## 3 Results and Discussion
### Hardened State Properties
#### 3.4.8 Chloride Ion Penetration  
Figure 12a shows the chloride ion diffusion coefficient after 28 and 91 days of curing. As expected, the diffusion coefficients decreased from 28 to 91 days by 34% for fad = 30% and 48% for fad = 60% on average. Despite the decrease, the incorporation of MBIA caused an increase in the diffusion coefficient when compared to the RC. This increase was more evident in mixes with an increasing percentage of MBIA. Again, this may have been due to the greater porosity prompted by the production of H2 gas, incorporation of an addition with a lower amount of reactive phases and also the relatively higher content of Cl\({}^{-}\) present in MBIA, which may have also affected the chloride ion migration coefficient. [PERSON] et al. [55] found that, by replacing 30% of cement with wet ground MBIA, the profile of chloride ion penetration, after six months of exposure to chloride immersion cycles, was lower than in the other mixtures (i.e., 30% FA from incinated MSW and 30% dry ground MBIA) and similar to the control concrete (50% at depths close to 0 mm and less than 5% at depths of 35 mm). This result was explained by the decrease in porosity produced by the pozzolanicity as well as filler effect of wet ground MBIA.  
The ternary mixtures with FA and calcareous filler studied by [PERSON] [59], showed the same trend of increasing diffusion coefficient with the decreasing amount of FA in the mixture. Since the round shape of FA particles contributed to greater compactness of concrete, this led to a greater tortuosity of the microstructure for Cl\({}^{-}\) ions to penetrate. Furthermore, the high amount of amorphous phases (i.e., Al2O3 and SiO2) present in the FA, which exist in greater concentration than in cement (Table 2), lead to the formation of C-S-H and Friedel's salt (Ca2 Al(OH)6(Cl, OH)\(\cdot\)2H2O) compounds, which physically and chemically bind chloride ions, respectively, thereby decreasing their diffusion in concrete.  
Figure 12b shows that the electrical resistivity increased with age in all mixes as expected. For a fad = 30%, an average decrease of 47% was observed when compared to the RC. After 91 days, the trend changes slightly, wherein the SCC with a higher percentage of FA (C20 FA10 BA and C40 FA20 BA) accompanied the RC in a more pronounced rise in electrical resistivity, possibly due to the development of additional compounds capable of biding chloride ions. As for mixes C10 FA20 BA and C20 FA40 BA, at 91 days, these showed a decrease of 63% and 45%, respectively, when compared to the RC. These results point towards a considerable setback to the electrical resistivity of concrete with an increasing  
Figure 12: Chloride diffusion coefficient (**a**) and electrical resistivity (**b**) at 28 and 91 days.  
amount of MIBA as partial replacement of FA and cement. As stated, not only does it increase overall porosity due to the corrosion of metallic Al, but it also contains a fewer amount of amorphous phases capable of reacting with the cement's products of hydration, thereby leading to a decreased quantity of mineralogical phases capable of reducing ionic concentration.