Innovative Testing Solution for Testing of Prestressing Steel

Prestressing steel is a high-strength steel that is used to pre-stress concrete, for example, for the building of bridges or high-rise constructions.

The steel can come in three different forms. Bar steel, wire and strands (of three or seven twisted individual wires). These forms place high demands on materials testing. ZwickRoell is delivering a Z330 testing machine to Indonesia for this purpose.

In addition to proper gripping, a particular challenge in testing these types of specimens is measurement of elongation up to break.

Parallel-closing hydraulic grips are used to grip the specimen. Through the testing software, the gripping pressure can be accurately adjusted to the specimen, which reduces the number of jaw breaks. Specially designed jaws for this application provide an optimal gripping surface and prevent the specimen from slipping during the test.

Strain measurement is carried out using the videoXtens 6-680. With a field of view of 680 mm and a resolution of 0.6 µm, this system provides the ability to precisely measure the elongation for both long gauge lengths (steel strands) and short gauge lengths (wire). Features at a glance:

  • Measurement of the yield strength to ASTM A1061
  • No damage caused to the extensometer at the point of break, since the extensometer measures without making contact.
  • Automatic determination of strain at break
  • Through connection to the crosshead, the gauge marks are always in the center of the field of view (FOV), making optimal use of the measurement range