The CBR test

The dynamic CBR test (California Bearing Ratio-test) is performed in the laboratory on crushed samples whose maximum grain size is 22 mm and whose sieve residue is normally not more than 50%. This test can be performed as an alternative to the static CBR test to Technical Test Requirement for Soil and Rock in Road Construction (TP BF - StB Part B 7.1 [1]). It is used in particular due to the short time required as a quick-testing method as part of in-house monitoring tests for production control during the manufacture of mineral aggregate mixture from steelworks slags. Advantage compared with the CBR test to TP BF - StB Part B 7.1 [1] is the elimination of the need for a loading frame and the associated static loading device.

The CBR value

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

It serves e.g. for checking the frost resistance or to estimate the ride qualities and compactability as well as the load-bearing strength of the laid mineral aggregate mixtures.

CBR laboratory test, dynamic
CBR laboratory test, dynamic
CBR-field trial, dynamic
CBR-field trial, dynamic

The CBR test

The dynamic CBR test can be performed as an alternative to the static CBR test to Technical Test Requirement for Soil and Rock in Road Construction TP BF - StB Part B 7.1 [1]. It is used in particular due to the short time required as a quick-testing method as part of in-house monitoring tests for production control during the manufacture of mineral aggregate mixtures. Advantage compared with the CBR test to TP BF - StB Part B 7.1 [1] is the elimination of the need for a loading frame and the associated static loading device (compression test machine).