Analysis of binary Bitumen – Polymer mixtures

Abstract

Bitumen is a black material composed of a mixture of various natural hydrocarbons. Bitumen has been commonly used in road paving and roofing applications thanks to its hydrophobic and adhesives properties. The production of Polymer Modified Bitumens (PMB) has allowed the development of materials with better performance in comparison to pure bitumen. This work presents the effect of addition of polymer to a Colombian bitumen from its morphological, rheological and thermal properties, in order to identify different modification levels. The polymers used as modifiers were polyethylene wax (CPE), styrene butadiene styrene (SBS) and crumb rubber (CR). They were added to bitumen in proportions between 3 to 15% w / w. Both neat bitumen and PMB were characterized by penetration and softening point. Thermal and rheological characteristics were analyzed by differential scanning calorimetry (DSC) and rotational rheometry, respectively. Changes in the morphology were measured by atomic force microscopy (AFM). The experimental results showed that the CPE mixtures had the most pronounced effect on the conventional properties, achieving a 75% reduction in penetration and a 250% increase in the softening point compared to neat bitumen. The results obtained by DSC allowed identifying three glass transition temperatures (Tg) in neat bitumen. Mixtures with SBS altered Tg, showing changes on the thermal characteristics of neat bitumen. Mixtures with CPE and SBS showed the highest values of G*. The results obtained by AFM help identifying three different phases in neat bitumen and its variation with the addition of different polymer modifiers, showing considerable structural changes that led to changes in the material properties at the macroscopic level.