Mechanism for salt scaling of a cementitious surface

Title: Mechanism for salt scaling of a cementitious surface
Author(s): John J. Valenza II, George W. Scherer
Paper category : conference
Book title: International RILEM Symposium on Concrete Science and Engineering: A Tribute to Arnon Bentur
Editor(s): J. Weiss, K. Kovler, J. Marchand, and S. Mindess
Print-ISBN: None
e-ISBN: 2912143926
Publisher: RILEM Publications SARL
Publication year: 2004
Nb references: 30
Language: English

Abstract: Freezing and thawing of a cementitious body in the presence of deicer salts results
in superficial damage known as salt scaling. Scaling damage consists of the removal
of small flakes from the surface, leaving the body susceptible to water and ion
ingress, thus posing a significant threat to the durability of the body. None of the proposed
mechanisms for salt scaling account for all of the phenomenology observed during
previous studies. We report a novel experimental method designed to measure the
stress that arises when a pool of aqueous solution is frozen on a cementitious plate.
These experiments uncovered the occurrence of a thermal expansion mismatch (or, bimaterial)
mechanism that accounts for all of the observed salt scaling phenomenology.
According to the bimaterial mechanism, scaling occurs when the stress in the freezing
layer rises above the tensile strength of the brine-containing ice, resulting in cracking. A
viscoelastic analysis of the stresses in the brine/ice layer shows that pure ice would not
crack, but a layer containing >1% NaCl would. This scaling mechanism is similar to
glue-spalling, a technique used to decorate the surface of glass. The damage from
cracking of the ice is exacerbated by weakening of the cement paste by exposure to concentrated
brine. Experimental evidence is presented to demonstrate the magnitude of
the stresses resulting from contact with brine and from thermal expansion mismatch
between ice and cement paste.

Online publication: 2004-03-25
Classification: Freeze-Thaw
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2912143926.056

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