Title:
Salt Hydration Distress
Author(s):
William G. Hime, Ross A. Martinek, Lisa A. Backus, and Stella L.Marusin
Publication:
Concrete International
Volume:
23
Issue:
10
Appears on pages(s):
43-50
Keywords:
DOI:
Date:
10/1/2001
Abstract:
Deterioration due to the exposure of concrete, mortar, stone, or stuccoed surfaces to sodium sulfate solutions is often evidenced as white efflorescence and loss of surface. Our studies of many of these occurrences have shown: 1. That the mechanism of deterioration is "salt hydration distress" (SHD), a term we coined to best describe the process, which essentially relates to the repeated reconversions of sodium sulfate between its anhydrous and hydrated forms. Conversion of anhydrous sodium sulfate (thenardite) to the decahydrate (mirabilite) involves an expansion of 317%. 2. That the usual methods of investigation of such instances of distress have removed the very evidence for its existence. 3. That, as a consequence, the deterioration is misidentified by others as "sulfate attack,” “salt crystallization,” “salt damp,” or "physical salt distress." Some reasons for erroneous investigations and conclusions, and our development of more appropriate and definitive ones, are detailed in the article.