This study seeks to find the influence of replacing a portion of the asphalt–rubber binder with the bio-based material “guayule resin.” This replacement could be beneficial in terms of sustainability, economics, and environmental concerns related to the asphalt industry. Nine asphalt–rubber–guayule binders were investigated to find their rheological properties. Consecutively, the study proceeded with five selected binders being compared to the original asphalt (PG64-22). Investigations underwent whole matrices (crumb rubber modifier (CRM) residue included) and liquid phases (CRM residue extracted). Additionally, these properties were partially sought for their corresponding asphalt–rubber binders to compare and judge the contribution of the guayule resin. Likewise, a thermo-gravimetric analysis was done for the guayule resin to recognize its moisture and composition complexity. Such an analysis was also done for the as-received CRM and some extracted CRMs to determine the release and residue of rubber components. Outcomes showed that the guayule resin has the potential to compensate the performance required against the original asphalt at elevated temperatures while greatly decreasing the asphalt cement proportion. For instance, a blend of 62.5% asphalt, 12.5% CRM, and 25% guayule resin provided better performance than that of the original asphalt.
Crumb rubber modifier (CRM) is considered one of the most commonly used modifiers that enhances the rheological properties of asphalt binders. Optimizing the interaction process between CRM and asphalt binder to enhance the asphalt binder’s elasticity without additional additives is the main purpose of the article. Rheological properties were measured in this article for neat asphalt and crumb rubber modified asphalt (CRMA) binders. Two sets of interactions were selected. In the first interaction set, one interaction temperature (190°C), one interaction speed (3,000 rpm), and different interaction times (0.5, 1, 2, 4, and 8 h) were used. The used CRM percentage was 10 % by weight of the neat asphalt binder. Two sources of asphalt binder, one source and different percentages of CRM, one interaction temperature (190°C), one interaction speed (3,000 rpm), and different interaction times were selected for the second interaction set. This set was designated to confirm the rheological properties obtained for the first set. Thermogravimetric analysis (TGA) was performed on CRM particles before and after their interaction with asphalt binder after different interaction times. The CRMA binders that interacted for the entire 8-h interaction times had significantly enhanced properties, especially the elasticity, as compared to the neat asphalt binder. The 8-h interaction time showed the highest CRM dissolution percentage by dissolution and TGA testing. At this interaction time, more CRM components were released into the asphalt binder liquid phase, which was detected by observing Fourier-transform infrared peaks at 966 cm−1 for polypropylene and 699 cm−1 for polystyrene.
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