Title: Tobermorite and Related Phases in the System CaO-SiO2-H2O
Author(s): George L. Kalousek
Publication: Journal Proceedings
Appears on pages(s): 989-1011
Keywords: no keywords
The hydrothermal reactions at temperatures of 125 to 175 C between Ca(OH)2 and quartz or silicic acid have been studied in detail with regard to the reaction products to form particularly in the range of molar compositions of 0.8 CaO: SiO2 to 1.25 CaO: SiO2. The solid phases were studied by x-ray, DTA, BET nitrogen adsorption,, electron microscopy and chemical analysis. The products prepared from mixtures made with silicic acid were fibrous in form and ranged in composition from 0.8 to 1.25 C/S. The same or closely related solids were also prepared with quartz. The fibrous C4S5Hn, transformed to tobermorite C4S5H5, a platy crystalline solid. The transformation was very rapid in mixes made with quartz but comparatively slow in mixtures made with silicic acid. Although the fibrous and platy phases are similar, the differences between the two, particularly in physical properties, appear to be real. The fibrous phase does not integrate and, upon drying, undergo a marked shrinkage.. The platy phase integrated into dimensionally stable solids of superior strengths.