The National Asset Centre of Excellent recently published its 2 year project NACOE S67: Future Availability of Fly Ash for Concrete Production in Queensland (2022–24).

The Ash Development Association of Australia welcome the reports findings which align well its view that stored coal combustion products (CCPs) which includes fly ash, have considerable potential for harvesting for use in the cement and concrete sectors.

Fly ash is an essential supplementary cementitious material (SCM) used in concrete manufacturing to improve overall durability and mitigate alkali-silica reaction (ASR). Currently, fly ash is sourced directly from coal-fired power stations in Queensland. However, as these power stations are planned to close as part of the Toward Zero Emissions strategy, the exploration of alternative sources of fly ash for potential incorporation into Queensland Department of Transport and Main Roads (TMR) concrete is imperative.

Report key findings

Critical Role in Concrete, fly ash is essential as a supplementary cementitious material (SCM) in Queensland due to its ability to:

• Improve concrete durability
• Mitigate alkali-silica reaction (ASR)
• Enhance workability and resistance to chemical attack
• Current Supply Status

Queensland’s fly ash is currently sourced from eight coal-fired power stations. Supply is expected to remain viable until around 2040, after which significant reductions are expected due to power station closures aligned with Queensland’s Toward Zero Emissions strategy.

Risk of Future Shortages.

• The Queensland Energy and Jobs Plan accelerates the phase-out of coal-fired plants, threatening future fly ash availability for infrastructure works.
• TMR mandates 20–25% fly ash in most concrete mixes—posing challenges when supplies diminish.

Viable Alternative: Ponded (Reclaimed) Fly Ash

• Ash dams in Queensland hold an estimated 250+ years’ supply of ponded fly ash, based on current consumption.
• Laboratory analysis of six ponded fly ash samples showed 5 out of 6 met Australian Standard AS 3582.1 (after processing).
• Major issues include high loss on ignition (LOI) and moisture content, both manageable through drying and grinding.

Performance & Processing

• Processing methods such as drying, grinding, and thermal treatment can restore ponded ash to a usable quality.
• Concrete made with processed ponded fly ash demonstrates comparable strength and ASR mitigation to fresh fly ash.

Other SCM Alternatives

• Assessed materials include: GGBFS, metakaolin, recycled glass, nano calcium carbonate, biomass ashes (e.g., sugarcane bagasse ash), pumice, and diatomaceous earth.
• However, most lack the availability, consistency, or standards required for large-scale use in Queensland infrastructure.

Conclusion. Stored [Ponded] fly ash from Queensland ash dams is the most promising and feasible long-term alternative to fresh fly ash. It offers environmental benefits and substantial availability but requires investment in processing and standardisation to support future infrastructure needs post-2040. Copy of the report can be downloaded from https://www.nacoe.com.au/wp-content/uploads/2025/01/S67_Y2-_23_24_Future-Availability-of-Fly-Ash-for-Concrete-Production-in-Queensland-Final-Report_DCES-For-Publication.pdf