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Cement accelerator


A cement accelerator is an admixture for the use in concrete, mortar, rendering or screeds. The addition of an accelerator speeds the setting time and thus cure time starts earlier. This allows concrete to be placed in winter with reduced risk of frost damage. Concrete is damaged if it does not reach a strength of 500 pounds per square inch (3.4 MPa) before freezing.

Typical chemicals used for acceleration today are calcium nitrate (Ca(NO3)2) and sodium nitrate (NaNO3). Calcium chloride (CaCl2) is the most efficient and least expensive accelerator and was formerly very popular but is corrosive to reinforcement bars so its use is not recommended and in many countries is actually prohibited. Thiocyanate compounds can also corrode reinforcing but are safe at recommended dosage levels. Sodium compounds might compromise the long term compressive strength if used with alkali-reactive aggregates.



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