Deformation behaviour of geopolymer mortars with silica glass under different curing conditions

In order to explore the alkali-silica reactivity (ASR) of armorphous silica and the method for assessing the alkali-aggregate reaction in geopolymeric materials, the expansion behavior of fly ash based geopolymer mortars with silica glass cured under various conditions (i.e., 23 and 38°C with relative humidity over 95%, immersed in 1mol/L NaOH solution at 80°C and autoclaved in 10% KOH solution at 150°C) was investigated via linear defromation test and scanning electron microscopy. The results show that there is little harmful expansion in geopolymer mortars with silica glass with the criteria specified for OPC system under the curing conditions. However, the geopolymer binder and armorphous silica could experience different reaction processes under the different curing conditions, leading to a different deformation behavior, especially with additional alkalis and at elevated temperatures. It was suggested that a high temperature with the additional alkali for accelerating AAR in the traditional OPC system could not be appropriate for the assessment of the alkali-aggregate reactivity behavior in geopolymers designed under normal conditions.