Field Inspection of Rebar - Page 4

    Welded splices of rebar to rebar present the same difficulty of inspection as welded structural steel connections. As mentioned previously, the location should be shown by the engineer or architect. The type most often used is the electric shielded arc weld. The Structural Welding Code - Reinforcing Steel, AWS D1.4 is usually specified as governing rebar welding procedures. The inspector should review the mill test report to determine the carbon equivalent (C.E.) and the preheat requirements. The inspector should verify the welder's certification, make certain that the correct electrodes (oven dry) are available, and that the preheat temperature crayon sticks are at hand. Continuous inspection is usually specified to ascertain that the welder uses the proper number of passes, controls the interpass heat loss, and uses a wire brush and chipping hammer to get rid of any slag.
    For some projects, the engineer will specify radiographic inspection of the welded splices. This procedure is time consuming and costly, and is frequently inconclusive. More often a specimen taken at random is removed for a laboratory tension test and analysis.
    The inspector should not allow tack welding of rebar to rebar even if low-alloy steel reinforcing bars conforming to ASTM A706 are specified. Tack welding can cause a metallurgical notch which reduces strength and can also have a detrimental effect on ductility and fatigue resistance. Tack welding is not a substitute for tie wire.

CONCLUSIONS
    All the foregoing seems to indicate that the inspector has a formidable assignment when inspecting in-place reinforcing steel. This is not necessarily true, but it is an exacting task, one that assures the workers perform their job to the best of their ability. However, mistakes can and will happen, but an inspector is expected to find them and have them corrected. All persons involved in a building project, from designer to constructor, attempt to do error-free work. A quality control program by the contractor helps in achieving this goal, which makes final inspection easier. The inspector should not perceive his job as adversarial, but as supplementary to the workers in support of good construction techniques and practice. Good inspection is insurance of a properly built structure, one which all involved in can take pride.
    For further information on inspection, tolerances, industry standard practices, fabricating, placing, mechanical splices, and welded splices consult the following references.

REFERENCES

"Standard Specifications for Tolerances for Concrete Construction and Materials (ACI 117-90)," American Concrete Institute, Farmington Hills, Michigan.

ACI Detailing Manual - 1994, Publication SP-66, American Concrete Institute. Includes "Details and Detailing of Concrete Reinforcement (ACI 315-92)."

"Building Code Requirements for Structural Concrete (ACI 318-95) and Commentary (ACI 318R-95)," American Concrete Institute.

"Specifications for Structural Concrete (ACI 301-96)," American Concrete Institute.

"Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement (A615/A615M-96a)," ASTM, West Conshohocken, Pennsylvania.

"Standard Specification for Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement (A706/A706M-96b)," ASTM.

"Standard Specification for Rail-Steel Deformed and Plain Bars for Concrete Reinforcement (A616/A616M-96a)," ASTM.

"Standard Specification for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement (A617/A617M-96a)," ASTM.

"Standard Specification for Epoxy-Coated Reinforcing Steel Bars (ASTM A775/A775M-97)," ASTM.

"Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars (A934/A934M-97)," ASTM.

"Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement (ASTM A767/A767M-97)," ASTM.

"Standard Specification for Deformed and Plain Stainless Steel Bars for Concrete Reinforcement [Metric] (A955M96)," ASTM.

"Standard Specification for Welded or Forged Headed Bars for Concrete Reinforcement (A970/A97OM-98)," ASTM.

Manual of Standard Practice, 26th Edition, 1997, CRSI.

Placing Reinforcing Bars, 7th Edition, 1997, CRSI.

Reinforcement Anchorages and Splices, 4th Edition, 1997, CRSI.

"Field Corrections to Rebars Partially Embedded-in Concrete;' Engineering Data Report No. 12, CRSI.

"Using Soft Metric Reinforcing Bars in Non-Metric Construction Projects," Engineering Data Report No. 42, CRSI.

Structural Welding Code-Reinforcing Steel (ANSI/AWS D1.4-98), American Welding Society, Miami, Florida.

This publication is intended for the use of professionals competent to evaluate the significance and limitations of its contents and who will accept responsibility for the application of the material it contains. The Concrete Reinforcing Steel Institute reports the foregoing material as a matter of information and, therefore, disclaims any and all responsibility for application of the stated principles or for the accuracy of the sources other than material developed by the Institute.