Paving the way with Zwick new asphalt tester

Zwick has developed a servo-hydraulic testing system so that building materials can be tested under circumstances that simulate the effects of parking and moving vehicles.

Asphalt is a composite material mainly used for the construction of roads, pavements and parking lots.

Mineral aggregates and binder are mixed and placed in layers then compacted.

The method of manufacturing has been relatively unchanged for many years, and as a result the empirical values determine the essential features concerning deformation behaviour, liability of cracking, fatigue resistance, ageing characteristics and adhesiveness.

The European EN 12697 Standard now makes it possible to directly test the properties of the asphalt.

In addition to static testing procedures, dynamic tests are especially required since the asphalt is often subject to dynamic strain from rolling tyres.

To address this requirement Zwick has developed a servo-hydraulic testing system complete with all necessary tooling and equipped with the latest software so that building materials can be tested under circumstances that simulate the effects of parking and moving vehicles.

The asphalt testing system is based on the recently developed HB10 load frame, with the hydrostatic actuator, servo-valve and pressure accumulator unit mounted on the upper fixed crosshead.

The load cell with its accelerometer is installed directly onto the actuator.

A temperature chamber with cooling unit is equipped for environmental testing, and the temperature chamber is mounted on a rail system which reduces the time taken to change machine configurations.

A large selection of special equipment enables flexible testing.

For example:.

- Indirect tensile test (dynamic disk test) for the determination of maximum tensile strength, maximum strain and fracture characteristics according to EN 12697-24.

- Dynamic stamp indentation test for the determination of permanent deformation and creep according to EN 12697-25A.

- Cylindrical tri-axial test according to EN 12697-25B for the determination of permanent deformation, creep, dynamic inherent stability and phase loss angle.

- 4-point flexural-type test according to EN 12697-24 for the determination of dynamic flexural stiffness and fatigue resistance.

Zwick's proven HydroWin 9610 system is used as the measurement and control electronics, and this offers a measurement data capture frequency of 10 kHz and a 19 bit resolution.

The required test sequences are produced and evaluated with user-friendly workshop software with dynamic analyser and profile software.

The measurement data can be transferred to an MS Excel programme in ASCII format making it easy for the user to format the presentation of the test reports.

The testing machine can both be used for the testing of the suitability of new materials as well as the evalution of finished goods.

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