Resistance to acid attack of portland cement mortars produced with red mud as a pozzolanic additive

Portland cement structures are usually exposed to aggressive environments, which requires the knowledge of the performance of these materials under deleterious conditions. In this study, it was evaluated the resistance to acid attack of mortars that contain ordinary (CPI) and compost (CPII-Z) Portland cements, adding to the first red mud (RB) as a pozzolanic additive in different conditions: without calcination, calcined at 400 ° C and at 600 ° C. The specimens were subjected to HCl and H₂SO₄ solutions, both with concentration of 1.0 Mol L^-1 for 28 days, monitoring the weight loss and leached material nature by atomic emission inductively coupled plasma (ICP). The hydration products were studied by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) of the hydrated cement pastes. It was observed a reduction of portlandite amount in the RB containing cement pastes, indicating a possible pozzolanic activity of the red mud. The mortars prepared with RB were more resistant to HCl, while that ones with calcined RB present a better performance in H₂SO₄ attack. (author)