Investigation on the Ageing Behaviour of High-Modulus Modified Bitumen Based on Rheological and Chemical Approaches

With outstanding resistance for permanent deformation, high-modulus modified bitumen (HMB) has garnered widespread attention in recent years and has been employed in the construction of bitumen pavements across various regions. However, limited research exists on the ageing behaviour of HMB, and conventional short-term ageing protocols for bitumen may not be applicable to HMB due to its exceptionally high viscosity. Therefore, this study aims to assess the ageing behaviour of HMB and propose a suitable short-term ageing process for HMB utilizing dynamic shear rheometer (DSR) and gel permeation chromatography (GPC) approaches. For comparison purposes, the ageing behaviour of a type of SBS-modified bitumen and a kind of base bitumen were also analyzed. Initially, the study involved a comparison of the properties of bitumen subjected to short-term ageing at various temperatures and those of bitumen within mixtures undergoing short-term oven ageing tests. Subsequently, both the chemical and rheological properties of bitumen under diverse ageing conditions were examined. Finally, investigations were conducted to establish relationships between rheological properties and the molecular weight distribution of HMB. The reported results indicate that the suggested ageing temperature for the thin-film oven test (TFOT) should be increased to 193 °C for HMB, achieving a more accurate simulation of short-term ageing in HMB mixtures during on-site mixing, transport, and paving processes. Compared to base bitumen and SBS-modified bitumen, HMB exhibits superior ageing resistance. Furthermore, the molecular weight distribution of HMB is strongly correlated with its rheological properties. This correlation offers a promising approach to predict the rheological properties of bitumen in HMB mixtures by directly analyzing the chemical molecular weight distribution of the binders, thereby eliminating the need for an extraction process.