4.1 Reinforcing Steel Specifications, Bar Sizes & Mill Markings (ASTM A615, A706, A996)

4.1 Reinforcing Steel Specifications, Bar Sizes & Mill Markings

Before placement, compare the approved schedule and bar list with the physical reinforcement and the manufacturer's records. Model IBC Table 1705.3 lists reinforcement and placement as periodic special inspection. A bar's size, material standard and grade answer different questions. A substitute with the same nominal yield strength can still have different tensile, elongation or welding requirements.

Identify the applicable steel specification

ICC lists A615/A615M-04 through -16 and A706/A706M-05a through -16 as 47C reference options. The examples below use the -16 editions. Apply the specified edition and the code limits for the actual member and reinforcement function.

ASTM A706/A706M-16 Table 2 sets Grade 60 yield at 60 to 78 ksi and Grade 80 yield at 80 to 98 ksi. Their minimum specified tensile strengths are 80 and 100 ksi respectively. The measured tensile strength must also be at least 1.25 times the measured yield strength. For A706-16 Grade 60, the 8-inch fracture elongation minima are 14% for No. 3–6, 12% for No. 7–11 and 10% for No. 14 and 18. Grade 80 has its own table values. The material specification's carbon-equivalent cap is a product requirement. Weld acceptance also depends on the procedure, bar size and conditions.

Use nominal dimensions

These are common inch-pound nominal values from the ASTM bar tables. For a No. 8, $8/8=1$ inch. Use 1.128 inches for a No. 9 from the table. Caliper measurements over deformations are not nominal diameter. Check ACI 318-19 Sections 25.5.1.1 and 25.5.5.3–.4 before accepting a detail involving No. 14 or No. 18 laps. The allowed compression transition is covered in Section 6.1 of this guide.

Read markings and trace the delivery

ASTM A615/A615M-16 and A706/A706M-16 Section 19 identify the mill, bar size, steel type and grade where required. A mill symbol followed by 8, W and 60 identifies a No. 8 A706 Grade 60 bar. Under A615-16, an offset single grade line identifies Grade 60, two identify Grade 75, three identify Grade 80, and Grade 100 can use four lines, 100 or C. Numeric designations also apply to the other marked grades. Grade 40 under A615-16 has no required grade mark. Use the applicable marking diagram when distinguishing grade lines from the ordinary ribs. Where dual marking is permitted, the letters S and W indicate both specifications. Verify the supporting records before accepting material.

Match bundle heat or test identification with the material test report and the rolled marks with the approved size, grade and steel type. Confirm the results required for the application, such as yield, tensile strength, elongation, bend testing, and chemical composition or carbon equivalent where applicable. Retain traceability as bundles are separated. Report a mismatch and verify the disposition through the inspection process.

Verify special seismic material separately

ACI 318-19 Section 20.2.2.5 governs the stated earthquake-resisting deformed longitudinal reinforcement and anchor reinforcement applications. Its A706 route allows Grades 60, 80 and 100 for special structural walls and Grades 60 and 80 for special moment frames, subject to the applicable design provisions. This is a design-code allowance. The A706-16 product edition shown above lists Grades 60 and 80.

For the A615 Grade 60 route under Section 20.2.2.5(b), all four checks apply. Actual yield may exceed specified yield by at most 18 ksi. Actual tensile strength divided by actual yield must be at least 1.25. Minimum fracture elongation in 8 inches is 14% for No. 3–6, 12% for No. 7–11 and 10% for No. 14 and 18. Minimum uniform elongation is 9% for No. 3–10 and 6% for No. 11, 14 and 18. The two elongation measurements have different purposes and both are required.

For a No. 8 A615 Grade 60 bar proposed for this route, an actual yield of 74 ksi and tensile strength of 96 ksi give a 14 ksi yield overage and a ratio of approximately 1.30. If its fracture elongation is 13% and uniform elongation is 8%, it misses the 9% uniform requirement. Report the deficiency even though the strength results meet the stated criteria.