Siliceous fly ash is a byproduct of the combustion of pulverized coal in electric power-generating plants. Composed primarily of silicon dioxide (SiO 2), along with alumina (Al 2O 3) and iron oxide (Fe 2O 3), it is categorized as a pozzolanic material. When mixed with lime and water, siliceous fly ash reacts to form calcium silicate hydrates, which are the same binding products formed during the hydration of Portland cement. This reaction not only helps in stabilizing the mix but also significantly enhances the final product’s strength and durability by filling voids and making the concrete denser.