Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

Softening Point
Penetration
Soft. Point (ºC)
80
70
60
50
40
25
0 1 2 3 4 5 6 7 8 9 10
SBS Weight Concentration (%)
55
50
45
40
35
30
Penetration (dmm)
Figure 15: Effect of SBS Concentration on PMA (16)
As Figure 15 illustrates, increasing SBS content resulted in substantially improved
softening point and penetration characteristics up to a critical concentration of about 5%
to 6%. Chen et al note that as the concentration of polymer reaches about 5%, the
asphalt and polymer phases both become continuous – that is, each phase forms an
interconnected and interwoven matrix. At polymer concentrations in excess of 5%, the
SBS becomes the dominant matrix, forming a continuous film around droplets of almost
pure asphalt. Moreover, because improvements in softening point and penetration
begin to stabilize at concentrations higher than about 6%, Chen suggests that this level
of SBS is optimal for the particular asphalt tested (i.e., AC-30) (17). Figure 16 depicts
the effect of SBS content on the complex shear modulus of test samples as measured
using the DSR. As Figure 15 illustrates, adding about 5% SBS results in an
approximately 6-fold increase in the complex modulus over neat asphalt cement.
Furthermore, increasing SBS content from 3% to 5% yields a proportionally larger
increase in complex modulus than do increases in excess of 5%.
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