The CBR test - California Bearing Ratio

Since 2008, the dynamic CBR test (California Bearing Ratio) according to TP Gestein-StB Part 5.6 has been undertaken in the laboratory on crushed samples with a maximum grain size of 22 mm and with an oversize portion of not more than 50% as a rule. This test can also be used as an alternative to the static CBR test according to TP BF - StB Part B 7.1 [1]. 

Due to the short time required, it is used above all during in-house monitoring tests for production control during the manufacture of mineral aggregate mixtures from steel slag. Advantageous in comparison to the CBR test according to TP BF - StB Part B 7.1 [1] is the elimination of the need for the loading frame and the related static loading device.

More interesting details you can find on Wikipedia. 

The CBR value

The dynamic CBR value is a complex strength characteristic that is dependent on the strength, the grain shape, the frost resistance and the grain roughness of the individual grain, the grain composition, the fines content, the water content and the compaction of the mineral aggregate mixture.

It can be used, e.g., to assess the sensitivity to frost or to estimate suitability for traffic and the compactability, as well as the load-bearing capacity of the mineral aggregate mixtures laid.


In field trials, the dynamic CBR test is carried out on undisturbed samples, whilst in laboratory trials it is performed using a Proctor pot. Among other things, it assesses

  • recycled materials, steelworks slag and fly ash,
  • tests installed and compacted recycled concrete,
  • determines the compaction work by comparison with the laboratory test and
  • serves as evidence of soil improvement or soil stabilisation on site.

How do you turn a ZORN ZFG Light Weight Deflectometer into a Dynamic CBR testing device?

This video shows the conversion from the standard ZFG (LWD) to the CBR configuration. Step by step and designed so that the user can perform the conversion independently.

For our CBR flyer and data sheet please have a look to the download area.

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