High-temperature deformation of a geopolymer.

Compressive creep under constant load (stresses of 0.5-10 MPa) of a geopolymer was investigated between 975 and 1025°C. The geopolymer was derived from Class F fly ash, kaolin, granulated blast furnace slag, sodium and potassium silicate and carbonate. Silicate-based aggregates constituted 48% of the total mass. The temperature range of testing was small because of limited plasticity below 975°C and decomposition above 1050°C. The maximum accumulated strain was 15%. A regime of true steady-state creep probably did not exist. Damage occurred at aggregate/geopolymer interfaces, induced in part by the stress concentrations there. Microstructural evolution was also observed, with calcium segregating from the geopolymer matrix toward the aggregates interfaces. The tests revealed that the geopolymer supported modest compressive stresses and exhibited significant strain or pseudo-plasticity.