Effects of silane on reaction process and microstructure of metakaolin-based geopolymer composites

Abstract A series of metakaolin-based geopolymer (MG) organic-inorganic composites were prepared by incorporating with different contents of silane. The silane was used as coupling agent to recombine different components in geopolymer pastes. During the hydration process, the hydration heat evolution, structure and chemical compositions were obtained to characterize the reaction kinetics. The use of silane (APTES) retarded the geopolymer hydration significantly with the increase of silane content. Fourier transform infrared (FT-IR) spectroscopy and solid-state 29Si nuclear magnetic resonance (NMR) indicated that the tetrahedral structure ([SiO4]4- and [AlO4]4-) of aluminosilicate was decomposed and migrated and recombined to form a new tetrahedral network. SEM microscope images and EDS maps showed that the addition of silane enabled geopolymer to achieve a structural homogeneity, which resulted in the significant increase of the content of carbon and the formation of the chemical bonding reaction in organic-inorganic geopolymer composites.