Development of Nano-Reinforced Green Alternative to Cementitious Matrix for Structural Composites using Rice Husk Ash

Abstract

The worldwide growing demand for rice production raises a deep concern about the management of non-bio-degradable rice husk. Currently the rice millers in the world produce 530 million metric tons of rice annually. Rice husk makes up approximately 20% of the total rice production. Bangladesh is the fourth largest rice producing country in the world with an estimated production of 38.2 million metric tons annually which makes up approximately 8 million tons of rice husks. United States produce around 10 million metric tons of rice annually. Most common applications of rice husk are thermal power plant and charcoals for household cook stoves etc. However, one of the most promising applications of rice husk ash is in the silica fume based geopolymer for the matrix of continuous fiber composite. At first two types of rice husks were collected directly from rice fields of the different parts of Bangladesh to evaluate the pozzolanic activity and compatibility of the derived RHAs with the major geopolymer precursors. Then compression strength, flexural and short beam shear strength were performed to investigate the synergistic effect of RHA derived silica and commercially available silicon carbide whiskers (SCW) on this Metakaolin based geopolymer. Results have shown that RHA derived spherical silica nanoparticle reduced nanoporosities of die geopolymer by ~20% and increased compressive strength by ~100%. Also the additions of silica nanoparticles and simultaneous additions of silica nanoparticles and silicon carbide whiskers resulted in the increase in flexural strength by ~27% and ~97%, respectively. The increase in compressive strength due to the inclusion of silica nanoparticles is strongly related to the reduction in porosities. The increase in flexural strength due to simultaneous inclusion of silica and SCW suggest that silica particles are compatible with die metakaolin based geopolymer which is effective in consolidation and SCWs are effective in increasing bridged network and crack bridging resistance.