A test portion of mass 350 ± 1.0 g of the 10/14 mm fraction of an aggregate is dried at 105 ± 5 ° C. This is placed in the impact tester and subjected to 15 blows of a hammer of mass 14.00 ± 0.02 kg falling from a height of 400 ± 5 mm. The test portion is then sieved on a 1.60 mm sieve, and the result of the test, the FD value, is the amount of the test portion that passes the sieve, expressed as a percentage by mass of the test portion.
The FD test that is the subject of this report is used in France. Several European countries (including Sweden, the Netherlands, and the UK) have similar tests. The equipment used for the test is portable and less expensive than the equipment required by other methods of measuring the fragmentation resistance of aggregates (such as the Los Angeles test, the Schlagversuch, or the Dutch Compression test). It is known that the support condition of the apparatus affects the results of the test, and that its reproducibility is poor. (It is common practice to fix the apparatus to a concrete block to reduce the influence of the support condition.) Because of its simplicity, the FD test, or tests like it, are used in aggregate production plants as production control tests. The FD test is included in the programme of cross-testing experiments so that its precision can be measured using the same three aggregates that have been used in cross-testing experiments on other mechanical tests, and so that its suitability as an indirect test can be assessed.
Participants in the cross-testing experiment were sent copies of the current French version of the method (AFNOR, 1990. P 18-574 Granulats. Essai de fragmentation dynamique).