Fly Ash Powder, Brand Name : Tata, Jindal, NTPC

Fly ash is a fine, powdery material that's a byproduct of burning coal in power plants. It's classified into two main types: Class C and Class F, based on the chemicals they contain:

Class C fly ashContains more calcium oxide than Class F, making it more commonly used in structural concrete. It's also chemically resistant to expansion and has self-hardening properties. Class C fly ash is often used in pre-stressed concrete and soil stabilization.

Class F fly ashContains particles covered in melted glass, and is low in calcium. It's typically used at dosages of 15% to 25% by mass of cementitious material. 

Fly ash can also be classified based on its color, which can vary from tan to dark gray:

Tan or light-colored: Typically has a high lime contentBrownish: Typically has an iron content

Dark gray to black: Typically has a higher unburnt carbon content