Fly ash is the mostly mineral residue left over from burning coal by coal-fired power plants. Fly ash is pozzolanic, meaning that it has cementitious properties that make it valuable for use in ready-mix concrete as a partial replacement for Portland cement. It also may be used in the manufacture of other building materials such as bricks, tiles and blocks. The addition of fly ash in concrete mixes offers a number of benefits for construction purposes, but it’s also great for the environment. For one, leftover fly ash won’t need to be sent to landfills. For another, producing cement requires a high-temperature calcination process that releases CO2 emissions. For every pound of fly ash used to replace cement in concrete, nearly one pound of CO2 is prevented from entering the atmosphere.
For construction purposes, fly ash in ready-mix concrete offers several advantages versus normal Portland cement only concrete, including:
– Durability: Concrete mixed with fly ash requires less water for production, which creates a denser product that is less prone to shrinking. This makes it stronger and less prone to cracking or permeability. Less permeability provides great cold-weather resistance by keeping moisture and road chemicals out, which can shrink and expand as the temperatures vary by season.
– Workability: The spherical shape of fly ash particles helps to facilitate the movement of the concrete, even at reduced water compared to normal concrete. This makes it easier to pump, easier to place, easier to mold, and it creates a smoother finish with sharp details.
– Economics: Cement is the most expensive component of ready-mix concrete. By using fly ash as a substitute, concrete producers can create a better product that is less expensive to produce. A better product that is cheaper to make is a blessing for those watching the bottom line.
Raw, untreated fly ash often contains residual coal char, or carbon, which can impact its performance or even its ability to be used in concrete. The ST Equipment & Technology electrostatic separation process can treat raw fly ash by removing the unwanted residual coal char. The resulting product is a mineral rich concrete grade fly ash, trademarked ProAsh®. The STET process can be used on both fresh and historically produced landfilled or impounded fly ash.