Processor derives GGBF slag-level performance from fly ash
- Written by CP Staff
Texas-based VHSC Cement has introduced a concrete binder, PozzoSlag 1.2, citing its potential for 50 percent or higher portland cement replacement, plus performance characteristics including early set times and long-term strength development.
VHSC’s proprietary reactor and treatment system use physical and chemical means to transform Class F fly ash into a new cementitious material. With 17- to 20-micron mean particle sizing, and 45-micron top size, PozzoSlag 1.2 matches ASTM C989 Standard Specification for Slag Cement for Use in Concrete performance requirements. “It uses raw fly ash as a base to produce a blend of material that meets grade 120 slag strengths based on ASTM C989 testing protocols,” affirms VHSC President Buddy Pike.
Internal tests using ASTM C989 and C109 procedures show a 50/50 PozzoSlag 1.2 and Type I portland cement specimen eclipsing a 100 percent Type I specimen in strength development at three days. “At cement replacement factors in the 55–65 percent range, PozzoSlag yields concrete of high durability,” Pike contends. “We take good ash and make it a lot better, or transform secondary ash to concrete-grade material. This particular technology does not remove carbon; it improves binding and other performance characteristics.”
“PozzoSlag provides significant value by allowing customers to produce high grade concrete while increasing profits, and to recycle coal fly ash, which may otherwise be dumped in landfills and ponds,” adds David Waxman, VHSC principal. “It is produced in an environmentally friendly way, netting carbon dioxide emissions at a level approximately 90 percent below that of portland cement.”
Since November 2012, Texas practitioners have used or approved PozzoSlag 1.2 for ready mixed and manufactured concrete. Leading the adopters is Oldcastle Architectural, which has incorporated the product in mix designs for its Jewell concrete masonry line. VHSC has also secured approval for Texas Department of Transportation work, including Federal Highway Administration-funded projects, plus public works contracts in Austin, Dallas and Houston.
Seasoned powder professional
Buddy Pike led development of the PozzoSlag 1.2 production process on the heels of 30 years in coal ash testing and treatment. He started as a Georgia Power plant chemist, proceeding to Headwaters Resources’ Atlanta-based predecessor, JTM Industries, where duties included research on the use of concrete-grade fly ash and other coal combustion byproducts. After transitioning to ISG Resources—the rebranded JTM and Headwaters forerunner—he founded CSA Resources, a Texas business marketing bottom furnace slag.
Evaluating prospects for a commercial scale process converting Class F ash to a slag-like binder, Pike and private investors launched VHSC in 2011. Through November 2012, VHSC tested several generations of PozzoSlag in its lab and through demonstrations with Texas ready mixed and precast concrete producers. Process refinement led to PozzoSlag 1.2, which imparts properties and performance similar to GGBF slag and can be milled at volumes to ensure users consistent supply. In addition to the flagship product, VHSC is also producing small volumes of fly ash-based agents, shipped mostly in 5-gallon containers, for specialty applications, including concrete repair.
VHSC has set up production on 10 acres in Jewett, Texas, which lies off Interstate 45 about midway to Houston from Dallas. The company has introduced a modified rotary mill reactor, running in sheltered, open-air space and feeding a 1,500-ton main silo and 300 tons of mobile vessels. VHSC has a primary Class F ash source, but has attained performance matching or comparable to PozzoSlag 1.2 using Class C ash, natural pozzolans, and various ashes from about 20 sources, some overseas. The results from a range of raw materials underscore expansion prospects for the company’s patent-pending equipment and process technologies, domestically and internationally. — VHSC Cement LLC, The Woodlands, Texas, 281/419-2422; www.pozzoslag.com