Determination of crack bridging properties

At the RMI the test method of crack bridging can be offered again.

Determination of crack bridging properties

Since December, crack-bridging properties of coating materials and coating systems for exterior masonry and concrete have been determined at the Dr. Robert-Murjahn-Institute again. This property describes the ability of a coating to overcome strains caused by a crack in the substrate.

After the successful reconstruction of the servohydraulic testing machine and the renewal of controller and software, various systems can now be precisely checked. For example, the tests may be carried out in accordance with the European Standard 1062-7, according to the Directive of the German Committee for Structural Concrete, according to the admission principle of the DIBt or even according to customer requirements.

A climatic chamber envelops the testing machine, which covers a range from ambient temperature to -20 °C.

Following procedures can be performed:

Ø  Static crack bridging in which the cracks from the ground are continuously widened e.g. on facade paints and protective coatings

Ø  Dynamic crack bridging in which periodically trapezoidal crack opening cycles are superposed with sinusoidal load changes e.g. on coating systems for car parks.

The test setup for dynamic crack bridging is shown as an example in the figure below.

Afterwards, the mechanically stressed samples are examined for their leak tightness. Therefor the cracked coating is treated with aqueous fluorescein-sodium solution for 24 hours. Leaking areas are thus made visible by means of UV light. Using a reflected-light microscope, it is possible to obtain final clarity about separations, top or bottom incipient cracks of the protective layer or even through-thickness cracks.

If you have any questions please don’t hesitate to contact

Mr. Michael Vonrhein                                                       Mr. Philipp Kröber

(+49)6154-71-71378                                  or                    (+49)6154-71-72495

michael.vonrhein(at)                                           philipp.kroeber(at)


Abbildung/figure: Prüfaufbau der dynamischen Rissüberbrückung / Setup of the dynamic crack bridging