Effect of ageing on the morphology and creep and recovery of polymer-modified bitumens

Abstract

Polymer additives are used to improve the properties of road bitumens including their oxidative resistance. However, their usage as anti-oxidative materials remains relatively unclear. This study aims to investigate the changes in the morphology and the rheological response of polymer modified bitumens used in road pavement construction caused by ageing. An elastomer (radial styrene butadiene styrene, SBS) and a plastomer (ethyl vinyl acetate, EVA) polymer were mixed with one base bitumen at three polymer concentrations. The bitumens were RTFO and PAV aged. The morphology of the bitumens was captured by fluorescence microscopy while the rheological properties were measured by means of the multiple stress creep and recovery (MSCR) test. The results show that the morphology of the SBS modified bitumen degrades with ageing as a function of polymer concentration and dispersion, with higher dispersion being more resistant. The morphology of the EVA modified bitumen has a low ageing susceptibility irrespective of polymer concentration. The MSCR response of EVA modified bitumens does not differ from that found for unmodified bitumen, where the hardening produces a decrease in the non-recoverable compliance. In the case of SBS modified bitumen, the degradation of the polymer backbone affects the bitumen hardening as much as the polymer phase dispersed and networked in the bitumen phase. Furthermore, in the case of the elastomer, the average percent recovery is in agreement with the variation of the morphology with ageing. Therefore, the use of the average percent recovery as a valuable rheological index of the integrity of the polymer network can be advocated.

Rheological behavior and antiarthritic activity of Pterodon pubescens nanoemulsion

“…The second step is to remove instantaneously the stress to allow the sample to recover as function of their properties after the yield stress test and to reapply a constant load to the sample. Creep and recovery is widely used to evaluate the deformation mechanism of polymeric systems and, associated with other techniques, predict the behavior and workability characteristics of pharmaceutical systems (Cuciniello et al, 2018). In the creep phase (section I), after 355 s of stress load, the system reached maximum deformation, JMAX for that period of time, where was observed an instantaneous increase in strain (maximum creep, higher peak).…”

Short- and Long-Term Epoxy Modification of Bitumen: Modification Kinetics, Rheological Properties, and Microstructure

“…or polymeric wastes (plastic from agriculture, tire crumb rubber, etc.) [2][3][4][5][6][7]. This bitumen modification is achieved through a suitable dispersion of the polymer into the molten bitumen.…”

Investigating the Effect of Artificial Ageing on the Creep and Recovery of SBS-Modified Bitumen

“…Besides the enhancement of the mechanical properties, polymer modified bitumen (PMBs) are expected to be stable at storage and ageing resistant [4]. However, if the oxidative mechanism of unmodified bitumen is relatively clear, in the case of PMBs the effect of polymers on the bitumen oxidative ageing needs to be investigated [4][5][6].…”

“…Therefore, the effect of the thermo-oxidative degradation of the polymer chains on the mechanical response of PMBs needs to be investigated at higher strain levels. Nevertheless, this approach has not been well considered so far [6,26].…”

“…Specifically, the Jnr is representative of the overall resistance to the accumulation of permanent deformation of the system bitumen + polymer. Differently, the average percent recovery (R) is considered an indicator of the quality of modification and of the integrity of the polymer network through ageing [6,24,25].…”