Ground Glass Pozzolans

Ground Glass Pozzolans (GGP) are supplementary cementitious materials produced by finely milling post-consumer or post-industrial recycled glass to a particle size distribution comparable to that of Portland cement. The milling process increases the reactive surface area of the glass, enabling it to participate in the pozzolanic reaction, in which amorphous silica reacts with calcium hydroxide liberated during Portland cement hydration to form additional calcium silicate hydrate gel, the primary binding compound in hardened concrete.

The pozzolanic reactivity of ground glass is strongly dependent on particle fineness. Research has demonstrated that glass ground to a median particle size below approximately 15 µm exhibits pozzolanic activity broadly comparable to that of natural pozzolans and fly ash, whilst coarser particles may act primarily as inert filler. This particle size threshold is a critical quality parameter, verified by laser diffraction analysis.

A key technical benefit of Ground Glass Pozzolans is their ability to mitigate alkali-silica reaction (ASR) in concrete. ASR is a deleterious expansion reaction between reactive silica in aggregates and alkalis in the cement pore solution, which can cause cracking and structural deterioration over time. Finely ground glass reduces the alkali concentration in the pore solution and consumes reactive silica in a controlled pozzolanic reaction, suppressing the expansive mechanism.

ROCC Global sources GGP from established producers in Europe with documented quality management systems and consistent production records.

Ground Glass Pozzolans are used as a partial replacement for Portland cement in ready-mix concrete, precast concrete, and site-batched structural mixes, typically at replacement levels of 15 to 30% by mass of cementitious content. At these dosage levels, GGP contributes to long-term compressive strength development through continued pozzolanic reaction, with strength gains extending beyond 28 days. The material is particularly effective in mitigating alkali-silica reaction in concrete mixes incorporating reactive aggregates, where its high amorphous silica content and fine particle size suppress the expansive reaction mechanism that causes long-term cracking and deterioration. In low-permeability concrete for water-retaining structures, tunnels, and below-ground infrastructure, GGP reduces chloride diffusion coefficients and improves resistance to sulphate attack by densifying the concrete microstructure.