Leaching of monolithic geopolymer mortars

The environmental compatibility of geopolymers was investigated in this work in terms of the leaching properties of major components, heavy metals and trace elements from monolithic mortars. Fly ash geopolymer, metakaolin geopolymer and a commercial geopolymer mortar were used. Leaching mechanism analysis demonstrates that the leaching of chemical components is mainly controlled by diffusion, while surface wash-off, solubility and depletion also take place. The results were compared with cement-based materials and the regulatory limits in Germany and in the Netherlands for environmental compatibility assessment. Leaching of studied heavy metals and trace elements (except B, V and Mo) from geopolymer are in a similar range as cementitious materials. Only the cumulative release of V is higher than the threshold in Germany, but it still meets the requirement in the Netherlands. Strength decrease after leaching was detected, which was 11.8%, 9.4% and 14.9% for fly ash geopolymer, metakaolin geopolymer and the commercial geopolymer, respectively. In addition, no difference in terms of phase composition in the surface layer was detected after leaching.