Resumen de Effect of the strontium aluminate and hemihydrate contents on the properties of a calcium sulphoaluminate based cement

G. Velazco, J.M. Almanza, Dora Alicia Cortes Hernández, José C. Escobedo Bocardo, José Iván Escalante García

• The effect of strontium aluminate (SrAl2O4) on the hydration process of a calcium sulphoaluminate (C4A3S) cement was investigated. Cement pastes were prepared by mixing C4A3S , hemihydrate (CaSO4· ½H2O, CSH0.5) and 0, 10 or 20wt% of SrAl2O4 (SrA). The amount of CSH0.5 was 15, 20 or 25wt% based on the C4A3S quantity. The cement pastes were hydrated using water to cement ratios (w/c) of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa) after 28 d of curing. The main product after hydration was ettringite (C6AS3H32). The morphology of this phase consisted of thin needle-shaped crystals.