What can you do if rebars partially embedded in concrete have been fabricated or placed incorrectly, have become accidentally misaligned, or are no longer properly located because there has been a design change? Should such rebars be bent or rebent in the field? If so, should they be bent cold or hot, and what are the limitations on such bending?
There have been a number of studies that have shed light on this subject. In one of them The Associated Reinforcing Bar Producers Concrete Reinforcing Steel Institute undertook a program to study cold versus hot bending; effects of the type, degree and axis of bend; effect of bar size and deformation pattern; effect of cold-temperature bending; and the differences between accidental and deliberate bending.
As a result of this and earlier studies, the Concrete Reinforcing Steel Institute concluded essentially that reworking of bars partially embedded in concrete entails some risk; that bars of #8 or smaller size can be successfully field bent or straightened at temperatures above about 32 degrees F; that bar sizes #9, #10, and #11 have a better chance of being successfully bent or straightened if the bend area is uniformly pre-heated to 1400 to 1500 degrees F and extreme care is exercised in the bending or straightening operation; and that the applicability of these conclusions to size #14 to #18 bars is uncertain.