Standard rebar sizes can break at loads up to 2,000 kN (400,000 lbf), with some large higher-grade bars breaking at loads as high as 4,000 kN (800,000 lbf). Because of these high forces, we selected a hydraulically powered univeral testing system (
model 1000HDX) for this test. This SATEC™ Series frame provided the high capacity we needed and several nice options for testing large rebar samples.
We used the frame's open front, inhead wedge grips and a set of V-grooved jaw faces to secure the round rebar sample. The inhead grips allowed us to test up to full machine capacity. The jaw faces we selected were constructed from shock- resistant tool steel with a coarse tooth pattern. We've found that 8 to 20-teeth per inch works well for testing rebar. The coarse tooth pattern is necessary to bite into the irregular surface of the rebar samples and prevent specimen slippage. In contrast, we've found that a fine tooth pattern quickly becomes loaded with scale and debris. The jaw faces also include a mechanical stress relief on the initial portion of the tooth face to prevent premature failures.
To capture specimen strain during the test we used an extensometer specially designed for rebar testing. This extensometer is designed to be clamped to the irregular surface of rebar samples and supported the typical rebar gauge length of 200 mm (8 in). These extensometers are available in averaging and non-averaging styles and with other gauge lengths.
Finally, we used the tension template in Partner™ software to set up the test. The software prompted us for the test control, speed, break sensor, and results we needed.