In a previous paper presented at the 2008 E&E Congress, the French mirror group (BNPé/P04/GE1) of the CEN/TC336 WG1 committee (bituminous binder) has reported the results of a round robin test on DSR complex modulus measurements involving two paving grade bitumen (10/20 and 50/70 classes) and three modified binders (plastomer, elastomer and cross-linked elastomer). This paper presents the outcome of the follow-up studies which had been decided at the time. In a first step, a number of dedicated investigations have been made to identify the potential contribution of different factors to the variation in measurement results. In particular, the impact of waiting time after test sample preparation, gap setting procedure, bonding temperature, conditioning times and temperature sweep procedure have been investigated. How to establish the limits of the linear domain of visco-elasticity is another issue which has been dealt with. This has allowed to define more stringent operating conditions which have then been followed by the participating laboratories for a final round robin limited to a pure bitumen (50/70) and the most difficult PmB (high level of plastomer modified product). In comparison to the first round robin, reproducibility was indeed improved, even for the modified product. The BNPé/P04/GE1 work does thus further open the way for the definition of binder performance indicators based on DSR measurements. This will however only be possible (especially for modified binders) if operating conditions are strictly defined and followed.
Measuring the rheological properties of bituminous binders final results from the round robin test of the BNPÉ/P04/GE1 Working Group (France)