Page 53 - MODELING OF ASPHALT CONCRETE

Modeling of Asphalt Binder Rheology and Its Application to Modified Binders 31

Reference

Terrel and Epps 1989 Peterson Romine et al. Moratzai and Moulthrop McGennis Isacsson and Lu 1995 Banasiak and Geistlinger

Modifier 1993 1991 1993 1995 1996
Thermoplastic X X X X X X X
Polymers
Thermoset Polymers X X X X X X X
Fillers/Reinf. Agents/ X X X X X X X
Extenders
Adhesion Promoters X X X X X X
Catalysts or Chemical X X X X X X X
Reaction Modifiers
Aging Inhibitors X X X X X X X
Others X X X X
Total number of - 46 - 82 48 31 62
existing brands or (27 ASA)
types

ASA: Antistripping additives

TABLE 2-2 Recent Surveys of Asphalt Modifiers

dissolve in the asphalt. The modifiers range from organic to inorganic materials, some of
which react with the asphalt while others are added as inert fillers. The modifiers generically
vary in their specific gravity as well as other physical characteristics. They are expected to
react differently to environmental conditions, such as oxidation and moisture effects.
Not all these types of modifiers are being currently used. The frequency of use varies
significantly depending on marketing of the modifiers, experience of contractors and
agencies, and cost. In a survey conducted in 1997, state highway agencies indicated that
polymer modifiers are among the most widely known and used in practice. Table 2-3
depicts the results of the survey (Bahia 1998b).
Table 2-3 shows that the elastomeric polymer styrene-butadiene-styrene (SBS) is
the most frequently used to target a variety of distresses among which permanent
deformation is the most common. As indicated in Table 2-3, many agencies did not
indicate the specific target distress for which they are using the modifier.

Critical Properties of Modified Asphalts

Effects of Modification on Viscoelastic Properties
Measuring properties of modified binders has in general followed the testing technology
used for unmodified asphalts but in many specifications expanded to capture some