Sulfate Attack of Cementitious Materials: Volumetric Relations and Expansions

摘要

A model was developed which predicts the conditions under which volumetricexpansion 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.