Alkali silicate binders: effect of SiO2/Na2O ratio and alkali metal ion type on the structure and mechanical properties |
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Authors: | Taisiya Skorina Irina Tikhomirova |
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Affiliation: | 1. Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ, 85287-1604, USA 2. Department of General Technology of Silicates, D.I. Mendeleev University of Chemical Technology of Russia, 9, Miusskaya Square, Moscow, Russia, 125047
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Abstract: | The influence of SiO2:Na2O molar ratio and the nature of an alkali metal (Na vs. K) in commercial aqueous alkali silicate on the microstructure, textural
properties, phase composition, and hydrolytic stability of an alkali silicate binder have been investigated using scanning
electron microscopy, nitrogen adsorption/desorption technique, X-ray diffractometry, thermal analysis, and dissolution tests.
It has been found that microstructure and textural properties of the alkali silicate binder depend both on silica to alkali
molar ratio and type of alkali metal (Na vs. K). Sodium silicate binder obtained from commercial silicate solution with lower
SiO2:Na2O molar ratio (2.2) exhibits a globular microstructure of silica xerogel with high content of micropores, whereas the binder
formulated with SiO2:Na2O molar ratio 3.2 is characterized by more open cluster structure with lower content of micropores. It is observed that surface
specific area estimated by Brunauer, Emmett, and Teller method and mesopore volume obtained by the Barrett–Joyner–Halenda
method for sodium silicate binder are substantially higher than those for potassium silicate binder. The ultimate hydrolytic
stability of the sodium silicate binder increases slightly with increase in the silica to alkali molar ratio within the studied
range. Decreasing in SiO2:Na2O molar ratio and replacement of sodium silicate solution by potassium silicate solution in the corresponding filled composition
lead to the improvement of mechanical properties and decrease in open porosity. |
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