Topic 04 / Ad
Concrete admixtures
Admixtures are added to concrete in small amounts to change how it places, sets or lasts.
The common types
Water reducers let a mix flow with less water. Accelerators speed up setting in cold weather, and retarders slow it down in heat. Air entraining agents add tiny bubbles that help concrete survive freeze and thaw cycles.
Who decides
Admixtures are part of the mix design, so the engineer and the ready mix supplier usually choose them together. Adding products on site without that conversation can cause problems with set time or strength.
Where it is used
- Hot and cold weather pours
- Pumped and self consolidating concrete
- Exposed slabs in freeze and thaw climates
- Structures that need lower permeability
Things to check
- Interactions between admixtures
- Effect on finishing and set time
- Dosage control at the plant
- How a later coating will bond to the slab
General information only. Product behavior varies, so confirm details with the manufacturer data sheet and a qualified professional.
