Strätlingite: compatibility with sulfate and carbonate cement phases

The silicate AFm, stratlingite, has been shown to be stable in high aluminosilicate cement systems but its stability with respect to the anion content of hydrated Portland cement paste is unknown. The stability of stratlingite in the presence of sulfate and carbonate phases relevant to cement systems are reported. Results show that stratlingite persists at the sulfate activity conditioned by gypsum, ettringite and at carbonate activity conditioned by the presence of calcite, carbonate AFm, or carbonate AFt. Structural incorporation of anions such as carbonate or sulfate in stratlingite was not observed in the temperature range 20-85 degrees C.