Concrete incorporating rice-husk ash without processing

The rice-husk is a residue with low nutritional properties for animals. When it is incinerated rice-husk generates a great quantity of ashes (RHA). The use of RHA as a supplementary cementing material is of great interest to many developing countries where rice production is in abundance. A highly reactive pozzolan is obtained when RHA is burnt under controlled conditions. In other conditions a “residual RHA” is produced with a lower quality, but it can be improved by grinding. In this paper the residual RHA was used “as nature”, without any previous grinding. Mixing RHA together with the coarse aggregates during a convenient period of time, before incorporating the other component materials, an adequate RHA particle size can be obtained. The fresh and mechanical properties and the water permeability were analysed in concretes replacing cement by residual RHA. The incorporation of natural RHA in structural concrete represents a good alternative for the disposal of this residue, even without the previous optimization through a grinding process.