This study included five different recovery methods for six emulsions (CRS-2, CRS-2P, CRS-2L, SS-1, SS-1L, and SS-1H) and their corresponding unaged base binders. These five recovery methods consisted of different curing times, temperatures, and vacuum pressures. The goal of this study was to understand the effect of these variables on the rheological properties of the recovered asphalt emulsion residue during the recovery process. Rheological properties such as G*/sin δ, phase angle, and average percent strain recovery were determined to quantify stiffness, oxidative aging, and change in creep recovery due to polymer modification. One new recovery method using a vacuum drying oven was explored in this study. This method reduced the effects of oxidative aging and reduced the recovery time to 6 h. The results show that this newly proposed vacuum drying method ensured better drying of the sample and produced residue that was not unnecessarily aged and was similar to unaged base binder in stiffness, whereas with ASTM D7497 oxidative aging plays a significant role in residue stiffness by almost doubling the stiffness relative to unaged base binder. Also, this 6-h vacuum drying method allowed us to clearly identify the presence of polymer. Overall, this report explains the reasons for the differences between the stiffnesses of unaged base binder and emulsion residue, considering oxidative aging, remaining moisture, emulsifier, and polymer modification.

Fog seal increases pavement life and postpones major rehabilitation. The reduction of permeability caused by fog sealing will reduce moisture-induced damage, but this benefit comes with a temporary loss of surface friction. However, quantifying the effectiveness of fog sealing by measuring permeability is a difficult task. Although fog seal may be a good low-cost maintenance option for low-volume roads, the rate of recovery of friction may be very slow because of less rubbing action between the fog-sealed surface and tires. Four low-volume parish roads in Caddo Parish, Louisiana, were selected for this study. Two emulsions, CSS-1H and E-Fog, with three application rates, were used to evaluate the reduction in hydraulic conductivity and to assess the characteristics of friction over time. Results showed that fog seal can be expected to be fully cured within 2.5 to 3.5 hours for an application rate of 0.2 to 0.4 gallons per square yard (gal/yd2). The same field cores were tested before and after fog sealing to quantify exactly the reduction in hydraulic conductivity. It was observed that fog seal has a significant potential to reduce hydraulic conductivity. Considering all four pavements and application rates of 0.1 to 0.22 gal/yd2, the average reduction in hydraulic conductivity was 38.5%. Reduction in hydraulic conductivity shows very slight sensitivity to the application rate. Irrespective of road type, emulsion, and application rate, fog seal causes a sudden drop in the International Friction Index parameter F60 by 20% to 40%. A fog-sealed surface does not return to the original level of friction after three months; however, the rate of recovery was the highest for the busiest of the observed Caddo Parish roads.

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