Conditioning Highly Concentrated Borate Solutions with Calcium Sulfoaluminate Cement

The early age hydration by borate solution of three CSA cements containing, respectively, 0 %, 10 % and 20 % of gypsum by weight of cement was studied using isothermal calorimetry and dynamic mode rheometry. XRD and TGA analysis were carried out on pastes with increasing hydration degrees (up to 90 days) to specify the mineralogy and to figure out the mechanisms of borate immobilization. It has been shown that the retarding effect of borate anions is due to the precipitation of the amorphous calcium borate C2B3H8; borate anions were then incorporated in Aft-type phases. The macroscopic properties of hydrated binders (compressive strength, length change) were also followed during 180 days.