Technology shears cost of processing fly ash to match silica fume performance

A New York investor announced, at 2011 World of Concrete last month in Las Vegas, an industrial-scale process economizing the grinding of fly ash, or secondary grinding of ground granulated blast furnace slag or portland cement, to 6-, 3- or 1-micron median particle sizes. With $30 to $75 per ton processing plus $20 to $100 per ton raw feed (fly ash, GGBF cement or Type I/II portland cement) costs, the technology can yield premium binding agents whose performance properties in finished concrete and grouts match those of ultra-fine, high-reactivity metakaolin or silica fume—typically commanding $300 to $700 per ton.

“Historically, the industry has not seen a lot of fine grinding of pozzolans because the energy input was greater than the price finished materials could bring,” says IgniteIP Managing Director Brandon Williams. The company is promoting its process and proprietary equipment to cement or pozzolan producers and marketers, toll blenders, and larger concrete operators through Flyanic LLC, Newark, N.J.

Flyanic holds rights to a stirred media grinding process under license with developer New Jersey Institute of Technology (NJIT). In contrast to large, horizontal ball grinding mills for cement clinker, the stirred media method consists of a cylindrical vessel, vertical agitation shaft and tiny grinding balls similar to BBs or buckshot. The technology is especially conducive to extracting greater binding capability from Class F fly ash, as stirred media fracture spherical particles to shard- and flake-like shapes that increase reactive area with minimal added water demand in the concrete mix.

Along with an equipment partner, Alabama-based RSG Inc., Flyanic will tailor small-footprint installations whose capacity can match projected market consumption. With grinding, air classifier and packaging equipment, a prototype with 2,000-tpy capacity occupies an approximately 5,000-sq-ft building with bay height under 30 feet.  —

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