This report gives the results of a cross-testing experiment on an impact test involving 20 French laboratories. The same three materials were used in this experiment as in other cross-testing experiments in the same programme on tests of mechanical properties of aggregates.
When assessed by the criterion that the reproducibility standard deviation should not exceed 8 % of the average, the impact test is found to be unsatisfactory for the purpose of assessing the compliance of aggregates with specifications that impose an upper limit on the results of tests.
It could be of use as an indirect test, for aggregates that meet specifications for mechanical strength by a wide margin, provided that allowances are made for the reproducibility of the impact test and for the uncertainty in the correlation between the impact test and the reference test.
The results of the experiment allow the precision of the impact test to be stated (in FD units) as:
r1 = 1.14 + 0.043 X
R1 = 3.14 +0.134 X
where "X" represents the average of the test results.