How are alkali-activated materials impacted by incorporating low viscosity organic liquids?

This research determines an adequate alkali-activated material (AAM) for the incorporation of huge amounts (20 or 40% vol) of low viscosity organic liquids (LVOL), e.g. for waste stabilization/solidification. The selected AAM are either based on high-Ca content blast furnace slag, or on low Ca-content metakaolin, i.e. on a geopolymer matrix. First, the selection of the AAM is performed to ensure no LVOL leakage and a sufficient compressive strength f c (> 8 MPa). Surfactants are compulsory to allow incorporation. After 90 days curing, for slag pastes, f c ranges between 10 and 20 MPa at 20% vol LVOL, but it is zero at 40% LVOL, whatever the surfactant. For geopolymer pastes, the AAM-LVOL composites have an average f c of 25 MPa at 20% vol LVOL, and of 15 MPa at 40% LVOL. With surfactant, the AAM solid pore structure of slag pastes is denser (with smaller specific surface area and micropore amount); it is unchanged for geopolymer pastes. Whatever the surfactant, air entrained bubbles are present. Their proportion is maximal with Glucopon. Together with LVOL presence, this generally contributes to decreasing f c . The emulsion (entrained air + LVOL droplets) is characterized in hardened AAM by combining 2D Scanning Electron Microscopy and 3D X Ray micro-computed tomography. Surfactants significantly decrease the emulsion droplet size distribution. For geopolymer pastes up to 40% vol LVOL, the most adequate surfactants are Brij O10 and CTAB; for slag paste up to 20% vol LVOL, it is CTAB. Moreover, the setting reactions are not impacted by LVOL or surfactants, and neither are the reaction products. It is concluded that the decrease in mechanical performance of AAM-LVOL composites is only due to physical reasons, particularly the decrease in AAM proportion, the emulsion quality (coalescence, droplet size and shape) and air entrained bubbles.