Test Standard Category

DUCTILITY AND ELASTIC RECOVERY


Different bitumen properties can be analyzed thanks to the use of a Ductilometer, a machine capable of applying a sample elongation at a fixed speed.

1) Ductility:

The ductility is a measure of tensile properties of bituminous materials.

It is measured by the distance to which a bituminous material will elongate before breaking when two ends of a briquet specimen of the material are pulled apart at a specified speed and at a specified temperature. The specimen will be continuously immersed in water, while the two clips are pulled apart at a uniform speed.

2) Elastic Recovery:

The elastic recovery of a bitumen is expressed as a percentage of the distance between the ends of the half-threads, which has developed 30 min after the division relative to the elongation length of 200 mm. 

A bitumen specimen is stretched at a temperature of 25 °C and a constant rate of 50 mm/min to a predetermined elongation (200 mm). The bitumen thread thus produced is cut in the middle to obtain two halves of thread. After a predetermined time for recovery has elapsed, the shortening of the half threads is measured and expressed as the percentage of the elongation length. This value is especially applicable to bituminous binders modified with thermoplastic elastomers.

3) Deformation Energy:

The deformation energy is the energy supplied by test pieces, until a certain displacement of the moving element is achieved. For each test specimen, the energy calculation is accomplished from the computerised data of couples force/elongation. 

Appropriate ductilometer permits the following measurements to be made:

  • tensile force exerted on the specimen, by calibrated load cells;
  • elongation of the specimen, by following the movement of the attachment points.
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