Steel Rebar Grades — A Number Means Nothing Without Its Standard

ASTM A615 / A615M

Carbon-steel deformed and plain bars for concrete reinforcement. It is the standard that defines the familiar two-digit grade numbers, and it fixes minimum yield strength as the property those numbers denote.

How grades are written

Grades are expressed as tens of thousands of pounds per square inch of minimum yield, with a bracketed SI equivalent in the metric companion. The number and its bracket are one designation; the bracket is not a separate grade.

Bar form covered

Deformed and plain, in the sizes the standard tabulates.

• Grade 40 [280] — A 40,000 psi [280 MPa] minimum-yield designation under this standard.
• Grade 60 [420] — A 60,000 psi [420 MPa] minimum-yield designation under this standard.
• Grade 75 [520] — A 75,000 psi [520 MPa] minimum-yield designation under this standard.
• Grade 80 [550] — An 80,000 psi [550 MPa] minimum-yield designation under this standard.

ASTM A706 / A706M

Low-alloy steel deformed bars for concrete reinforcement, where controlled chemistry is directed at weldability and ductility. It is a different standard with a different purpose, not a higher tier of the previous one.

How grades are written

Grades use the same two-digit shorthand, but they are not interchangeable with the carbon-steel standard's grades of the same number — the chemistry requirements attached to them are what differ.

Bar form covered

Deformed bars, in the sizes the standard tabulates.

• Grade 60 [420] — A 60,000 psi [420 MPa] minimum-yield designation carrying this standard's controlled-chemistry requirements.
• Grade 80 [550] — An 80,000 psi [550 MPa] minimum-yield designation carrying this standard's controlled-chemistry requirements.

BS 4449 / EN 10080

Steel bars for the reinforcement of concrete under the British standard, with a European framework standard structuring how reinforcing steel is specified. Grades here are named by target yield strength in megapascals, with a ductility class attached.

How grades are written

A grade such as B500 is the target yield in MPa, and the trailing letter is a ductility class — a property in its own right, not a revision marker. Read the class as part of the designation.

Bar form covered

Deformed bars, in the sizes the standard tabulates.

• B500B — A 500 MPa target-yield designation carrying ductility class B under this standard.
• B500C — A 500 MPa target-yield designation carrying ductility class C under this standard.

JIS G3112

Deformed steel bars for concrete reinforcement under the Japanese standard, with its own grade and dimensional framework and its own declaration format on the certificate.

How grades are written

Grades are written as SD followed by the target yield in newtons per square millimetre — an entirely separate naming convention that does not map onto the two-digit shorthand.

Bar form covered

Deformed bars, in the sizes the standard tabulates.

• SD390 — A 390 N/mm² target-yield designation under this standard.
• SD490 — A 490 N/mm² target-yield designation under this standard.

Gap 1

The edition year is missing

A designation is published by a standard at an edition. Requirements, permitted chemistries and tolerances can and do move between editions, so a designation quoted without its edition is not yet a fixed requirement — it is a designation waiting for one.

A consignment that satisfies one edition being checked against another, which surfaces at inspection rather than at order.

Gap 2

The test package is unspecified

A designation fixes what properties the steel must have. It does not by itself say which tests will be run to demonstrate them, or on what sampling basis. Those are chosen by the specification, and they determine what the certificate has to contain.

Material that meets the grade being held at inspection because the evidence supplied does not match the package the project assumed.

Gap 3

The bar form has not been reconciled with the standard

Not every standard addresses every bar form. Where a project nominates a plain round bar under a standard written around deformed reinforcement, or the reverse, the form and the standard have to be reconciled before the designation can be relied on.

A designation confirmed against a standard that does not cover the form being ordered, discovered at the point of acceptance.