Ceramics-Silikáty 52, (1) 16 - 23 (2008)

Natural pozzolans are aluminosilicate-type materials which can be activated with solutions of NaOH and Na₂SiO₃. Using a pumice-type natural pozzolan and different alkali-activators based on combinations of Na₂SiO₃ and NaOH, a number of geopolymer cement systems were designed and studied. Water-to-dry binder ratio, silica modulus, and sodium oxide concentration of the systems were adjusted at different levels and setting time, workability, and 28-day compressive strengths of the systems were studied. The results obtained reveal that natural pozzolans of pumice-type can be activated using a proportioned mixture of Na₂SiO₃ and NaOH resulting in the formation of a geopolymer cement system exhibiting suitable workability and acceptable 28-day compressive strengths. All the measured final setting times are acceptable compared to standard values given for Portland cement.