Accelerating Admixture

Summary

Accelerating Admixture - (or accelerator) is a chemical which can be added to a concrete mix to speed up the hydration process.

Technical Information

Accelerating admixtures are often used whilst concreting in cold weather as the low temperature can slow down the hydration reactions in the cement paste. They can also be used in conjunction with superplasticisers when high early strength or the early removal of formwork is required.

They can either speed up the initial setting or hardening of the concrete but rarely both. Therefore it is important to choose the correct accelerator for the requirements of the situation.

Accelerators containing calcium chloride are restricted to non steel reinforced members due to the corroding effects that chloride ions have on steel.