WORKABILITY AND SETTING TIMES OF ALKALIACTIVATED NATURAL POZZOLAN IN RELATION WITH CHEMICAL COMPOSITION

In this research work, properties of alkali-activated pumice-type natural pozzolan including initial and final setting times and paste workability were studied by changing parameters of chemical composition, i.e. SiO2/Na2O molar ratio of activator and total molar ratios of Na2O/Al2O3, and H2O/Al2O3. At constant H2O/Al2O3 total molar ratio, the spread diameter of the freshly prepared paste depends on both SiO2/Na2O molar ratio of activator and total Na2O/Al2O3 molar ratio. In this case, both initial and final setting times sharply decrease as the Si/Na molar ratio increases from 0.3 to 0.6, especially for lower molar ratios of Na2O/Al2O3. System prepared at SiO2/Na2O=0.6 and Na2O/Al2O3=0.77 and exhibiting the shortest initial and final setting times, i.e. 20 and 37 min respectively, behaves as a fast set cement compared to Portland cement. By changing in the amount of H2O/Al2O3 total molar ratio it has been observed that the paste workability and setting times are not only a function of H2O/Al2O3 molar ratio, but also a function of Na2O/Al2O3molar ratio.

کلیدواژه ها:

Alkali-activation ، Chemical composition ، Natural pozzolan ، Setting time ، Workability