Mechanism of Sulfate Expansion in Hydrated Portland Cement

Abstract

The origin of sulfate expansion was studied on a series of cements of different compositions and on mixes of pure compounds. The observed data support the theory that the expansion is related to a topochemical formation and/or oriented growth of ettringite. An uptake of water from the environment is not essential for the expansion to take place even though it enhances the extent of expansion. The absence of expansion in iron‐rich cements appears to be due to reduced and delayed ettringite formation in these cements and to an altered morphology of the formed ettringite.