applicable. The data presented in this study are available upon reasonable request.