Effect of Particle Size of Residual Rice-Husk Ash in Consumption of Ca(OH)2

Some researchers suggest the use of residual rice-husk ash (RHA) finely divided as a mineral addition to cement, despite the reduced content of amorphous silica compared to RHA produced by controlled burning. This article presents an investigation of the pozzolanic activity of residual RHA A and residual RHA B, with high and low contents of amorphous silica, respectively, showing different particle size distributions. Scanning electron microscopy (SEM), magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and determination of amorphous silica through the rapid analytical method were used for the microstructural characterization of the RHA samples. The RHA B with low content of amorphous silica increases the consumption of calcium hydroxide when its particle size decreases.