Frequently Asked Questions
Q:
Is Rust Ok?
A:There are a number of things that can get onto the surface of rebar and affect the bond strength between the rebar and concrete. Oil and grease need to be wiped off with a solvent. Dirt and mud can be washed off or cleaned off using a wire brush. However, rust, mill scale, and surface irregularities actually increase the bond because they increase the roughness of the rebar. So yes, rust is OK... except if there is so much rust that the weight, dimensions, or cross-sectional area of the rebar have reduced to below the minimum specified by the material standard. |
Q:
Is it okay to bend or to re-bend reinforcing bars in the field?
A:The bending or rebending of steel reinforcing bars in the field is one of the most common and one of the most controversial procedures that frequently come into question related to cast-in-place reinforced concrete construction. These situations may arise as the result of unplanned occurrences (when rebar is accidentally run over by a vehicle, for example), because of on-site corrections and adjustments, or as intentional building changes. The best advice for dealing with these situations is to always involve the architect/engineer and to follow the guidelines presented in the ACI 318 Building Code (Section 7.3.2), and the ACI 301 Specification (Section 3.3.2.8). |
Q:
Will bending or rebending reinforcing bars in the field weaken them?
A:Basically, no. Those concerned about the resulting mechanical properties should consult the test results summarized in the accompanying table (see below). [insert table on Field Bending and Straightening of Reinforcing Steel] K. Babei and N.M. Hawkins, "Field Bending and Straightening of Reinforced Steel," Concrete International, 1992. |
Q:
What about cutting reinforcing bars in the field? Is that okay?
A:Field cutting may be required when design changes or errors in detailing, fabrication, or placement create extra length in bars that are either stockpiled or already embedded in concrete. Smaller-sized reinforcing bars, #10, #13, and #16, for example, may be cut with bolt cutters. Bar sizes #19 and larger may be cut with either an abrasive saw or, more often, with an oxy-acetylene torch. |
Q:
Will flame cutting affect uncoated reinforcing bars?
A:Recent tests have demonstrated that oxy-acetylene flame cutting of reinforcing bars has virtually no effect on the material properties of the bar, affecting only 3/16 inch from the cut end. Flame cutting of epoxy-coated bars, however, is not recommended. |
Q:
Can epoxy-coated bars be flame-cut?
A:No, using this procedure on epoxy-coated bars is not recommended. Use flame cutting on uncoated reinforcing bars only. Also, the ends of epoxy-coated bars that are cut with either bolt cutters or an abrasive saw should always be treated with coating material provided to repair damaged coating. |
Must-Have Resources
Technical Note (CTN-G-2-10): Frequently Asked Questions (FAQs) about Reinforcing Bars (PDF Download, myCRSI)
CRSI's technical staff receives numerous inquiries about cast-in-place reinforced concrete construction. This report provides answers to the most commonly asked questions. Replaces EDR 44.
