Salt River Materials leverages Class C feed to boost Class F ash output

Sources: Salt River Materials Group, Scottsdale, Ariz.; CP staff

Responding to electric power generation market forces affecting cementitious materials availability across the concrete industry, Salt River Materials Group (SRMG) has begun shipping an ASTM C618-grade Class F fly ash from its 19th Avenue Terminal near downtown Phoenix. The material raises the company’s net Class F fly ash output and stems from new blending systems installed as part of an upgrade at the terminal—one of five SRMG powder distribution facilities serving Phoenix market ready mixed and precast concrete producers.

The Cyclonaire Blend-Veyors rest at the base of 400-ton Class C and Class F fly ash silos (right). Air slides crisscrossing lower and mezzanine levels, and linking the two silos and their 200-ton companion vessels (left), maximize the variety of Class C-F blends deliverable on short leads.

Twin Cyclonaire CB-150 Series Blend-Veyors have been deployed at the base of the 19th Avenue Terminal’s 400-ton Class C and Class F fly ash silos. Through precise weighing and robust blending in up to 90-second cycles, they finish powder with calcium oxide content and other properties equivalent to an ASTM C618 Class F ash.

“We have blended Class C and Class F ashes by a more conventional, but less precise method: Blowing material simultaneously from two railcars into a dedicated silo,” says SRMG Senior Vice President, Pozzolans Dale Diulus, P.E. “The new equipment supports a reproducible process, with much more verifiable blends of Class C and Class F ash feeds.”

The producer landed an ash management contract last year for the Coronado Generating Station in St. John’s, Ariz., where twin, 400-megawatt units run on low sulfur, Powder River Basin coal, and yield up to 150,000 tons of Class C ash annually. Coronado joins contracts SRMG has acquired since 1973 covering Class F fly ash management at five Arizona, New Mexico and Utah generating stations. Although widely adopted in manufactured concrete and stucco, Class C fly ash is restricted in key Southwest markets due to agency concerns with the material’s limited role in combating alkali-silica reactivity.

SRMG has conducted extensive testing on ASR potential and sulfate resistance of concrete specimens prepared with the blended Class F-grade ash, securing its inclusion on the Arizona Department of Transportation Approved Materials Source List–Fly Ash, Natural Pozzolan and Lime. The 19th Avenue Terminal is among 22 SRMG distribution or material processing points: seven Arizona, six California, five New Mexico, plus individual Colorado, Nevada, Texas and Utah sites. Fly ash marketing goes hand in hand with portland cement sales from the charter business, Phoenix Cement in Clarkdale, Ariz., and aggregates from Salt River Sand & Rock in Phoenix. —


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