## 3 Results and Discussion
### Absorption Capacity and Swelling and Sealing during Chloride Ingress  
In general, for the cracked specimens, it was expected that the presence of SAPs in the cracks could trigger an immediate sealing effect, reducing the crack width and the chloride ingress. However, considering the constant submersion regime, it is likely that the swelling time of the SAPs in the chloride solution was not fast enough to completely seal the cracks and effectively reduce the ingress of the chloride solution. When considering the wet/dry cycles regime, although the overall area affected by the chlorides is numerically similar among the specimens with SAPs and WR1, it is also noticeable that in the SAP mixtures, there seems to be a lower chloride penetration perpendicular to the crack. This might be an indication that the SAPs could be entrapping some of the chloride ions during the wet cycles (as mentioned in Section 3.2.2): SAPs in the vicinity of the crack absorb the chloride solution and swell, and during the dry cycle they release the solution with a lower content of chloride ions, working as a buffer with limited action. This sealing effect was studied in the literature using low-pressure water-permeability testing [3; 41; 42]. To better understand the possible effects of sealing during chloride ingress, it is important to observe the absorption capacity and swelling of the SAPs during the process. The absorption capacity of both SAPs in the sodium chloride solution (35 g/L) was stable during a monitoring period of 24 h (see Figure 18), with average values around 55 g/g for SAP1 and 37 g/g for SAP2. These values are both superior to those found for the SAPs in cement pastes, 21 g/g and 13 g/g for SAP1 and SAP2, respectively [5]. Considering both values of absorption capacity (in cement paste and sodium chloride solution), the theoretical swelling of the SAP particles can be determined (see Figure 19). Considering the theoretical size of the swollen particles upon contact with the sodium chloride solution, it could be expected that the presence of either type of SAP would be enough to seal the cracks investigated in this study (crack width of 250 \(\upmu\)m). However, there are some conditions that need to be considered. The specimens were cracked under a Brazilian splitting test and the location of the dry SAP particles in the crack may vary: (1) some particles might become loose and separate from the crack; (2) some particles might remain attached to the concrete surface or stuck inside the crack. In the first case, these particles will not take part in the sealing, and for the second case, there is the possibility of the SAPs becoming separated/dislocated from the crack by the ascending and descending flow of the testing solution (in the case of the cracked specimens subjected to wet/dry cycles). Figure 18: Absorption capacity of SAP1 and SAP2 in the sodium chloride solution (35 g/L). The lower swelling of SAP2 will result in smaller macropores and lower total porosity. This will have less influence on mechanical performance [3]. As SAP1 has been added primarily as an internal curing agent, swelling should be of the same order of magnitude as the one found. The sealing effect is an added benefit. SAP2, however, can be added for purposes other than internal curing, including sealing and healing effects [41], where swelling during mixing is less important. Swelling during sealing and healing must be sufficiently high to induce recovery of impermeability, without reducing the overall mechanical properties to too great an extent. As the swelling of SAP2 is greater than the expected crack width of 300 \(\upmu\)m, a reduction in permeability is expected. In addition, both particles are large enough not to be dislocated from the cracks. The combination of the two SAPs will lead to lower autogenous shrinkage (using SAP1) and therefore a lower degree of autogenous shrinkage cracking. This is likely to increase the durability of the overall structure [43].