Rebar and Steel Testing: ASTM A615, A370, E8 and E290 Tensile and Bend Tests Explained
Steel mills, rebar fabricators and third-party labs run the same handful of tests over and over: full-section tensile tests and bend tests on reinforcing bar, tensile tests on plate and machined specimens, and Charpy impact tests. This guide walks through how ASTM A615, A370, E8 and E290 fit together, what each test needs, and the grips and fixtures that keep results valid.
How the standards fit together
ASTM A615 is the product specification for deformed and plain carbon-steel reinforcing bar. It sets the grades, the tensile and bend requirements and how often to test.
ASTM A370 gives the test methods for steel products in general: tension, bend, hardness and Charpy impact. Product specs like A615 point to it.
ASTM E8 is the core tension test method for metals: specimen geometry, strain rates and how to determine yield, tensile strength and elongation.
ASTM E290 covers bend testing of metals for ductility using guided, semi-guided and free bend methods.
ASTM E23 covers Charpy and Izod notched bar impact testing, called up by A370 when toughness is specified.
Rebar tensile testing to ASTM A615
Rebar is tested full-section, deformations and all, so the grips have to bite through the ribs without breaking the bar in the jaws. For Grade 60 bar, A615 requires a minimum yield strength of 60 ksi (420 MPa) and a minimum tensile strength of 90 ksi (620 MPa). Minimum elongation in 8 in. (200 mm) depends on bar size, from 9% for No. 3 to No. 6 bars down to 7% for No. 9 and larger. Check the current A615 table for other grades.
Testing frequency: A615 calls for one tension test and one bend test per heat for each bar size, at minimum.
Gauge marks: mark the 8 in. gauge length before testing so elongation can be measured after fracture.
Grips: use hydraulic or wedge grips with V-groove or rebar-specific inserts that match the bar diameter. Flat jaws on round deformed bar cause slipping and jaw breaks.
Capacity: a No. 18 Grade 60 bar at its minimum tensile strength already takes about 1,600 kN (360,000 lbf) to break, so large bar sizes need a high-capacity servo-hydraulic frame.
See our hydraulic wedge grips and servo-hydraulic universal testing machines for full-section rebar and bar testing.
Rebar bend testing to ASTM A615
The bend test checks that the bar can be bent around a pin of a specified diameter without cracking on the outside of the bend. For Grade 60 bar, the pin diameter grows with bar size:
No. 3 to No. 5: 3.5 × nominal bar diameter (d), bent 180°.
No. 6 to No. 8: 5d, bent 180°.
No. 9 to No. 11: 7d, bent 180°.
No. 14 and No. 18: 9d, bent 90°.
Other grades use different pin diameters, so check the A615 bend table for the grade you are testing. A bend fixture for rebar needs interchangeable mandrels and supports that let the bar wrap fully around the pin.
Our A615 rebar bend fixtures and guided bend fixtures cover the full range of pin diameters.
Bend testing metals to ASTM E290
E290 is the general bend-for-ductility method that many product specs reference. It covers three approaches:
Guided bend: the specimen is forced into a die or around a mandrel by a plunger, giving a controlled bend radius.
Semi-guided bend: the specimen is bent around a pin while held at one end or supported at two points.
Free bend: the specimen is pre-bent and then compressed between flat platens until it reaches the required angle.
For welded joints, ASTM E190 covers the guided bend test for weld ductility, with the weld and heat-affected zone placed in the zone of maximum strain.
Tensile testing steel plate and machined specimens to ASTM E8 and A370
When the product is plate, sheet, pipe or forgings, specimens are machined to the E8 (or A370) geometry. Key points:
Specimen type: rectangular specimens for plate and sheet, round specimens for bar and forgings. E8M round specimens use a 5D gauge length (62.5 mm for the standard 12.5 mm specimen).
Strain rate: Method B controls strain rate at 0.015 ± 0.006 mm/mm/min through yield, then 0.05 to 0.5 mm/mm/min to fracture.
Extensometer: needed for yield by the offset method. Class B-2 or better is typical.
Test temperature: room temperature tests run between 10 and 38 °C.
See the ASTM E8 page for specimen dimensions and grips, and wedge grips for flat and round specimens.
Charpy impact testing to ASTM E23
When a product spec requires toughness, A370 calls up Charpy V-notch impact tests per ASTM E23. Specimens are 10 × 10 × 55 mm with a 2 mm deep V-notch, tested at a specified temperature, and the absorbed energy is reported in joules or ft-lbf.
Common mistakes
Jaw breaks on rebar: inserts that don't match bar diameter concentrate stress at the jaw. A break in or at the jaw edge may need a retest.
Wrong bend pin: the pin diameter depends on grade and bar size. Using the wrong mandrel makes a pass or fail meaningless.
Too much speed through yield: E8 limits strain rate through yield. Going faster raises the measured yield strength.
Undersized frame: large rebar and heavy plate need the capacity and stiffness of a servo-hydraulic machine.
Steel and rebar testing FAQ
Is A370 or E8 the right tension test method for steel?
Use what the product specification calls for. Steel product specs such as A615 usually reference A370, which in turn draws on E8 for many specimen and procedure details. For non-steel metals, E8 is typically referenced directly.
Can I test rebar on an electromechanical machine?
Small bar sizes can be tested on a high-capacity electromechanical frame, but most rebar labs use servo-hydraulic machines with hydraulic grips because of the forces involved and the need to grip deformed bar firmly.
What grips do I need for rebar?
Hydraulic wedge grips with V-groove or rebar inserts sized to the bar diameter are the standard choice. Contact us with your bar sizes and grades and we will recommend grips, inserts and bend mandrels.
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