# Steel Corrosion Behavior in Light Weight Fly-Ash Based Alkali Activated Mortars
## 4 Conclusions  
Durability results were first achieved in this study in terms of chloride-induced corrosion of steel coated with light weight alkali activated mortars optimized for fire protection applications by electrochemical techniques.  
Exposure to neutral environment (tap water) showed encouraging results since similar behavior in corrosion potential and anodic polarization curves was observed regardless the different pore distribution of the mortar layers. For the 60-day exposure in tap water, similar corrosion potentials and corrosion current density values were obtained by both light and normal weight mortars. However, an increase of aggressiveness of the electrolyte (0.2 M NaCl aqueous solution) induced that after 40 days of exposure, steel started to corrode, as depicted by corrosion potential values. Compared to steel samples covered by light weight mortar, normal weight mortar layer exhibited a larger extent of corrosion products precipitated on steel surfaces at the end of exposure, which acted as physical barrier producing a slowdown in the corrosion current density values measured by anodic polarization curves.  
Results of the electrochemical investigation of steel coated with light and normal weight mortars suggested that other aspects are also influencing the corrosion mechanisms, due to the fact that same mix design was applied for both the mortar layer. Indeed, it was found that the environment of the pore solution (pH and composition) in the binder strongly influenced the steel corrosion behavior. Leachate pore solution obtained from the 28-days cured mortars (pH = 12.8) allowed passivation of the steel, as highlighted by anodic polarization curves. However, the lowering of mortar pH (pH - 11) measured after one-year exposure to the atmosphere did not allow steel passivation, thus steel corrosion protection is not completely guaranteed. Further analyses of the morphology and composition of corrosion products formed in the different tested solutions are planned to confirm this point. In addition, the effect of chloride addition increased the corrosion current densities values regardless of the solution pH and in the case of leachate pore solution chlorides are responsible of a less stable and smaller passive region.  
Finally, passive fire protective coating consisting in light weight alkali activated mortar can partially ensure durability of the steel structures in terms of steel corrosion mitigation. However, additional solutions should be considered to improve these durability aspects, such as the application of a sealing treatment to applied on the light weight mortar  
Figure 9: Anodic polarization curves of sand blasted steel (S) in (**a**) 0.1 M NaOH and (**b**) 0.001 M NaOH aqueous solutions without and with the addition of 0.2 M NaCl.  
layer, in order to slow down the ingress of aggressive species, i.e., chloride ions, and carbonation phenomena.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to confidentiality reason.  
[PERSON], [PERSON], and [PERSON] are acknowledged for their valuable help in characterization techniques. The author would thank [PERSON] for valuable discussion and [PERSON] for the help in the experimental.  
The author declares no conflict of interest.