NPCA Staff Report
Ground-glass pozzolans (GGP) are a supplementary cementitious material (SCM) that can offer precast concrete manufacturers another viable option for partial replacement of ordinary portland cement.
Though GGPs have been in the marketplace for more than 10 years, an ASTM standard for the material – ASTM C1866, “Standard Specification for Ground-Glass Pozzolan for Use in Concrete” – was not developed and published until 2020.
In addition to exhibiting traditional pozzolanic behavior, research has shown GGP provides benefits to concrete, such as improved resistance to chloride penetration, sulfate attack and freeze/thaw damage. Additionally, GGP use in concrete mixes has been linked to improved resistance to alkali-silica reactivity when reactive aggregates are present. Since GGP diverts regionally available waste material from landfills and partially replaces ordinary portland cement, its use also boosts the sustainability and reduces the carbon footprint of the final product.
Like the early days of fly ash when product variability hampered wide acceptance of its use, GGP offers a wide spectrum of physical attributes that vary among different source materials and producers. However, ASTM C1866 sets requirements for acceptable physical and chemical characteristics to help limit variability and enhance predictability and consistency.
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