Alkali–aggregate reaction (AAR) is a chemical reaction in concrete between the alkali hydroxides in Portland cement and reactive siliceous aggregates. This reaction produces a gel that absorbs water and swells, leading to internal stress within the concrete, expansion, and eventual cracking. This phenomenon is a significant durability issue in concrete, leading to premature deterioration and structural failure, particularly under severe environmental conditions where moisture and temperature variations exacerbate the reaction. Understanding the mechanisms and effects of AAR is crucial for enhancing the longevity and performance of concrete structures worldwide.