After beta tests with cast stone and architectural precast producers, swimming pool contractors and other white portland cement users, Vitro Minerals announced at World of Concrete 2007 (Jan. 23-26, Las Vegas) commercial launch of two highly reactive pozzolans, VCAS-8 and VCAS-micronHS. Derived from high-silica, low-alkali content fiberglass manufacturing byproducts, the VCAS (vitreous calcium aluminosilicate) agents impart additional calcium silicate in hardened concrete through reactivity with lime produced during cement hydration. The reactivity phase can span months, depending on moisture encountered after initial hardening, and results in a surface or structure with higher density or compressive strength, and potentially greater resistance to sulfate attack.

VCAS production entails proprietary shredding, grinding and classification of fiberglass byproducts. Ball mill grinding, similar to that used in the clinker-to-finished portland cement process, yields powder with gradations akin to slag cement and a little finer than Type I portland (8 micron mean diameter), and silica fume or metakoalin (3 micron mean diameter). Vitro Minerals officials note that VCAS technology represents the first large-scale application of recycled glass in concrete, augmented by the availability of a consistently low-alkali content feedstock.

Target applications for the two pozzolans include cast stone, architectural precast, and masonry units containing white cement; glass fiber-reinforced concrete; swimming pool plaster; or, high-performance mixes for which engineers might otherwise specify silica fume or metakaolin. VCAS-8 and VCAS-micronHS will be comparably priced with white cement and silica fume, respectively, and available in 50-lb. bags, super sacks, or bulk. Vitro Minerals is processing under contract at a South Carolina grinding operation, while officials eye a dedicated ball mill elsewhere in the Southeast. Much like fly ash and coal-fired power generating stations, VCAS processing is sited with fiberglass production.