Cement pre-hydration occurs when cement comes into contact with a source of moisture – moist air or water – before its final use. Depending on the degree of pre-hydration, deterioration of relevant engineering properties of the cement may take place, the most noticeable being:
Reduced powder flowability
Loss of workability and set retardation during mortar or concrete production
Reduction of compressive strength
In addition, the effectiveness of chemical admixtures such as accelerators and retarders can be compromised, and their performance rendered less predictable.