The Effect of Na2O on the Pore Structure and Water Permeability of Alkali Activated Fly Ash

摘要

The pore structure of alkali activated materials can provide important information on the water transport properties and durability of the materials. In this study, the porosity and pore size distribution of the alkali activated fly ash with different Na2O content in the activator (from 1 mol/kg to 1.5 mol/kg per fly ash weight) were studied by mercury intrusion porosimetry (MIP) method at the curing ages of 7 days and 28 days respectively. The water permeability of the specimens was also measured with the same curing age. The results indicate that the total porosity decreased when higher Na2O content was used. For specimen with lower Na2O content, the pore structure development was very slow after 7 days curing, and the water permeability did not significantly decrease between 7 days and 28 days. The results also reveal that the critical pore diameter and the effective porosity obtained by MIP method correlate well with the water permeability of alkali activated fly ash. The total porosity, on the other hand, did not show consistent trend with permeability.