Mitigating acid attack-induced deterioration of cement mortar through the application of montmorillonite nanosheets

This work aimed to examine the efficacy of montmorillonite nanosheets (MNs) in mitigating nitric acid's impact on cement mortar. External/internal acid-induced damages and residual mechanical strengths, were evaluated in 28-day mortars with varying MN contents, exposed to the nitric acid solution over a 90-day period. Mineralogical alterations due to acid attack were explored using X-ray diffraction, thermogravimetric analysis, and field emission-scanning electron microscopy. Results demonstrated that exposure to the acid solution induced various external damages, such as softening, cracking, and a porous texture, accompanied by reduced adhesion among cementitious composite constituents. Internally, damages were manifested through indicators like ultrasonic pulse velocity (UPV) loss, cross-sectional area loss, and corrosion depth. . Notably, after 90-day exposure , the plain mixture exhibited UPV loss, c ross-sectional area loss, and corrosion depth values of 75.0%, 81.7%, and 12.5 mm, respectively; meanwhile the mortar containing 2 wt% MNs (MN2) recorded measurements of 57.0 %, 50.3 %, and 6.2 mm, respectively. Furthermore, MN2 specimen demonstrated the highest residual mechanical strengths. Importantly, although MN inclusion had no impact on the mineralogy of the altered cementitious matrix exposed to acid solution, it hindered acid species penetrationinto cementitious composites, enhancing resistance to calcium ion leaching from the binder phases in acidic solution.