Geopolymer synthesis using alkaline activation of natural zeolite

The influence of activator ratio, time, and curing temperature on the mechanical strength of geopolymers synthesized from natural zeolite was evaluated by employing silicate solutions and sodium hydroxide. The results demonstrated that an increase in the activator ratio as well as that of curing time favors mechanical strength in the material. Nevertheless, with 90 day of curing time and 80 degrees C or a greater curing temperature, have a negative effect on strength. Through characterization by X-ray diffraction a slight shift along with an increase in the amorphous halo between 20 degrees and 30 degrees (2 theta) was observed and is characteristic of geopolymers. SEM-EDS analysis indicated the presence of Na and an increase in the Si/Al ratio from 8 to 11.5 with the incorporation of activators. The results indicate that the use of alkali and silicate activators on non commercial zeolite could be use in the synthesis of geopolymers. (C) 2010 Elsevier Ltd. All rights reserved.