Critical examination of drying damage to cement pastes

Several methods of drying cement paste prior to determining its physical properties, for example pore size distributions, are critically studied. Phase-pure preparations of ettringite and calcium monosulfoaluminate are used as sensitive indicators of damage. Oven drying at 105 degrees C and drying over strong desiccants, for example MgClO4, is damaging. D-drying for 2-3 h is recommended as a robust but relatively non-damaging treatment. D-drying reduces the water content of ettringite to similar to 30 H2O per formula unit but removal of its zeolitic water similar to 1.7 H2O, does not degrade the structure. Monosulfoaluminate, AFm, is reduced from 12 to 10 H2O with shrinkage of its basal spacing from similar to 90 to similar to 82 Angstrom. However D-drying of pastes from commercial calcium sulfoaluminate rich in AFm usually gives mixtures of the similar to 9.0 and similar to 8.2 Angstrom phases.