Glass transitions in bituminous binders

Abstract

The RILEM TC 272 PIM (Phase and Interphase behavior of innovative bituminous Materials)—TG1 Binder has initiated an inter-laboratory program investigating the phase and interphase behaviour of bituminous binders. Within the scope, four laboratories evaluated the low temperature properties of seven binders with differential scanning calorimetry (DSC). DSC has been accepted as a powerful tool to evaluate, among others, the glass transitions, Tg, monitoring the endothermic or exothermic heat flow of a material under controlled temperature conditions. There are different ways to run the test, conventional temperature linear-DSC (TL-DSC), and temperature modulation-DSC (TM-DSC). The latter has been proven as an efficient method differentiating the structural relaxation phenomena from the heat capacity. In this study, emphasis was placed on comparing the Tg measured by TL- and TM-DSC to improve the interpretation of binder glass transitions. In this study, the scope was restrained to two Polymer modified Binders (PmBs): a commercially available modified binder named PmB1 and a highly modified binder (7.5 wt% high vinyl SBS) named PmB2, were evaluated and compared with two neat bituminous binders. Based on the thermographs of the PmB2 obtained through this inter-laboratory program, it was observed that the modification by 7.5% SBS resulted in a decrease of the Tg. This reduction of Tg reflects the positive influence of SBS at low temperatures.

Crystallinity of Bitumen via WAXD and DSC and Its Effect on the Surface Microstructure

“…However, for bitumen, these DSC signals are typically very broad, they can be combined with exothermic transitions upon reheating and the thermal history of the samples before testing may significantly affect the DSC signals. Because of this, in the literature, these thermal transitions have been interpreted in different ways and have been attributed also to other phenomena not related to crystallisation or melting [28]. Alternative tools that are able to complementarily provide deeper insights into the wax crystallinity exist, but are rather uncommon for bitumen [29].…”

Laboratory Study on Influence of Blending Conditions on Chemo-Thermal Characteristics of Lignin-Modified Bitumen

“…The last and 4th cycle had a slightly different setup from the others. As reported in the Apostolidis et al (2021) research, their study showed that Temperature Modulation-DSC (TM-DSC) is a more accurate technique than Temperature Linear-DSC (TL-DSC) for analyzing bitumen [59]. They also found that TM-DSC can detect the glass transition (T g ) region in bitumen with high precision.…”

Assessing the impact of ultra-thin diamond nanothreads on the glass transition temperature of a bituminous binder

“…Since the T g decreases with the cooling rate in experiments, [51][52][53] the T g acquired from simulation can be treated as the estimation of the lower boundary value for the T g in experiments. 50,54,55 Extrapolating the T g value to the experimental cooling rate is quite complex because the changing rate varies for different molecular structures and relaxation processes, 34,56 and some of them are beyond the computation capability of MD simulation for large systems with macromolecules.…”