The Effect of Firing Temperature on the Composition and Microstructure of a Geocement-Based Binder of Sodium Water-Glass

摘要

The fire performance of a geocement-based binder was investigated with a combination of analytical techniques, in terms of changes in composition and microstructure. Geocement, formulated as Na_2O·A1_2O_3·6SiO_2·20H_2O, was prepared using metakaolin, sodium water-glass, rotten stone and sodium hydroxide. The mixture was homogenized by passing through a hydrodynamic cavitator. Cubes of 20 mm were prepared, hardened at laboratory conditions for 28 days, and subsequently burnt at 600, 800 and 1200 ℃ in a laboratory furnace. Cavitation treatment resulted in a highly amorphous binder; amorphous fraction decreased upon firing up to 800 ℃ due to crystallization, and increased above 1000 ℃ because of melt formation. Porosity increased with firing temperature and pores larger than 1 mm in diameter prevailed at 1200 ℃. The material remained stable up to 1200 ℃. The results indicate the adequacy of this geocement-based binder for preparing fire-protecting materials.