A comparison of different methods of analysing dynamic creep test results

The dynamic load creep test, provided that its precision is acceptable, has potential as an end product specification for quantifying the resistance to permanent deformation of bituminous roadbase and basecourse material. For this reason the test is being considered by the BSI panel B/510/1/WG2 for submission to the Comite Europeen de Normalisation for bituminous products. However, previous work involving testing material cored from the M53 and M56 motorways, as part of performance specification trials, has shown poor correlation between the mix variables and the results of the test when carried out according to the Draft for Development developed by the British Standards Institution (BS DD 185). This indicated that it would be impractical for a contractor to use the test to control the quality of his material. This report investigates some of the possible causes of the poor correlation and examines whether the correlation can be improved by analysing the data from the previous trials in different ways. The investigation did not identify a better method of analysing the data than that already defined in BS DD 185. The results of this limited study call into question the suitability of the test for compliance purposes. (A)