Production and properties of amorphous silica extracted from olivine for use as a supplementary cementitious material

Amorphous precipitated silica (APS) produced by acid leaching of olivine has been characterised and assessed for use as a supplementary cementitious material (SCM). The APS was thermally treated between 400 and 1000°C to modify its pore structure, surface area, composition and reactivity. Pastes and mortars containing APS were cast with CEM I replacement levels from 0 to 30 wt.% and water-to-binder ratio of 0.5. TGA-MS, Q-XRD, FTIR and R 3 tests show that APS has moderate to high pozzolanic reactivity. Mortars with 10 wt.% as-produced APS showed 30% increase in 28-day compressive strength compared to the control (50 MPa). Mortars with 20 wt.% replacement had comparable strengths to the control. Thermal treatment moderately reduced APS specific surface area and water demand, and improved mix workability, with mortars retaining comparable strengths to samples containing as-produced APS. The research demonstrates that silica derived from olivine has potential to be used as an SCM.