Q. Is there any accelerator that can be used in prestressed concrete?

A. This would have to be something that doesn't contain any chloride.

There are accelerating admixtures on the market that do not contain calcium chloride or other chlorides. At the present time we know of two products:Darex Set Accelerator

W.R. Grace &Company
62 Whittemore Street
Cambridge, Massachusetts 02140

Arcal Arco-Set New
Arcal Chemicals Inc.
223 Westhampton Avenue
Seat Pleasant, Maryland 20027

The need to avoid use of chloride-containing accelerators in prestressed concrete cannot be too heavily emphasized. ACI Committee 201, Durability of Concrete, recommends a limit of 0.06 percent chloride by weight of cement in such concretes. The reason that the limit is not set at zero is that it is hard to prevent small amounts of chloride from being introduced as an impurity in the cement, aggregate or water.