| Abstract [eng] |
Calcium silicate hydrates are used to make some of the best heat-resistant insulating products, which have an operating temperature of 1050 °C. These products are made of 1.13 nm tobermorite and synthetic xonotlite. The first compound can be synthesized from a variety of wastes and by-products from other industries, but these raw materials frequently contain impurities, particularly compounds containing aluminum, which significantly affect the kinetics and properties of the formation of 1.13 nm tobermorite. Several analytical methods have demonstrated that while pure 1,13 nm tobermorite with high crystallinity is more easily formed in mixtures without the addition of aluminum, Al3+ ions initially encourage the formation of 1.13 nm tobermorite at the start of the hydrothermal synthesis before beginning to inhibit the recrystallization of C-S-H(I). 1.13 nm tobermorite shape is similarly influenced by aluminum ions. Within 24 hours, hydrothermal synthesis creates long, thin fibers (needles), which then form into rectangular crystals. Agglomerates, which have crystalline platelets partially covering their surface, predominate in the 24-hour synthesis result when alumina is added. The amorphous aggregates vanish and the crystals get more square as the synthesis time increases. |
