Abstract
Reliable surface free energy characterization is required in order to implement the suitable recycling agent into aged asphalt. One proven method to estimate asphalt surface free energy is to calculate it using contact angles measured with various liquids. The efficiency of recycling agent in terms of its impact on rheology and surface free energy of asphalt cement is vital in the decision of recycling aged asphalt concrete. In this investigation, asphalt cement of penetration grade 40-50 was subjected to aging using the thin film oven test. The aged and the control asphalt cement samples have been digested with various percentages of two type of polymer recycling agents (Polyethylene and crumb rubber). Recycled and control asphalt cement specimens were subjected to physical and rheological properties determination, while the surface free energy was determined using Wilhelmy plate and Sessile drop methods. It was observed that the surface free energy decreases after aging, while it increases after digestion with polymers. Digestion of aged asphalt cement with polyethylene was able to retain the original surface free energy of asphalt cement before aging, while a higher percentage of 1.5 polyethylene has improved the surface free energy beyond the requirements. Digestion of aged asphalt cement with crumb rubber was able to increase the surface free energy of asphalt cement by one-fold of that before aging when Wilhelmy plate method was implemented, while a higher percentage of 1.0 of crumb rubber has improved the surface free energy beyond the requirements.
Highlights
Recycling of aged asphalt concrete is considered as major requirement of sustainable pavement
It was concluded that the work of adhesion calculated from surface free energy can be utilized to choose the best combination of asphalt and aggregate, which can work as a reference in the selection of materials
It was stated by Sarsam and Abdulhussain, [8] that the addition of 10% carbon black exhibit an increment of surface free energy of (7.7 and 5.8)% when tested by Wilhelmy plate and sessile drop methods respectively as compared to control asphalt
Summary
Recycling of aged asphalt concrete is considered as major requirement of sustainable pavement. It was concluded that the work of adhesion calculated from surface free energy can be utilized to choose the best combination of asphalt and aggregate, which can work as a reference in the selection of materials It was stated by Sarsam and Abdulhussain, [8] that the addition of 10% carbon black exhibit an increment of surface free energy of (7.7 and 5.8)% when tested by Wilhelmy plate and sessile drop methods respectively as compared to control asphalt. The modifications included aging or addition of liquid anti-strip agents Of these 24 binders, the surface free energy components of 21 different types of asphalt binders was determined by obtaining samples from the same source at two different points in time. Wilhelmy plate method shows that the surface free energy is lower by 6.3% and higher by 10% for carbon black and sulfur respectively when the pressure vessel technique was implemented as compared to oven heating technique
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