Pozzolanic materials, such as fly ash, silica fume, and volcanic ash, are siliceous or siliceous and aluminous substances that chemically react with calcium hydroxide at room temperature to form compounds possessing cementitious properties. These materials are integral to the concrete mix, especially under severe environmental conditions, as they enhance the mechanical properties and durability of concrete. The mechanism by which pozzolans improve concrete involves the reaction of the pozzolan with calcium hydroxide released during the hydration of cement to form additional calcium silicate hydrate (C-S-H), the binder that contributes to the strength and durability of concrete. This reaction not only helps in densifying the concrete matrix but also significantly reduces the permeability, thus enhancing the material’s resistance to aggressive chemical attacks, such as chloride penetration and sulfate attack.