Durability of Alkali-Activated Concretes Under 5% Sulfuric Acid Environment

The investigation focused on the resistance to 5% sulfuric acid degradation of the alkali-activated concretes (AAC). The AAC was manufactured using a blended binder of 50% slag and 50% F-type fly ash. The AAC was activated using a blend of 14 M sodium hydroxide and sodium silicate, with a hydroxide-to-silicate ratio of 1/2,5. Six AAC were produced against a 5% sulfuric acid environment, varying the binder amounts (400–500–600 kg/m3) and activator-binder (A/B) ratios (0,45–0,55). The chemical resistance of AAC was evaluated by visual appearance, variation in weight and compressive strengths. The findings pointed out that more gypsum and higher weight gain were obtained on the AAC specimens having 600 kg/m3 binder content. There is no or negligible influence of A/B ratio was found on the visual appearance and weight variation after acid attack. The results revealed that the highest durability was achieved with the maximum binder content of 600 kg/m3 combined with the 0,45 A/B ratio, while the lowest resistance was achieved with the minimum binder content of 400 kg/m3 and 0,55 A/B ratio. The additional water content of 7,5% by binder weight should be reduced to achieve higher mechanical strength for the AAC, especially for high-binder mixes (>400 kg/m3).