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Testing on Asphalt

Tests on Asphalt

Asphalt used for road coverings is subject to changing stresses caused by environmental influences and loads imposed by goods vehicles, leading to constantly increasing demands on the materials used in road construction. Intensive development work is taking place on new formulations and additives for asphalt mixes. These must be tested for suitability; the main area of interest here is the change in properties due to dynamic loads. Dynamic test methods are also used for continuous quality control.

European asphalt mixture producers are required to test their various mixture types in accordance with unitary standard EN 12697 in order to obtain the mandatory CE mark. Parts 24, 25 and 26 of this standard define different dynamic test methods. These are implemented in national test standards such as the Technical Testing Standards of the German Research Association for Highway and Traffic Engineering (FSGV). Different European countries favor different test methods, resulting in a variety of test devices being required.

Zwick’s response to this situation was to develop a flexible servo-hydraulic testing system equipped with the necessary test fixtures and appropriate testing and evaluation software.

The asphalt testing system is based around a specially adapted load frame from the HB range. Mounted on the upper fixed crosshead is a testing actuator with hydrostatic bearings, servo valve and hydraulic accumulator unit. A load cell with accelerometer is installed on  the piston rod of the testing actuator. The testing system is available for test loads up to 10 kN, 25 kN and 50 kN. As all tests must be performed at defined temperatures, a temperature chamber with cooling unit is also available. The temperature chamber is mounted on guide rails and can simply be pushed back out of the way to facilitate installation of test fixtures.

Measurement and control electronics are in the form of HydroWin 9610, which has a data acquisition frequency of 10kHz combined with a resolution of 19 bits. The required test sequences are performed via the user-friendly Workshop software with dynamic analyser and sequence scripts developed in-house. The test data are stored in ASCII format. Excel programs which import and evaluate test data from all individual tests at the push of a button are available for standard-compliant evaluation of complete test series.

The devices developed specially for the asphalt testing system open up a range of flexible testing options.