Low-calcium fly ash, often referred to as Class F fly ash, is a byproduct of coal combustion in power plants and is characterized by its low calcium oxide (CaO) content, typically less than 10%. This type of fly ash is predominantly composed of silica, alumina, and iron oxide, making it highly pozzolanic but with minimal cementitious properties on its own. When used as a supplementary cementitious material (SCM) in concrete, low-calcium fly ash enhances the material’s durability, workability, and sustainability. The use of fly ash in concrete not only diverts waste from landfills but also reduces the demand for Portland cement, which in turn lowers the overall carbon footprint of concrete production.