Because concrete has high compressive strength but lower tensile strength, it is reinforced by steel embedded in it. Reinforcing steels are mainly produced in diameters from approx. 5 mm to approx. 60 mm. The smaller diameters are
then further processed into mats or lattices before having concrete
poured over them on site. Testing these ribbed steels poses a particular
challenge because apart from cutting to length, no further mechanical
specimen preparation takes place. The on-specimen strain measurement
required for precise determination of the yield point is predominantly
performed using the Macro extensometer, which records the strain up to break reliably with no detrimental effects to itself.

The Macro extensometer has the following features:

• High robustness for measurements up specimen failure
• Swivelling knife-edge on sensor-arm tip
• Automatic attachment and removal of sensor arms to/from specimen
• Large diameter range
• Fully integrated into automatic test sequence
• No manual operation necessary
• Optional automatic withdrawal from specimen area