Introducing a new specimen shape to assess the fatigue performance of asphalt mastic by dynamic shear rheometer testing

Abstract

Early failure of asphalt pavements is acommon issue all around the world. Damages arecaused by various reasons like insufficient binder oraggregate quality, an inadequate mix design orimproper handling in the production/constructionprocess. The effects of binder, aggregates and mixdesign have been widely studied and state-of-the-arttesting methods are available for both, hot-mix asphalt(HMA) and for each component. An important part inHMA belongs to the asphalt mastic, where nostandardized method is available to allow a qualitycontrol. Asphalt mastic is the mix of bitumen withaggregates smaller than 63 (125)lm and covers thecoarse aggregates as the actual binding component inthe mix. This research aims at developing a testingmethod for asphalt mastic based on fatigue tests. Thedynamic shear rheometer (DSR) was found as asuitable device for this purpose. The DSR fatigue testconsists of the 8 mm parallel-plate geometry widelyused for binder performance grading with a sampleheight of 3 mm. Instead of a cylindrical specimenshape, a hyperboloid of one sheet is applied. Thisshape predetermines the point of failure and preventsadhesion/interface failures between the mastic spec-imen and the upper or lower DSR stainless steel plate.The specimens are prepared directly in the DSRemploying a silicone mould to ensure an exactspecimen shape. This test can be applied to all DSRdevices without costly changes or additional equip-ment as long as sufficient cooling capacity and torquecan be provided from the DSR. This fatigue test makesit possible to assess the fatigue performance of bindersand mastic samples.