Internal sulfate attack refers to the chemical reaction that occurs when sulfates within the concrete components react with the compounds formed during the hydration of cement. Unlike external sulfate attack, where sulfates are introduced from the environment, internal sulfates are inherently present in the raw materials used in cement production, such as gypsum-contaminated aggregate or excess gypsum in the cement itself. The reaction primarily involves the formation of ettringite and thaumasite, which can lead to significant volumetric expansion, ultimately causing distress and deterioration in the concrete structure. This type of attack is critical to understand and mitigate, especially in structures where durability and longevity are paramount.