Long-term strength and porosity of mortars based on ettringite binder

Ettringite binder is widely used in mortars for technical applications such as patching mortars, self-leveling screeds, repair mortars thanks to their fast hardening ability and high early strength. However, depending on the amount and types of raw materials used in the composition, the properties of these types of binder have different behaviors at early-age and at long term. In this work, the influence of the nature and dosage of calcium sulfate in ettringite binder on the long-term strength of mortar in different curing conditions was determined. The results showed that the increase of calcium sulfate content in ettringite binder from 10–25 % improves the strength of mortars regardless of the calcium sulfate nature. In all curing conditions (endogenous, drying, outdoor), the strength of ettringite mortars with anhydrite is smaller than that of mortars containing hemihydrate. There is no major difference in the porosity of the mortars in different types of curing conditions before 28 days. However, after 28 days the porosity of mortar in drying condition is about 2–3 % higher than that of the mortars in endogenous and outdoor conditions.