Effect of Heat Treatment on the Pore Structure and Drying Shrinkage Behavior of Hydrated Cement Paste

The effect of a short heat treatment on hydrated cement paste has been investigated by measuring the weight and length changes of specimens as they undergo various combinations of heating, drying, and resaturation. Heating a cement paste to 60°C coarsens the capillary pore system, decreases the volume of mesopores, and increases the degree of polymerization of the silicates. In addition, the saturated weight of the paste is permanently decreased by a heat treatment. This weight loss can be explained by conversion of bound hydroxyl groups into liquid water during polymerization of the C-S-H gel phase. These experiments help reconcile and interpret published results describing the properties of cement cured at various temperatures, the effects of a short heat treatment on cement paste, and the thermal expansion behavior of saturated and dry cement paste.