Effect of process parameters on the physical properties of porous geopolymers obtained by gelcasting

Open cell geopolymer foams with a total porosity as high as 80 vol% were produced by gelcasting, and the effect of processing (mixing speed, amount and type of surfactant) on some physical properties of the components was investigated. The data show that, as expected, the permeability increased while the compression strength decreased with increasing the amount of open porosity. No great statistically significant difference could be observed when using either one of the surfactants, but we can suggest that the use of Tween 80 as a surfactant is more amenable to the formation of interconnected cell structures and high levels of total porosity. The gas permeability data indicate that these foams perform similarly to granular filters and other ceramic foams produced by gelcasting. Heating the geopolymer foams to intermediate (700 degrees C) or high (1200 degrees C) temperature reduced the specific surface area, the total and the open porosity, due to the crystallization of leucite and partial viscous sintering. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. (AU)