Photo: Larry Sutter: SEM micrograph of fly ash particles
illustrating the spherical particle shape typical of coal fly ash
The highway construction industry’s utilization of coal fly ash has made many of our concrete pavements and bridges more durable and reduced landfill waste. However, with the shuttering of more and more coal-fired electric power plants, fly ash from coal-fired utilities is in increasingly short supply. Yet high-quality fly ash remains available, deposited in landfills at the time when the coal-fired power plant supply still exceeded concrete industry demand.
Click to go to 11-page Tech Guide PDF
As part of the cooperative agreement “Advancing Concrete Pavement Technology Solutions”, the CP Tech Center has recently produced a tech brief on reclaimed fly ash titled “Use of Reclaimed Fly Ash in Highway Infrastructure“, describing how its ready availability improves the reliability of the supply chain and how proper harvesting leads to matched chemical and physical properties as well as more consistent quality relative to freshly produced fly ash. Sponsored by the Federal Highway Administration (FHWA), the purpose of the Tech Brief is to describe the characteristics of harvested or reclaimed coal fly ash and identify considerations for its use in highway infrastructure. The document is intended for highway agency and contractor engineers.
Coal fly ash is an integral part of durable concrete for use in highway infrastructure. Historically, fly ash has been obtained directly from coal-fired power plants as it is being produced. Recent changes in fly ash production and availability, however, have resulted in challenges regarding both the supply and quality of fly ash in some markets, which in turn has caused providers to turn to a new source for the material, harvested fly ash.
Although the principal source of fly ash is evolving, the need for durable pavements and bridges has not changed. The concrete industry has weathered many changes before and reclaimed fly ash has potential to help us weather the current transition.
To download the 11-page tech brief PDF, please go to: https://intrans.iastate.edu/app/uploads/2020/09/use_of_reclaimed_fly_ash_TB.pdf