Letter to the Editor: On the thermorheological complexity and relaxation modes of asphalt cements

The interpretation of dynamic mechanical measurements on asphalt cements (A Cs) has become quite controversial in the past decade. The questions remain whether ACs are thermorheologically simple and whether they exhibit more t han one relaxation mechanism. An increasing literature debates this issue, for it has crucial implications about the structure of ACs and is, therefor e, of prime importance for the development of highperformance paving-grade binders such as polymer-modified asphalts [Lesueur et al., J. Rheol. 42, 10 59-1074 (1998)]. This letter comments on the results reported in a recent p aper by Stastna and Zanzotto [J. Rheol. 43, 719-734 (1999)] in order to sho w how their data can be interpreted in the light of other results and evide nce found in the literature.