Fly ash

Fly ash – is a fine powder that is a byproduct of burning coal in power plants and other industrial processes. 

Depending on the combustion process, source, and composition of the coal being burned, the components of Fly Ash vary considerably, but all include significant amounts of silicon dioxide (SiO₂) (both amorphous and crystalline), aluminum oxide (Al₂O₃), and calcium oxide (CaO), as well as unburned carbon.

It’s collected from flue gases using electrostatic precipitators or filter bags.

Phase-mineralogical studies of the ash composition of various types of solid fuels show that the main phase of all types of ash is glass. The crystalline phase is represented by various amounts of quartz, hematite, magnetite and various calcium silicates.

Chemical composition and physical characteristics

Pozzolanic Properties:

Fly ash acts as a pozzolan, reacting with calcium hydroxide in the presence of water to form cementitious compounds like calcium-silicate-hydrate (C-S-H), contributing to concrete strength and durability. 

Applications:

Fly ash is widely used as a supplementary cementitious material (SCM) in concrete, offering several benefits. 

• Concrete:Fly ash is a common additive in concrete mixes, improving workability, reducing water demand, enhancing strength, and increasing resistance to sulfate attack and alkali-silica reaction. 
• Structural Fill:It can be used as a fill material in road construction and other structural applications. 
• Bricks and Blocks:Fly ash is used in the production of bricks and other building materials, offering sustainability benefits.