This report provides the results of a cross-testing experiment on the Schlagversuch, carried out with the participation of sixteen laboratories in Germany. Three aggregates were used in the investigation - the same three aggregates that were used throughout the four-year programme of cross-testing experiments on European tests for the mechanical properties of aggregates.
The Schlagversuch is an impact test that has been developed in Germany. The draft European Standard that describes methods of measuring the resistance of aggregates to fragmentation gives the Los Angeles test as the reference test, and the Schlagversuch as the alternative test.
The experiment shows that the reproducibility of the Schlagversuch is satisfactory if it is to be used to check the compliance of aggregates with specifications that impose an upper limit on the test results. The results also show that it might be possible to improve the precision of the Schlagversuch. This would be of benefit for aggregates that give values close to specification limits, so it is recommended that the cross-testing experiments should be followed-up by regular proficiency testing.
It is concluded that the range of the determinations on three specimens from the same laboratory sample should rarely differ by more than 1.5 SZ units. It is recommended that laboratories should use this last value as a routine check.
The results of the European cross-testing experiment allow the repeatability of the Schlagversuch to be stated (in SZ units) as:
r1 = 0.350 + 0.0129 X
where "X" represents the level. The reproducibility appears to depend on the level as follows:
Level: X = 11.0 (SZ units)
Reproducibility: R1 = 1.1 (SZ units) Coefficient of variation CR1 = 3.7 (%)
Level: X = 21.6 (SZ units)
Reproducibility: R1 = 1.7 (SZ units) Coefficient of variation CR1 = 2.8 (%)
Level: X = 27.7 (SZ units)
Reproducibility: R1 = 3.4 (SZ units) Coefficient of variation CR1 = 4.4 (%)