Figure 5 shows that polymer asphalt concretes are much more resistant to rutting than asphalt concretes, as η0 of PMB is entirely unattainable for road bitumen.

The fact that η0 is very well correlated to rutting strength of road top allows to conclude that this property can be regulated by increasing the amount of polymer in PMB.

Figure 6 shows rheological curves for sand based asphalt concrete for road and construction bitumen and for polymer asphalt concrete with 4.2% polymer in tar.

Apparently, the presence of elastic structure even in very low viscosity system causes its true strength РК2 at 50°С to be much higher than that of asphalt concrete based on thick road bitumen.

Furthermore, the correlations shown in figure 27 between strength limit of uniaxial compression at 50°СR50 and РК2 indicate that even at low РК2, e.g. 0.5 MPa, a high РК2 of 9.5Pa is reached.

This value of РК2  for asphalt concrete based on road bitumen is reached with R50 = 1.25 MPa, and for construction bitumen – 1.65 MPa.

Therefore it is apparent that to ensure required shear strength, the required R50for polymer asphalt bitumen can be significantly lowered.

Shell – W. Vonk

The correlation between η0 and rutting
rate in the LTT as obtained with different wearing courses of the same dense
asphaltic concrete, but with different binders, is shown in
Figure 4. RUTTING RfTf, mm/10** wheel


Figure 4. Rutting rate in LTT vs. zero shear viscosity of Rolling Thin Film Oven Test (RTFOT) aged binders