Page 52 - MODELING OF ASPHALT CONCRETE

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FIGURE 2-6 Schematics shown the target change in rheological and failure properties expected
from modifi cation.

improve asphalt properties. This chapter covers some of the key techniques to measure
properties of modified asphalts and gives the background of these techniques. Ideally a
modifier will change rheological properties to match requirements as defined by
resistance to pavement distresses as shown in the first part of Fig. 2-6. It would also
change failure properties such that binders would tolerate higher stresses and strains
before failure due to static or repeated loading as shown in the second part of Fig. 2-6.

Asphalt Modifiers Currently Used
There are currently a large number of modifiers used for paving grade asphalts.
Table 2-2 lists several published surveys of asphalt modifiers and identifies the
general types of modifiers that each study had identified.
Asphalt modifiers can be classified based on the mechanism by which the modifier
alters the asphalt properties, based on composition and physical nature of the modifier,
or based on the target asphalt property that needs to be modified. In the NCHRP 9-10
project (Bahia et al. 2001) a list of modifiers classified based on the nature of the modifier
and the mechanism by which it alters asphalt properties was developed. A total of 55
modifiers classified in 17 generic classes were identified.
The information gathered about these modifiers indicates that they vary in many
respects. Some modifiers are particulate matters while others disperse completely or