Critical examination of drying damage to cement pastes

Several methods of drying cement paste prior to determining its physical pr operties, for example pore size distributions, are critically studied. Phas e-pure preparations of ettringite and calcium monosulfoaluminate are used a s sensitive indicators of damage. Oven drying at 105 degrees C and drying o ver 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 un it but removal of its zeolitic water similar to 1.7 H2O, does not degrade t he structure. Monosulfoaluminate, AFm, is reduced from 12 to 10 H2O with sh rinkage of its basal spacing from similar to 90 to similar to 82 Angstrom. However D-drying of pastes from commercial calcium sulfoaluminate rich in A Fm usually gives mixtures of the similar to 9.0 and similar to 8.2 Angstrom phases.