Mineralogy and Performance of Cement Based on High Sulfate Clinker

Abstract The question of whether or not the release of sulfates from the clinker phases in portland cement can result in late or renewed ettringite formation has been addressed through a series of physical tests and by mineralogical examination. The cements tested contained clinker with SO3 contents ranging up to 3%, including high belite contents and sufficiently low alkali contents to ensure the presence of anhydrite. The physical testing consisted of expansion tests of mortars cured and stored at 20°C, in addition to compressive strength determinations. The mineralogical examination consisted of monitoring the consumption of anhydrous phases by X-ray diffraction and microscopy on the SEM. Linear expansion at 10 months was negligible for all cements with no significant loss in strength. No significant late, or renewed development of ettringite was observed. Calculations based on the distribution of elements between phases in the clinker included in the investigation show that the potential for late ettringite formation from the unreacted clinker is negligible, even when making the most pessimistic assumptions.