Effect of dolomite powder on the hydration and properties of calcium sulfoaluminate cements with different gypsum contents

The present study investigates the effect of dolomite powder on the hydration and properties of calcium sulfoaluminate (CSA) cements with different gypsum contents, with limestone powder as a comparison. Hydration kinetics was tested using isothermal calorimetry. The hydration assemblage was examined using X-ray diffraction and thermal analysis. Results indicate that the hydration of CSA cements is accelerated with the addition of either dolomite or limestone powder. Similar to limestone, dolomite can participate in hydration reaction to form hemicarbonate and to stabilize ettringite when gypsum is insufficient, but dolomite is less reactive due to its slow dissolution rate. The reaction of the carbonates is suppressed with the increase in gypsum content. Both compressive strength and expansion of CSA mortars decrease with the addition of dolomite, regardless of the gypsum contents. In general, the dolomite and limestone modified mortars show similar strength and expansion, however except a higher expansion in the dolomite mortar without gypsum. Moreover, the strength loss of CSA mortar is mitigated when dolomite or limestone is used.