Abstract
The microstructural effects of exposure to a 15% magnesium sulphate, 15% sodium sulphate, and mixed solutions were observed in mortars with and without silica fume, using the non-destructive impedance spectroscopy technique. The non-destructive “Wenner” resistivity test and the classical mercury intrusion porosimetry were used as contrast techniques. The compressive strength of the mortars was also studied. In view of the results obtained, impedance spectroscopy was the most sensitive technique for detecting changes in the porous network of the studied mortars. The addition of silica fume results in a more refined microstructure and a higher compressive strength in mortars exposed to aggressive sulphate solutions.
Highlights
The use of non-destructive techniques for characterizing the microstructure of cement-based materials has become an important research field [1,2,3,4,5,6,7]
This is in agreement with previously discussed microstructure results, and it shows the beneficial effect of silica fume on compressive strength, as well as the possible role of Na2 SO4 as an activator of pozzolanic reactions of silica fume
The lowest compressive strengths in the long-term for silica fume mortars were observed in magnesium sulphate solutions, especially in the mixed sulphate solution
Summary
The use of non-destructive techniques for characterizing the microstructure of cement-based materials has become an important research field [1,2,3,4,5,6,7]. Among these techniques, impedance spectroscopy has been greatly developed during the last few years. The use of impedance spectroscopy to study the effects of sulphate attack on the microstructure of cement-based materials in general has hardly been considered [13]. Little attention has been paid to the non-destructive study of the microstructural origins of changes in these properties, and especially in the case of the partial replacement of cement with silica fume, used as an addition to improve the sulphate resistance of cements [17,18,19] (among other positive effects)
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