Calcium chloride is the classic accelerator, dosed at up to 2 percent by weight of cement, and it can cut setting time by hours on a cold day. Because chloride corrodes steel, it is barred from prestressed work and tightly limited in reinforced concrete, where non-chloride accelerators based on calcium nitrate and similar salts take its place. Ready-mix plants usually pair it with hot water through the winter.
Give me hot water and one percent non-chloride accelerator on the slab loads, it's dropping to 28 tonight.
A finisher who asks for one percent calcium wants calcium chloride; on rebar jobs the inspector will expect to see non-chloride on the ticket.
Also heard as
- calcium
- calcium chloride
- non-chloride accelerator
- NCA
Do not mix it up with
- Retarder: A retarder does the opposite, delaying set to buy working time in heat or on long pours.
Related terms
Retarder
An admixture that delays setting, used in hot weather, on long hauls and for big continuous placements.
Cold weather concreting
Placing and protecting concrete when air temperatures are at or expected to drop below 40 F.
Admixture
A product dosed into a concrete batch, usually by the ounce, to change its flow, set time, air or durability.
Initial set
The point at which fresh concrete stops being workable and begins to stiffen into a solid.