Fly ash is a fine powder that is a byproduct of burning pulverized coal in electric power generating plants. It is one of the most commonly used industrial byproducts and has various applications in construction and other industries. Here are some key points about fly ash:

1. Formation: Fly ash is formed when coal is burned at high temperatures in power plants. The mineral impurities in the coal fuse and form tiny, spherical particles that are carried away by the flue gases.
2. Composition: The composition of fly ash depends on the type of coal being burned and the combustion process. Generally, it consists of silicon dioxide (SiO2), aluminum oxide (Al2O3), iron oxide (Fe2O3), calcium oxide (CaO), and other trace elements.
3. Types of Fly Ash:
   • Class F: Typically produced from burning anthracite or bituminous coal. It has less than 5% loss on ignition (LOI), meaning it is more pozzolanic in nature.
   • Class C: Produced from burning sub-bituminous coal. It has a higher LOI (between 5% and 10%) and often has cementitious properties.
4. Pozzolanic Properties: Fly ash is known for its pozzolanic properties, which means it can react with lime in the presence of water to form compounds with cementitious properties. This makes it a valuable supplementary material in the production of concrete.
5. Use in Construction:
   • Concrete Production: Fly ash is commonly used as a partial replacement for Portland cement in concrete. It improves workability, reduces heat of hydration, and enhances long-term strength.
   • Stabilization of Soils: It can be used to stabilize soils in construction projects, improving their engineering properties.
   • Road Construction: Fly ash can be used in the construction of embankments and road bases, providing stability and reducing permeability.
6. Environmental Benefits: Utilizing fly ash in construction materials reduces the need for traditional cement, thereby decreasing the demand for raw materials and lowering greenhouse gas emissions associated with cement production.
7. Regulatory Considerations: Depending on the region, there may be regulations governing the use and disposal of fly ash due to its potential environmental impact. Proper handling and management are essential.