Testing of industrial products - Aggregates for construction

Micro-Deval Test - Summary

This report gives the results of two cross-testing experiments on the micro-Deval test, a "European" experiment involving 20 laboratories from 11 countries, and a "French" experiment involving 37 French laboratories. (Two of the French laboratories are included in both experiments.) The three materials that were used in these experiments are to be used throughout the four-year programme of cross-testing experiments involving tests of the mechanical properties of aggregates.

The results of the experiment show that the reproducibility of the micro-Deval test is adequate for it to be used to check the compliance of aggregates with specifications that impose an upper limit on the result of the test. The results also show that it should be possible to improve its reproducibility. As this will be beneficial to aggregates that give results close to specification limits, it is recommended that the cross-testing experiments should be followed-up, in those laboratories that gave the highest and the lowest average results, by comparisons of equipment and procedures, and by experiments to identify the causes of laboratory biasses.

It is concluded that the repeatability of the test is such that the results of tests on two test specimens from the same laboratory sample should rarely differ by more than 1.0 (MDE units).

The results of the "European" experiment allow the precision of the micro-Deval (MDE) test to be stated (in MDE units) as:

r1 = 0.893 + 0.003 X and R1 = 0.260 + 0.137 X

where "X" represents the average of the test results.