Fly ash is used as a supplementary cementitious material (SCM) in the production of portland cement concrete. A supplementary cementitious material, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both.

What are cementitious materials?

Cementitious materials are one of the principal ingredients that make up the concrete mixture. There are two types of cementitious materials: hydraulic cement and supplementary cementitious materials (SCMs). Hydraulic cements set and harden by reacting chemically with water.

Which type of material fly ash is?

Fly ash is a fine gray powder consisting mostly of spherical, glassy particles that are produced as a byproduct in coal-fired power stations. Fly ash has pozzolanic properties, meaning that it reacts with lime to form cementitious compounds. It is commonly known as a supplementary cementitious material.