Study of the system CaO-SiO2-H2O at 30 C and of the reaction of water on the anhydrous calcium silicates
Year: 1934
Type: article
Abstract: A graph has been prepared representing the solubility of silica at 30 C in solu- tions containing increasing concentrations of lime up to saturation, the solutions being in "equilibrium" with solid phases composed of hydrated combinations of lime and silica.An electrometric and analytical study of both supersaturated and unsaturated solutions of silica at definite concentrations of lime, when corre- lated with these equilibrium solubility relationships, indicates the existence of definite compounds in the system CaO-Si0 2 -H 2 which may be the hydrated calcium salts of orthosilicic acid.Experimental values were obtained for the hydrolysis constants of these salts from which ionization constants for the four steps in the dissociation of orthosilicic acid were calculated.A study of the reaction of water upon the anhydrous calcium silicates (CaO Si02 , 3CaO-2Si0 2 , 7-2CaO-Si0 2 , ,3-2CaO Si0 2 , 3CaOSi0 2 ) showed that the products formed depend upon the equilibrium relationships of the system CaO-Si0 2 -H 2 0. Of these compounds all but monocalcium silicate (CaO-Si0 2 ) form solutions which pre- cipitate hydrated calcium silicate on standing.Application of the same methods to a study of the reaction of water upon a portland cement indicated that hydrated calcium orthosilicate is formed during the hydration of portland cement.A study of the reaction between diatomaceous silica and lime solution and between silica gel and lime solution is also included. CONTENTS PageIt will be shown that the generalization of Le Chatelier 3 that hydraulic materials possess metastable solubilities, applies to the calcium silicates occurring in portland cement.Finally the reactions of diatomaceous silica and of silica gel with lime in solution are compared and the relationship of the results to the system CaO-Si0 2 -H 2 is discussed briefly.
DOI: 10.6028/jres.012.060
Authors: E.P. Flint, L.S. Wells
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2330104472