Incorporating Rice Husk Ash in Metakaolin-Based Geopolymer Binder

Geopolymers are interesting materials synthesized by activating aluminosilicate source(s) with alkaline activator(s). The activators often used for this purpose are alkali metals of silicates and hydroxides. Environmental impact assessment carried out on geopolymers however indicates adverse contribution of this process to several other environmental indices despite the reduction in CO2 emission. Several biomass sources are known to possess a high silica content. This research investigates the effect of incorporating rice husk ash (RHA) in the production of geopolymers. 2, 4, 5, 6, 8 and 10 g of RHA was introduced as a source of silica into the geopolymer binders. Sodium silicate to sodium hydroxide ratio of 0, 1 and 1.5 was used for the synthesis. From the compressive and flexural strength tests, increasing the RHA content improved the performance of the binders. Optimum compressive and flexural strength was obtained at 10 g (15.25 MPa) and 4 g (3.45 MPa) RHA, content respectively. Binders produced with only sodium hydroxide (SH) solution and RHA showed a significant increase in strength as the RHA content increased.