Abstract
The oxidative aging of bituminous binders affects the performance and durability of pavements. In the case of polymer-modified binders, aging involves both bitumen and polymers and has a strong impact on the whole architecture of the material. Rheology may help in understanding these structural changes, and interesting information may be obtained by analysing the evolution of apparent molecular weight distributions. This was demonstrated with a bituminous binder modified with a poly(styrene-butadiene) block copolymer and subjected to prolonged artificial aging. Isothermal frequency sweep tests were used to construct master curves of the phase angle and magnitude of the complex modulus. The master curves were then used to calculate relaxation spectra and apparent molecular weight distributions of the binders, as well as simulated temperature sweep tests. A comparison of the behaviour of the base and modified bitumen highlighted the role of the polymer in aging. Polymer degradation significantly damages the elastomeric network, yet the residual polymer chains still interact with the bitumen molecules and reduce their oxidative aging. The apparent molecular weight distributions were deconvoluted to create an aging index specifically developed for polymer-modified bitumen.
Highlights
The oxidative aging of bituminous binders has been the subject of several studies and reviews over the last few decades [1,2,3,4]
Cuciniello et al [43] showed that for bitumens modified with high contents of poly(styrene-butadiene-styrene) block copolymer (SBS), using the temperature superposition principle (TTSP) can be difficult especially in unaged binders with a high polymer content due to the integrity of the complex structure formed by the polymeric network which is swollen with bitumen molecules
At low temperatures, the bituminous matrix remains rigid, while at intermediate temperatures, the two components cooperate with each other. These differences in the temperature susceptibility explain the failure of the TTSP induced by temperature
Summary
The oxidative aging of bituminous binders has been the subject of several studies and reviews over the last few decades [1,2,3,4]. The mechanism of aging is extremely complex and involves the entire colloidal structure of bitumen, the main chemical transformations associated with oxidation are the formation of carbonyl compounds (basically ketones) and sulfoxides [5, 6]. One way to quantify aging is to use chemical indexes based on the infrared analysis of those functional groups [7,8,9]. Xu et al [10] showed the correlation of infrared-derived indexes with mechanical properties such as the complex and Young’s modulus. The results of the latter study lead to different conclusions depending on the method chosen to calculate the aging indexes. The indexes only provide a reliable comparison of the aging when “used on the same type of initial mixture.”
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
