Fly Ash

Fly ash is a fine, glassy powder recovered from the flue gases of coal-fired power plants. As a supplementary cementitious material (SCM), fly ash improves the performance, durability, and sustainability of concrete. Eco Material Technologies is one of the largest fly ash suppliers in the United States, with a network of utility partners and distribution terminals that ensures reliable supply to ready-mix producers, precast manufacturers, and contractors across the country.

When used to replace a portion of portland cement in concrete, fly ash reduces the heat of hydration, lowers permeability, and enhances long-term strength development while simultaneously reducing the carbon footprint of the mix; in general concrete containing fly ash develops properties not attainable by the use of cement alone. Fly ash is specified using ASTM C618 or AASHTO M295, which classifies it into two primary types based on its calcium oxide content.

Class F Fly Ash

Class F fly ash is produced from the combustion of bituminous and sub-bituminous coals and is characterized by low calcium oxide content (less than 18% CaO). It is predominantly pozzolanic in nature; it does not exhibit cementitious properties on its own but reacts with calcium hydroxide released during cement hydration to form additional cementitious compounds.

Class F fly ash is widely used in ready-mix concrete, precast concrete, and mass concrete applications. Key performance benefits include:

• Reduced heat of hydration, making it well-suited for mass concrete pours
• Improved long-term strength gain
• Enhanced resistance to sulfate attack and alkali-silica reaction (ASR)
• Lower water demand and improved workability
• Reduced permeability and increased durability

Eco Material Technologies’ Class F fly ash can be used as a pozzolan in virtually any concrete application. When correctly proportioned, Class F fly ash will add many benefits such as increased strength, increased durability, and reduced permeability.

Fly ash is stored inside a covered facility

Class C Fly Ash

Class C fly ash is produced from the combustion of lignite and sub-bituminous coals and is distinguished by its higher calcium oxide content (greater than 18% CaO). In addition to its pozzolanic properties, Class C fly ash exhibits self-cementing characteristics; it will hydrate and harden when mixed with water, even without the presence of portland cement.

These properties make Class C fly ash particularly versatile. It is commonly used in ready-mix concrete and is also well-suited to soil stabilization, road base applications, and controlled low-strength material (CLSM). Key performance benefits include:

• Self-cementitious behavior enabling use at higher replacement rates
• Faster early strength development relative to Class F
• Effective for soil and subgrade stabilization
• Reduced shrinkage in certain mix designs
• Contribution to long-term durability

Eco Material Technologies’ Class C fly ash can be used as a pozzolan in virtually any concrete application. When correctly proportioned, Class C fly ash will add many benefits, such as increased strength, increased durability, and reduced permeability.