Thermomechanical and microstructural evaluation of hybrid rubberised bitumen containing a thermoplastic polymer

Crumb Tire Rubber (CTR) modification of bitumen has been extensively proven that exerts a notable improvement the in-service properties. However, the problem of its inherent storage instability is a major concern that limits the industrial application. With this aim, here, Hybrid Systems were formulated by the addition of selected polymers (SBS, EBA, EBA and EPDMs) to a model rubberised bitumen (10 wt% CTR) and cured with sulphur. The resulting binders were characterised by Theological techniques, technological tests, Modulated Scanning Calorimetry and fluorescence microscopy. The results obtained pointed out that both, in-service properties and storage stability were notably enhanced by the development of a complex multiphasic structure of: polymer-rich and asphaltene-rich phases, non-degraded rubber particles and digested rubber chains. The capability of modification of the polymeric additives were established as follows: SBS > EBA > EVA > EPDMs. The Hybrid System containing SBS (HS-SBS) presented, by far, the best overall performance due to the development a continuous SBS-rich network structure as a consequence of sulphur crosslinking reactions. (C) 2017 Elsevier Ltd. All rights reserved.