Performance at high temperature of alkali-activated slag pastes produced with silica fume and rice husk ash based activators

This study assessed the mechanical properties, and structural changes induced by high temperature exposure, of alkali-silicate activated slag cements produced with sodium silicates derived from silica fume (SF) and rice husk ash (RHA). Similar reaction products were identified, independent of the type of silicate used, but with subtle differences in the composition of the C-S-H gels, leading to different strength losses after elevated temperature exposure. Cements produced with the alternative activators developed higher compressive strengths than those produced with commercial silicate. All samples retained strengths of more than 50 MPa after exposure to 600 °C, however, after exposure to 800 °C only the specimens produced with the RHA-based activator retained measurable strength. This study elucidated that silicate-activated slag binders, either activated with commercial silicate solutions or with sodium silicates based on SF or RHA, are stable up to 600 °C.