Low temperature sulfoaluminate clinkers: The role of sulfates and silicates on the different hydration behavior

The study addresses the hydration behavior of different sulfoaluminate clinkers produced in a pilot kiln at burning temperature comprised between 1150 and 1300 °C. The clinkers contain different relative amount and distribution of sulfates and silicates. The hydration behavior from 4 h up to 3 months has been investigated by means of a multi-technique approach. The results indicate that two contributions regulate the different reactivity of these sulfoaluminate clinkers. On one hand, the presence of a readily-available sulfate source allows the faster development of ettringite, whereas, the reactivity of silicate component takes the advantage of the lack of sulfate. Moreover, the first effect influences the early reactivity, while the second one is observed only when medium to long term hydration behavior is considered. Low-temperature sulfoaluminate clinker showed similar performances in comparison with a high-temperature clinker, however, a significant reduction in burning energy (temperature is 150 °C lower) and CO2 emissions (limestone is 5% less) are envisaged.