Influence of particle size and specific surface area on the pozzolanic activity of residual rice husk ash

The effect of the particle size distribution and specific surface area on the pozzolanic activity of a residual rice husk ash (RHA) was investigated in this work. Different samples of RHA obtained from ultrafine grinding were characterized with respect to particle size analyses by laser granulometry, BET and Blaine specific surface areas, pore volume distribution by mercury intrusion porosimetry, surface texture by scanning electron microscopy, pozzolanic activity using the cement mortar method and activity with lime using the Chapelle method. From the results, it was concluded that a good correlation exists between the ‘external’ specific surface area, that is, the surface area associated with the measured particle size distribution, and the pozzolanic activity of the residual RHA. On the other hand, nearly no correlation was identified between the pozzolanic activity and the specific surface area measured using the BET method, an observation that is particularly related to the cellular nature of the internal structure of this RHA.