A novel green approach for making hybrid inorganic- organic geopolymeric cementitious material utilizing fly ash and rice husk

Abstract

A novel green process11Patented in India and USA: US 9120, 701 B2, Date of Patent September 1, 2015. has been presented in this paper for preparation of hybrid inorganic −organic geopolymeric cementitious material utilizing fly ash, and rice husk which helps in reduction of greenhouse gas (GHG) carbon dioxide thus addressing the issue of global warming. The process involves synergistic and simultaneous chemical reactions among glassy silico- aluminous phase present in fly ash and amorphous silica and organic molecules present in rice husk in presence of alkali. This results in in −situ synthesis of sodium silicate and transformation of tetra coordinated silicon complexes originally present in fly ash and rice husk to penta coordinated silicon complexes in hybrid inorganic −organic geopolymeric material. This has been confirmed by 29Si NMR spectra of hybrid inorganic −organic geopolymeric material. The organic molecules present in rice husk resulting in development homogenous, non brittle hybrid inorganic −organic matrix. Hybrid inorganic −organic geopolymeric material possess 25% more flexural strength with a value of 2–4MPa in comparison to conventional geeopolymeric material which possess flexural strength of 1–2MPa only. The formation of hybrid inorganic −organic matrix is confirmed by presence of peaks of organic and inorganic phases in XRD. The presence of organic and inorganic linkages in FTIR spectra of hybrid inorganic organic geopolymeric material further confirms formation of hybrid matrix. The presence of characteristic 27Al NMR signal of geopolymeric material at around 59ppm in both conventional as well as in hybrid inorganic-organic geopolymeric material confirmed the formation of geopolymeric material in both the cases.