Title: An Investigation of Hydrating Cements and Related Hydrous Solids by Differential Thermal Analysis

Author(s): George L. Kalousek, Curtis W. Davis, Jr., and William E. Schmertz

Publication: Journal Proceedings

Volume: 45

Issue: 6

Appears on pages(s): 693-712

Keywords: no keywords

DOI: 10.14359/12180

Date: 6/1/1949

Abstract:
Differential thermal analysis was used to identify some of the hydrous solids formed in cements and to follow partially the the course of some of the hydration reactions. Pastes of nine commercial portland cement clinkers with and without additions of gypsum were tested at 1, 3, 7, 28 and 90 days and 9 months. Among the individual solids prepared and studied were the calcium sulfoaluminates, hydrous calcium aluminates, lime-silica gels made from different starting materials, with and without additions of Al2O3, SO3, and Na2O. Thermal analysis results show that isometric tricalcium aluminate hexahydrate does not form in hydrating cements. The trisulfate form of the calcium sulfoaluminate and the solid solution, appear as metastable products only. The stable sulfate-bearing phase has not yet been isolated but presumably is characterized in thermal analysis by an endothermic bulge at 130-140 C. A possible role of Fe2O3 in the formation of this new phrase is considered. The lime-silica gels may occur in two forms, one exhibiting two distinctive thermal changes and the other not showing any marked changes; the former is the more unstable of the two, transforming in prolonged tests to the latter. Alumina appears to stablize the less stable form of these gels.