Sulfate Attack of Cementitious Materials: Volumetric Relations and Expansions.
Sulfate Attack of Cementitious Materials: Volumetric
Relations and Expansions.
(926 K)
Clifton, J. R.; Pommersheim, J. M.
NISTIR 5390; 22 p. April 1994.
Available from:
National Technical Information Service
Order number: PB94-187317
Keywords:
building technology; cements; concretes; ettringite;
expansion; modeling; sulfate attack; tricalcium
aluminate
Abstract:
A model was developed which predicts the conditions
under which volumetric expansion of cementitious
materials are most likely and the amount of expansion
expected. Model parameters include concrete
composition, phase densities, water-cement ratio, degree
of hydration, extent of expansive reaction and reaction
stoichiometry. The model was applied to several
different reactions involving sulfate attack of
concrete, including gypsum and ettringite formation
reactions. The model predicted that ettringite
formation from monosulfate would not cause general
expansion. However, local expansion could occur if
ettringite occupied the same space vacated by reacting
monosulfate. The model predicted that if sufficient
unhydrated tricalcium aluminate (C3A) was available in
mature cement paste and it reacted with gypsum to form
ettringite, the reaction could cause expansion at low
water-to-cement ratios.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899