Long-Term Corrosion Risk of Thin Cement Composites Containing Untreated Sugarcane Bagasse Ash

The corrosion risk in reinforced mortar slabs containing untreated sugarcane bagasse ash (UtSCBA) (0%, 10%, and 20% replacement of cement) was analyzed for 75 months. The mortars were prepared with a constant 0.63 water/cementitious-materials ratio. Cylinders and reinforced slabs were cast with the mortars. Two galvanized wire meshes were used as reinforcement for the slabs. Curing regimes of 0, 7, and 28 days were applied to the samples. The cylinders were used to obtain the compressive strength (CS) and the chloride diffusion coefficient ($D_{eff}$) of the mortars. To evaluate the corrosion risk, the slabs were exposed to wet-dry cycles of 12 h each in a 3% NaCl solution. Corrosion potential measurements and linear polarization resistance tests were taken every 28 days for that purpose. It was found that the addition of 10% and 20% UtSCBA reduces the workability of the mortar binders and leads to a slight decrease in the CS of hardened mortars. However, it significantly reduced the $D_{eff}$ of the mortars by 50% and 65% ($p\ll 0.05$), respectively, and also decreased the corrosion risk of mortar slabs over time.