Companies mining and processing the top three classes of supplementary cementitious materials (SCM) in concrete mixtures reached a new watermark in 2024, while also forging ahead with site or plant development projects, yielding significant capacity increases by 2030.
Fly ash, natural pozzolan and slag cement producers are addressing construction market demand fueled by concerns surrounding the carbon dioxide emissions associated with portland cement production; concrete binder supply chain flexibility; and SCMs’ proven performance characteristics for a broad range of slabs and structures in public or private construction.
American Coal Ash Association (ACAA), Natural Pozzolan Association (NPA) and slag cement figures or estimates indicate that combined 2024 shipments to U.S. concrete and cement-based product customers exceeded 20 million tons. In tandem with slag cement industry insights, ACAA and NPA officials highlighted members’ instrumental role in concrete production during “Construction Materials Carbon Progress,” an early-December industry and media briefing at the National Press Club in Washington, D.C.
FLY ASH
The event saw the release of the ACAA 2025 Production and Use Survey, reflecting utility and marketing members’ 2024 data. ACAA Government Affairs Committee Chair John Ward cited shipments of coal combustion products (CCP), primarily “live” Class F and Class C fly ash collected directly from power generating stations, totaling 14.7 million tons to Concrete/Concrete Products/Grout category stakeholders. ACAA will revise the figure upward in early 2026 as members engaged in the emerging practice of ash harvesting – extracting legacy, marginal CCP from station impoundments or landfills and beneficiating to concrete-grade levels – consolidate 2024 data.
NATURAL POZZOLANS
NPA Executive Director Joseph Thomas reviewed the product classes defined in ASTM International’s recently published C1945-25, Standard Specification for Raw or Activated Natural Pozzolan for Use in Concrete. Raw natural pozzolans are mined from volcanic pumice deposits and graded to augment portland and blended cements. Activated grades are processed by thermally treating kaolin clays and include premium metakaolin SCM, well established in high-performance concrete practice.
Thomas mapped producers’ decade-long ramp-up of capacity for the concrete industry: In 2014, NPA members had permitted or were operating six plants in the U.S. and Canada. By 2013, that figure had increased to 15, while an additional 25 natural pozzolan deposits or processing operations are in permitting phases. In 2024, NPA members shipped an estimated 2.5 million tons of C1945-grade product to the concrete market. That figure spans direct shipments to producers as well as to their cement suppliers, five of whom are now promoting a blended binder of Type I portland cement and natural pozzolan, designated in ASTM C595 as Type IP. At present demand, natural and activated pozzolan uptake rates among U.S. concrete practitioners will justify capital outlays supporting 3.5 million to 4 million tons of capacity by 2028.
SLAG CEMENT
Heidelberg Materials North America Director of Sustainable Innovations and Development Claire Nowasell updated Carbon Progress attendees on the stability of slag cement consumption in the U.S., where annual shipments have ranged from 3.7 million to 4 million metric tons since 2019. She also tracked industry prospects for capacity increases despite producers’ perceived supply chain challenges from blast furnace (BF) steel operations, where molten slag is a) water quenched and granulated in a glass state, netting product with reactive properties for concrete mixtures; or, b) air cooled to a nonreactive state with application limited to use as aggregate of average grade.
While their volume is tempered with the industry’s shift to less carbon-intensive electric arc furnace production methods, BF steelmakers are positioned to granulate slag at higher than historical rates, thereby raising slag cement mills’ potential throughputs. Among slag cement producers, Heidelberg Materials has the highest level of announced capacity upgrades, stemming from investments in Cape Canaveral, Fla., Speed, Ind. and Port of Houston slag granule grinding and finishing lines.
INDUSTRY FIRST
Announcement of the SCM data dovetailed a Carbon Progress opener from the American Cement Association, where President and CEO Mike Ireland outlined members’ Roadmap to Carbon Neutrality pursuits – including proactive measures to increase SCM adoption. Joining ACA, ACAA, NPA and Heidelberg Materials at the briefing were two concrete and steel peer groups. With an eye to spotlighting the significant carbon management undertakings by those producers – three of the top construction supply chain parties – the briefing was hosted by SEMCO Publishing’s Concrete Products and Cement Optimized brands, along with California-based Climate Earth, a leading developer of construction materials sustainability software and forerunner in expedited cement, aggregate and concrete environmental product declaration delivery.
