Tensile Testing Rebar

Steel reinforcing bars or rebar is used in concrete construction to enhance tensile strength, complementing concrete's excellent compressive properties. Rebar also helps maintain structural integrity as concrete cracks from expansion and contraction cycles. The tensile strength of rebar steel and the tensile rebar-concrete bond strength are extremely important properties of rebar.

Tensile tests are the most popular type of test for testing rebar. Other tests include bend tests and fatigue tests. Tensile testing of rebar is relatively straightforward. No modifications to the material geometry are required as lengths of the actual rebar are used to determine the strength and elongation of the rebar.

Testing the concrete-rebar bond strength is a more involved process because reinforced concrete samples must be poured and cured, ensuring a consistent bond length between samples. The concrete specimens are then secured and a tensile load applied by clamping and pulling on the exposed rebar end, using a test machine.

Rebar Tensile Test Equipment

At TestResources, we market, sell and support our test machines out of our factory in Minnesota using advanced internet capabilities. We do not have expensive field sales and service offices everywhere around the USA and the world. This is a lower cost and more effective way of serving you. You can work directly with our best technical experts out of our factory in Minnesota. We can serve you via remote operation of your test machine over the internet for fast diagnosing of any problem and for low-cost, effective training. This saves money, and we pass those savings onto you.

This series is designed so that you can buy just what you need for your current testing needs. As your needs grow it is easy and affordably upgradeable in the field. This enables us to build our machines at a lower cost than our competitors. We recommend using one of the following high force test machines for tensile and bend tests of rebar. First determine test machine and grip mechanical load capacity based on the maximum and minimum sample sizes and their grades.This information will impact the machine size you will need. Large samples break at higher loads and high sample grades require high loads. The equipment you need depends on your test requirements, space, preferences and budget.

Our 300 Series electromechanical test machine (suggested for #2 through #6 rebar) offers floor mounted models that range from 100 to 500 kN (22 to 112 kip). The 300 Series test machine has a single crosshead which can travel the entire vertical length of the machine. The test machine performs tensile testing by having the crosshead move upward and compression tests, including bend tests, have the crosshead moving downward. These test machines generally are more universal and can handle more applications than 600 or 900 series machines. And offer load frames that test at lower forces, featuring longer strokes and a broader range of test speeds. The 300 series test machines can accommodate a wider range of tensile grips, bending fixtures and other accessories. Smaller rebar can be tested and both hydraulic side opening grips and wedge grips are available. Electromechanical test machines are quiet, clean, smooth and extremely accurate. A wide range of grips and fixtures for rebar testing applications are available.

Hydraulic Wedge Grip for Tensile Testing Rebar

Our 600 Series electrohydraulic test machine (suggested for all rebar up to #14) offers a force range from 300 kN to 2 mN (67 kip to 450 kip). The 600 Series electrohydraulic systems offer higher force capacity and is budget friendly. This test machine has two crossheads. The crosshead in the middle of the machine is stationary. The actuator is at the base of the machine. The tensile specimen is mounted in the upper part of the grips that are included with the machine. The 600 series features a tensile test space with integrated wedge grips and a separate compression test space for bend tests. Dual test space frame eliminate the need to swap out test fixtures from one test to the other. The bend test specimen is mounted in the lower part of the machine. Due to the high force of these machines, it is extremely important to make sure you use the proper configuration for both the safety of the operator and the test specimen. Safety enclosures are available for added safety.

If you want an electromechanical machine or you already own one, then you need to consider grips or fixtures for rebar testing. Grip design changes dramatically from the low force range to the high force range for this type of testing. For example, at the highest force testing you most likely need hydraulic grips with super hardened jaws and at the lower end you can manually clamp the jaws with a good stout wrench. Because high force grips are robust and rather large, it is not easy to change. Some machine designs allow for interchangeable grips while others do not. Unlike lower force machines, the weight of the grips and fixtures is significant on high force tests. Depending on the test, grips can have different mass and this tare weight can impact the results and might not be appropriate for a selected load cell. TestResources’ offers a solution, our controllers have tare weight adjustment to address this weight issue.

Rebar test samples can be taken from large coils of bulk material. Since the material is coiled, the samples need to be straightened out prior to testing. The straightening process is not perfect, resulting in samples that are slightly bent. Hydraulic side action grips with spherical seat jaws improve sample alignment, reducing the chances of premature failure of the sample by reducing the potential for high stress concentrations as a result of the bent specimens. This also reduces the potential harm to the grip by reducing the amount of side loading on the grip itself. Hydraulic side action grips are also ideal for the testing of rebar couplers as prescribed in AC133, as well as other cycling tests. Contact TestResources’ experienced engineers to discuss the details of gripping requirements for your specific application.

Depending on the scope of the test, rebar extensometers may or may not be required. Rebar extensometers can differ from rebar coupling extensometers and wire strand extensometers. For instance, many higher grades of rebar do not exhibit a distinct yield point. In these cases it is usually necessary to determine the yield strength from the offset method. This requires measuring strain with an extensometer and plotting a stress-strain curve from which a 0.2% offset yield strength can be determined. We will help you figure out what you need and don’t need. Contact us today and one of our applications engineers will quickly help you configure your machine or confirm your selections.

Application Standards

ASTM and other industry standards organizations have specified standard test methods to test the tensile properties of steel reinforcing bars. Our test machines and and rebar accessories can be configured to meet specific ASTM, ISO, DIN, EN requirements.

Common Test Standards:

These methods attempt to simulate the use of rebar in construction and measure the strength in these conditions. Popular test standards are ASTM A370 for steel products and ASTM A944 for the bond strength of steel rebar and concrete. Machines and tensile grips for tensile testing of steel reinforcing bars must be capable of applying very high loads. Based on ASTM specifications for various grades of rebar, the ultimate tensile strength to break rebar can range from 50 kN (11 kip) to 600 kN (135,000 lbf) for one size of rebar. We work with you to reduce the risk of selecting the wrong machine by performing trial testing when appropriate or necessary to save time and help you improve your ROI (Return on Investment).

Recommended Test Machines

Recommended Testing Accessories

Already have a hydraulic test machine? TestResources can help you get your current system ready to test rebar by upgrading your existing equipment by simply upgrading your controls, software or by upgrading to the right specimen grips or fixtures. This can be an extremely cost effective solution if you have a tight budget. Contact TestResources’ application engineers today to discuss your options.