Abstract
This study was conducted to investigate the effect of ageing on bitumen, before and after modification. Nano-clay modified bitumen (NCMB) was produced by adding nano-clay (NC) to 60/70 penetration grade bitumen; then, the binder was tested using conventional tests for properties such as penetration, softening point and viscosity. These tests were carried out on the modified binder before and after ageing. A rolling thin film oven (RTFO) was used to simulate short-term ageing (STA), and a pressure ageing vessel (PAV) was used to simulate long-term ageing (LTA) for the modified binder. After initial results showed an improvement for the modified bitumen regarding the effect of ageing, the investigation continued using Fourier transform infrared spectroscopy (FTIR), where the microstructure distribution of the modified binder before and after ageing was observed. Finally, there was no doubt that the effect of ageing on mixtures should be investigated. For this step, the indirect tensile strength (ITS) test, which highlights the strength changes that occur for the mixtures after ageing, was selected. The results indicated that the tensile strength of mixtures made with modified bitumen showed better resistance against ageing when NC was added, which is in good agreement with the results of previous binder tests. The results of this study show that the modification of bitumen using nano-clay as an additive improves the ageing resistance of the binder, which is consequently reflected in the strength of the asphalt mixture.
Highlights
Bitumen is the main material in asphalt mixtures affected by ageing, with demonstrated chemical changes that are reflected in its physical properties [6,7], the aggregate and the designation of the asphalt mixture with high void content play a significant role in accelerating pavement ageing [1,4]
The indirect tensile strength (ITS) test was carried out on asphalt mixtures prepared with modified bitumen, before and after ageing simulations, to study the effect of the addition first assessed, and the effect of ageing was evaluated for all binders
Based on the results obtained for modified binders, it can be concluded that NC had a considerable effect on the stiffness of the modified binders before ageing
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The hardening rate increases due to increased temperature and due to exposure to sunlight during the summer [4,7] These two factors are considered the main reasons for early ageing of the surface layer of pavement, even if there is no traffic load in the desert region. The internal strength of an asphalt mixture for flexible pavement can be affected by many factors, such as water infiltration, ageing conditions and traffic load over its service time, resulting in the appearance of permanent deformation (rutting) and fatigue cracking [22,23]. The ITS test was carried out on asphalt mixtures prepared with modified bitumen, before and after ageing simulations, to study the effect of the addition first assessed, and the effect of ageing was evaluated for all binders. Carried out on asphalt mixtures prepared with modified bitumen, before and after ageing simulations, to study the effect of the addition of NC on the strength of the asphalt mixture
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