Sulfate Resistance of Mortar Bars in Calcium, Magnesium, and Sodium Sulfate Using a Vacuum Impregnation Technique

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Title: Sulfate Resistance of Mortar Bars in Calcium, Magnesium, and Sodium Sulfate Using a Vacuum Impregnation Technique

Author(s): Federico M. Aguayo, Thano Drimalas, and Kevin J. Folliard

Publication: Special Publication

Volume: 317

Issue:

Appears on pages(s): 1-20

Keywords: accelerated method, calcium, magnesium, microstructural, sodium, sulfate attack, sulfate resistance

Date: 6/1/2017

Abstract:
A number of research studies on chemical sulfate attack have been conducted, and considerable disagreement over the mechanisms still exist. They reveal that several factors can influence the severity and type of attack including the concentration of sulfate ions, pH level, temperature, and the nature of the associated cation. However, the biggest challenge that still remains is a performance test method that can determine the sulfate resistance of cement-based systems within a reasonable timeframe. This laboratory experiment – which was part of an extensive doctoral research program – investigated the use of a new vacuum impregnation technique to accelerate the degradation observed during sulfate attack. The mortar bars were immersed in various sulfate solutions and cation types including sodium, magnesium, and calcium sulfate. The results showed an increased rate of linear expansion from the use of the vacuum impregnation technique when compared to the traditional ASTM C1012 method. However, the measured expansion was significantly influenced by the chemical composition of the binders as well the type of sulfate solution used during testing. The microstructural study revealed that the mechanism of expansion seen when using the vacuum impregnation technique was comparable to mechanisms commonly seen in classic cases of external sulfate attack.