Hydration characteristics of portland cement after heat curing: I, degree of hydration of the anhydrous cement phases

The degree of hydration of the four major anhydrous cement phases in three U.K. portland cement mortars has been observed during the period of mater s torage at room temperature after an initial short-term heat cure. Such a he at cure at 85 degrees or 100 degreesC for 12 h generally accelerated the in itial hydration of the four major anhydrous minerals in portland cement. Su bsequent retardation of the degree of hydration of the alite, tricalcium al uminate, and ferrite phases was observed when these heat-cured mortars Tt e re stored at ambient temperature. General similarity but some differences i n hydration behavior were observed between the three cements. The hydration of belite in the heat-cured mortars during storage at room temperature pro duced porous inner products that favored deposition of ettringite and reduc ed the risk of expansive ettringite formation. The substantial retardation in hydration of the aluminate-bearing phases, especially the ferrite phase, during the storage at room temperature raised the overall SO3/Al2O3 ratio of the cement hydrates formed, bringing about a potential for ettringite fo rmation and hence the risk of expansion through delayed ettringite formatio n.